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

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33 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 ...
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27 views

Raster calculation with string in modeler

In my model I have one raster file and also a string input (factor for further calculation). I tried to use the grass r.mapcalculator where I can find the raster and also the string input. I tried to ...
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1answer
26 views

Why does the composite raster pixel values not cover the full range of RGB and what does this mean for reclassification after conversion to int?

I have about 30 or so composite rasters in IMG format that I need to 1.) Preserve the date that the raster was created and 2.) Combine all of them. My workflow is: Step 1: raster calculator, ...
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1answer
21 views

Multiply raster by Numpy derived float value

So I have a python script that uses numpy to calculate the mean of a field, then I try to use that mean value in a raster multiplication as follows: na = ...
4
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61 views

Focal Statistics for Special Neighborhood

I'm looking to calculate focal statistics for each cell of a raster, within a neighborhood of a specified criteria. Background - I have three binary rasters, each representing a single vegetation ...
4
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1answer
62 views

Raster Calculator making incorrect calculations in ArcGIS for Desktop?

I am trying to use raster calculator (ArcMap 10.2.2.3552) to apply a poisson generalized linear model to estimate species abundances based on elevation. The outputs don't make any sense to me, and I'm ...
2
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1answer
36 views

Adding rule to raster calculator?

IF there are one or two urban cells in the Moore neighbourhood AND there is a road running through this cell. How do I add this rule in my raster calculater?
3
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1answer
30 views

Fast editing in raster calculator — adding lots of images together

I need to add pictures together to make one raster. In one session there are about 150 - 200 images (named randomly - see syntax example) There are about 50 sessions (named randomly) Is there any ...
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16 views

Trouble with reading Leaf area index (LAI) Modis on QGIS

I am having trouble reading my Modis LAI data on QGIS. I imported my Modis hdf files and I used the QGIS raster calculator to apply the scale factor and all I get is a blank gray tile. My goal is to ...
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29 views

Problem with Raster Calculator in Model Builder

I have created a model which repeatedly uses the raster calculator. My problem is that unlike that of the other tools, the output name of the raster calculator does not change. This means that I can ...
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36 views

Merge Raster Layers with Raster Calculator

I am looking to merge three raster layers together, we are only allowed to use the Raster Calculator tool in Spatial Analyst, ArcToolBox. Using ArcMap 10.2
3
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2answers
51 views

How to calculate the a list of rasters?

I'm writing ArcPy code in ArcGIS trying to calculate a list of rasters. I get an error message that says: TypeError: unsupported operand type(s) for -: 'unicode' and 'unicode'. Here's my ...
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50 views

Why do comparisons in QGIS 2.4.0 Raster Calculator return -3.40282e+38 aka no_data?

I tried to use comparisons as conditional statements in QGIS 2.4.0 raster calculator. My statement is: (a < 230) * 230 + (a >= 230) * a The expected result is raster a with all values lower ...
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1answer
42 views

How to calculate raster data in vector area?

I have two layers. One is a layer of USA ecoregions (there are 9 ecoregions). It is not raster (so it's vector?). The other layer is the National Land Use Data set (so I know where there's ...
2
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2answers
49 views

How to use OR in a CON statement, in the ArcGIS Raster Calculator?

I'm trying to compare two rasters, and create an output based on a formula like: if raster1 > 10 or raster2 < 20 then raster3 = 30 How can I specify the OR in the raster calculator's CON ...
3
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29 views

Raising raster to a power gives no data values

When performing the following operation in QGIS Raster calculator: 10 ^ (("20091201_20100101_chl_modis_malvinas_ns@1" * 0.0000581)-2) I get no dada values for every cell where I should get < 1, ...
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1answer
35 views

Making color map in ArcGIS for Desktop?

I have bands 2, 3, 4, and 5 map. How can I use these to make a color map in ArcGIS 10.1 for Desktop? Can you give me steps? Also I want to make attribute table of colormap. How this can be ...
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1answer
33 views

QGIS raster calculator using abs() function

Is it possible to use the Abs() function in the raster calculator in QGIS? I've tried it, but it didn't work.
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1answer
41 views

ArcGIS Raster Calculator output raster has one band but cannot build attribute table?

I built a raster using the raster calculator of ArcGIS 10.1 for Desktop. The properties of the output raster ("usle_1") indicate that this raster has one band. There is no attribute table but I ...
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2answers
37 views

Get raster expression

In Arcmap I have made a new raster with ArcToolBox -> Spatial Analyst Tools -> Map Algebra -> raster calculator. Now, months later, I have forgotten the source formula expression. How can I ...
2
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1answer
29 views

Adding additional parameters to image classification in ArcGIS for Desktop?

I have an RGB ortho rectified Image and I have another grid data with Elevation values. However, an image with only three bands does not give a good classification of landcover, so it is important ...
2
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1answer
60 views

Map algebra from files in multiple directories

I'm a rookie in python programming. I want to do map algebra for multiple rasters but these rasters are in different folders. Here's the code ive created so far: #Importing modules import arcpy from ...
7
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2answers
94 views

Rules of Nodata value?

What are the arithmetic rules that govern Nodata values? Regardless of how these null values are defined? I am using ArcMap Raster Calculator. I am thinking specifically of operations like 1*Nodata ...
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1answer
36 views

R.Mapcalc giving only blank maps as result

No matter what function I put in the r.mapcalc in the GRASS GUI I get a blank map full of null values. I even tried DEM+0 (I can see my DEM) and this also yielded a blank map.
3
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1answer
95 views

SAGA raster calculator, ifelse command syntax problem?

I am trying to get the saga raster calculator in QGIS to spit out all values of a raster that are inferior to 10, and make all other values zero. I think the syntax is correct but I keep getting the ...
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0answers
27 views

Multiply Rasters with Scalar Numbers as Input in QGIS Modeler

I built a little model in the QGIS modelbuilder which uses the raster calculator with the command gt(a,threshold) I need to run the model with varying thresholds from 2 to 30 so it would be ...
2
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1answer
63 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 ...
3
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1answer
85 views

Running focal statistic with iterator in ModelBuilder?

I need to extent the Value of a grid (water mirror elevation) within the nodata area until reaching a specific barrier (the limit of the watershed), in ArcGIS 10.2 for Desktop. I am using this: ...
3
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2answers
81 views

Use Values from Raster Statistics (e.g. sum of all cells) in Raster Calculator

I need to do calculations on raster layers which require the sum of all cells of the raster. I've used the zonal statistics tool for that but it gets a little annoying to do those extra steps (run the ...
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0answers
39 views

Error 000539 I am new to Raster Calculator and can not figure out what is going wrong

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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0answers
56 views

Raster Calculator

I have a slope dataset. How do I calculate the real surface area for this slope dataset using the raster calculator. This is the example I was given: orthogonal area of a raster cell in square ...
0
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1answer
44 views

Raster Calculator Blurring Image Results

I am trying to run a NDVI analysis using raster calculator on Arg Map 10.2.1 and the results create blurry or bleeding image, almost as if the map has been dipped in water. I am using the default ...
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1answer
72 views

Issues calculating range with QGIS 2.0 raster calculator

I would like to calculate a simple range using the QGIS 2.0 Raster Calculator, but am getting strange results. I believe I am not using the correct syntax. To get all values between .003-.5, I ...
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54 views

plug logistic regression equation into Raster Calculator when one predictor is nominal

I am conducting a study that aims at building a Logistic Regression model for land productivity quality (binary dependent variable: good, no good) using different predictors such as slope, elevation, ...
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1answer
42 views

How I can sum 360 raster files in a folder with the Arcgis raster calculator?

In a folder I have 360 precipitation raster files and I want to sum them all to the raster calculator
0
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1answer
59 views

QGIS – Raster Calculator: Using flat (no data) areas of an aspect-raster in the raster calculator

I´m playing around with the Raster tools, following more or less the qgis-tutorial but using my own data. When I calculate the aspect of a DEM, flat areas are (logically) left without data. However, ...
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1answer
86 views

Raster map calculation

I figured out a way to filter a raster by using the r.mapcalculator or the raster calculator. The problem is that I have to use Qgis 2.2 because some of my models doesn't work with 2.4. In 2.2 the ...
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1answer
125 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: ...
0
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1answer
73 views

How to convert raster negetive pixel value to positive

I was working on ground water Level. I used raster math minus function and the Output raster grid data contains negetive cell values. ma resulting raster contains values ranges from High : 0,187477 ...
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2answers
98 views

Error in which.max() : not yet implemented for large objects in R

I am going to create raster by Julian day that observed maximum value of NDVI within a single year. Actually, I want to know which julian day (or raster) has max value in each cells and get result by ...
0
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2answers
94 views

How to create raster map by day that observed maximum NDVI from multiple raster data in R?

I have 11 NDVI raster data, representing single summer. I want to create raster by day (Julian day or name of raster) that observed maximum value. In other words, I want to know which day (which ...
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1answer
79 views

Calculating field length in certain directions (raster)

Currently I'm working on winderosion. For my purpose I like to calculate the length of agricultural fields in certain wind direction. I would like to do it for raster. To be more precise: I have ...
0
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1answer
81 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 ...
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2answers
111 views

DEM mosaic: gaps

I have generated DEMs (bare earth) from Lidar data. For computational reasons, I have processed via ArcGis the lidar files in chunks, so I came up with different single DEMs. After, I used "Mosaic to ...
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1answer
104 views

QGIS Slope Classification Issues

I am very new to QGIS for the primary purpose of creating a slopes layer so we know where slopes are above 15% or 20% or whatever we finally decide. I have used our DEM to create a slope geotif and ...
0
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1answer
53 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?
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1answer
80 views

QGIS raster calculator manual or help

There is plenty unknown about how to use raster calculator, for example: how to write NODATA (Null) value in expression is it possible to use within (polygonLayerName) to clip result between shown ...
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0answers
56 views

Arcpy raster calculation producing random no data cell in output

I've been trying to get the raster calculation below to work using python: import arcpy from arcpy import env import os from arcpy.sa import * arcpy.CheckOutExtension("spatial") KSat_mm = ...
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1answer
74 views

Need to calculate values for a cell based on surrounding landscape

I have a raster file with the urban development of a county mapped out (values: 1=urban 0=not urban). I also have a raster file with several blocks of forested land, each block of land has its own ...
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2answers
184 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: ...