A tool in some GIS software programs for performing algebraic operations on rasters.

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1k views

How to evaluate raster calculator expressions from the console?

How can I execute from the console an expression that should be used with the raster calculator? I'm searching for something like this: qgis.someRasterCalcClass.evaluate("boh@1 + boh@2", ...
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2answers
3k views

How to standardize raster output from 0 to 100 using raster algebra?

I am working on generating an integrated moisture index based on the following equation: IMI = (hill shade * 0.5) + (curvature * 0.15) + (flow accumulation * 0.35) Iverson et al. 1997 Another ...
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1answer
4k views

Can Compound Topographic Index (CTI) / Topographic Wetness Index (TWI) produce negative values?

I am calculating Topographic Wetness Index for a study area using SRTM DEM (90 and 30m). I've seen several versions of TWI (CTI). I have been using: TWI = ln(As +1 / tanB) where As = ...
6
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1answer
7k views

How to crop raster layer?

Can anyone tell me how to crop a raster layer in QGIS? I want to make contours from a section of a layer, and including the whole layer will create far more data than I need and slow down the ...
4
votes
1answer
1k views

How to reclassify in Rastercalc?

I now need to reclassify, I'm using rastercalc... but I can't get the syntax right!! I need that values >0 become 1 I found this example... eq( [relief]@1, [mask]@4, 150 ) so I tried: ( [raster A ...
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1answer
250 views

Getting Error 000539 from Raster Calculator?

I am new to Arc and 10.2 but can not seem to figure out why this won't work. Executing: RasterCalculator Con(("SLOPE_SLO.tif" >= .015) & ("SLOPE_SLO.tif" <= .15,1,0)) ...
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2answers
1k views

Create an X,Y latitude and longitude grid from an raster

I have a satellite image (LandSat 5), I want create a raster with X,Y coordinates, this is possible in Model Builder of ArcGis 10.0? or other option. I know that the option $$YMAP ($$XMAP) not work ...
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3answers
3k views

QGIS Raster Calculater Syntax

I am trying to use the raster calculator in QGIS to combine a number of rasters. I want to calculate a mean, this is easy: (raster_1@1 + raster_2@1 + raster_3@1) / 3 I then want to create a max. ...
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1answer
69 views

ArcGIS Raster Calculator error 000539 ImportError: No module named numpy?

I am running ArcGIS 10.2.1 on Win7 64bit. I have finished doing an NDVI, and after defining a vegetation presence threshold at 0.05, opened the Raster Calculator (via Map Algebra in the Arc Toolbox) ...
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1answer
134 views

How to measure Fracture in area using ArcGIS Cut and Fill?

I want to measure fracture in an area.I know I have to use cut and fill tool. But I wonder how to give input for this tool? it has Input before raster surface and Input after raster surface ! what ...
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3answers
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30,000 data points… can this be reasonably served using openlayers?

I'm trying to tackle a web GIS problem and need to figure out the best strategy. I have a map with 30,000 cells on it forming a grid for the province of Alberta. I have a list of data points for ...
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1answer
1k views

Piping output of Iterate Raster tool into Raster Calculator tool using ModelBuilder?

ArcGIS v10.1 ModelBuilder Using ModelBuilder and map algebra, I want to compute a ten year average grid from a stack of 10. The problem is that only 1 grid (%raster%), the last one through the ...
4
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1answer
1k views

Python syntax error from raster calculator in ArcGIS ModelBuilder?

I am experiencing a problem with the raster calculator in the ModelBuilder under ArcMap 10. I need to combine two layers: a drainage map (issued from a series of previous operations on a DEM) and ...
2
votes
1answer
207 views

How to iterate GRASS region definition?

I am using GRASS r.skyview command (v.7, Windows) to determine "urban canyon effect" on pollution due to the presence of buildings. The command nicely works, unfortunately I need to process a very ...
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0answers
126 views

How to Normalize or rescale the NDVI raster image

I have processed my landsat band 3 and band 4 of different years to derive NDVI values the possible values of Normalized difference vegetation index is -1.0 to +1.0. The bands were atmospherically ...
5
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1answer
748 views

Raster processing with Python or Arc raster calculator

I have 4-band NAIP imagery that require the following processing steps: Convert to 8 bit unsigned B/W Reverse (note not inverse) the image, so that dark values appear light and light values appear ...
4
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3answers
224 views

How to find buffer radius around raster cell that covers a defined sum of raster cells?

I want to do a neigbourhood analysis on some raster data. I need to know how big a circle around each raster cell must be to include a certain amount of specified raster cells. Let's say that for ...
3
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0answers
108 views

Single Tree detection

I was wondering how I could extract "crown area" of single trees in a forest from a high-resolution image with only 3 band (RGB) in ArcMap. ( No NIR to use NDVI as any threshold). I need a fast ...
3
votes
1answer
579 views

How to exclude some parts of raster classes based on size of area?

I have a raster file with 5 classifications. I've calculated area for all of the classes via Zonal geometry, Arcmap 10. Now, I want to exclude patches which are smaller than 100 sq. km. and ...
3
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1answer
145 views

Issue with Sextante r.map calculator and modeler

I am trying to build a model with Sextante modeler and the r.mapcalculator algorithm but when I run the model I get the error message: ‘Could not load layer: ‘….’Check sextant log to look for errors ...
3
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1answer
344 views

An error in raster calculator in Arcgis

I wrote and ran this formula in raster calculator in ARCGIS. But the following error gets me into trouble. Does anyone have a suggestion to overcome this? Here is the formula I wrote and the error ...
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2answers
1k views

Normalize raster values to 0-255

I need to normalize the values attained from a band ratio to 0-255. I'm using QGIS. How do I do this? Any ideas?
2
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1answer
45 views

How to use the math tool (“times”) in ArcGIS modelbuilder to multiply two raster sets while using an iterator?

I have two sets of rasters (in the same gdb), representing "loss" and "forestmask". I would like to multiply each forestmask raster (value 1 = forest) with its corresponding loss raster (value ...
2
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2answers
62 views

Raster calculator - addition

Help!!! What am I doing wrong? I have generated two rasters from vector layers. They cover the same extent and have the same projection (Irish Transverse Mercator) and cell size (5m x 5m). I have ...
2
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1answer
195 views

Efficiently check for equal adjacent values in raster calculator

I have a raster consisting of integer values in each cell. I want to check every adjacent cell in a 3x3 grid to see if any one of the adjacent cells has a value EQUAL to the center cell, and if so, ...
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1answer
99 views

ArcGIS Raster Calculator fails with Error 000539

I have been using Raster Calculator in ArcMap 10.2, today it started returning error 000539 for all actions. Previously it had worked fine. I have not made any change ot my ArcGIS, Python, or Windows ...
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3answers
122 views

Can't use Raster Calculator with two different rasters

So, I have several maps like this one: And with the proximity tool and a coastline shapefile I made this output, representing the distance to shoreline: Now, I want to combine both using the ...
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2answers
431 views

Replacing raster values in one raster with another raster in QGIS … how to?

I have a raster (DEM) and want to replace a few cell's values with the values from another raster in QGIS. I would have done this with the "over" tool in the raster calculator in ArcGIS. Specifics: ...
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1answer
792 views

Rasterize vector layers with different extents into identical raster grids with QGIS

I am working on a quite simple spatial potential analysis using QGIS. I have some ArcGIS knowledge, but I am new to QGIS. My task is to identify the functional inner city of a region based on ...
1
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1answer
513 views

How to add rasters of different sizes with Arcmap or Qgis raster calculators?

I've got 8 rasters all of different sizes. What is the proper syntax, for the raster calculators of either Arcmap or Qgis, that will output a raster that covers the extent of all my data not just the ...
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1answer
203 views

Cause of ArcGIS Raster Calculator Parsing error <type 'exceptions.SyntaxError'>: invalid syntax?

This is my first attempt at much code in the raster calculator of ArcMap 10.0, but I think I'm close. I have nine rasters (A-I below) and want a new raster with value = 1 where any of the rasters ...
0
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2answers
474 views

Change detection with raster calculator

After applying the Diff operator of the raster calculator in arcgis to view changes in land use, would like to see the areas of increased and areas of decreased. This is possible using the raster ...