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I'm trying to complete a Multi-Criteria Evaluation for an MSc assessment and am in the process of standardising my factor maps. Unfortunately, my DEM layer (ASCII file) keeps changing from this:

enter image description here

To this:

enter image description here

The syntax used in Raster Calculator is: (“DEM” – 0) / (544 – 0) where DEM is the layer, 0 is the minimum values and 544 is the max value.

Has anyone come across this before? Does anyone know how to standardise it so the surface variation is still present?

I've done the same for Topographic Wetness Index but that's done ok (both layers are visualised the same)

tbalbone
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  • Could you add a screenshot of what your table of contents looks like? Or your symbology properties? My first thought is that there might be something that needs changed with your display properties, similar to this question here: http://gis.stackexchange.com/questions/127696/querying-slope-data-using-raster-calculator-why-are-all-results-true – MaryBeth Dec 18 '15 at 14:15
  • Done. Thank you, I've taken a look at that post. My problem is that I need to standardise the DEM from 0-544 to 0-1. The syntax keeps creating a 0 or 1 value instead. I've only just started with GIS so am not that experienced. – tbalbone Dec 18 '15 at 14:37

1 Answers1

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by default the output raster will be integer type. You must convert to float in order to have decimal output, or multiply by 100 to have percentage

Float(“DEM” – 0) / (544 – 0)

(100*(“DEM” – 0)) / (544 – 0)

As a remark, for normalizing, you can compute min and max on the fly as in my answer here

Float(“DEM” – "DEM".minimum) / (“DEM”.maximum – "DEM".minimum)
Community
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radouxju
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  • Multiplying by 100 seems to have worked, thank you. I can now standardise the rest of my layers to be on the same scale. The float syntax didn't seem to work in the calculator, it threw up a processing error. – tbalbone Dec 18 '15 at 15:19
  • Float syntax is case sensitive – radouxju Jan 05 '16 at 20:03