changing extent of GIS file

Another update to my GIS information:

For some reason some of the methods I've outlined in my earlier post (1/12/2011) don't necessarily work !

So, an update to extending the extent of a file is as follows:

This seems pretty impossible to do with shape file, be it a feature, polygon, polyline or point. This makes life more difficult than it needs to be (typical), so the only alternative at the moment is to

1. convert the shape file to a raster

2. Via spatial analyst toolbar (View - Toolbars - Spatial Analyst)

Options - Analysis Extent - same as Layer "TotalClip" (or whatever the file of the right size is, and this needs to be a shape file) - snap extent to 'total area' (this needs to be a raster file).

3. The above method seems to work most effectively at getting the extent of the file to the required area, so its good to ensure you have both a shape file and a raster of the required area.

4. Now all that needs to be done is to add the raster you want to extend to the raster of the required area. In my case this is adding 'finalRoads' to 'totalarea'.

         totalarea has a value of 1 for every cell within the layer as its only purpose is to show the extent of the area I want to use in my simulations.

        Spatial Analyst toolbar - Raster Calculator - [finalRoads] + [totalarea] - evaluate

5. A new temporary file is now created called Calculation and this needs to be made permanent:

       right click on Calculation - Data - Make Permanent - then go to appropriate folder and name the file (allRoads in my case) - save

6. This new permanent file does not get automatically added, so this needs to be manually added if required.

7. For some reason, some of the classes change slightly (all mine increased by 1). The raster can be reclassified from either the temporary Calculation file or the permanent new allRoads file. Reclassifying the Calculation file means that a permanent reclassified file gets created so you no longer need to make the Calculation file permanent.