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I'm trying to make a Potential Distribution map for an animal species that, we think, should be dependent on edaphic variables. The problem is the only maps I could find with edaphic information are shapefiles with the info stored in their attribute tables. Climatic data is easy because worldclim let you download the variables as .bil + .hdr, files MAXENT uses to generate the map.

I have no idea how to convert the shapefiles into, for example, individual variable files that MAXENT can use.

Of course, I'm a complete noob and have zero experience with any GIS. I installed QGIS here and I have access to ArcGIS 10.2.1 in my University.

Any ideas?

tinlyx
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Dante Nahuel Ciai
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  • Guys, thank you for the answers and sorry for the delay, I had some health issues. So I rasterized the shapefile and selecting one of the attributes from the Table. But I have new doubts Before rasterizing, the software asks me to select CELL SIZE. I understand this is the resolution. The world clim .bil has a resolution of: 0,00833 The default CELL SIZE when I try to rasterize is 0.15 So:
    1. How do I know the shapefile resolution or CELL SIZE?
    2. If I change the 0.15 to 0,008333, the raster is generated anyway. How do I know the data I'm obtaining is usable for analysis anyway?
     – Dante Nahuel Ciai Jun 02 '17 at 13:55
  • This is a complex question. Shapefiles don't have a resolution. Whether or not there is any validity to differences shown at 1km, is impossible to say. Depends on the original scale of the edaphic data. – toms Jul 26 '17 at 18:09

2 Answers2

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General summary:

You have to create raster from your vector layer (rasterizing) which must have the exactly same extent, cell size and coordinate system as your other environmental data. Than set this data as categorical variable in MaxEnt.

QGIS solution:

  1. You have to create new attribute with intiger codes of categories. Use field calculator, if your edaphic categories are strings, you can use something like this:

    CASE 
WHEN  "edaphic" = 'string_value' THEN 1 
WHEN  "edaphic" = 'string_value2' THEN 2
END

  2. Use rasterize function from menu Raster -> Conversion -> Rasterize (Vector to Raster)... and as for pixel values choose attribute from step 1. You can also use some other rasterize functions from processing toolbox. Set the same resolution as other data (variables)

  3. Achieve required extent raster layer using Raster -> Extraction -> Clipper... or Raster -> Align Raster or in the same way you preparing other environmental data.

Oto Kaláb
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0

In ArcGIS or QGIS, first convert the shapefile to raster, and then save/export as an ASCII Grid.

As a first step you may want to create a numeric field that has an id for each edaphic class (if one doesn't exist already).

toms
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