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I have a DEM built from Lidar data and bathymetry survey points for a river which flows on the DEM surface.

My understanding is that Lidar data is not able to capture bathymetry under the river flow.

How can I stitch survey points and DEM together and build a new DEM?

  • We have done similar modelling. Sometimes we get issues with the banks not matching up with the bathymetric survey (survey to far away from banks). This might be due to different tide heights from when both surveys were conducted or sand banks, dredging etc. One solution is to create a tin of the bathymetric and try and interpolate it to an appropriate bank level (on the DEM). This can be painful to get right. Once happy with the interpolating for the bathymetric Tin, we create a raster and then stamp it to the DEM using Mosaic To New Raster tool. – TsvGis Aug 11 '15 at 5:13
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If your bathymetric data are current in the form of survey points then you should interpolate them onto a raster grid of the same resolution and extent as your LiDAR data. There are several methods for interpolating these points available in ArcGIS such as splining, IDW and kriging. The most appropriate method to use will depend on your data characteristics (e.g. density and accuracy) and on the application. Now, I assume that the LiDAR raster DEM has NoData values for the areas within the river. This is usually the case for LiDAR. You can use the CON to create a conditional evaluation statement such that the output raster grid is assigned the LiDAR DEM elevation value for all cells where the LiDAR DEM has a non-NoData value (i.e. a valid value) and the bathymetric DEM value for all cells where the LiDAR DEM is equal to the NoData value. It's essentially an IF-THEN-ELSE where IF LiDAR_DEM != NoData assign output LiDAR_DEM value, else assign output Bathymetric_DEM value.

  • But if data has value, then what should I do? what is your advice?cheers – Mike Oct 21 '14 at 3:52
  • In cases grid cells where there is both lidar and baggy entry choose the lidar. That's what I'd do because it has higher accuracy. – WhiteboxDev Oct 21 '14 at 11:36
  • Sorry, 'baggy entry' = bathymetry in my last comment...that's why you shouldn't reply on your cell phone! – WhiteboxDev Oct 21 '14 at 23:27
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Take a look at terrain datasets inside a file geodatabase if you also have your LiDAR in vector format. Otherwise I think you will find Mosaic Datasets useful. That allows you to combine multiple DEMs or other image types on the fly and allow you to apply functions on the fly to create hillshades or slope rasters, etc. ArcGIS help has a very good section on managing elevation data in a mosaic dataset. I would link it but I am on my phone.

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