Contour Lines in DXF

[jazzyj]

I have a request to provide a topographic map in the form of a DXF file with contour lines every foot for a 1,500 acre area.  I believe this is for import into AutoCAD (I think the Civil 3D version I'm guessing at this point - still more info to come.)  Can the DXF file generated by Photoscan be used for this or do the contour lines need to be generated first by an intermidiary GIS software (like QGIS) or generated within Civil 3D itself.  Essentially, if someone is asking for DXF format that can generate contour lines, can I just give them the DXF straight out of Photoscan?  If not, what other processing do I need to do?

[SAV]

Hi jazzyj,

DXF straight out of PhotoScan should work fin.
Just make sure that you have cleaned any 'untidy' edges of your photogrammetric model. You don't want to generate and export contour lines for such areas.

I would normally generate my DEM (which is needed first to compute contour lines) from the Dense Cloud. You can either classify or delete 'rogue points' (e.g., at edges) in your dense cloud so that you can exclude them during DEM generation. This means you can then generate clean contour lines from the resulting, clean DEM.

Unfortunately it is not possible to clip contour lines in PhotoScan based on digitized shapes/polygons. You could, however, do so using QGIS (free & open source).

All the best.

Regards,
SAV

[Alexey Pasumansky]

As a current workaround for generating the contour lines for the part of the DEM it is possible to draw the outer boundary polygon, export DEM, then import it back and use Generate Contours option.

Contours are generated as a separate shape layer in the chunk contents and can be exported in KML, SHP and DXF formats.

[jazzyj]

Is there a setting somewhere to specify how close together you want the contour lines drawn?

[SAV]

Hi jazzyj,

When you generate your contour lines (TOOLS > GENERATE CONTOURS) you can choose your desired INTERVAL. If you want to have them drawn closer together, just reduce the INTERVAL value for example from 5m to 1m, which means instead of 5m contours (1 line every 5m) it will now draw 1m contours (1 line every m).

Regards,
SAV

[jazzyj]

What is the process for doing a countour map (eventually exported as DXF) if I don't want the lines spaced a fixed distance apart but I just want the lines to show elevations at ever 1 foot of elevation?

[SAV]

Then you would simply choose an interval value of 1 foot when generating your contour lines.

Regards,
SAV