Global Mapper Pro

Contour Tiles

cevely
cevely Global Mapper UserTrusted User
I have a large dataset of LAS tiles that I am trying to create contours from, with the result being a separate polyline shapefile for each LAS file. To reduce the memory usage to a manageable level, I have written a script to process a single tile at a time.

This script does the following for each of the LAS tiles:
- Loads the LAS points from the tile in question, as well as the points from the surrounding 8 tiles to cover the edges.
- Loads a breakline shapefile
- Generates an Elevation Grid using the points plus the breaklines as constraints for the bounding rectangle of all 9 tiles.
- Generates contours from the Elevation Grid, also to the bounds of all 9 tiles
- Exports a line shapefile from the contour layer, clipped to the bounds of the original tile.

This workflow works extremely well, with the one lone, huge exception: along the tile edge, the contours do not line up perfectly. The endpoints will typically be offset by around .01 feet or so.

I have tried several different combinations of parameters, including disabling smoothing, increasing the overedge and overriding the default grid size, but the resulting files still have the same issue.

I'm hoping there is simply a parameter I am overlooking. Any help you could give would be very much appreciated.

Thanks!

Chad Evely

Best Answer

  • cevely
    cevely Global Mapper User
    Accepted Answer
    Sorry, I never received a notification and didn't realize someone had answered. For anyone finding this via search, I ended up using the "GRID_SAVE_TIN" parameter to save the TIN layer, then generated contours from the TIN rather than the grid. When including a reasonable amount of overedge, this now makes my contours match exactly along the tile edges.

    So... problem solved!

Answers

  • bmg_bob
    bmg_bob Global Mapper Programmer
    What version of Global Mapper are you using? If you are using v16, have you updated to the latest released version?

    If the problem persists in the latest version, please send a description of your workflow, a copy of your data (if possible), and the results to Blue Marble Geographics Support (geohelp@bluemarblegeo.com). This will ensure that the support team will be notified of the problem and can work on a solution.
Sign In or Register to comment.