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Questions tagged [map-algebra]

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

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3answers
53 views

Showing two sets of points from two different fields in QGIS?

I made a union of two adjacent shp (points) files with the same theme (Geochemistry) so the resulting attribute table gave duplicated fields, for example: ID, As_ppm, Ag_ppm, Pb_ppm, ... , ID_2, ...
0
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1answer
33 views

Creating custom Operation for encapsulating some map algebra using GeoTools?

In GeoTools, I need to perform a one-to-one pixel computation between a bunch of GridCoverage2D. In short: some map algebra. As I understood I can do things like summing values of coverages using: ...
1
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0answers
39 views

Using minus in water drainage model

I'm doing a lab and I'm trying to understand exactly why I'm using the tool "minus". I have a raster which I'm calling "heights". I also have two rasters with water surfaces and watercourse. I have ...
0
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0answers
43 views

Using tool “minus” in height model?

I'm doing a lab and I'm trying to understand exactly why I'm using the tool "minus". I have a raster which I'm calling "heights". I also have two rasters with water surfaces and watercourse. I have ...
0
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0answers
18 views

Buggy intermediate datasets in map algebra

I created a for loop to perform a (simplified here) series of operations over tiles from a larger dataset. My initial code looked like this: ext_template = bingmean_odd totalextent = arcpy.Describe(...
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3answers
182 views

Working with 2 rasters, having different extents but same resolution, in ArcGIS raster calculator?

I am working with 2 rasters, having different extents but same coordinate system and resolution, in Arcgis 10.5. The larger raster has 0 and smaller raster has 1 values. I want to make a new raster ...
0
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1answer
53 views

Converting DEM units using Map Algebra and Python

I am trying to write a bit of code that combines a bunch of DEMs that match up perfectly and convert the elevation values of the pixel cells from meters to feet. This is all using Pyscripter and ...
1
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2answers
81 views

Reclassify in python doesn't reclassify things

I'm trying to reclassify the pixel values of NLCD_2011 data to a binary representation of developed vs. undeveloped land. import arcpy arcpy.CheckOutExtension("Spatial") nlcd = ('file ...
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0answers
72 views

Saving rasters in Arcpy loop

I'm trying to do Map Algebra on a bunch of rasters by iterating through a for loop and saving them in an empty geodatabase. However, they aren't saving properly. Only the last raster is created and it ...
2
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0answers
62 views

Map Algebra loop only creating one raster

I'm trying to transform a bunch of rasters in arcpy according to specific functions to create suitability rasters. This portion of the code is supposed to find all the rasters with interpolated ...
1
vote
1answer
71 views

Merging two rasters, obtain only highest values, overwrite raster in ArcGIS Desktop?

In order to run a hydrologigal analysis I'd like to to merge two raster datasets (DEM and buildings) to get as result one raster with only the highest values (elevations) of both. In other words: To ...
2
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2answers
71 views

Applying Map Algebra to List of Rasters and Saving New File in New Directory?

I am trying to multiply each raster by coefficient using Map Algebra in Python. I receive the following error for the code below: calcRaster.save(calcRasterName) AttributeError: 'unicode' object ...
0
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1answer
90 views

ExecuteError: ERROR 000539: Error running expression: rcexec()

from arcpy import * arcpy.CheckOutExtension('Spatial') arcpy.env.workspace=r'D:\work\USA' #pathway to all rasters in workspace directory rasters = arcpy.ListRasters('*.tif') # Local variables: ...
1
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0answers
74 views

Iterate a multistep Map Algebra

I am trying to write my first ArcPy script to iterate a Band Math process with requires a few steps. The uniterated, working script for a single group of bands in one Landsat scene is: #import ...
1
vote
1answer
178 views

ArcGIS Raster Calculator Con-Statement

I am trying to manipulate bad pixel values in a raster by using the Con-Statement via ArcPy. Using the build-in Map Algebra function "Raster Calculator", the results are good. To transfer the work ...
1
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1answer
700 views

Gdal_calc NDVI for many rasters

Can anybody help me to solve a problem with running gdal_calc for many rasters? I have several multispectral images and I need a batch to perform NDVI calculation. I started with gdal code for one ...
1
vote
1answer
75 views

Get argmax of PostGIS raster bands

I have a four band raster, and I would like to generate a new raster that has the argmax of the bands for each pixel. For example, if band 3 holds the maximum value at that pixel, the new raster ...
2
votes
2answers
1k views

Calculate NDVI using ArcPy Spatial Analyst

My goal is to calculate NDVI using map algebra syntax. import arcpy from arcpy.sa import * red_band_raster = (r"C:\B3.tif") nir_band_raster = (r"C:\B4.tif") #Calculating NDVI float raster ...
2
votes
2answers
2k views

Adding two rasters using map algebra in ArcPy?

I want to simply add two rasters within a python script using map algebra, which from what I understand is the equivalent to adding two rasters in the raster calculator. If I do this using raster ...
1
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2answers
68 views

Arcpy Map Algebra: Maximum Number of Nestings

When using Map Algebra you can nest multiple expressions as can be seen in the Esri example below. Is there a limit on how many long of a statement you can have OR a limit on how many Con statements ...
4
votes
1answer
186 views

Passing additional arguments to ST_MapAlgebra callback?

I've written a custom callback function for ST_MapAlgebra and I want to pass additional arguments to it. The function is pretty useless - it just generates a raster filled with normal random values ...
1
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0answers
385 views

ArcGIS Raster Calculator Error 000539

I am getting the error-000539: Error running expression: rcexec(). I've seen that other people have this same issue but I am not sure how to fix mine. I just want to average the values of 10 rasters, ...
1
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1answer
109 views

Error using random raster for raster calculations

I have created a random raster in ArcGIS Pro using the following Python command: arcpy.CreateRandomRaster_management(Path, "rnraster", "INTEGER", "", 10) Which works fine. Performing map algebra ...
1
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2answers
48 views

How to set urban areas to NoData in a DTM?

In ArcGIS 10.1, I have a DTM and a polygon layer representing urban areas. For processing reasons, I want to exclude the urban areas from the DTM (i.e., setting urban areas to NoData). How can I ...
4
votes
1answer
97 views

Getting rid of small objects on raster in ArcMap?

What I want to do is to get rid of 'dark' objects which are on the green areas. My input looks like this: And I want my result to look like here: Raster value of green is 1, the rest has 0 value....
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0answers
81 views

Writing Raster Calculator Map Algebra expression?

I have the following map algebra expression to be used in Raster Calculator. The "Output raster" should satisfy the following conditions: If (IsUseAWSSites == True): if (InputRaster exists): ...
2
votes
1answer
114 views

Checking if input raster exist or not in Raster Calculator?

I am with Raster Calculator in ModelBuilder on ArcGIS Desktop 10.2. In the Raster Calculator's Map Algebra expression window, I need to check if a Raster dataset has already existed or not. Can ...
3
votes
2answers
183 views

Looping Map Algebra using Python

I am new to Python and am having difficulties trying to loop multiple rasters into a conditional statement. I want to extract all land-uses that have the value 21 from a folder with three different ...
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1answer
199 views

Raster processing and query PostGIS [closed]

I have around 2000 raster file in TIFF format of 4.5Gb size. I want to store them in a PostGIS DB in order to do some mapalgebra operation between them and than query the results of the calculation ...
1
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1answer
66 views

ArcPy map algebra equivalent for “any”?

I have binary (0-1) rasters. I'm trying to do an operation equivalent to: z = arcpy.sa.Con((Raster(a) | Raster(b) | Raster(c) | ... | Raster(y)) where the raster files a-y are dynamically generated ...
2
votes
1answer
471 views

PostGis's ST_MapAlgebra rasters do not have the same alignment

I'm having a problem with ST_MapAlgebra. An error stating The set of rasters provided (custom extent included, if appropriate) do not have the same alignment is shown. I've been trying to know where ...
0
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1answer
58 views

Execute Equation in Map Algebra

I am in the process of shifting my raster calculations over from manually entering them into Raster Calculator to executing them in a Python script. I am curious if I can execute equations such as the ...
1
vote
1answer
291 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 ...
1
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2answers
168 views

While loop in Map Algebra ArcPy, associate output raster name with input raster

I have an ArcMap document open with LandSat images from one day in different bands as rasters. They're named: LC80541162014003LGN00_B1.TIF LC80541162014003LGN00_B2.TIF and so on, B1 through to B9 (...
0
votes
2answers
172 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 ...
2
votes
1answer
541 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 ...
1
vote
1answer
347 views

Raster result is different for arcpy.sa CON and arcpy.gp.Con_sa

I have to add two rasters, one bigger than the other, but before adding I have to set the value of NODATA of smaller raster to the value of bigger raster. So i used the following code to do it: ...
3
votes
1answer
147 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 ...
1
vote
1answer
119 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. ...
3
votes
2answers
331 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 ...
1
vote
1answer
409 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 ...
1
vote
1answer
397 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 ...
2
votes
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 ...
-1
votes
1answer
720 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, ...
0
votes
1answer
689 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 ...
1
vote
2answers
352 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 ...
6
votes
2answers
618 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 ...
2
votes
0answers
403 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 ...
1
vote
2answers
92 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 ...
0
votes
1answer
74 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 ...