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

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2answers
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?
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1answer
286 views

How to subtract out the slope (in general) of a DEM?

I'm searching for a solution process to subtract out the slope of a DEM like this: I have a high resolution DEM and want to reconstruct historical/old/not active parts of a river. The problem is ...
3
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1answer
334 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 ...
3
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2answers
115 views

How to update raster pixel values based on another raster with conditions in QGIS?

I have 2 land cover rasters. I want to update parts of the first raster with values from the second using QGIS. The workflow should be like this: 1. Select values equal to 30 and 34 in the first ...
3
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2answers
2k views

Querying raster in ArcGIS Desktop?

I am using ArcGIS 10 (includes spatial and geostatistical analyst). I have a raster (GRID) with a value range of -167 to 18. I would like to query the raster and create a new one with only the ...
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1answer
39 views

Using raster calculator to show multiples of particular value?

How do I use raster calculator so that the new raster only shows multiples of 128? I'm not sure what the expression should be.
3
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1answer
97 views

Calculate Volume over sloped ground in GRASS GIS

I am trying to do some volume calculations on a DEM with GRASS GIS. However, I believe r.volume measures everything from 0. The ground underneath the pile I'm measuring is sloped. I would ...
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1answer
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 ...
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1answer
3k views

extend the size (area) of raster

My problem is that I would like to multiply two rasters using raster calculation tool. Both rasters have values 0 and 1, but the covered area of first raster is bigger (100 x 100 miles) then the area ...
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1answer
764 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 ...
3
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1answer
58 views

Convert 0's to NoData in QGIS Raster Calculator [duplicate]

What is the easiest way to convert cells with a value of 0 to NoData in QGIS Raster Calculator?
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3answers
219 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 ...
3
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1answer
137 views

How to center continuous raster layer by subtracting mean and dividing by standard deviation using QGIS raster calculator?

I'm trying to extrapolate a spatial model to a map in QGIS using the raster calculator. The model predicts the value of a pixel given the environmental conditions at this location (e.g. elevation, ...
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1answer
422 views

Where is qgis getting the NO DATA value from?

I have a project that contains an 8-bit paletted layer (call it the mask layer) and a float 32 single band layer (call this the clip layer). I create a new raster by using the raster calculator, ...
3
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1answer
830 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
788 views

How to enter formula into ArcGIS Raster Calculator?

i have the following formula: L = (l/22,1)^m (l = Flow length) m is calculated like this: m = 0,5 when slope is >4 degrees m = 1,2 * sin^1/3a when slope is <4 degrees (a = slope in ...
3
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1answer
62 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: ...
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2answers
774 views

Calculating average raster grid values perpendicular to a barrier and transferring values to adjacent cells

I was hoping I could get a little help for 2 questions dealing with raster datasets. I have access to ArcMap 10.2 and ArcView 3 to do this. Here is what I am trying to do: 1) I need to calculate an ...
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2answers
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 ...
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1answer
383 views

Measuring polyline lengths running through a raster - is this possible?

I have a reclassified raster layer with 4 values and a vector layer of polylines. I would like to discover the length of the lines running through each raster value, or the percentage of the lines ...
3
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1answer
361 views

how can I obtain the areas where my rasters overlap, using Qgis?

I have a bunch of raster files showing the distribution of different species of mammals, and I would like to obtain the areas where they overlap, the areas in whitch more than one species can be found ...
3
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1answer
28 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 ...
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2answers
29 views

Raster conditional tool unexpected results. What's wrong?

I have a DEM raster (High: 53441, Low: -3444, unit: cms) with negative values, and I want to make all values 100 or less to be 100. I've tried Raster Calculator, and also python. I've got the same ...
3
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1answer
37 views

QGIS Raster Calculator syntax

I have tried this several different ways and get lots of NaN. I need to specify that in my raster 'test1', I want a certain set of values to equal 1 and the rest to equal zero. For instance, I want ...
3
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1answer
161 views

How to use the con statement in raster calculator to include a raster as a condition in an existing raster

So, I'm busy doing an assignment where we have to use a Weighted overlay to generate a raster of suitable places to plant crops. I've put all the factors in the weighted overlay and generated my ...
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1answer
150 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 ...
3
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1answer
908 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 ...
3
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1answer
684 views

Expand raster extent and set expanded values using nearest neighbor sampling

I have run a hydrodynamic model which has given me a grid of surface elevations throughout a bay. I am trying to process the results in ArcMap (or QGIS if needed). My goal is to take the current grid ...
3
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1answer
41 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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1answer
24 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 ...
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1answer
129 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 ...
3
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2answers
128 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 ...
3
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1answer
47 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 ...
3
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2answers
414 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 ...
3
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1answer
181 views

Cell Statistics in QGIS

Cell Statistics in ArcGIS will calculate the mean (or statistic of choice) among multiple rasters on a cell-by-call basis. Can QGIS do this? If so, how?
3
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1answer
115 views

Cell values to No data

I need to set cell values in one raster to NoData based on another raster. Both rasters have the same extent and some cells overlap. For those cells that overlap I want to set them to NoData in ...
3
votes
1answer
490 views

Nearest Neighbor Focal Statistics and Map Algebra

I would like to use a nearest-neighbor type analysis to iterate over a raster. The nearest neighbor analysis will give a cell value of 1 IF AND ONLY IF the cell being analyzed has a cell value larger ...
3
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2answers
849 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 ...
3
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1answer
154 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
votes
1answer
148 views

Stack sat images and run operation on all

I have about 300 MODIS satellite with different acqusition dates, covering the same area. I am not used to work with so many tiles at once so I ask for advice. I am working with ArcMap10.1 What I ...
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0answers
47 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 ...
3
votes
1answer
76 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 ...
3
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1answer
44 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 ...
3
votes
1answer
59 views

Polarity of Slope raster for use in Multi Criteria Evalution

I'm looking to use a slope raster in a MCE however i am struggling to ensure it has the correct polarity. The polarity of my other two layers is high values = good and low values = bad. The slope ...
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0answers
42 views

Raster calculators in SAGA return incorrect results

Here's a sample of my dataset (one cell) with 28 different raster values, representing 28 individual Float32 rasters with identical parameters. 0.0000264434, 0.0049953502, 0.0007529828, ...
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1answer
43 views

Performing raster calculations along line feature or within polygon using QGIS?

I need to add a value to a dem file along a polyline feature or within a polygon. How can I add 100 to the values of the raster cells intersected by my line feature or within my polygon feature. I ...
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0answers
436 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
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0answers
150 views

Creating a new raster based on pixel value of original raster using raster calculator but new layer is not evident [closed]

I am trying to create a new raster based on a current raster (w001001 - NVIS) which has one paletted band, with palette values ranging from 1 to 29, with each palette/value representing a vegetation ...
3
votes
1answer
381 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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3answers
53 views

Add value to entire column in attributes

Is there a way to add a value to the entire column? I don't think i can use raster calculator because it's a text i want to add, the letter "B". Here is a picture. This is what happends when i use ...