5

Using the hillshade tool (ArcMap 10) on a 30m SRTM raster downloaded from NED the result is the one in the picture. Why are there those crossed lines all over the raster? How could I remove them?

enter image description here

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A few thoughts:

  • A previous answer correctly recommends resampling during display to smooth out the irregularities in the hillshade. This is primarily used for cartographic effect when you are finishing a map.

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  • Find better elevation data. 10 m NED Data is available for the conterminous USA and 3m is available in select areas. I like to download NED data from the National Map

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  • Finally, to put everything together, consider using advanced overlay methods in Image Analyst, rather than using washed out transparent overlays. Here is a great blog that describes these techniques.

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  • Thank you very much for your answer. I tried the first three methods. The first one does not seem to work on my case, since it just seems to decrease slightly the appearance of those crossed lines. For what concerns the Image Analysis window I can open it but all the tools under "display" and "processing" are unselectable, why? And is the national map downloading site openable outside USA? (I'm in Italy). Because it does not load the page. Thank you again, Michele. – Michele Cordini Jun 27 '13 at 17:03
  • Sorry I was then able to select the smoothing option. It made it better though didn't clean it completely. – Michele Cordini Jun 27 '13 at 17:13
  • Make sure to highlight and check the image in the top window, then all of the processing tools should become available. The National Map is available for USA data, although I do not know if there is any download restrictions out of the country. It looks like Italy has a 10m DEM dataset available: tinitaly.pi.ingv.it/download.html. – Aaron Jun 27 '13 at 17:16
  • I should also add that you can make multiple passes too with any of the processing tools. – Aaron Jun 27 '13 at 17:18
  • 2
    If you cannot access the National Map, try downloading 10m DEMs at GIS Data Depot: data.geocomm.com – Aaron Jun 27 '13 at 17:48

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