4

I have the DEM of a State in ERDAS Imagine (.img) format. I have a shapefile containing the counties of that state.

I want to split the whole raster into DEMs of the individual counties. The counties are irregular polygons. So this isn't as easy as splitting the Raster into tiles.

How do I split a raster with a vector polygon shapefile?

I am looking for what is basically the Raster equivalent of the Split tool.

I tried using Clip tool, and the Extract by mask tool, but both of them are unhelpful since they work only on single polygons.

I have looked at the answer given here: Need to clip raster based on field name in ArcGIS 9.3 , but Hawth Tools aren't available for ArcGIS 10.0

I have ArcGIS 10.0+ Spatial Analyst Extension, and QGIS 1.8. A solution in either will be acceptable.

3

This model builder workflow will extract a section of the DEM for each county polygon

enter image description here

  • Set the Group by Field variable to be County Name
  • Set the model processing extent to be the same as County
  • Thanks! I basically created a script which does basically the same thing. – Devdatta Tengshe Aug 22 '13 at 16:17
  • Regarding the model above, how does this give multiple outputs? I always get only one output, one raster instead of many. – Adam H Sep 25 '14 at 9:43
1

You could write a script to loop through your polygons and clip the raster to that. But the following might be quicker.

Hawth's tools has been replaced by the Geospatial Modelling Environment (GME). You will need to have the R program installed in order to run the GME. Also, GME doesn't seem to work yet in ArcGIS 10.2.

The tool you want is the Clip Raster by Polygons tool.

The description of the tool is:

This tool clips an input raster using the polygons in a polygon data source. The command cycles through each polygon, clips the raster if there is overlap, and writes one new raster image per polygon. The extent of the new raster is the intersection of the extent of the polygon and the extent of the raster.

This tool is designed to work with these three raster formats: grids, TIFF/GeoTIFF, and ERDAS Imagine rasters. Note that not all raster formats support all datatypes. When you are clipping a raster it is recommended you consider two strategies to avoid these pixel data type problems: 1) ensure the output format matches the input format, or 2) always use the Imagine img format as the output format as this supports all the data types. The output format is specified by adding the appropriate file extension to the file name. No extension is interpreted as the grid format, the '.tif' extension is the GeoTIFF format, and the '.img' extension is the Imagine format.

Note that all clips will preserve the cell alignment of the input raster (no shifting of pixels will occur at all). However, the display properties of the input raster are not transferred to the output raster, so if you are clipping digital photos or satellite images you should expect the appearance of the clipped images to differ from that of the original image.

0

In QGIS, RASTER|EXTRACTION|CLIPPER with the clipping mode set to Mask Layer will do it if I understand your question correctly.

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.