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I have a DEM interpolated from a TLS point cloud at 1 mm cell resolution. This resolution is too fine for use in a 2D surface inundation model with the required timestep, without the model taking far too long to run. I would like to know if there is any way to proportionally increase the size of each cell and its z value in the raster?

For example, if a cell is currently 0.001 x 0.001 m, is it possible to multiply these dimensions and the z value for each cell by 1000, resulting in a raster that preserves the morphology of the DEM but is at 1 m resolution?

Note also that each DEM is referenced to a local coordinate system set up in a lab.

I'm working in Arc 10.4.1 desktop (advanced licence), but happy to try other open source GIS options.

  • It is not possible at all unless you DEM is flat. – FelixIP Nov 9 '17 at 20:05
  • Oh my goodness, 1mm resolution! I advise you to first investigate what would be the coarsest cell size which gives the acceptable coarseness with respect to your purpose instead of taking it 1 metres. I cannot help myself to put this into the resolution context of my job. You are talking about a 1000x scaling up and in the spatial context, say if I have 1m DEM (presumingly it is pretty fine to me), the level of detail would not be acceptable if I take it to 1km resolution but around 5-10 metres would be OK. – fatih_dur Nov 9 '17 at 23:55
  • As @FelixIP touched on, you employ different resolutions for different areas based on your purpose/need by mosaicking, instead of trying to "resample" for all. – fatih_dur Nov 10 '17 at 0:00
  • Thanks for the comments. Unfortunately the surface features that I am looking at are somewhere in a range from sub-cm to < 5 cm. If I could increase the cell size by a factor of 100, the inundation model will run, but it would have to be across the whole DEM to preserve the spatial relationships between the surface features. It's a moot point anyway, as I had a feeling what I was trying to do wasn't really possible. – GoWithTheFlow Nov 10 '17 at 10:20
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Aggregate is a way to change raster resolution. The aggregation method uses a specified statistical aggregation method within a neighborhood to derive values in the output raster at the different resolution. This method is used by the Aggregate and Block Statistics tools. This tool works by aggregating the individual values of a group of cells and producing a single, coarser resolution cell of that value. In the aggreagte function, set the "cell_factor" to 1000.

If you want to change Z value: Use Times tool.

Note: Change of the DEM resolution is not a good idea. You certainly lose DEM precision. Extract the DEM with certain cell size from the source of interpolation(Imagery or other sources).

  • Thanks, but unfortunately I need a solution that does not combine any cell values. – GoWithTheFlow Nov 10 '17 at 10:21
  • There is no way. It's imposible – BBG_GIS Nov 10 '17 at 10:23
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As BBG_GIS told, Aggregate is the way to go but it will change the values of the output raster. Each output cell contains the Sum, Minimum, Maximum, Mean, or Median of the input cells that are encompassed by the extent of that cell. You can also use Resample on your finer resolution raster with different resampling type. Note that BILINEAR resampling and Aggregate produces the same result.


For multiplying the z-values, you can simply use Raster Calculator.

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