diff --git a/pyModeS/__init__.py b/pyModeS/__init__.py
index c43679b..b8a4cca 100644
--- a/pyModeS/__init__.py
+++ b/pyModeS/__init__.py
@@ -2,8 +2,10 @@ from __future__ import absolute_import, print_function, division
 
 from .decoder.util import *
 from .decoder import adsb
+from .decoder import els
 from .decoder import ehs
 from .decoder import util
 from .decoder import modes
+from .decoder import bds
 from .extra import aero
 from .extra import beastclient
diff --git a/pyModeS/decoder/bds/__init__.py b/pyModeS/decoder/bds/__init__.py
new file mode 100644
index 0000000..bf10e0a
--- /dev/null
+++ b/pyModeS/decoder/bds/__init__.py
@@ -0,0 +1,101 @@
+from __future__ import absolute_import, print_function, division
+
+import numpy as np
+from pyModeS.extra import aero
+from pyModeS.decoder.modes import allzeros
+from pyModeS.decoder.bds.bds10 import isBDS10
+from pyModeS.decoder.bds.bds17 import isBDS17
+from pyModeS.decoder.bds.bds20 import isBDS20
+from pyModeS.decoder.bds.bds30 import isBDS30
+from pyModeS.decoder.bds.bds40 import isBDS40
+from pyModeS.decoder.bds.bds50 import isBDS50, trk50, gs50
+from pyModeS.decoder.bds.bds60 import isBDS60, hdg60, mach60, ias60
+
+
+def is50or60(msg, spd_ref, trk_ref, alt_ref):
+    """Use reference ground speed and trk to determine BDS50 and DBS60
+
+    Args:
+        msg (String): 28 bytes hexadecimal message string
+        spd_ref (float): reference speed (ADS-B ground speed), kts
+        trk_ref (float): reference track (ADS-B track angle), deg
+        alt_ref (float): reference altitude (ADS-B altitude), ft
+
+    Returns:
+        String or None: BDS version, or possible versions, or None if nothing matches.
+    """
+    def vxy(v, angle):
+        vx = v * np.sin(np.deg2rad(angle))
+        vy = v * np.cos(np.deg2rad(angle))
+        return vx, vy
+
+    if not (isBDS50(msg) and isBDS60(msg)):
+        return None
+
+    h50 = trk50(msg)
+    v50 = gs50(msg)
+    h50 = np.nan if h50 is None else h50
+    v50 = np.nan if v50 is None else v50
+
+    h60 = hdg60(msg)
+    m60 = mach60(msg)
+    i60 = ias60(msg)
+    h60 = np.nan if h60 is None else h60
+    m60 = np.nan if m60 is None else m60
+    i60 = np.nan if i60 is None else i60
+
+    XY5 = vxy(v50*aero.kts, h50)
+    XY6m = vxy(aero.mach2tas(m60, alt_ref*aero.ft), h60)
+    XY6i = vxy(aero.cas2tas(i60*aero.kts, alt_ref*aero.ft), h60)
+
+    allbds = ['BDS50', 'BDS60', 'BDS60']
+
+    X = np.array([XY5, XY6m, XY6i])
+    Mu = np.array(vxy(spd_ref*aero.kts, trk_ref*aero.kts))
+
+    # compute Mahalanobis distance matrix
+    # Cov = [[20**2, 0], [0, 20**2]]
+    # mmatrix = np.sqrt(np.dot(np.dot(X-Mu, np.linalg.inv(Cov)), (X-Mu).T))
+    # dist = np.diag(mmatrix)
+
+    # since the covariance matrix is identity matrix,
+    #     M-dist is same as eculidian distance
+    dist = np.linalg.norm(X-Mu, axis=1)
+    BDS = allbds[np.nanargmin(dist)]
+
+    return BDS
+
+
+def infer(msg):
+    """Estimate the most likely BDS code of an message
+
+    Args:
+        msg (String): 28 bytes hexadecimal message string
+
+    Returns:
+        String or None: BDS version, or possible versions, or None if nothing matches.
+    """
+
+    if allzeros(msg):
+        return None
+
+    is10 = isBDS10(msg)
+    is17 = isBDS17(msg)
+    is20 = isBDS20(msg)
+    is30 = isBDS30(msg)
+    is40 = isBDS40(msg)
+    is50 = isBDS50(msg)
+    is60 = isBDS60(msg)
+
+    allbds = np.array([
+        "BDS10", "BDS17", "BDS20", "BDS30", "BDS40", "BDS50", "BDS60"
+    ])
+
+    isBDS = [is10, is17, is20, is30, is40, is50, is60]
+
+    bds = ','.join(sorted(allbds[isBDS]))
+
+    if len(bds) == 0:
+        return None
+    else:
+        return bds
diff --git a/pyModeS/decoder/bds/bds10.py b/pyModeS/decoder/bds/bds10.py
new file mode 100644
index 0000000..26b28bf
--- /dev/null
+++ b/pyModeS/decoder/bds/bds10.py
@@ -0,0 +1,67 @@
+# Copyright (C) 2018 Junzi Sun (TU Delft)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from __future__ import absolute_import, print_function, division
+from pyModeS.decoder.util import hex2bin, bin2int
+from pyModeS.decoder.modes import data, allzeros
+
+# ------------------------------------------
+# BDS 1,0
+# Data link capability report
+# ------------------------------------------
+
+def isBDS10(msg):
+    """Check if a message is likely to be BDS code 1,0
+
+    Args:
+        msg (String): 28 bytes hexadecimal message string
+
+    Returns:
+        bool: True or False
+    """
+
+    if allzeros(msg):
+        return False
+
+    d = hex2bin(data(msg))
+
+    # first 8 bits must be 0x10
+    if d[0:8] != '00010000':
+        return False
+
+    # bit 10 to 14 are reserved
+    if bin2int(d[9:14]) != 0:
+        return False
+
+    # overlay capabilty conflict
+    if d[14] == '1' and bin2int(d[16:23]) < 5:
+        return False
+    if d[14] == '0' and bin2int(d[16:23]) > 4:
+        return False
+
+    return True
+
+def ovc10(msg):
+    """Return the overlay control capability
+
+    Args:
+        msg (String): 28 bytes hexadecimal message string
+
+    Returns:
+        int: Whether the transponder is OVC capable
+    """
+    d = hex2bin(data(msg))
+
+    return int(d[14])
diff --git a/pyModeS/decoder/bds/bds17.py b/pyModeS/decoder/bds/bds17.py
new file mode 100644
index 0000000..5c6c5dd
--- /dev/null
+++ b/pyModeS/decoder/bds/bds17.py
@@ -0,0 +1,70 @@
+# Copyright (C) 2018 Junzi Sun (TU Delft)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+from __future__ import absolute_import, print_function, division
+from pyModeS.decoder.util import hex2bin, bin2int
+from pyModeS.decoder.modes import data, allzeros
+
+# ------------------------------------------
+# BDS 1,7
+# Common usage GICB capability report
+# ------------------------------------------
+
+def isBDS17(msg):
+    """Check if a message is likely to be BDS code 1,7
+
+    Args:
+        msg (String): 28 bytes hexadecimal message string
+
+    Returns:
+        bool: True or False
+    """
+
+    if allzeros(msg):
+        return False
+
+    d = hex2bin(data(msg))
+
+    if bin2int(d[28:56]) != 0:
+        return False
+
+    caps = cap17(msg)
+
+    # basic BDS codes for ADS-B shall be supported
+    #   assuming ADS-B out is installed (2017EU/2020US mandate)
+    if not set(['BDS05', 'BDS06', 'BDS09', 'BDS20']).issubset(caps):
+        return False
+
+    return True
+
+def cap17(msg):
+    """Extract capacities from BDS 1,7 message
+
+    Args:
+        msg (String): 28 bytes hexadecimal message string
+
+    Returns:
+        list: list of suport BDS codes
+    """
+    allbds = ['05', '06', '07', '08', '09', '0A', '20', '21', '40', '41',
+              '42', '43', '44', '45', '48', '50', '51', '52', '53', '54',
+              '55', '56', '5F', '60', 'NA', 'NA', 'E1', 'E2']
+
+    d = hex2bin(data(msg))
+    idx = [i for i, v in enumerate(d[:28]) if v=='1']
+    capacity = ['BDS'+allbds[i] for i in idx if allbds[i] is not 'NA']
+
+    return capacity
diff --git a/pyModeS/decoder/bds/bds20.py b/pyModeS/decoder/bds/bds20.py
new file mode 100644
index 0000000..7d40a55
--- /dev/null
+++ b/pyModeS/decoder/bds/bds20.py
@@ -0,0 +1,76 @@
+# Copyright (C) 2018 Junzi Sun (TU Delft)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from __future__ import absolute_import, print_function, division
+from pyModeS.decoder.util import hex2bin, bin2int
+from pyModeS.decoder.modes import data, allzeros
+
+# ------------------------------------------
+# BDS 2,0
+# Aircraft identification
+# ------------------------------------------
+
+def isBDS20(msg):
+    """Check if a message is likely to be BDS code 2,0
+
+    Args:
+        msg (String): 28 bytes hexadecimal message string
+
+    Returns:
+        bool: True or False
+    """
+
+    if allzeros(msg):
+        return False
+
+    d = hex2bin(data(msg))
+
+    # status bit 1, 14, and 27
+
+    if bin2int(d[0:4]) != 2 or bin2int(d[4:8]) != 0:
+        return False
+
+    cs = callsign(msg)
+
+    if '#' in cs:
+        return False
+
+    return True
+
+
+def callsign(msg):
+    """Aircraft callsign
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS40) string
+
+    Returns:
+        string: callsign, max. 8 chars
+    """
+    chars = '#ABCDEFGHIJKLMNOPQRSTUVWXYZ#####_###############0123456789######'
+
+    d = hex2bin(data(msg))
+
+    cs = ''
+    cs += chars[bin2int(d[8:14])]
+    cs += chars[bin2int(d[14:20])]
+    cs += chars[bin2int(d[20:26])]
+    cs += chars[bin2int(d[26:32])]
+    cs += chars[bin2int(d[32:38])]
+    cs += chars[bin2int(d[38:44])]
+    cs += chars[bin2int(d[44:50])]
+    cs += chars[bin2int(d[50:56])]
+
+    return cs
diff --git a/pyModeS/decoder/bds/bds30.py b/pyModeS/decoder/bds/bds30.py
new file mode 100644
index 0000000..c075130
--- /dev/null
+++ b/pyModeS/decoder/bds/bds30.py
@@ -0,0 +1,51 @@
+# Copyright (C) 2018 Junzi Sun (TU Delft)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from __future__ import absolute_import, print_function, division
+from pyModeS.decoder.util import hex2bin, bin2int
+from pyModeS.decoder.modes import data, allzeros
+
+# ------------------------------------------
+# BDS 3,0
+# ACAS active resolution advisory
+# ------------------------------------------
+
+def isBDS30(msg):
+    """Check if a message is likely to be BDS code 2,0
+
+    Args:
+        msg (String): 28 bytes hexadecimal message string
+
+    Returns:
+        bool: True or False
+    """
+
+    if allzeros(msg):
+        return False
+
+    d = hex2bin(data(msg))
+
+    if d[0:8] != '00110000':
+        return False
+
+    # threat type 3 not assigned
+    if d[28:30] == '11':
+        return False
+
+    # reserved for ACAS III, in far future
+    if bin2int(d[15:22]) >= 48:
+        return False
+
+    return True
diff --git a/pyModeS/decoder/bds/bds40.py b/pyModeS/decoder/bds/bds40.py
new file mode 100644
index 0000000..00c719e
--- /dev/null
+++ b/pyModeS/decoder/bds/bds40.py
@@ -0,0 +1,114 @@
+# Copyright (C) 2018 Junzi Sun (TU Delft)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+from __future__ import absolute_import, print_function, division
+from pyModeS.decoder.util import hex2bin, bin2int
+from pyModeS.decoder.modes import data, allzeros, wrongstatus
+
+# ------------------------------------------
+# BDS 4,0
+# Selected vertical intention
+# ------------------------------------------
+
+def isBDS40(msg):
+    """Check if a message is likely to be BDS code 4,0
+
+    Args:
+        msg (String): 28 bytes hexadecimal message string
+
+    Returns:
+        bool: True or False
+    """
+
+    if allzeros(msg):
+        return False
+
+    d = hex2bin(data(msg))
+
+    # status bit 1, 14, and 27
+
+    if wrongstatus(d, 1, 2, 13):
+        return False
+
+    if wrongstatus(d, 14, 15, 26):
+        return False
+
+    if wrongstatus(d, 27, 28, 39):
+        return False
+
+    # bits 40-47 and 52-53 shall all be zero
+
+    if bin2int(d[39:47]) != 0:
+        return False
+
+    if bin2int(d[51:53]) != 0:
+        return False
+
+    return True
+
+
+def alt40mcp(msg):
+    """Selected altitude, MCP/FCU
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS40) string
+
+    Returns:
+        int: altitude in feet
+    """
+    d = hex2bin(data(msg))
+
+    if d[0] == '0':
+        return None
+
+    alt = bin2int(d[1:13]) * 16    # ft
+    return alt
+
+
+def alt40fms(msg):
+    """Selected altitude, FMS
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS40) string
+
+    Returns:
+        int: altitude in feet
+    """
+    d = hex2bin(data(msg))
+
+    if d[13] == '0':
+        return None
+
+    alt = bin2int(d[14:26]) * 16    # ft
+    return alt
+
+
+def p40baro(msg):
+    """Barometric pressure setting
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS40) string
+
+    Returns:
+        float: pressure in millibar
+    """
+    d = hex2bin(data(msg))
+
+    if d[26] == '0':
+        return None
+
+    p = bin2int(d[27:39]) * 0.1 + 800    # millibar
+    return p
diff --git a/pyModeS/decoder/bds/bds44.py b/pyModeS/decoder/bds/bds44.py
new file mode 100644
index 0000000..d3a9ef2
--- /dev/null
+++ b/pyModeS/decoder/bds/bds44.py
@@ -0,0 +1,219 @@
+# Copyright (C) 2018 Junzi Sun (TU Delft)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from __future__ import absolute_import, print_function, division
+from pyModeS.decoder.util import hex2bin, bin2int
+from pyModeS.decoder.modes import data, allzeros, wrongstatus
+
+# ------------------------------------------
+# BDS 4,4
+# Meteorological routine air report
+# ------------------------------------------
+
+def isBDS44(msg, rev=False):
+    """Check if a message is likely to be BDS code 4,4
+    Meteorological routine air report
+
+    Args:
+        msg (String): 28 bytes hexadecimal message string
+        rev (bool): using revised version
+
+    Returns:
+        bool: True or False
+    """
+
+    if allzeros(msg):
+        return False
+
+    d = hex2bin(data(msg))
+
+
+    if not rev:
+        # status bit 5, 35, 47, 50
+        if wrongstatus(d, 5, 6, 23):
+            return False
+
+        if wrongstatus(d, 35, 36, 46):
+            return False
+
+        if wrongstatus(d, 47, 48, 49):
+            return False
+
+        if wrongstatus(d, 50, 51, 56):
+            return False
+
+        # Bits 1-4 indicate source, values > 4 reserved and should not occur
+        if bin2int(d[0:4]) > 4:
+            return False
+    else:
+        # status bit 5, 15, 24, 36, 49
+        if wrongstatus(d, 5, 6, 14):
+            return False
+
+        if wrongstatus(d, 15, 16, 23):
+            return False
+
+        if wrongstatus(d, 24, 25, 35):
+            return False
+
+        if wrongstatus(d, 36, 37, 47):
+            return False
+
+        if wrongstatus(d, 49, 50, 56):
+            return False
+
+        # Bits 1-4 are reserved and should be zero
+        if bin2int(d[0:4]) != 0:
+            return False
+
+    vw = wind44(msg, rev=rev)
+    if vw is not None and vw[0] > 250:
+        return False
+
+    if temp44(msg):
+        if temp44(msg) > 60 or temp44(msg) < -80:
+            return False
+
+    elif temp44(msg) == 0:
+        return False
+
+    return True
+
+
+def wind44(msg, rev=False):
+    """reported wind speed and direction
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS44) string
+        rev (bool): using revised version
+
+    Returns:
+        (int, float): speed (kt), direction (degree)
+    """
+    d = hex2bin(data(msg))
+
+    if not rev:
+        status = int(d[4])
+        if not status:
+            return None
+
+        speed = bin2int(d[5:14])   # knots
+        direction = bin2int(d[14:23]) * 180.0 / 256.0  # degree
+
+    else:
+        spd_status = int(d[4])
+        dir_status = int(d[14])
+
+        if (not spd_status) or (not dir_status):
+            return None
+
+        speed = bin2int(d[5:14])   # knots
+        direction = bin2int(d[15:23]) * 180.0 / 128.0  # degree
+
+    return round(speed, 0), round(direction, 1)
+
+
+def temp44(msg, rev=False):
+    """reported air temperature
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS44) string
+        rev (bool): using revised version
+
+    Returns:
+        float: tmeperature in Celsius degree
+    """
+    d = hex2bin(data(msg))
+
+    if not rev:
+        # if d[22] == '0':
+        #     return None
+
+        sign = int(d[23])
+        value = bin2int(d[24:34])
+
+        if sign:
+            value = value - 1024
+
+        temp = value * 0.125   # celsius
+        temp = round(temp, 1)
+    else:
+        # if d[23] == '0':
+        #     return None
+
+        sign = int(d[24])
+        value = bin2int(d[25:35])
+
+        if sign:
+            value = value - 1024
+
+        temp = value * 0.125   # celsius
+        temp = round(temp, 1)
+
+    return -1*temp if sign else temp
+
+
+def p44(msg, rev=False):
+    """reported average static pressure
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS44) string
+        rev (bool): using revised version
+
+    Returns:
+        int: static pressure in hPa
+    """
+    d = hex2bin(data(msg))
+
+    if not rev:
+        if d[34] == '0':
+            return None
+
+        p = bin2int(d[35:46])    # hPa
+
+    else:
+        if d[35] == '0':
+            return None
+
+        p = bin2int(d[36:47])    # hPa
+
+    return p
+
+
+def hum44(msg, rev=False):
+    """reported humidity
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS44) string
+        rev (bool): using revised version
+
+    Returns:
+        float: percentage of humidity, [0 - 100] %
+    """
+    d = hex2bin(data(msg))
+
+    if not rev:
+        if d[49] == '0':
+            return None
+
+        hm = bin2int(d[50:56]) * 100.0 / 64    # %
+
+    else:
+        if d[48] == '0':
+            return None
+
+        hm = bin2int(d[49:56])    # %
+
+    return round(hm, 1)
diff --git a/pyModeS/decoder/bds/bds50.py b/pyModeS/decoder/bds/bds50.py
new file mode 100644
index 0000000..7d759bd
--- /dev/null
+++ b/pyModeS/decoder/bds/bds50.py
@@ -0,0 +1,190 @@
+# Copyright (C) 2018 Junzi Sun (TU Delft)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from __future__ import absolute_import, print_function, division
+from pyModeS.decoder.util import hex2bin, bin2int
+from pyModeS.decoder.modes import data, allzeros, wrongstatus
+
+# ------------------------------------------
+# BDS 5,0
+# Track and turn report
+# ------------------------------------------
+
+def isBDS50(msg):
+    """Check if a message is likely to be BDS code 5,0
+    (Track and turn report)
+
+    Args:
+        msg (String): 28 bytes hexadecimal message string
+
+    Returns:
+        bool: True or False
+    """
+
+    if allzeros(msg):
+        return False
+
+    d = hex2bin(data(msg))
+
+    # status bit 1, 12, 24, 35, 46
+
+    if wrongstatus(d, 1, 3, 11):
+        return False
+
+    if wrongstatus(d, 12, 13, 23):
+        return False
+
+    if wrongstatus(d, 24, 25, 34):
+        return False
+
+    if wrongstatus(d, 35, 36, 45):
+        return False
+
+    if wrongstatus(d, 46, 47, 56):
+        return False
+
+    if d[2:11] != "000000000":
+        roll = abs(roll50(msg))
+        if roll and roll > 60:
+            return False
+
+    gs = gs50(msg)
+    if gs is not None and gs > 600:
+        return False
+
+    tas = tas50(msg)
+    if tas is not None and tas > 500:
+        return False
+
+    if (gs is not None) and (tas is not None) and (abs(tas - gs) > 200):
+        return False
+
+    return True
+
+
+def roll50(msg):
+    """Roll angle, BDS 5,0 message
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS50) string
+
+    Returns:
+        float: angle in degrees,
+               negative->left wing down, positive->right wing down
+    """
+    d = hex2bin(data(msg))
+
+    if d[0] == '0':
+        return None
+
+    sign = int(d[1])    # 1 -> left wing down
+    value = bin2int(d[2:11])
+
+    if sign:
+        value = value - 512
+
+    angle = value * 45.0 / 256.0    # degree
+    return round(angle, 1)
+
+
+def trk50(msg):
+    """True track angle, BDS 5,0 message
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS50) string
+
+    Returns:
+        float: angle in degrees to true north (from 0 to 360)
+    """
+    d = hex2bin(data(msg))
+
+    if d[11] == '0':
+        return None
+
+    sign = int(d[12])   # 1 -> west
+    value = bin2int(d[13:23])
+
+    if sign:
+        value = value - 1024
+
+    trk = value * 90.0 / 512.0
+
+    # convert from [-180, 180] to [0, 360]
+    if trk < 0:
+        trk = 360 + trk
+
+    return round(trk, 3)
+
+
+def gs50(msg):
+    """Ground speed, BDS 5,0 message
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS50) string
+
+    Returns:
+        int: ground speed in knots
+    """
+    d = hex2bin(data(msg))
+
+    if d[23] == '0':
+        return None
+
+    spd = bin2int(d[24:34]) * 2    # kts
+    return spd
+
+
+def rtrk50(msg):
+    """Track angle rate, BDS 5,0 message
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS50) string
+
+    Returns:
+        float: angle rate in degrees/second
+    """
+    d = hex2bin(data(msg))
+
+    if d[34] == '0':
+        return None
+
+    if d[36:45] == "111111111":
+        return None
+
+    sign = int(d[35])    # 1 -> negative value, two's complement
+    value = bin2int(d[36:45])
+    if sign:
+        value = value - 512
+
+    angle = value * 8.0 / 256.0    # degree / sec
+    return round(angle, 3)
+
+
+def tas50(msg):
+    """Aircraft true airspeed, BDS 5,0 message
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS50) string
+
+    Returns:
+        int: true airspeed in knots
+    """
+    d = hex2bin(data(msg))
+
+    if d[45] == '0':
+        return None
+
+    tas = bin2int(d[46:56]) * 2   # kts
+    return tas
diff --git a/pyModeS/decoder/bds/bds53.py b/pyModeS/decoder/bds/bds53.py
new file mode 100644
index 0000000..6275548
--- /dev/null
+++ b/pyModeS/decoder/bds/bds53.py
@@ -0,0 +1,182 @@
+# Copyright (C) 2018 Junzi Sun (TU Delft)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from __future__ import absolute_import, print_function, division
+from pyModeS.decoder.util import hex2bin, bin2int
+from pyModeS.decoder.modes import data, allzeros, wrongstatus
+
+# ------------------------------------------
+# BDS 5,3
+# Air-referenced state vector
+# ------------------------------------------
+
+def isBDS53(msg):
+    """Check if a message is likely to be BDS code 5,3
+    (Air-referenced state vector)
+
+    Args:
+        msg (String): 28 bytes hexadecimal message string
+
+    Returns:
+        bool: True or False
+    """
+
+    if allzeros(msg):
+        return False
+
+    d = hex2bin(data(msg))
+
+    # status bit 1, 13, 24, 34, 47
+
+    if wrongstatus(d, 1, 3, 12):
+        return False
+
+    if wrongstatus(d, 13, 14, 23):
+        return False
+
+    if wrongstatus(d, 24, 25, 33):
+        return False
+
+    if wrongstatus(d, 34, 35, 46):
+        return False
+
+    if wrongstatus(d, 47, 49, 56):
+        return False
+
+    ias = ias53(msg)
+    if ias is not None and ias > 500:
+        return False
+
+    mach = mach53(msg)
+    if mach is not None and mach > 1:
+        return False
+
+    tas = tas53(msg)
+    if tas is not None and tas > 500:
+        return False
+
+    vr = vr53(msg)
+    if vr is not None and abs(vr) > 8000:
+        return False
+
+    return True
+
+
+def hdg53(msg):
+    """Magnetic heading, BDS 5,3 message
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS53) string
+
+    Returns:
+        float: angle in degrees to true north (from 0 to 360)
+    """
+    d = hex2bin(data(msg))
+
+    if d[0] == '0':
+        return None
+
+    sign = int(d[1])    # 1 -> west
+    value = bin2int(d[2:12])
+
+    if sign:
+        value = value - 1024
+
+    hdg = value * 90.0 / 512.0   # degree
+
+    # convert from [-180, 180] to [0, 360]
+    if hdg < 0:
+        hdg = 360 + hdg
+
+    return round(hdg, 3)
+
+
+def ias53(msg):
+    """Indicated airspeed, DBS 5,3 message
+
+    Args:
+        msg (String): 28 bytes hexadecimal message
+
+    Returns:
+        int: indicated arispeed in knots
+    """
+    d = hex2bin(data(msg))
+
+    if d[12] == '0':
+        return None
+
+    ias = bin2int(d[13:23])    # knots
+    return ias
+
+
+def mach53(msg):
+    """MACH number, DBS 5,3 message
+
+    Args:
+        msg (String): 28 bytes hexadecimal message
+
+    Returns:
+        float: MACH number
+    """
+    d = hex2bin(data(msg))
+
+    if d[23] == '0':
+        return None
+
+    mach = bin2int(d[24:33]) * 0.008
+    return round(mach, 3)
+
+
+def tas53(msg):
+    """Aircraft true airspeed, BDS 5,3 message
+
+    Args:
+        msg (String): 28 bytes hexadecimal message
+
+    Returns:
+        float: true airspeed in knots
+    """
+    d = hex2bin(data(msg))
+
+    if d[33] == '0':
+        return None
+
+    tas = bin2int(d[34:46]) * 0.5   # kts
+    return round(tas, 1)
+
+def vr53(msg):
+    """Vertical rate
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS60) string
+
+    Returns:
+        int: vertical rate in feet/minutes
+    """
+    d = hex2bin(data(msg))
+
+    if d[46] == '0':
+        return None
+
+    sign = int(d[47])    # 1 -> negative value, two's complement
+    value = bin2int(d[48:56])
+
+    if value == 0 or value == 255:  # all zeros or all ones
+        return 0
+
+    value = value - 256 if sign else value
+    roc = value * 64     # feet/min
+
+    return roc
diff --git a/pyModeS/decoder/bds/bds60.py b/pyModeS/decoder/bds/bds60.py
new file mode 100644
index 0000000..9836942
--- /dev/null
+++ b/pyModeS/decoder/bds/bds60.py
@@ -0,0 +1,190 @@
+# Copyright (C) 2018 Junzi Sun (TU Delft)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from __future__ import absolute_import, print_function, division
+from pyModeS.decoder.util import hex2bin, bin2int
+from pyModeS.decoder.modes import data, allzeros, wrongstatus
+
+# ------------------------------------------
+# BDS 6,0
+# Heading and speed report
+# ------------------------------------------
+
+def isBDS60(msg):
+    """Check if a message is likely to be BDS code 6,0
+
+    Args:
+        msg (String): 28 bytes hexadecimal message string
+
+    Returns:
+        bool: True or False
+    """
+
+    if allzeros(msg):
+        return False
+
+    d = hex2bin(data(msg))
+
+    # status bit 1, 13, 24, 35, 46
+
+    if wrongstatus(d, 1, 2, 12):
+        return False
+
+    if wrongstatus(d, 13, 14, 23):
+        return False
+
+    if wrongstatus(d, 24, 25, 34):
+        return False
+
+    if wrongstatus(d, 35, 36, 45):
+        return False
+
+    if wrongstatus(d, 46, 47, 56):
+        return False
+
+    ias = ias60(msg)
+    if ias is not None and ias > 500:
+        return False
+
+    mach = mach60(msg)
+    if mach is not None and mach > 1:
+        return False
+
+    vr_baro = vr60baro(msg)
+    if vr_baro is not None and abs(vr_baro) > 6000:
+        return False
+
+    vr_ins = vr60ins(msg)
+    if vr_ins is not None and abs(vr_ins) > 6000:
+        return False
+
+    return True
+
+
+def hdg60(msg):
+    """Megnetic heading of aircraft
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS60) string
+
+    Returns:
+        float: heading in degrees to megnetic north (from 0 to 360)
+    """
+    d = hex2bin(data(msg))
+
+    if d[0] == '0':
+        return None
+
+    sign = int(d[1])    # 1 -> west
+    value = bin2int(d[2:12])
+
+    if sign:
+        value = value - 1024
+
+    hdg = value * 90 / 512.0  # degree
+
+    # convert from [-180, 180] to [0, 360]
+    if hdg < 0:
+        hdg = 360 + hdg
+
+    return round(hdg, 3)
+
+
+def ias60(msg):
+    """Indicated airspeed
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS60) string
+
+    Returns:
+        int: indicated airspeed in knots
+    """
+    d = hex2bin(data(msg))
+
+    if d[12] == '0':
+        return None
+
+    ias = bin2int(d[13:23])    # kts
+    return ias
+
+
+def mach60(msg):
+    """Aircraft MACH number
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS60) string
+
+    Returns:
+        float: MACH number
+    """
+    d = hex2bin(data(msg))
+
+    if d[23] == '0':
+        return None
+
+    mach = bin2int(d[24:34]) * 2.048 / 512.0
+    return round(mach, 3)
+
+
+def vr60baro(msg):
+    """Vertical rate from barometric measurement, this value may be very noisy.
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS60) string
+
+    Returns:
+        int: vertical rate in feet/minutes
+    """
+    d = hex2bin(data(msg))
+
+    if d[34] == '0':
+        return None
+
+    sign = int(d[35])    # 1 -> negative value, two's complement
+    value = bin2int(d[36:45])
+
+    if value == 0 or value == 511:  # all zeros or all ones
+        return 0
+
+    value = value - 512 if sign else value
+
+    roc = value * 32   # feet/min
+    return roc
+
+
+def vr60ins(msg):
+    """Vertical rate messured by onbard equiments (IRS, AHRS)
+
+    Args:
+        msg (String): 28 bytes hexadecimal message (BDS60) string
+
+    Returns:
+        int: vertical rate in feet/minutes
+    """
+    d = hex2bin(data(msg))
+
+    if d[45] == '0':
+        return None
+
+    sign = int(d[46])    # 1 -> negative value, two's complement
+    value = bin2int(d[47:56])
+
+    if value == 0 or value == 511:  # all zeros or all ones
+        return 0
+
+    value = value - 512 if sign else value
+
+    roc = value * 32   # feet/min
+    return roc
diff --git a/pyModeS/decoder/ehs.py b/pyModeS/decoder/ehs.py
index 0d5e2f7..56e8386 100644
--- a/pyModeS/decoder/ehs.py
+++ b/pyModeS/decoder/ehs.py
@@ -1,1122 +1,7 @@
-# Copyright (C) 2016 Junzi Sun (TU Delft)
-
-# This program is free software: you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
-
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-
-# You should have received a copy of the GNU General Public License
-# along with this program.  If not, see <http://www.gnu.org/licenses/>.
-
-"""
-A python package for decoding ModeS (DF20, DF21) messages.
-"""
-
 from __future__ import absolute_import, print_function, division
-import numpy as np
-from pyModeS.decoder import util, modes
-from pyModeS.extra import aero
 
-def icao(msg):
-    return modes.icao(msg)
-
-def data(msg):
-    """Return the data frame in the message, bytes 9 to 22"""
-    return msg[8:22]
-
-def allzeros(msg):
-    """check if the data bits are all zeros
-
-    Args:
-        msg (String): 28 bytes hexadecimal message string
-
-    Returns:
-        bool: True or False
-    """
-    d = util.hex2bin(data(msg))
-
-    if util.bin2int(d) > 0:
-        return False
-    else:
-        return True
-
-def wrongstatus(data, sb, msb, lsb):
-    """Check if the status bit and field bits are consistency. This Function
-    is used for checking BDS code versions.
-    """
-
-    # status bit, most significant bit, least significant bit
-    status = int(data[sb-1])
-    value = util.bin2int(data[msb-1:lsb])
-
-    if not status:
-        if value != 0:
-            return True
-
-    return False
-
-
-# ------------------------------------------
-# BDS 1,0
-# Data link capability report
-# ------------------------------------------
-
-def isBDS10(msg):
-    """Check if a message is likely to be BDS code 1,0
-
-    Args:
-        msg (String): 28 bytes hexadecimal message string
-
-    Returns:
-        bool: True or False
-    """
-
-    if allzeros(msg):
-        return False
-
-    d = util.hex2bin(data(msg))
-
-    # first 8 bits must be 0x10
-    if d[0:8] != '00010000':
-        return False
-
-    # bit 10 to 14 are reserved
-    if util.bin2int(d[9:14]) != 0:
-        return False
-
-    # overlay capabilty conflict
-    if d[14] == '1' and util.bin2int(d[16:23]) < 5:
-        return False
-    if d[14] == '0' and util.bin2int(d[16:23]) > 4:
-        return False
-
-    return True
-
-def ovc10(msg):
-    """Return the overlay control capability
-
-    Args:
-        msg (String): 28 bytes hexadecimal message string
-
-    Returns:
-        int: Whether the transponder is OVC capable
-    """
-    d = util.hex2bin(data(msg))
-
-    return int(d[14])
-
-# ------------------------------------------
-# BDS 1,7
-# Common usage GICB capability report
-# ------------------------------------------
-
-def isBDS17(msg):
-    """Check if a message is likely to be BDS code 1,7
-
-    Args:
-        msg (String): 28 bytes hexadecimal message string
-
-    Returns:
-        bool: True or False
-    """
-
-    if allzeros(msg):
-        return False
-
-    d = util.hex2bin(data(msg))
-
-    if util.bin2int(d[28:56]) != 0:
-        return False
-
-    caps = cap17(msg)
-
-    # basic BDS codes for ADS-B shall be supported
-    #   assuming ADS-B out is installed (2017EU/2020US mandate)
-    if not set(['BDS05', 'BDS06', 'BDS09', 'BDS20']).issubset(caps):
-        return False
-
-    return True
-
-def cap17(msg):
-    """Extract capacities from BDS 1,7 message
-
-    Args:
-        msg (String): 28 bytes hexadecimal message string
-
-    Returns:
-        list: list of suport BDS codes
-    """
-    allbds = ['05', '06', '07', '08', '09', '0A', '20', '21', '40', '41',
-              '42', '43', '44', '45', '48', '50', '51', '52', '53', '54',
-              '55', '56', '5F', '60', 'NA', 'NA', 'E1', 'E2']
-
-    d = util.hex2bin(data(msg))
-    idx = [i for i, v in enumerate(d[:28]) if v=='1']
-    capacity = ['BDS'+allbds[i] for i in idx if allbds[i] is not 'NA']
-
-    return capacity
-
-
-# ------------------------------------------
-# BDS 2,0
-# Aircraft identification
-# ------------------------------------------
-
-def isBDS20(msg):
-    """Check if a message is likely to be BDS code 2,0
-
-    Args:
-        msg (String): 28 bytes hexadecimal message string
-
-    Returns:
-        bool: True or False
-    """
-
-    if allzeros(msg):
-        return False
-
-    d = util.hex2bin(data(msg))
-
-    # status bit 1, 14, and 27
-
-    if util.bin2int(d[0:4]) != 2 or util.bin2int(d[4:8]) != 0:
-        return False
-
-    cs = callsign(msg)
-
-    if '#' in cs:
-        return False
-
-    return True
-
-
-def callsign(msg):
-    """Aircraft callsign
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS40) string
-
-    Returns:
-        string: callsign, max. 8 chars
-    """
-    chars = '#ABCDEFGHIJKLMNOPQRSTUVWXYZ#####_###############0123456789######'
-
-    d = util.hex2bin(data(msg))
-
-    cs = ''
-    cs += chars[util.bin2int(d[8:14])]
-    cs += chars[util.bin2int(d[14:20])]
-    cs += chars[util.bin2int(d[20:26])]
-    cs += chars[util.bin2int(d[26:32])]
-    cs += chars[util.bin2int(d[32:38])]
-    cs += chars[util.bin2int(d[38:44])]
-    cs += chars[util.bin2int(d[44:50])]
-    cs += chars[util.bin2int(d[50:56])]
-
-    return cs
-
-
-# ------------------------------------------
-# BDS 4,0
-# Selected vertical intention
-# ------------------------------------------
-
-def isBDS40(msg):
-    """Check if a message is likely to be BDS code 4,0
-
-    Args:
-        msg (String): 28 bytes hexadecimal message string
-
-    Returns:
-        bool: True or False
-    """
-
-    if allzeros(msg):
-        return False
-
-    d = util.hex2bin(data(msg))
-
-    # status bit 1, 14, and 27
-
-    if wrongstatus(d, 1, 2, 13):
-        return False
-
-    if wrongstatus(d, 14, 15, 26):
-        return False
-
-    if wrongstatus(d, 27, 28, 39):
-        return False
-
-    # bits 40-47 and 52-53 shall all be zero
-
-    if util.bin2int(d[39:47]) != 0:
-        return False
-
-    if util.bin2int(d[51:53]) != 0:
-        return False
-
-    return True
-
-
-def alt40mcp(msg):
-    """Selected altitude, MCP/FCU
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS40) string
-
-    Returns:
-        int: altitude in feet
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[0] == '0':
-        return None
-
-    alt = util.bin2int(d[1:13]) * 16    # ft
-    return alt
-
-
-def alt40fms(msg):
-    """Selected altitude, FMS
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS40) string
-
-    Returns:
-        int: altitude in feet
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[13] == '0':
-        return None
-
-    alt = util.bin2int(d[14:26]) * 16    # ft
-    return alt
-
-
-def p40baro(msg):
-    """Barometric pressure setting
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS40) string
-
-    Returns:
-        float: pressure in millibar
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[26] == '0':
-        return None
-
-    p = util.bin2int(d[27:39]) * 0.1 + 800    # millibar
-    return p
-
-
-# ------------------------------------------
-# BDS 4,4
-# Meteorological routine air report
-# ------------------------------------------
-
-def isBDS44(msg, rev=False):
-    """Check if a message is likely to be BDS code 4,4
-    Meteorological routine air report
-
-    Args:
-        msg (String): 28 bytes hexadecimal message string
-        rev (bool): using revised version
-
-    Returns:
-        bool: True or False
-    """
-
-    if allzeros(msg):
-        return False
-
-    d = util.hex2bin(data(msg))
-
-
-    if not rev:
-        # status bit 5, 35, 47, 50
-        if wrongstatus(d, 5, 6, 23):
-            return False
-
-        if wrongstatus(d, 35, 36, 46):
-            return False
-
-        if wrongstatus(d, 47, 48, 49):
-            return False
-
-        if wrongstatus(d, 50, 51, 56):
-            return False
-
-        # Bits 1-4 indicate source, values > 4 reserved and should not occur
-        if util.bin2int(d[0:4]) > 4:
-            return False
-    else:
-        # status bit 5, 15, 24, 36, 49
-        if wrongstatus(d, 5, 6, 14):
-            return False
-
-        if wrongstatus(d, 15, 16, 23):
-            return False
-
-        if wrongstatus(d, 24, 25, 35):
-            return False
-
-        if wrongstatus(d, 36, 37, 47):
-            return False
-
-        if wrongstatus(d, 49, 50, 56):
-            return False
-
-        # Bits 1-4 are reserved and should be zero
-        if util.bin2int(d[0:4]) != 0:
-            return False
-
-    vw = wind44(msg, rev=rev)
-    if vw is not None and vw[0] > 250:
-        return False
-
-    if temp44(msg):
-        if temp44(msg) > 60 or temp44(msg) < -80:
-            return False
-
-    elif temp44(msg) == 0:
-        return False
-
-    return True
-
-
-def wind44(msg, rev=False):
-    """reported wind speed and direction
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS44) string
-        rev (bool): using revised version
-
-    Returns:
-        (int, float): speed (kt), direction (degree)
-    """
-    d = util.hex2bin(data(msg))
-
-    if not rev:
-        status = int(d[4])
-        if not status:
-            return None
-
-        speed = util.bin2int(d[5:14])   # knots
-        direction = util.bin2int(d[14:23]) * 180.0 / 256.0  # degree
-
-    else:
-        spd_status = int(d[4])
-        dir_status = int(d[14])
-
-        if (not spd_status) or (not dir_status):
-            return None
-
-        speed = util.bin2int(d[5:14])   # knots
-        direction = util.bin2int(d[15:23]) * 180.0 / 128.0  # degree
-
-    return round(speed, 0), round(direction, 1)
-
-
-def temp44(msg, rev=False):
-    """reported air temperature
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS44) string
-        rev (bool): using revised version
-
-    Returns:
-        float: tmeperature in Celsius degree
-    """
-    d = util.hex2bin(data(msg))
-
-    if not rev:
-        # if d[22] == '0':
-        #     return None
-
-        sign = int(d[23])
-        value = util.bin2int(d[24:34])
-
-        if sign:
-            value = value - 1024
-
-        temp = value * 0.125   # celsius
-        temp = round(temp, 1)
-    else:
-        # if d[23] == '0':
-        #     return None
-
-        sign = int(d[24])
-        value = util.bin2int(d[25:35])
-
-        if sign:
-            value = value - 1024
-
-        temp = value * 0.125   # celsius
-        temp = round(temp, 1)
-
-    return -1*temp if sign else temp
-
-
-def p44(msg, rev=False):
-    """reported average static pressure
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS44) string
-        rev (bool): using revised version
-
-    Returns:
-        int: static pressure in hPa
-    """
-    d = util.hex2bin(data(msg))
-
-    if not rev:
-        if d[34] == '0':
-            return None
-
-        p = util.bin2int(d[35:46])    # hPa
-
-    else:
-        if d[35] == '0':
-            return None
-
-        p = util.bin2int(d[36:47])    # hPa
-
-    return p
-
-
-def hum44(msg, rev=False):
-    """reported humidity
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS44) string
-        rev (bool): using revised version
-
-    Returns:
-        float: percentage of humidity, [0 - 100] %
-    """
-    d = util.hex2bin(data(msg))
-
-    if not rev:
-        if d[49] == '0':
-            return None
-
-        hm = util.bin2int(d[50:56]) * 100.0 / 64    # %
-
-    else:
-        if d[48] == '0':
-            return None
-
-        hm = util.bin2int(d[49:56])    # %
-
-    return round(hm, 1)
-
-
-# ------------------------------------------
-# BDS 5,0
-# Track and turn report
-# ------------------------------------------
-
-def isBDS50(msg):
-    """Check if a message is likely to be BDS code 5,0
-    (Track and turn report)
-
-    Args:
-        msg (String): 28 bytes hexadecimal message string
-
-    Returns:
-        bool: True or False
-    """
-
-    if allzeros(msg):
-        return False
-
-    d = util.hex2bin(data(msg))
-
-    # status bit 1, 12, 24, 35, 46
-
-    if wrongstatus(d, 1, 3, 11):
-        return False
-
-    if wrongstatus(d, 12, 13, 23):
-        return False
-
-    if wrongstatus(d, 24, 25, 34):
-        return False
-
-    if wrongstatus(d, 35, 36, 45):
-        return False
-
-    if wrongstatus(d, 46, 47, 56):
-        return False
-
-    if d[2:11] != "000000000":
-        roll = abs(roll50(msg))
-        if roll and roll > 60:
-            return False
-
-    gs = gs50(msg)
-    if gs is not None and gs > 600:
-        return False
-
-    tas = tas50(msg)
-    if tas is not None and tas > 500:
-        return False
-
-    if (gs is not None) and (tas is not None) and (abs(tas - gs) > 200):
-        return False
-
-    return True
-
-
-def roll50(msg):
-    """Roll angle, BDS 5,0 message
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS50) string
-
-    Returns:
-        float: angle in degrees,
-               negative->left wing down, positive->right wing down
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[0] == '0':
-        return None
-
-    sign = int(d[1])    # 1 -> left wing down
-    value = util.bin2int(d[2:11])
-
-    if sign:
-        value = value - 512
-
-    angle = value * 45.0 / 256.0    # degree
-    return round(angle, 1)
-
-
-def trk50(msg):
-    """True track angle, BDS 5,0 message
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS50) string
-
-    Returns:
-        float: angle in degrees to true north (from 0 to 360)
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[11] == '0':
-        return None
-
-    sign = int(d[12])   # 1 -> west
-    value = util.bin2int(d[13:23])
-
-    if sign:
-        value = value - 1024
-
-    trk = value * 90.0 / 512.0
-
-    # convert from [-180, 180] to [0, 360]
-    if trk < 0:
-        trk = 360 + trk
-
-    return round(trk, 3)
-
-
-def gs50(msg):
-    """Ground speed, BDS 5,0 message
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS50) string
-
-    Returns:
-        int: ground speed in knots
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[23] == '0':
-        return None
-
-    spd = util.bin2int(d[24:34]) * 2    # kts
-    return spd
-
-
-def rtrk50(msg):
-    """Track angle rate, BDS 5,0 message
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS50) string
-
-    Returns:
-        float: angle rate in degrees/second
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[34] == '0':
-        return None
-
-    if d[36:45] == "111111111":
-        return None
-
-    sign = int(d[35])    # 1 -> negative value, two's complement
-    value = util.bin2int(d[36:45])
-    if sign:
-        value = value - 512
-
-    angle = value * 8.0 / 256.0    # degree / sec
-    return round(angle, 3)
-
-
-def tas50(msg):
-    """Aircraft true airspeed, BDS 5,0 message
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS50) string
-
-    Returns:
-        int: true airspeed in knots
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[45] == '0':
-        return None
-
-    tas = util.bin2int(d[46:56]) * 2   # kts
-    return tas
-
-
-# ------------------------------------------
-# BDS 5,3
-# Air-referenced state vector
-# ------------------------------------------
-
-def isBDS53(msg):
-    """Check if a message is likely to be BDS code 5,3
-    (Air-referenced state vector)
-
-    Args:
-        msg (String): 28 bytes hexadecimal message string
-
-    Returns:
-        bool: True or False
-    """
-
-    if allzeros(msg):
-        return False
-
-    d = util.hex2bin(data(msg))
-
-    # status bit 1, 13, 24, 34, 47
-
-    if wrongstatus(d, 1, 3, 12):
-        return False
-
-    if wrongstatus(d, 13, 14, 23):
-        return False
-
-    if wrongstatus(d, 24, 25, 33):
-        return False
-
-    if wrongstatus(d, 34, 35, 46):
-        return False
-
-    if wrongstatus(d, 47, 49, 56):
-        return False
-
-    ias = ias53(msg)
-    if ias is not None and ias > 500:
-        return False
-
-    mach = mach53(msg)
-    if mach is not None and mach > 1:
-        return False
-
-    tas = tas53(msg)
-    if tas is not None and tas > 500:
-        return False
-
-    vr = vr53(msg)
-    if vr is not None and abs(vr) > 8000:
-        return False
-
-    return True
-
-
-def hdg53(msg):
-    """Magnetic heading, BDS 5,3 message
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS53) string
-
-    Returns:
-        float: angle in degrees to true north (from 0 to 360)
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[0] == '0':
-        return None
-
-    sign = int(d[1])    # 1 -> west
-    value = util.bin2int(d[2:12])
-
-    if sign:
-        value = value - 1024
-
-    hdg = value * 90.0 / 512.0   # degree
-
-    # convert from [-180, 180] to [0, 360]
-    if hdg < 0:
-        hdg = 360 + hdg
-
-    return round(hdg, 3)
-
-
-def ias53(msg):
-    """Indicated airspeed, DBS 5,3 message
-
-    Args:
-        msg (String): 28 bytes hexadecimal message
-
-    Returns:
-        int: indicated arispeed in knots
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[12] == '0':
-        return None
-
-    ias = util.bin2int(d[13:23])    # knots
-    return ias
-
-
-def mach53(msg):
-    """MACH number, DBS 5,3 message
-
-    Args:
-        msg (String): 28 bytes hexadecimal message
-
-    Returns:
-        float: MACH number
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[23] == '0':
-        return None
-
-    mach = util.bin2int(d[24:33]) * 0.008
-    return round(mach, 3)
-
-
-def tas53(msg):
-    """Aircraft true airspeed, BDS 5,3 message
-
-    Args:
-        msg (String): 28 bytes hexadecimal message
-
-    Returns:
-        float: true airspeed in knots
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[33] == '0':
-        return None
-
-    tas = util.bin2int(d[34:46]) * 0.5   # kts
-    return round(tas, 1)
-
-def vr53(msg):
-    """Vertical rate
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS60) string
-
-    Returns:
-        int: vertical rate in feet/minutes
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[46] == '0':
-        return None
-
-    sign = int(d[47])    # 1 -> negative value, two's complement
-    value = util.bin2int(d[48:56])
-
-    if value == 0 or value == 255:  # all zeros or all ones
-        return 0
-
-    value = value - 256 if sign else value
-    roc = value * 64     # feet/min
-
-    return roc
-
-
-# ------------------------------------------
-# BDS 6,0
-# ------------------------------------------
-
-def isBDS60(msg):
-    """Check if a message is likely to be BDS code 6,0
-
-    Args:
-        msg (String): 28 bytes hexadecimal message string
-
-    Returns:
-        bool: True or False
-    """
-
-    if allzeros(msg):
-        return False
-
-    d = util.hex2bin(data(msg))
-
-    # status bit 1, 13, 24, 35, 46
-
-    if wrongstatus(d, 1, 2, 12):
-        return False
-
-    if wrongstatus(d, 13, 14, 23):
-        return False
-
-    if wrongstatus(d, 24, 25, 34):
-        return False
-
-    if wrongstatus(d, 35, 36, 45):
-        return False
-
-    if wrongstatus(d, 46, 47, 56):
-        return False
-
-    ias = ias60(msg)
-    if ias is not None and ias > 500:
-        return False
-
-    mach = mach60(msg)
-    if mach is not None and mach > 1:
-        return False
-
-    vr_baro = vr60baro(msg)
-    if vr_baro is not None and abs(vr_baro) > 6000:
-        return False
-
-    vr_ins = vr60ins(msg)
-    if vr_ins is not None and abs(vr_ins) > 6000:
-        return False
-
-    return True
-
-
-def hdg60(msg):
-    """Megnetic heading of aircraft
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS60) string
-
-    Returns:
-        float: heading in degrees to megnetic north (from 0 to 360)
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[0] == '0':
-        return None
-
-    sign = int(d[1])    # 1 -> west
-    value = util.bin2int(d[2:12])
-
-    if sign:
-        value = value - 1024
-
-    hdg = value * 90 / 512.0  # degree
-
-    # convert from [-180, 180] to [0, 360]
-    if hdg < 0:
-        hdg = 360 + hdg
-
-    return round(hdg, 3)
-
-
-def ias60(msg):
-    """Indicated airspeed
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS60) string
-
-    Returns:
-        int: indicated airspeed in knots
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[12] == '0':
-        return None
-
-    ias = util.bin2int(d[13:23])    # kts
-    return ias
-
-
-def mach60(msg):
-    """Aircraft MACH number
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS60) string
-
-    Returns:
-        float: MACH number
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[23] == '0':
-        return None
-
-    mach = util.bin2int(d[24:34]) * 2.048 / 512.0
-    return round(mach, 3)
-
-
-def vr60baro(msg):
-    """Vertical rate from barometric measurement, this value may be very noisy.
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS60) string
-
-    Returns:
-        int: vertical rate in feet/minutes
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[34] == '0':
-        return None
-
-    sign = int(d[35])    # 1 -> negative value, two's complement
-    value = util.bin2int(d[36:45])
-
-    if value == 0 or value == 511:  # all zeros or all ones
-        return 0
-
-    value = value - 512 if sign else value
-
-    roc = value * 32   # feet/min
-    return roc
-
-
-def vr60ins(msg):
-    """Vertical rate messured by onbard equiments (IRS, AHRS)
-
-    Args:
-        msg (String): 28 bytes hexadecimal message (BDS60) string
-
-    Returns:
-        int: vertical rate in feet/minutes
-    """
-    d = util.hex2bin(data(msg))
-
-    if d[45] == '0':
-        return None
-
-    sign = int(d[46])    # 1 -> negative value, two's complement
-    value = util.bin2int(d[47:56])
-
-    if value == 0 or value == 511:  # all zeros or all ones
-        return 0
-
-    value = value - 512 if sign else value
-
-    roc = value * 32   # feet/min
-    return roc
-
-
-def isBDS50or60(msg, spd_ref, trk_ref, alt_ref):
-    """Use reference ground speed and trk to determine BDS50 and DBS60
-
-    Args:
-        msg (String): 28 bytes hexadecimal message string
-        spd_ref (float): reference speed (ADS-B ground speed), kts
-        trk_ref (float): reference track (ADS-B track angle), deg
-        alt_ref (float): reference altitude (ADS-B altitude), ft
-
-    Returns:
-        String or None: BDS version, or possible versions, or None if nothing matches.
-    """
-    def vxy(v, angle):
-        vx = v * np.sin(np.deg2rad(angle))
-        vy = v * np.cos(np.deg2rad(angle))
-        return vx, vy
-
-    if not (isBDS50(msg) and isBDS60(msg)):
-        return None
-
-    h50 = trk50(msg)
-    v50 = gs50(msg)
-    h50 = np.nan if h50 is None else h50
-    v50 = np.nan if v50 is None else v50
-
-
-    h60 = hdg60(msg)
-    m60 = mach60(msg)
-    i60 = ias60(msg)
-    h60 = np.nan if h60 is None else h60
-    m60 = np.nan if m60 is None else m60
-    i60 = np.nan if i60 is None else i60
-
-    XY5 = vxy(v50*aero.kts, h50)
-    XY6m = vxy(aero.mach2tas(m60, alt_ref*aero.ft), h60)
-    XY6i = vxy(aero.cas2tas(i60*aero.kts, alt_ref*aero.ft), h60)
-
-    allbds = ['BDS50', 'BDS60', 'BDS60']
-
-    X = np.array([XY5, XY6m, XY6i])
-    Mu = np.array(vxy(spd_ref*aero.kts, trk_ref*aero.kts))
-
-    # compute Mahalanobis distance matrix
-    # Cov = [[20**2, 0], [0, 20**2]]
-    # mmatrix = np.sqrt(np.dot(np.dot(X-Mu, np.linalg.inv(Cov)), (X-Mu).T))
-    # dist = np.diag(mmatrix)
-
-    # since the covariance matrix is identity matrix,
-    #     M-dist is same as eculidian distance
-    dist = np.linalg.norm(X-Mu, axis=1)
-    BDS = allbds[np.nanargmin(dist)]
-
-    return BDS
-
-
-def BDS(msg):
-    """Estimate the most likely BDS code of an message
-
-    Args:
-        msg (String): 28 bytes hexadecimal message string
-
-    Returns:
-        String or None: BDS version, or possible versions, or None if nothing matches.
-    """
-
-    if allzeros(msg):
-        return None
-
-    is10 = isBDS10(msg)
-    is17 = isBDS17(msg)
-    is20 = isBDS20(msg)
-    is40 = isBDS40(msg)
-    is44 = isBDS44(msg)
-    is44rev = isBDS44(msg, rev=True)
-    is50 = isBDS50(msg)
-    is53 = isBDS53(msg)
-    is60 = isBDS60(msg)
-
-    allbds = np.array([
-        "BDS10", "BDS17", "BDS20", "BDS40", "BDS44", "BDS44REV",
-        "BDS50", "BDS53", "BDS60"
-    ])
-
-    isBDS = [is10, is17, is20, is40, is44, is44rev, is50, is53, is60]
-
-    bds = ','.join(sorted(allbds[isBDS]))
-
-    if len(bds) == 0:
-        return None
-    else:
-        return bds
+from pyModeS.decoder.bds.bds40 import *
+from pyModeS.decoder.bds.bds44 import *
+from pyModeS.decoder.bds.bds50 import *
+from pyModeS.decoder.bds.bds53 import *
+from pyModeS.decoder.bds.bds60 import *
diff --git a/pyModeS/decoder/els.py b/pyModeS/decoder/els.py
new file mode 100644
index 0000000..1e9f0b0
--- /dev/null
+++ b/pyModeS/decoder/els.py
@@ -0,0 +1,6 @@
+from __future__ import absolute_import, print_function, division
+
+from pyModeS.decoder.bds.bds10 import *
+from pyModeS.decoder.bds.bds17 import *
+from pyModeS.decoder.bds.bds20 import *
+from pyModeS.decoder.bds.bds30 import *
diff --git a/pyModeS/decoder/modes.py b/pyModeS/decoder/modes.py
index 379f986..e61776f 100644
--- a/pyModeS/decoder/modes.py
+++ b/pyModeS/decoder/modes.py
@@ -140,3 +140,41 @@ def gray2int(graystr):
     num ^= (num >> 2)
     num ^= (num >> 1)
     return num
+
+
+def data(msg):
+    """Return the data frame in the message, bytes 9 to 22"""
+    return msg[8:-6]
+
+
+def allzeros(msg):
+    """check if the data bits are all zeros
+
+    Args:
+        msg (String): 28 bytes hexadecimal message string
+
+    Returns:
+        bool: True or False
+    """
+    d = util.hex2bin(data(msg))
+
+    if util.bin2int(d) > 0:
+        return False
+    else:
+        return True
+
+
+def wrongstatus(data, sb, msb, lsb):
+    """Check if the status bit and field bits are consistency. This Function
+    is used for checking BDS code versions.
+    """
+
+    # status bit, most significant bit, least significant bit
+    status = int(data[sb-1])
+    value = util.bin2int(data[msb-1:lsb])
+
+    if not status:
+        if value != 0:
+            return True
+
+    return False
diff --git a/tests/test_ehs.py b/tests/test_ehs.py
deleted file mode 100644
index ce9e60b..0000000
--- a/tests/test_ehs.py
+++ /dev/null
@@ -1,69 +0,0 @@
-from pyModeS import ehs
-from pyModeS import modes
-
-def test_ehs_icao():
-    assert ehs.icao("A0001839CA3800315800007448D9") == '400940'
-    assert ehs.icao("A000139381951536E024D4CCF6B5") == '3C4DD2'
-    assert ehs.icao("A000029CFFBAA11E2004727281F1") == '4243D0'
-
-
-def test_modes_altcode():
-    assert ehs.modes.altcode("A02014B400000000000000F9D514") == 32300
-
-def test_modes_idcode():
-    assert ehs.modes.idcode("A800292DFFBBA9383FFCEB903D01") == '1346'
-
-
-def test_ehs_BDS():
-    assert ehs.BDS("A0001838201584F23468207CDFA5") == 'BDS20'
-    assert ehs.BDS("A0001839CA3800315800007448D9") == 'BDS40'
-    assert ehs.BDS("A000139381951536E024D4CCF6B5") == 'BDS50'
-    assert ehs.BDS("A00004128F39F91A7E27C46ADC21") == 'BDS60'
-
-def test_ehs_isBDS50or60():
-    assert ehs.isBDS50or60("A0001838201584F23468207CDFA5", 0, 0, 0) == None
-    assert ehs.isBDS50or60("A0000000FFDA9517000464000000", 182, 237, 1250) == 'BDS50'
-    assert ehs.isBDS50or60("A0000000919A5927E23444000000", 413, 54, 18700) == 'BDS60'
-
-def test_ehs_BDS20_callsign():
-    assert ehs.callsign("A000083E202CC371C31DE0AA1CCF") == 'KLM1017_'
-    assert ehs.callsign("A0001993202422F2E37CE038738E") == 'IBK2873_'
-
-
-def test_ehs_BDS40_functions():
-    assert ehs.alt40mcp("A000029C85E42F313000007047D3") == 3008
-    assert ehs.alt40fms("A000029C85E42F313000007047D3") == 3008
-    assert ehs.p40baro("A000029C85E42F313000007047D3") == 1020.0
-
-def test_ehs_BDS50_functions():
-    assert ehs.roll50("A000139381951536E024D4CCF6B5") == 2.1
-    assert ehs.trk50("A000139381951536E024D4CCF6B5") == 114.3
-    assert ehs.gs50("A000139381951536E024D4CCF6B5") == 438
-    assert ehs.rtrk50("A000139381951536E024D4CCF6B5") == 0.125
-    assert ehs.tas50("A000139381951536E024D4CCF6B5") == 424
-    # signed values
-    assert ehs.roll50("A0001691FFD263377FFCE02B2BF9") == -0.4
-
-def test_ehs_BDS60_functions():
-    assert ehs.hdg60("A00004128F39F91A7E27C46ADC21") == 42.7
-    assert ehs.ias60("A00004128F39F91A7E27C46ADC21") == 252
-    assert ehs.mach60("A00004128F39F91A7E27C46ADC21") == 0.42
-    assert ehs.vr60baro("A00004128F39F91A7E27C46ADC21") == -1920
-    assert ehs.vr60ins("A00004128F39F91A7E27C46ADC21") == -1920
-
-def test_graycode_to_altitude():
-    assert modes.gray2alt('00000000010') == -1000
-    assert modes.gray2alt('00000001010') == -500
-    assert modes.gray2alt('00000011011') == -100
-    assert modes.gray2alt('00000011010') == 0
-    assert modes.gray2alt('00000011110') == 100
-    assert modes.gray2alt('00000010011') == 600
-    assert modes.gray2alt('00000110010') == 1000
-    assert modes.gray2alt('00001001001') == 5800
-    assert modes.gray2alt('00011100100') == 10300
-    assert modes.gray2alt('01100011010') == 32000
-    assert modes.gray2alt('01110000100') == 46300
-    assert modes.gray2alt('01010101100') == 50200
-    assert modes.gray2alt('11011110100') == 73200
-    assert modes.gray2alt('10000000011') == 126600
-    assert modes.gray2alt('10000000001') == 126700
diff --git a/tests/test_modes.py b/tests/test_modes.py
new file mode 100644
index 0000000..e3772a3
--- /dev/null
+++ b/tests/test_modes.py
@@ -0,0 +1,66 @@
+from pyModeS import bds, modes
+
+def test_ehs_icao():
+    assert modes.icao("A0001839CA3800315800007448D9") == '400940'
+    assert modes.icao("A000139381951536E024D4CCF6B5") == '3C4DD2'
+    assert modes.icao("A000029CFFBAA11E2004727281F1") == '4243D0'
+
+
+def test_modes_altcode():
+    assert modes.altcode("A02014B400000000000000F9D514") == 32300
+
+def test_modes_idcode():
+    assert modes.idcode("A800292DFFBBA9383FFCEB903D01") == '1346'
+
+
+def test_bds_infer():
+    assert bds.infer("A0001838201584F23468207CDFA5") == 'BDS20'
+    assert bds.infer("A0001839CA3800315800007448D9") == 'BDS40'
+    assert bds.infer("A000139381951536E024D4CCF6B5") == 'BDS50'
+    assert bds.infer("A00004128F39F91A7E27C46ADC21") == 'BDS60'
+
+def test_bds_is50or60():
+    assert bds.is50or60("A0001838201584F23468207CDFA5", 0, 0, 0) == None
+    assert bds.is50or60("A0000000FFDA9517000464000000", 182, 237, 1250) == 'BDS50'
+    assert bds.is50or60("A0000000919A5927E23444000000", 413, 54, 18700) == 'BDS60'
+
+def test_els_BDS20_callsign():
+    assert bds.bds20.callsign("A000083E202CC371C31DE0AA1CCF") == 'KLM1017_'
+    assert bds.bds20.callsign("A0001993202422F2E37CE038738E") == 'IBK2873_'
+
+def test_ehs_BDS40_functions():
+    assert bds.bds40.alt40mcp("A000029C85E42F313000007047D3") == 3008
+    assert bds.bds40.alt40fms("A000029C85E42F313000007047D3") == 3008
+    assert bds.bds40.p40baro("A000029C85E42F313000007047D3") == 1020.0
+
+def test_ehs_BDS50_functions():
+    assert bds.bds50.roll50("A000139381951536E024D4CCF6B5") == 2.1
+    assert bds.bds50.roll50("A0001691FFD263377FFCE02B2BF9") == -0.4     # signed value
+    assert bds.bds50.trk50("A000139381951536E024D4CCF6B5") == 114.258
+    assert bds.bds50.gs50("A000139381951536E024D4CCF6B5") == 438
+    assert bds.bds50.rtrk50("A000139381951536E024D4CCF6B5") == 0.125
+    assert bds.bds50.tas50("A000139381951536E024D4CCF6B5") == 424
+
+def test_ehs_BDS60_functions():
+    assert bds.bds60.hdg60("A00004128F39F91A7E27C46ADC21") == 42.715
+    assert bds.bds60.ias60("A00004128F39F91A7E27C46ADC21") == 252
+    assert bds.bds60.mach60("A00004128F39F91A7E27C46ADC21") == 0.42
+    assert bds.bds60.vr60baro("A00004128F39F91A7E27C46ADC21") == -1920
+    assert bds.bds60.vr60ins("A00004128F39F91A7E27C46ADC21") == -1920
+
+def test_graycode_to_altitude():
+    assert modes.gray2alt('00000000010') == -1000
+    assert modes.gray2alt('00000001010') == -500
+    assert modes.gray2alt('00000011011') == -100
+    assert modes.gray2alt('00000011010') == 0
+    assert modes.gray2alt('00000011110') == 100
+    assert modes.gray2alt('00000010011') == 600
+    assert modes.gray2alt('00000110010') == 1000
+    assert modes.gray2alt('00001001001') == 5800
+    assert modes.gray2alt('00011100100') == 10300
+    assert modes.gray2alt('01100011010') == 32000
+    assert modes.gray2alt('01110000100') == 46300
+    assert modes.gray2alt('01010101100') == 50200
+    assert modes.gray2alt('11011110100') == 73200
+    assert modes.gray2alt('10000000011') == 126600
+    assert modes.gray2alt('10000000001') == 126700