Tech Tips

Merging of DTM Surfaces

This tech tip explains how to merge DTM surfaces.


The merge DTM surfaces function will:
  • Copy all the points on that design surface into the relevant ground surface
  • Add the lines that describe terrace and banks to the ground surface
  • Connect the bank top and toe points into the terrain model
  • Delete all the ground points that previously fell under that terrace and it's banks
Note that after this function is complete the original terrace will still exist, even though it will have been merged into either the ground or the merge surface.

Naming the DTM Surfaces

Using multiple DTM surfaces can become confusing if the surfaces are not names correctly. (note: the function will still work if the surfaces have not been named) Its a good habit to get into, name the surfaces as you are working, not only does it help you but anyone else that has to work on the project at a later date.

Change to Terrain Mode

Applications Menu > Terrain

Settings Menu > Display Settings

In this example we name Surface 14 "Merged Surface", which will be the new surface created when we merge Surface 12 "Road 1 Final Levels" into Surface 1 "Ground Levels".

Merging the DTM Surfaces

Change to Terrain Mode

Applications Menu > Terrain

Terrain Menu > Terrace Merge

Always select a merged surface, so that the original surfaces remain, in case there are changes that have to be made to the ground and terrace surface. Once the merge is complete, run the Validate Model function to check the triangulation on the merged surface.

The validate merge surface option will validate the new merged surface, this can also be done manually at a later stage if required

If there are any errors with the triangulation an error will appear.

Correct the error and then re-run the validation. If there are no more errors the site will be successfully validated.

Once validated Save the project.

Merging Additional DTM Surfaces

If you need to merge more than 1 surface, the following process is followed. We will now merge Surface 13 "Road 2 Final Levels" into the new merged surface, Surface 14 "Merged Surface".

Terrain Menu > Terrace Merge

The second surface will be merged into the new merged surface, following this process you will still have all the original surfaces.

Follow the above steps for any additional terraces that need to be merged, remember to always Validate between each merge.

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