# Tagged Questions

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

2k 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", "outputfile....
7k 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 ...
6k 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 = ...
2k 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 ...
65 views

### Standardising DEM raster for a MCE

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: ...
2k views

### Why does Raster Calculator (RasterCalculator_sa) give ERROR 000539 in ArcPy?

I am getting a not executed error for a raster calculator. Here is part of the output: File "C:\projectTemp\FloodAnalysis\floodxsectionanalysis.py", line 107, in makeSeemless arcpy....
785 views

### How to separate raster bands in ModelBuilder?

I have a simple model that iterates through folders to collect imagery, mosaics them and clips the mosaic to a study area boundary. I need to produce an NDVI from the clipped 4-band mosaic "...
5k 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. ...
12k 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 ...
1k views

### Change NODATA pixel value in raster to arbitrary value

I want to change the value in all pixels that are currently 0 to 800 in QGIS 2.6.1. 0 is listed as the no-data value in Properties > Transparency. I have unchecked the No Data Value box there. Then I ...
2k views

### Specify a field in attribute table with raster calculator

How can I specify the attribute field to use in the raster calculator of ArcMap 10.2? In 9.x, I used the dot notation. i.e. To use the "New_Value" field, I could do the following: [MyRaster]....
4k views

### Averaging set of rasters using Raster Calculator of ArcGIS Desktop?

How do I average a set of rasters? I have remotely sensed chlorophyll a rasters for several days and I need to get an average of the days represented as one raster layer. I am using ArcMap 9.2.
379 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 ...
1k 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: ...
2k 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 ...
953 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)) D:\GEOG_480\Final2\...
62 views

### How to prevent RGB composite flatten to 1 band after raster calculation

I have a series of landsat wanting to process in raster calculator, but after doing the tool it happened these output images only contain one single band. They used to be RGB 3-band images. It is on ...
2k 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 ...
489 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) ...
2k views

### 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 ...
344 views

### Combining Geological Grids and extruding between them?

I have a situation where I have 3 Geological grids, each showing a different horizon + the Seabed Grid. I need to extrude between these grids in order to make the 3D polygon for the geological ...
3k views

### Conditional Statements in QGIS raster calculator?

What is the equivalent statement of the following expression in the QGIS raster calculator? Con(((Abs("DEM" - "FSMin") > 120) | (Abs("DEM" - "FSMax") > 120)), 1, 0) I have no problem ...
1k views

### What will happen if we subtract two raster with different cell size using Raster Calculator?

I want to subtract a topography raster with a depth raster. The problem is the two rasters have different cell size. The topography raster have a square cell size of 5, 5 while the depth raster have a ...
2k 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 ...
4k views

### Using individual bands from multi-band image in ArcGIS raster calculator?

I'm trying to use individual bands from a multi-band TM image (IMG file) within the raster calculator in ArcGIS 10 (SP2/3). I can add individual bands to my MXD, but raster calculator will only use ...
1k views

### Help with scripts for processing raster files with the raster calculator in QGIS

I am trying to process some raster files using python scripts in Qgis 2.20, and I have been having trouble finding any documentation on using raster calculator in scripts being run in the processing ...
2k 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 ...
790 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 ...
475 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 easy-...
134 views

### How do I replace cell values of a raster using values of another raster with differing extent?

I have two rasters (raster1 and raster2). The raster1 extent is smaller than raster2. I want to replace the value of raster2 pixels using raster1 pixels. How can I replace the values?
461 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 ...
353 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 ...
1k views

### Querying slope data using raster calculator: why are all results true?

I am using ArcGIS 10.2.2. From a DEM, I have created a new raster showing slope using the slope tool. The color scheme was automatically classified into 9 tiers. What I want to do is query this raster ...
864 views

### Scale raster in ArcGIS using raster calculator

I have a raster with values ranging from 0 to 8991130624. This raster is actually the result of a cost distance analysis. I want to scale the raster to range from 0 to 1 and take the inverse? so ...
384 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 ...
2k 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?
155 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 ...
297 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 1=...
164 views

### Combine multiple binary rasters to a single raster

I have 5 different species richness maps which I am trying to join in order to show one cohesive map. Each species raster layer has values of 1 and 0; 1 if the species lives there and 0 if the species ...
198 views

### Conditional statement in gdal_calc with result as float, not boolean

Many examples on gis.se that refer to gdal_calc give a boolean example. example 1 example 2 If I need to calculate a conditional statement on a float: If Raster_Value >= 1024, then 1024; else ...
368 views

### Why does every raster calcuation I try return with NAN values?

I am trying to work with DEM rasters from the USGS using the raster calculator. I have tried to change the units from meters to feet using an expression such as: "ned10m45111h8@1" * 3.28 However ...
299 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, ...
2k views

### Removing pixel values below 0 in Digital Elevation Model in ArcGIS for Desktop?

I made a DEM layer from a .las file (LiDAR). How can I remove the black area which contains negative values? Is it possible to set these values equal zero or null?
196 views

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 '...
151 views

### Raster calculator : How to make 0 + NoData = 0?

I have a point data layer (vector) that I converted to a raster layer. I want to replace the NoData value (between each raster point) in the point raster layer by 0. So, I made a background raster ...
75 views

### Calculating percentage of cells which are lower than site in Grass GIS?

In GRASS GIS: I have a shapefile with 300 hundred of sites (with height values for each point), and want to calculate the percentage or number of cells (of a given DEM) which are lower than the site'...
331 views

### Using Loop with Raster Calculator in ArcPy?

I am trying to loop through multiple rasters and extract cells that are above 0.1 The code I am trying to use is: import arcpy arcpy.CheckOutExtension('Spatial') arcpy.env.workspace=r'F:\Sheyenne\...
73 views

### QGIS Zonal Stats Plugin - Python Console - compute one specific statistic

I think this is more of a syntax problem that I have here. But I am absolutely not able to figure it out. On a different Linux machine I got the following working: zoneStat = QgsZonalStatistics (...