I have edited a surface by using the Delete Triangles command to remove unwanted triangles. However, when I translate the DTM to LandXML format, then reimported the newly created XML file, the unwanted triangles are retained. Why is this happening?
Because InRoads uses a feature-based DTM, it will be re-triangulated upon import based on the features. For that reason, any triangles previously deleted will be recreated. To overcome this, after deleting the triangles, use the command Surface > View Surface > Perimeter. You should then graphically import the perimeter as an exterior boundary feature using the command File > Import > Surface. This will preserve the edits after triangulation as well as retain them if the DTM is translated to a LandXML.