Tagged Questions

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

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1answer
85 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
103 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 ...
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2answers
97 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 ...
1
vote
1answer
91 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
votes
1answer
113 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 ...
1
vote
2answers
144 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 ...
1
vote
1answer
120 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 ...
1
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1answer
60 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
93 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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votes
0answers
62 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 = ...
1
vote
1answer
77 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 ...
1
vote
2answers
213 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: ...
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2answers
198 views

Change detection with raster calculator

After applying the Diff operator of the raster calculator in arcgis to view changes in land use, would like to see the areas of increased and areas of decreased. This is possible using the raster ...
0
votes
1answer
89 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 ...
0
votes
1answer
174 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
votes
1answer
64 views

Translating to Raster Calculator?

I am taking the Learning Spatial Analyst course, which is very good but written for Version 9. I and my students are using Version 10, so some of the syntax for Raster Calculator have changed. Can ...
-1
votes
1answer
148 views

Raster Calculator Workaround in Arcpy for Suitabiliy Analysis

This is my first attempt at a complex stand alone python code. I am self teaching the arcpy module, well at least attempting to. I am having a great deal of difficulty getting my site suitability ...
0
votes
1answer
52 views

IF (there are three or more developed cells in the Moore Neighbourhood of a cell) THEN (the cell is developed)

Hi I need to create an expression for that principle, so far I have figured out CON ("FocalStatisticsSum" >= 3,"FocalStatisticsSum"="FocalStatisticsSum"+1) Although I pretty sure I am missing ...
1
vote
1answer
152 views

Raster vs. Raster Scatter Plot in ArcGIS

I created two raster datasets from the same world view 2 image. One dataset is NDVI, the other is a normalized surface water index (NDSWI). I would like to create a scatter plot for a pixel by pixel ...
0
votes
1answer
98 views

Define a circular neighborhood for a custom raster calculator function? [closed]

I have a 1 meter resolution raster containing values from 0-3 which represent increasing levels of habitat suitability. I need to identify circular regions that have contiguous pixel values. For ...
0
votes
0answers
260 views

Help with scripts for processing raster files with the raster calculator in QGIS

I am trying to process some raster files using python scripts in Qgis 2.20, and I have been having trouble finding any documentation on using raster calculator in scripts being run in the processing ...
0
votes
1answer
23 views

Error 000539 - Band_# not defined

I'm trying to do an NDVI analysis of a some World View 2 imagery. It seems no matter what if I enter the term Band_# for any of the 8 bands I get the same error.
0
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2answers
117 views

Find the minimum elevation pixels from an elevation raster using arcpy

I want to create a python script to find the minimum elevation pixels from an elevation raster (aster,srtm) using arcpy and arcmap 10.1. The purpose is to reclassify these pixels. I have tried but I ...
3
votes
1answer
168 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 ...
0
votes
0answers
13 views

map composer grid annotation in DMS format [duplicate]

I have digitized a map using CRS EPSG:4326 in QGIS. In Map Composer I set the grid. I can't get the annotation to display as DMS (degrees-minutes-seconds) rather than DD (decimal degrees) format. What ...
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0answers
69 views

How to produce a hazard map using slope and geology information

for my project I need to display a landscape's susceptibility to erosion. I created a slope-map out of my DEM and added the bedrock geology as a polygon-feature shapefile. Now I want to tell ArcGIS ...
0
votes
1answer
92 views

How to isolate certain raster values using raster calculator?

I have a one band grayscale image. It has values 0-63 within the band. I need to isolate some of those values. Is there a way to do this in the raster calculator? QGIS 2.2//Windows 7
0
votes
1answer
102 views

How to measure Fracture in area using ArcGIS Cut and Fill?

I want to measure fracture in an area.I know I have to use cut and fill tool. But I wonder how to give input for this tool? it has Input before raster surface and Input after raster surface ! what ...
0
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0answers
57 views

Extract raster values under under each polygon buffer in qgis

In qGIS: I have raster file and >100 points. I constructed buffers polygons (vector-->geoprocessing-->buffer) around each of the points. Than I clipped (raster-->extraction-->clipper) the raster file ...
1
vote
1answer
303 views

How to make polygon volume in TIN surface?

I want to measure surface volume of an area in different elevation layer. For measuring the surface volume I have to make a Polygon Volume as well. I have problem with making this polygon over the ...
1
vote
2answers
778 views

Create an X,Y latitude and longitude grid from an raster

I have a satellite image (LandSat 5), I want create a raster with X,Y coordinates, this is possible in Model Builder of ArcGis 10.0? or other option. I know that the option $$YMAP ($$XMAP) not work ...
1
vote
3answers
544 views

Topography: How to get the x,y,z coordinates of highest or lowest point/pixel of a raster GIS?

Given a .tiff topographic raster image with mountains and deep sea, I am looking for the x,y,z specifics of the highest or lowest point. The x,y,z values being: altitude (z-coordinate) latitude ...
0
votes
1answer
35 views

How to map factors and their relative importance in ArcGIS 10.1 for Desktop?

I want to know how I can calculate a map from a set of factors (in the form of raster layers) and Their relative importance for example: slope 20% lithology 10% . . .
0
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0answers
58 views

Efficient manner to buffer streams with multiple attributes?

I need to buffer a very large, complex hydro vector layer based on different water quality designations and surrounding slope. Different water quality classifications have different buffer ...
1
vote
1answer
319 views

the min and the max in raster calculator Arcgis 10.1

Can you help me where I can find or how to calculate the minimum and maximum with raster calculator in arcgis 10.1
1
vote
1answer
127 views

Running model in QGIS gives ERROR: Missing mandatory parameter?

I am trying to make a batch model to convert band 2 and band 1 MODIS 8 day composites into NDVI. The input files are in tif format, but I want the output to be saved in Idrisi .rst format. I am ...
0
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0answers
28 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?
4
votes
1answer
223 views

Calculating Topographic Exposure with Raster Calculator

I need you help trying to calculate Topographic Exposure (TOPEX) on a DEM in ArcGIS. I am trying to figure out wind exposure on a DEM with 25m cells. There is a great blog post where someone explains ...
2
votes
1answer
75 views

Raster calculator help needed

I have time-series data (rasters) from which I need to calculate the direction of change (increase, no change or decrease) for every pixel from one time-step to the next. I further need an output ...
1
vote
1answer
49 views

How can I assign Raster2 pixel value to Raster1 where they overlay?

I want to assign Raster2 pixel value to Raster1(Bigger) where they overlay. Both of them have the same cell size. How can I accomplish this process in ArcGIS Desktop? (Like Raster Calculator ) ...
2
votes
1answer
161 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 ...
1
vote
1answer
210 views

Floating point calculations in QGIS

How do I manage floating point calculations in QGIS? I have carried out 3 consecutive calculations on landsat bands. I end up with 32 bit floating point rasters on which I can't carry out a 4th ...
3
votes
1answer
139 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, ...
2
votes
1answer
159 views

How to iterate GRASS region definition?

I am using GRASS r.skyview command (v.7, Windows) to determine "urban canyon effect" on pollution due to the presence of buildings. The command nicely works, unfortunately I need to process a very ...
0
votes
1answer
48 views

QGIS Raster Calculator dialog doesn't resemble that in documentation

I'm very new to QGIS. Raster Calculator looks (from online sources) like it ought to have all kinds of buttons and fields. Mine is rather stripped down. I have two rasters open, and I just want to ...
3
votes
1answer
640 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 ...
1
vote
2answers
204 views

How to change raster cell values within a polygon using QGIS GUI?

I would like to know how to change the values of raster cells which are within a polygon, leaving all cell values outside the polygon unchanged. I would like to subtract 1.5m from each raster cell ...
4
votes
2answers
329 views

Using Python and open source modules, how can I perform Raster Calculator functions?

I would like to perform mathematical functions similar to those you would use Raster Calculator for in ArcMap, however I'd like to do it in Python without using the Arcpy module. I have the osgeo ...
1
vote
1answer
143 views

Raster Calculator error

I'm trying to use the Raster Calculator inside ModelBuilder to get rid of null values, but I'm hitting a snag. I'm using the expression: ...
0
votes
0answers
40 views

How to find difference between terrain and groundwater potential map?

I want to find the difference between a terrain map and groundwater potential map to show where it is possible to apply SUDS (sustainable drainage systems) but the units makes no sense. First in ...