Questions tagged [map-algebra]

combining map data of similar dimension to produce new maps using algebraic operations

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340 views

Identifying row and column location of a raster image using ArcGIS 10.1

The solution already available online gives a python syntax error ERROR 000989 Python syntax error: Parsing error SyntaxError: invalid syntax (line 1) when I write $$rowmap + 1 in map ...
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2answers
211 views

Raster multiplication script not executing

I built this code to multiply rasters but it will not execute, it gives me the following error: ERROR 000732: Input Raster: Dataset in_raster1 does not exist or is not supported # Import arcpy module ...
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1answer
570 views

ArcGIS raster calculator: ERROR 000539: Error running expression: rcexec() <type 'exceptions.ImportError'>: No module named collections

My raster is in the GRID format, source type is continuous and pixel type is floating point (32bit). If i use the raster calculator ("dem" *1000 or "dem >= 2m" (to highlight certain heights) it ...
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2answers
757 views

Changing raster calculation values - shorten this script?

i'm doing something quite straightforward regarding raster algebra but am struggling either to find the correct function or make a function work correctly; Basically I have 2 rasters, representing ...
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2answers
2k views

QGIS from console: raster algebra

I'm newbie to programming in pyqgis. I need to perform a simple "GeoTiff * A" type of calculation(where A is a constant), but I am struggling to do so. I tried processing.runalg('saga:...
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1answer
4k views

NameError: name 'Con' is not defined

I have 365 rasters with the same extent, and I am trying to sum them together by month. I have the script below, which was working until I added the line out1 = Con(IsNull(raster), 0, raster) which is ...
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1answer
168 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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1answer
84 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 ...
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3answers
826 views

Nodata issues in map algebra

A dummy question. I need to change all values in my rasters into ones. I've been able to do this fine in the Rater Calculator just by multiplying the layer by zero and adding one (my_layer*0+1), but ...
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1answer
123 views

Map Algebra syntax

I'm trying to create a new raster from an existing slope raster where slopes are between 5 and 20 degrees. However, I'm receiving the error "ValueError: The truth value of a raster is ambiguous. ...
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2answers
357 views

PostGIS raster MapAlgebra callback optimization

I'm trying to speed up an ST_MapAlgebra callback function that essentially takes a raster with four bands, checks each band for values less than a given number, and where the check is true, return the ...
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3answers
1k views

Performing raster map algebra in open source web GIS?

Map algebra for raster is easy with ArcGIS Raster Calculator (or QGIS). I had thought this would be easy with web GIS servers such as GeoServer and MapServer plus OpenLayers etc. as well. What I want ...
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1answer
507 views

Changing raster value based on point feature

I am working on some landslide modeling. Within ArcMap I have a raster layer, representing the area of the county I am working in, and a point layer that shows landslide locations. I reclassified ...
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1answer
3k views

Using Raster Calculator expression in Python

I've posted about this problem before but I've got a few new questions. So here's the problem. I have two rasters containing bathymetry data: one containing the bathymetry of the sea floor, we'll ...
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1answer
443 views

Con statement not working in Raster Calculator of ArcGIS for Desktop?

I'm trying to combine two rasters in 10.3 using a con statement with the raster calculator in map algebra. (ie - con (raster 1 ==1, raster 1, raster 2)) where raster 1 is a smaller extent and does ...
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1answer
53 views

How to weigh the size of a spatial event with respect to the number of its hotspots?

This is probably a map algebra problem. I have a 2D map with values ranging 0.0 to 1.0 spread all over it. The algorithm that produces them is an application of the fractional Brownian motion. The map ...
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1answer
871 views

Adding Rasters with multiple Field Values using Map Algebra in ArcGIS for Desktop? [duplicate]

Embarrassed that I haven't looked at this for some time (can't quite get the syntax down). (ArcGIS 10.2, Win7x64). Within Map Algebra (Raster Calculator) Trying to add the cell values of 3 rasters, ...
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1answer
2k views

R giving error when attempting map algebra

I'm trying to manipulate some downloaded rasters using R, and keep getting the same error when I try to do any type of map algebra. The example below uses a raster file downloaded from http://www.csc....
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2answers
5k 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 ...
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2answers
372 views

Alternative to nested Con statements in python

I have a nested con statement that I'd like to put into a script, as it's hard to follow in its current form. The raster it produces is incorrect, so it'd be easier to debug in a script. The ...
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1answer
778 views

Calculating the difference between two grids in percent with QGIS

I'm using the QGIS GDAL Raster Calculator to get the difference in percent between two grids. Grid A contains an integer, and grid B contains an integer which may be the same as or larger than the ...
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0answers
418 views

Calculating Aerosol optical thickness from Landsat 7

EDIT I have added question down I am reading one paper and I found method to retrive AOT from landsat 7 image This should be simplifield equation, because they assumed observation zenit as 0. Than ...
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2answers
696 views

Map algebra in QGIS

How do you calculate standard deviation for each raster if you have set of rasters (100)? I was searching in raster calculator, but I didnt find it. Also google redirect me to using R or python. But I ...
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2answers
94 views

How can I stop my map algebra being limited to the size of my smallest raster?

I have five input rasters and I'm using map algebra to find areas where all of them have a value over 75, areas where all of them are over 25, and areas where one or more are under 25. I can do this ...
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1answer
1k views

Arcpy.Delete_management() not deleting folder?

I've written a script in Python that takes in two ascii files that represent surfaces, then convert them to Rasters, and finally Negate their values (i.e. multiply all cells by -1). In the script, I ...
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1answer
2k views

Map Algebra expression in a model fails on open workspace

I have model which runs 2 processes that create rasters and a third process that (attempts to) add the two of them using Map Algebra. The expression is very simple, just "%Raster_A%" + "%Raster_B%". ...
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0answers
151 views

How to correctly input complex multiband functions in Raster Calculator?

I'm trying to compute a MTVI2 (Modified Triangular Vegetation Index - Improved) and EVI (Enhanced Vegetation Index) from Landsat 8 imagery. My formulas are as follow (I'm using ModelBuilder): MTVI2= ...
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1answer
725 views

Error using con in Map Algebra in Python script

I am experiencing a painful problem in the middle of a Python script I am writing. When I get to a Map Algebra function, I have tried two different options and both return a different error. At first ...
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2answers
3k views

Access individual bands and use them in map algebra

I have a list of multiband rasters, consisting of: Red=Band 1, NIR=Band 2, SWIR1=Band 3 and SWIR2= Band 4. What I want is to access only the red and NIR bands and save it to new file. Then, I'll be ...
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0answers
104 views

Automating Raster Calculator [duplicate]

I am seeing mixed answers on other posts so I thought I would ask here. Is there a way to automate the raster calculator? I am trying to create a series of inundation maps at fine increments. It ...
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1answer
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 ...
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4answers
434 views

What are some Domain Specific Languages (DSLs) for GIS?

I'm curious what sort of domain specific languages (DSLs) are used in GIS. The only one I can think of is the DOCELL language that was provided in ArcInfo Workstation GRID, but is no longer supported....
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0answers
671 views

How to compute the ls factor equation for USLE model in qgis grass r.mapcalc

To compute the LS factor for the USLE model, the following equation easily works in ArcGIS. How can I perform the same in QGIS under GRASS r.mapcalc? LSfator = Power (("flowaccNW") * resolution/22.1,...
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3answers
1k views

Creating raster by randomly choosing cell value from multiple overlapping rasters?

I'm using ArcGIS Desktop 10 with its Spatial Analyst extension. How do I combine multiple rasters into one, always choosing randomly from the values of overlapping cells? I have an image that may ...
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1answer
2k views

Partially updating raster (DEM)?

How to update an .img DEM in ArcView 9.3? I do have DEM which need to be updated only if few parts. The area to be updated has been produced in separate DEM with Spline Interpolation with Barriers. ...
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1answer
682 views

How to calculate cumulative sum conditionally across raster?

I don't know if this is possible without coding, but I need to: Create a raster file that, for each value in the input raster, sums all pixel values across the entire extent that are less than or ...
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1answer
1k views

How to compare two rasters and reclass the greater value(python script)?

I am working on an assignment that requires us to reclass a raster(via python) from two rasters. We need to compare the power received at one cell(on raster1) and compare it to the same cell on raster ...
2
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1answer
3k views

Raster Multiplication - Can't Multiply Sequence by Non-Int of Type “Float”

I am trying to multiply a list of GRID raster datasets using a different value for each raster. The value is in the raster name. Some examples are [wse_1979_5,wse_1980_0,wse_1980_5], where 1979_5, ...
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1answer
2k views

Map Algebra - Grass GIS (r.mapcalc) merge two raster with NoData value

I have a slope raster and a road raster. The black pixels in the road raster are NoData values and the pink pixels have a value of 1. They don't cover exactly the same area. I want to create a new ...
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1answer
209 views

How to iterate RGB raster layers in ModelBuilder?

I have an RGB raster that I'm calculating color-based indices from. When I do the calculations manually, I can select a certain band of the RGB raster to calculate. I need to do the same operations on ...
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0answers
63 views

Map algebra from QGIS python console? [duplicate]

What command do I use to do map algebra on rasters from the QGIS python console?
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1answer
551 views

Map algebra expression with dynamic raster layers

Attached is the model that i am working on. The "To Value" and "From Value" are model parameters and hence subject to change each time according to requirements, This leads to varying number of files ...
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1answer
667 views

Raster produced by Con expression not saving

I cannot get a Con expression to work. Or, if it is working, I cannot get the raster produced by the Con expression to save. I have two rasters and I want the positive difference between the two, and ...
3
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1answer
700 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 ...
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2answers
1k views

How to produce a mean raster file based on other raster files? [duplicate]

Possible Duplicate: Tools to flatten the jp2 to a single band (average the bands)? I have a number of raster files from a same area, that coordinates of corresponding pixels perfectly match one ...
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1answer
784 views

Spatial Analyst tool Look up but in ArcView3.2

Is there any option how to do a Spatial Analyst tool "Look up" operation from ArcGIS 10 in ArcView 3.2? I have a grid with attributes and need to "extract" values from the table field (values from 0....
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0answers
204 views

Map Algebra in VB.NET Add-In Tool

I'm trying to run a map algebra expression in a vb.net add-in, and can't seem to get it to work. It's a roving window that interpolates noData areas in a DEM. The expression works in the Python window,...
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1answer
674 views

Change raster value for an area based on a class of another raster

I would like to change all raster values in raster A that fall into the locations of category/class 1 of raster B. Here, some more details. I did a calculation on a DEM resulting in different ...