Clipping a Raster without ArcInfo

    Start Open_EV, File > Open, navigate to a directory where your data is. For ArcInfo grids you can select the parent directory name or any of the *.adf, it doesn't matter which one.

    (Tip: the open dialog supports tab completion, type a letter or two and slap [tab].)

    Don't be surpised if it seems like nothing happened, it just means there is no colourmap. Go to the main openev window and push one of the image enhancement buttons (square box with shaped line through it).

    Use the same process to open an arcinfo coverage or shapefile to help you find your region of interest. With coverages, use ARC for the outline and PAL for a shaded polygon. (This is just for reference, unfortunately openev can not yet clip to a polygon.)

    In the Layers dialog, select the raster you wish to clip. Go to the main window and File > Export. Slap the Advanced Options button and then Draw ROI mode (Region Of Interest). To fine tune your ROI hover over a boundary line until it turns red and then drag it larger/smaller.

    • clipping ROI (in red) and reference poly (in green):
      clipping ROI (in red) and reference poly (in green)

    Go to the main window and draw a box where you want to clip the raster. When you go back to the Export window, the 'Input Window' section should be updated to the pixel coordinates you just drew. If it's not, make sure the raster is the active layer and try again.

    Fiddle with the other options as you wish and then Export. Et c'est fini!


    Geotiff is the most transportable format for use with other programs, including ArcView, while AAIGrid is the easiest to bring back into arcinfo (using ASCIIGRID command).





    TopicCategory HowTo



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