broke up original methods file into resprective functions for the live docs categories of obs measures

doc/boundaries_functions.md

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+# Boundaries Functions
+
+If you are using the [boundary methods](/dataobservatory/overview/#boundary-methods) from the Data Observatory, use the following functions to retrieve [Boundary](/dataobservatory/overview/#boundary-data) data. You can get global boundary geometries by point or polygon geometries.
+
+## OBS_GetGeometry(point_geometry, boundary_id)
+
+The ```OBS_GetGeometry(point_geometry, boundary_id)``` function returns a boundary geometry defined as overlapping the point geometry and from the desired boundary set (e.g. Census Tracts). See the [Boundary ID glossary](/dataobservatory/glossary/#boundary-ids). This is useful for performing aggregations of points.
+
+#### Arguments
+
+Name | Description
+--- | ---
+point_geometry | a WGS84 polygon geometry (the_geom)
+boundary_id | a boundary identifier from the [Boundary ID glossary](/dataobservatory/glossary/#boundary-ids)  
+
+#### Returns
+
+Value | Description
+--- | ---
+geom | WKB geometry
+
+#### Example
+
+Overwrite a point geometry with a boundary geometry that contains it in your table
+
+```SQL
+UPDATE tablename SET the_geom = OBS_GetGeometry(the_geom, ' "us.census.tiger".block_group')
+```
+
+<!--
+Should add the SQL API call here too
+-->
+
+## OBS_GetGeometryId(point_geometry, boundary_id)
+
+The ```OBS_GetGeometryId(point_geometry, boundary_id)``` returns a unique geometry_id for the boundary geometry that contains a given point geometry. See the [Boundary ID glossary](/dataobservatory/glossary/#boundary-ids). The function can be combined with ```OBS_GetGeometryById(geometry_id)``` to create a point aggregation workflow.
+
+#### Arguments
+
+Name |Description
+--- | ---
+point_geometry | a WGS84 polygon geometry (the_geom)
+boundary_id | a boundary identifier from the [Boundary ID glossary](/dataobservatory/glossary/#boundary-ids)  
+
+#### Returns
+
+Value | Description
+--- | ---
+geometry_id | a string identifier of a geometry in the Boundaries
+
+#### Example
+
+Write the geometry_id that contains the point geometry for every row as a new column in your table
+
+```SQL
+UPDATE tablename SET new_column_name = OBS_GetGeometryId(the_geom, ' "us.census.tiger".block_group')
+```
+
+## OBS_GetGeometryById(geometry_id)
+
+The ```OBS_GetGeometryById(geometry_id)``` returns the boundary geometry for a unique geometry_id. A geometry_id can be found using the ```OBS_GetGeometryId(point_geometry, boundary_id)``` function described above.
+
+#### Arguments
+
+Name |Description
+--- | ---
+geometry_id | a string identifier for a Boundary geometry
+
+#### Returns
+
+A JSON object containing the following properties
+
+Key | Description
+--- | ---
+geom | a WGS84 polygon geometry
+
+#### Example
+
+Use a table of geometry_id to select the unique boundaries. Useful with the ```Table from query``` option in CartoDB.
+
+```SQL
+SELECT OBS_GetGeometryById(geometry_id) the_geom, geometry_id FROM tablename GROUP BY geometry_id
+```