cell size and extent

[choni dorji]

i'm trying to see the distribution of 3 noxious invasive plant in Bhutan. for this i'm considering environmental variables like aspect, slope, landuse and bio climate data downloaded from worldclim. here i'm having problem in bringing all this environmental variables in same cell size and extent. i would be very thankful if any one from here could help me.

[Jamie M. Kass]

Many people who have the license use ArcGIS for this kind of stuff, but you can resample rasters (change cell size) and crop and mask (change extent) in QGIS (free) or R (free). If using R, check out the "raster" package's functions aggregate(), crop(), and mask().

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Jamie Kass
PhD Candidate, Department of Biology
City College of New York, CUNY Graduate Center

[Robert Pace]

I had an issue when clipping my data in which the cell size would lose squareness (either the x or y for cell size differed) or I would end up with either one or two extra columns or rows in my data.  After going through quite a bit of suggestions from the ArcGIS help forums, I finally found a solution which worked.

If you are using ArcGIS, you will need to have the Spatial Analyst license.

These are the steps I use to produce a series of rasters with the exact same extent and cell size.

1. Open a blank ArcGIS document

2.  Set the geographic coordinate system for the data layer to that of your location data (usually WGS1984).

3.  Get all your data layers in the same coordinate system that your location data is in (usually WGS1984).

4.  Cut all your data to a slightly larger extent than you plan on using for your analysis.

5.  Resample all rasters to the cell size of your lowest resolution raster.

6.  Cut one of your data layers to a boundary polygon shapefile.

7.  Use Extract By Mask (be sure to check the  to cut all the remaining raster files.

8.  Convert all your new rasters to ASC.

Within ArcGIS 10.4.1 the tools mentioned above can be found in ArcToolbox under Spatial analyist, Data Management, and Conversion folders.

[choni dorji]

Dear Jamie Kass,

Thank you very much for suggestions and steps provided to me.

Looking forward for same.

Thank you

[choni dorji]

Dear Robert,

Thank you very much for steps you provided to me, it really helped me to bring all variables into same cell size and extent.

thank you very much.

[Laura Patterson]

Hi

I am working with QGIS 3.6.

Could anyone share a brief list of steps, like below, for how to change cell size of a raster so they all match for Maxent?

Thans!