I want to combine a raster and a vector file. After combining, can I query on the resulting map to obtain a specific area? How?

  • No, I don't think you can or should combine raster and vector files. That defeats half the purpose of GIS – dassouki Jan 29 '11 at 9:52
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    Combine for what purpose? Just a combined visualisation can be accomplished in any ol' GIS program - pick your weapon from a wide range of free and open source to expensive proprietary packages. I like QGis myself. If you want to do more than just visualisation, then you will need to elaborate on your intent a bit more before anyone could provide a useful answer. – mvexel Jan 29 '11 at 11:55
  • I am using: v.db.select map=PHL_adm1 where=NAME_1='Bulacan' My vector map is over the raster map. I want to select the part of the raster map under the polygon(NAME_1='Bulacan') of a vector. Is it possible to do? – teamAngat Jan 29 '11 at 15:19
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    To transfer raster values to a vector map, use for example grass.osgeo.org/grass64/manuals/html64_user/v.what.rast.html . Then use v.report to get statistics. – markusN Jan 29 '11 at 19:10
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    So this is basically a duplicate of gis.stackexchange.com/questions/5620/… ? – underdark Jan 29 '11 at 23:03

If you want to identify a common area that exists on both the vector and the raster, I suggest you convert the vector to raster. There are a few things to consider when you do this;

  • make the spatial extents of the new raster the same as the original one
  • use the same raster cell size.

Then you can identify a common area between the two rasters using a few different techniques. One method is to assign certain values to cells within the new raster. For example you could make your new raster have a value of 1 where the vector object exists, and 0 elsewhere. Then you could multiply the rasters by each other, and the product (a third raster) will give you the intersection.

  • I used v.to.rast to convert my vector map to raster map. How can I "assign certain values to cells within the new raster"? What is the script for it? – teamAngat Jan 30 '11 at 13:44
  • What values are the raster cells? You could reclassify them using r.reclass See grass.osgeo.org/gdp/html_grass64/r.reclass.html – djq Jan 30 '11 at 14:39

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