DEM Editing

rreedrreed Global Mapper UserPosts: 30Trusted User
edited November 2013 in Technical Support
Hello,

I've been working with a number of DEMs now, and it seems like many of them do not have the resolution I'm looking for to adequately define a stream/river channel. This is even true for DEMs based on LiDAR.

Is there a way I can edit a DEM to better define a stream/channel cross section? For example, if I draw a line along the stream centerline, can you then "push" a cross section down that line and create a stream surface that could then be added to the larger DEM?

Similarly, where there are localized errors in the DEM, for example, where a bridge deck was not removed, how can you correct those errors?


Thanks.

Russ

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited November 2013
    Russ,

    It sounds like what you are after is 'hydro flattening', which can basically burn streams into Lidar data so that the Lidar is hydrologically consistent with the stream path. That is not something that Global Mapper can do yet, but it is on our todo list.

    For editing terrain, you can right-click on the DEM in the Control Center and select to create points at the grid cell centers. Once those points are there, select and delete the ones you don't want, then use the Analysis menu command to grid the data to create a new grid.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Guru
    geohelp@bluemarblegeo.com
    Blue Marble Geographics for Coordinate Conversion, Image Reprojection and Vector Translation
  • camreoncamreon Posts: 4
    Has this been checked off the todo list? Is there somewhere that i cant find a general set up or option to do this.

    I see a flatten option but every time I use it, it creates only the flatten area of the polygon I drew and doesn't change the DEM overall. Ideally I would draw a line or import a stream network, and then burn that into the already produced DEM from Lidar, but cant seem to find that option in global mapper. I am delineating several watersheds where this occurs and I liked global mappers new watershed tool.   
  • Ice Age MarkIce Age Mark Global Mapper User Posts: 294Trusted User
    Hello,

    I could be wrong (which would be nice) but I don't think GM will do this.

    There is a free open-source GIS program called Whitebox that has two tools described below.  It's Java based and seems to dislike Windows,   It's not very user friendly and expects you to know what you have and want, and what you're doing, but if I can make it go, you probably can too.


    Hydrological Tools.>DEM Pre-processing>

    Burn Streams at Roads:

    This tool decements (lowers) the elevations of pixels within an input digital elevation model (DEM) along an input vector stream network at the sites of roads. The user must specify the names of the input DEM, the streams and road network ShapeFiles, the output raster DEM, and the average road width, in pixels. The road width parameter is used to determine the length of channel along stream lines, at the junctions between streams and roads, that the burning (i.e. decrementing) operation occurs.

    Burn Streams:

    This tool can be used to decrement the elevation values in a digital elevation model (DEM) along a defined stream network. This is a so-called stream burning operation. The stream network can be either a vector shapefile or a raster image. If a raster streams file is chosen, it must have the same grid dimensions as the input DEM file. The user must also specify the decrement value. This parameter is in the same units as the elevation units of the DEM.

    Good luck,

    Mark
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