1

I currently have a DEM for an east coast city. Unfortunately, the elevation of an area containing a Dam is not accurate. I have the correct elevations as reported by the city. How would I go about editing the elevation values of a specific group of cells so that they accurately reflect the elevation difference of the dam?

For example, here is a portion of the DEM, where the point is the dam: enter image description here

I need to find a way to select a subset of the nearby DEM cells and edit them so they are accurate with the dam heights.

How do I do this using ArcGIS Desktop?

  • Are you looking for a way to manually set the pixel values (e.g. as if it were an Excel spreadsheet) or to replace determined pixels with values from another raster? Where are the correct elevations stored? – Marcelo Villa Jul 22 at 16:26
  • @MarceloVilla The former; looking to manually change pixel values – Jared Jul 22 at 16:37
  • And do you have a point for each pixel you want to replace? Or are you looking to manually replace arbitrary pixels around that point? – Marcelo Villa Jul 22 at 16:41
  • @MarceloVilla Ideally, I'd select a group of pixels in a certain area, and raise their values to a static amount, or just add X to all selected. – Jared Jul 22 at 16:47
  • you may use a filter expression like "where 2nd_correct_layer is not null 1st_wrong_layer == 2nd_correct_layer", i don't know how to in arc, but in r or qgis it's really simple – Elio Diaz Jul 22 at 17:19
3

The filter expression Elio Diaz is describing in the comments can be done via the Con (conditional) tool, either the standalone version or as part of Map Algebra. You would want to follow the examples for complex expressions described here, doing something like this:

Con(dam_layer == NULL, DEM, dam_layer)
(Where there are no dams use DEM, otherwise use the dam values)

This does require the dam values to be in a raster layer, which you could achieve via either Feature to Raster or Point to Raster, using the same environment settings as your DEM (specifically same projection, cell size, and extent).

EDIT: @Marcelo Villa pointed out that Jared wants to adjust the height of multiple pixels around the DEM, in which case you might want to manually create a polygon layer around each dam covering all the pixels to be updated, and then use Feature to Raster (or Polygon to Raster) on this layer instead of the dam points.

  • This would work for just one pixel value (i.e. the pixel where the point representing the dam is). However, @Jared wants to select an arbitrary group of pixels around that point. – Marcelo Villa Jul 22 at 18:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.