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

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How to round up/down an pixel value of a raster to a pixel value with 2 decimal places?

I have a raster (DTM) with floating points as pixel value. Now i want to round up/down the pixel values (to its next nearest value) to 2 decimal places. I use ArcGIS (with extensions) and tried the ...
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1answer
34 views

Iterate through rasters in subfolders using Model Builder

I have a directory folder of precipitation data; within this folder are subfolders for years 1901-2014. In each of these subfolders are 12 .asc grid files; each file represents a month of the year ...
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36 views

Using iterator in ModelBuilder for groups of rasters

I'm trying to do some raster calculations on Landsat imagery in ModelBuilder. I'm calculating basic indices using Raster Calculator followed by Zonal Statistics. The resulting tables are merged ...
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1answer
34 views

Classify Output Raster as percentage in arcGIS

I have water supply and water demand rasters.They are both of the same cell size and spatial reference. I need the ratio of water use to water demand. Then I want to classify this output in the ...
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30 views

Raster Calculator returning nodata for overlaying cells

I used raster calculator to divide two rasters setting the environment to intersection of inputs. The output has a nodata value in a cell where these two rasters clearly intersect. Any suggestions ...
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85 views

Calculating average NDVI

I would like to calculate average NDVI values. I have 3 values of NDVI: high:243 low:0 high:243 low:0 high:238 low:0 How can I use a a raster calculator to calculate the average valvue
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24 views

byte swap a mosaic raster

I'm getting into trouble to byte swap a raster. I'm using two DEM rasters that I mosaic using the function "mosaic to new raster". The new raster I get is called "mosaic". The cell range then shift ...
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2answers
24 views

Remove sections, defined by a line or polygon, from a raster in QGIS

(QGIS 2.6.0 on Windows.) I have created a raster layer of heights using the TIN interpolate function. I also have another raster layer with more accurate information on the height of particular areas ...
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52 views

Modifying raster values in a zone with a math expression

I'm currently doing an SIG project with the goal of calculating groundwater volumes in chalk and silex residuals aquifers. I have point data of underground water, chalk roof, and floor elevations, as ...
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36 views

Creating a Raster of Road Distance to Point

I am using QGIS 2.6. This question is in two related parts: I'm trying to create a raster of travel time from one point to another point travelling via the road system. Each raster pixel will roughly ...
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2answers
43 views

Using QgsRasterCalculator

I'm trying to make a sum of n rasters and create a new one using QgsRasterClaculator, the problem is, every time the code reaches processCalculation, it makes QGis close and create a dump file. I ...
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27 views

Only run r.neighbors if cell meets criteria

This is my first time using GRASS to work with Rasters, so please excuse my lack of knowledge on the subject. I want to run the GRASS r.neighbors function on cells that meet a specific criteria, ...
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157 views

Why is the result of a raster calculation integer when it should be decimal?

I'm trying to calculate the NDVI using raster calculator, but the result is integer instead of decimal. NDVI = (NIR - RED)/(NIR + RED) The result is normally in the range -1 to 1, but when i tried ...
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25 views

Create elevation dependent mean values in ArcGIS RasterCalculator

I have two rasters. Raster1 is a reclassified raster for certain elevation value ranges. Raster2 is an elevation raster too but with gaps. I want to fill the gaps of Raster2 by the median of the ...
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1answer
87 views

Raster Calculator syntax

I have two rasters depicting climate in two periods and I want to compare their values. I want to create a third raster returning: Values of raster 1 are within the minimum and maximum values of ...
2
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1answer
20 views

How to calculate values in a 3*3 matrix using raster calculator?

How to manipulate a raster values in a 3 X 3 matrix.. using raster calculator or any other method e.g. to find out how many cells are there in a 3 X 3 matrix having cell values less than the center ...
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1answer
53 views

ArcMap 10; Syntax for Minimum operator in raster calculator

I want to linear stretch my raster grid formate having column/rows 3128, 3503 with 30 meter resolution by using the following syntax in raster calculator of arcmap 10.1. ("raster" - ...
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48 views

Normalize the NDVI raster 0-255

NDVI values raster computed by using the band 3 and band 4 reflectance values b4-b3/b4+b3. The output raster is of 32bit type formate although the possible ranges that shows in statistics parameter ...
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69 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 ...
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2answers
63 views

How do I get rid of this thin band between raster layers created from TNM?

After hitting my head against the table for many days, I'm humbly presenting myself to the QGIS community. I downloaded 4 IMG files (1/3 arc second, elevation data) from The National Map on the USGS ...
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1answer
101 views

QGIS's raster calculator— running as a batch process?

I have a series of raster files (150 or so) that I need to multiply by a baseline raster. Unfortunately, the series of rasters have a different cell size (30mx30m aka .00027777778 degrees x ...
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59 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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38 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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61 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
33 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 = ...
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101 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 ...
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100 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 ...
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1answer
43 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?
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1answer
36 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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30 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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39 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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71 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
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2answers
59 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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74 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
64 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
79 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 ...
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34 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
45 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
50 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
86 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
39 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
32 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
74 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
98 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
40 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
183 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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36 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
180 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
126 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
121 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 ...