From Jason Beverage,

"I've attached fixes to DataSet that should fix the problems that Maya was seeing yesterday.  The issue was that the new interpolation code I submitted didn't use the SourceData's georef, it was assuming that the GDALDataSet had a proper geo-ref.  I've made the getInterpolatedValue method a member of SourceData and now it uses the georef the SourceData's georef.

I also forward declared the GDALRasterBand class in the DataSet header."

include/osgTerrain/DataSet

@@ -41,6 +41,7 @@
 
 // forward declare so we can avoid tieing osgTerrain to GDAL.
 class GDALDataset;
+class GDALRasterBand;
 
 namespace osgTerrain
 {
@@ -248,6 +249,8 @@ class OSGTERRAIN_EXPORT DataSet : public osg::Referenced
             virtual void readHeightField(DestinationData& destination);
             virtual void readModels(DestinationData& destination);
 
+            float getInterpolatedValue(GDALRasterBand *band, double x, double y);
+
             Source*                                     _source;
             
             bool                                        _hasGCPs;