Surfaces
A surface can be a topographical or non-topographical:
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A topographical surface is a digital representation of the shape of a land surface, formed by a mesh of contiguous triangles. The surface may be existing terrain, proposed grade surfaces, or a combination of both.
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A non-topographical surface is a representation of an object or the face of objects in a 3D model or BIM file.
The Trimble Access software supports topographical surfaces in the following file formats:
- gridded digital terrain models (.dtm)
- triangulated terrain models (.ttm)
- triangular 3D faces in a DXF file (.dxf)
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triangulated DTMs in a LandXML file (.xml)
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triangulated DTMs in a 12da file (.12da)
When the offset is applied perpendicular to the DTM, the cut/fill value is computed using the following steps:
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Determine the triangle that the current position lies on (1).
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Offset that triangle at a right angle by the specified offset value (2) to define a new triangle.
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Compute the elevation of the same position on the new triangle (3).
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Compute the cut/fill value from the computed elevation to the staked position (4).