# Tagged Questions

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

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### How can I calculate the percent of a raster cell covered by a polygon?

First, I am going to try and intersect a raster and a polygon shapefile. I'm not 100% sure how to do this (or if I need to do this for the next step), so if you have any suggestions please let me know!...
359 views

### Creating an R factor raster in RUSLE Soil Loss equation with multiple input rasters

I am attempting to obtain the rainfall erosivity "R" factor for the RUSLE Soil Loss equation using rainfall PRISM 30 year history data. I have both monthly and annual data that comes into ArcMap as ...
33 views

### con statement to change the default value in ArcGIS

I have obtained a flow accumulation map using Arc Hydro tools and obtained the default value in the range of 0-204567. Now I need to change these value by default so that it gives 1 instead of zero. I ...
65 views

### Summing pixel values from several raster layers with partial overlap in QGIS?

I have several presence maps (rasters values 1 and 0) from different species. They are all from South America, but they do not have the same extend (i.e., different sizes). So, I am trying to ...
31 views

### Problem with algebra formulas for work with gdal_calc.py

I'm trying to update some values of a raster based on another raster. 1st raster (A): landuse data (values from 10 to 240) 2nd raster (B): mask data (only nodata values and a given value, for ...
151 views

### How to reclassify raster data that falls within a polygon

Thansk for your response Okay so I will reword my question more clearly I'm currently using ArcGIS 10. My task is to map forest cover with the image classification tool. The problem is some of the ...
44 views

### unexpected output from raster calculator function

Working in ArcMap, I am trying to convert the logit values in raster into their actual probabilities (logistic regression,) using the following function: 1/(1+Exp(-"sn_topo_poly_log")) Ive used this ...
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### problem with raster calculator syntax [closed]

I am trying to build a raster representing the output from a logistic regression model. i keep getting syntax errors. heres the script: -2.41-(15.97 * "Topographic_Predictors\wadem10m_annsolrad") - (...
28 views

### Iterate variables in Con statement in Raster Calculator- model builder

I have this formula which works fine in raster calculator on its own. Here is a simplified version of it: Con((("Trial_analysis\winter_pm" == 2)) & ("Wind_directions\winter_pm_WD" <=b) & (...
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### Combining non-overlapping binary rasters with ArcGIS Raster Calculator?

The issues I keep seeing depend on unique combinations of values. I have three rocktype raster layers for area and they are edge-to-edge (they do not overlap). They each have "VALUE" fields and "...
60 views

### Constructing LS factor for RUSLE without outliers using ArcGIS for Desktop?

I'm using the following formula in RUSLE via raster calculator to obtain a LS factor Power(Flowacc)*1/22.1,.4)*Power(sin(slope)*.01745/.09,1.4)*1.4 My expected outcome is a raster from 0 to ...
26 views

### Curve Number equation

I have a floating point raster of Curve Numbers (70-91) and I'm attempting to use the curve number equation to create a weight raster for flow accumulation, to determine runoff for a single rainfall ...
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### Raster calculator fails with large raster in QGIS

I'm working in QGIS 2.14.1 with a DEM ranging from 200 feet to 1600 feet elevation called "dem_3m_Zft1b" (geotiff, 16822 X 33349 cells, No-data =-9999) If I enter "dem_3m_Zft1b" > 0 in the ...
126 views

### QGIS raster calculator wrong output

I am trying to create a mask from a DEM (SRTM tile) using raster calculator in QGIS. I have performed the same operation in ver 2.6 with no problem but in the current version the output is incorrect. ...
431 views

### PostGIS ST_MapAlgebra Assistance

I would like to perform the equivalent of the below ArcGIS raster calculator equation in PostGIS using the ST_MapAlgebra function and return it as a tif using ST_AsTIFF. Con(("Sol_gain_clipped.tif" &...
77 views

### ArcMap raster calculator error 000539

Using ArcMap 10.3, I am trying to perform map algebra on a raster with 2013 annual PRISM precipitation for the U.S. (http://prism.oregonstate.edu/recent/). The raster has 1 band an is floating point. ...
57 views

### Mapping habitat suitability using ArcGIS for Desktop?

I have been having somewhat of an issue recently with one of my projections. I am currently trying to map out the preferable habitat for a species in Arcgis. To do this, I performed a GLMM in R and ...
543 views

### Raster Calculator error

I'm trying to use the Raster Calculator inside ModelBuilder to get rid of null values, but I'm hitting a snag. I'm using the expression: Con(IsNull("%temp_ras%"),FocalStatistics("%temp_ras%",...
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### Recalculating raster based in number of cells?

I am working with binary rasters of fish species distributions (1=presence, 2=absence). I am looking to recalculate each raster in this way: Count the number of cells with value 1. Divide: 1/Number ...
22 views

### Why would having a reference string “boh@10” cause a crash?

When using the raster calculator in a pyqgis script, I have several layers to process. When it gets to "boh@10", the processCalculation() call crashes. I don't see anything in the code that requires ...
40 views

### Create Cost Surface Raster with slope as percentage of total costs

I know there is a similar question on this website (How to Create Cost Surface Raster for Least Cost Path Analysis?) , but I couldn't find the answer that I'm looking for. I'm currently working with ...
64 views

### Is QGIS Raster calculator faulty?

I am trying to perform some rounding operations on rasters. I have used GDAL to convert the raster to an integer which is fine but now I want to /100 which should be simple in raster calculator but ...
94 views

### Syntax Raster Calculator

I have never worked with the raster calculator before and I can't solve my problem. There are two raster datasets. One contains roads ( "closed", "in use", "under construction") and the other dataset ...
109 views

### Conditional statement in raster calculator - ArcMap

I'm Just wondering how to incorporate a conditional statement basically to say: if value in raster >= 128, then put in new raster, otherwise make the values null. Basically the purpose of this is ...
103 views

### Using Raster calculator in Modelbuilder ArcGis 10

I am using Modelbuilder to calculate several rasters with different parameters for each grid cell. One of the final steps is to calculate the log of one of the rasters using Raster calculator. ...
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]....
49 views

### Can I multiply fractions in map algebra?

I have a couple of rasters that show % of success in different things. I want to calculate the overall probability of success. The numerical values are integers so they represent the percentage. This ...
261 views

### Flow Accumulation Python or MATLAB Script

does anyone have any resources for scripting the D8 flow accumulation in Python or MATLAB after obtaining the flow direction values and filling in 'sinks' and 'flats'? I am trying to understand the ...
351 views

### How to compute NDSI in ArcGIS for Desktop?

How do I compute a Normalized Difference Snow Index (NDSI) in ArcGIS's Raster Calculator? I have a Landsat 8 scene (hdf4 format) that contains derived surface reflectance band-by-band. Each band is a ...
844 views

### Trying to run raster calculator to build an expression for ls factor

I am trying to run a raster calculator, but it failed. I believe that ArcGIS 10 does not understand when I use the variable resolution. What do I need to put in its place? I took the equation from ...
431 views

### Raster Calculator Iteration in ModelBuilder?

I have a large number of rasters and I want to add 1 to each of them (e.g. each raster's values currently range from 0 to 1, and I want to make them range from 1 to 2). I believe ModelBuilder, using ...
39 views

### raster calculator fail to sum?

I am having a question about the raster calculation as I am trying to create a tool which I want to link with my python script to sum weight rasters but if failed to do so. here is my code: #*the ...
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 ...
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### Combining information from multiple rasters into aggregate raster and populating fields accordingly

I am stuck on how to best combine the information from multiple rasters into one raster. Specifically, I am working with a time series of raster files, whereby each raster corresponds to a different ...
64 views

### Calculating maximum value in Raster Calculator of ArcGIS for Desktop?

I have MODIS NDVI data of four months and I have to calculate NDVImax. I am using the Raster Calculator of ArcGIS and have been using various algorithms like [MAX ("june2000", "july2000" , "...
56 views

### Using Con in Raster Calculator of ArcGIS for Desktop? [closed]

I have two images, "dvel.img" and "evi.img", and i want to extract water related pixels. The condition is: (("dvel.img" <= 0.05) & ("evi.img" <= 0.3)) I want to get an output by putting ...
30 views

### In ArcGIS raster calculator can you access the individual cells surrounding a central cell like you can in GRASS r.mapcalc

Is there a way to do the following in Raster Calculator in ArcGIS? In GRASS r.mapcalc you can access the cells surrounding the current cell by writing inputRaster[a,b] where a and b represent the ...
81 views

### Meaning of ERROR 000539: Error running expression: rcexec() <type 'exceptions.ImportError'>: No module named os?

In Raster Calculator using: (FocalSt_meanDEMtif5-FocalSt_minDEMtif1) / (FocalSt_maxDEMtif2-FocalSt_minDEMtif1) What is the meaning of ERROR 000539: Error running expression: rcexec() : No ...
41 views

### Compare euclidean distance with network distance

I have a raster file with euclidean distance. It contains information about how long it takes for a chopper to arrive to certain destinations. I then have a polygon made from a service area with ...
687 views

### Performing Raster Calculator functions using Python and open source modules?

I would like to perform mathematical functions similar to those you would use Raster Calculator for in ArcMap, however I'd like to do it in Python without using the ArcpPy module. I have the osgeo ...
81 views

### Using decimals in ArcGIS Raster Calculator tool?

I would like to create a new raster by using the following regression equation in the Raster Calculator tool in ArcGIS 10.3: Outputras=0,000826345+(0,000203494*"Roads_density.tif") ("Roads_density....
65 views

### Calculating Geometric Mean in Raster calculator

I am calculating Geometric Mean for land degradation mapping. I am applying following formula in ArcGIS 10.2- ("GW.img" * "LULC.img" * "Rain.img" * "Temp.img" * "Wind.img" * "NDVI.img" * "Livestock....
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### How it can be made a spherical cap surface with qgis raster calculator

I would like to make a test in QGIS raster calculation: I'd like to make in a flat raster surface (0m as elevation) a kind of hill or dome with the spherical cap geometry formula. P is the point ...
31 views

### Do rasters have to be of same extent for the QGIS Raster Calculator?

I am trying to use the Raster Calculator but, I get a raster with Nan values. My rasters are in the same projection system but, one of them, it is a classified landsat map which covers only some part ...
105 views

### Sediment transport index STI

To calculate the STI one applies the following formula in the raster calculator: Power(“FlowAccumulationArea_Raster”/22.13,0.6) * Power(Sin(“Slope_Raster”/0.0896),1.3) Now I have a problem which I ...
68 views

### Raster Calculator and Land Change with multiple classifications

I am looking at land cover data that is separated into three classes: upland, wetland, and open water. I have the data for varying years. I am interested in seeing how the land has changed over the ...
281 views

### NDVI from Landsat8 LandsatLook images

I have downloaded landsat image from this site and now Im wondering if i can get NDVI index from it. In raster calculator I have only 3 ranges, shouldnt be four? Or am I doing something wrong......
207 views

### Markov chains, cellular automata, and raster algebra

I need to build a probabilistic cellular automaton for simulating land-use changes and am wondering how to implement this in a GIS. I understand that Markov chains are a way of doing this, and IDRISI ...