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David Crompton

Conversion of VM grid to CAD format or vice versa

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Has anyone had any success with converting Vertical Mapper grids (xx.grd) to a format that AutoCad Civil 3D can read.

What we are trying to do is use the Vertical Mapper grid of ground elevation and some how convert this to a AutoCAD surface to allow design of basin and road profiles to be undertake in the same grid as the flood model results have been produced.

Any suggestions?????



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Hi David,

The inherent problem with this conversion is that you are trying to convert a raster data source (the VM grid) into a vector format to manipulate in CAD. The grid is an evenly sampled representation of the surface created by the available survey data. Depending on the resolution of your grid compared to the survey resolution, you may be losing survey detail or interpolating over areas of survey data gaps. If possible, it would be generally be preferable to create a TIN surface directly from the source if your ground grid (eg the raw survey, LIDAR, contours etc).

If you only have the raster grid, I think there is an "export to DXF mesh" option in the Tools --> Export dialog of the VM Grid Manager. Be prepared for a pretty big file though. Also what we've done on occasion is to export the grid as XYZ points at the centre of each grid cell, then TIN using 12D.

A final option would be to just use contours of the grid, but this probably won't give a great match between the two surfaces.

Hope that helps,


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