Raster is a data format consisting of regular grids of values, usually stored in an image-like format.

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Where can I download a raster dataset with the latitude and longitude of each pixel in geographic projection?

I want to do raster calculations in QGIS based on the latitude and longitude of each pixel. The calculations will compute the area of the pixel, but also do other calculations for various projections ...
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24 views

Invalid drop item: Calculate statistics

I have a number of rasters that I need to calculate histograms for. These are continuous rasters from 0 to 294.208 - many decimal places. I need to be able to classify the histogram down to at least ...
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17 views

Replacing white or black by alpha channel in raster in QGIS 2.8

I'd like to replace black or white in black and white raster in QGIS 2.8. I perceived that in some other raster where "nan" value automatically occurred and only white or black is being displayed.
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42 views

calculate Z~F from polygon and raster

I have a polygon shapefile and raster layer. How I can calculate the elevation and area (Z~F) relationship for each polygon by using QGIS or ArcMap?
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47 views

PostGIS: intersection of a polygon with 2 rasters

I'm trying to get the intersection of a Polygon with 2 raster layers in PostGIS. The rasters have the same size and pixel size and I'd like to retrieve for the polygon a list of something like that: ...
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15 views

Error in merging two raster files (precipitation) in QGIS

The newly computed geotiff shows the extent of both raster layers, but only the data of one. If I use identify features tool it gives me only the values of the visible part not of the other part. I ...
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16 views

Raster images overlaying each other but shouldn't

When I open a new map document and drag different raster images into the map the images stack on one another rather than form the complete image of a country. When I try zooming in, the multiple ...
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11 views

Recentering a tiled raster table in PostGIS?

Does anyone know a nice and easy way to recenter a tiled raster table in PostGIS? By recentering I mean that I have a raster that is centered on the Pacific, but I need to recenter it on ...
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52 views

ArcPy reading a raster in a moving window?

I typically read large raster data using gdal and setting up a moving window of 256*256 pixels (for example). I recently had to do some processing using arcpy, so I did the same thing, using ...
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31 views

Substract 2 rasters with Raster Calculator in ArcObjects (VB.NET)

I'm having a hard time substracting 2 raster with ArcObjects sdk 10.1. I keep getting a nullreference exception at the gp.execute() method, but I can't figure out where the problem is, I recall ...
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37 views

How to create ROI in Semi-Automatic Classification plugin QGIS

while trying to classify landsat images, I get the following problem: I click on the pixel I want to define a ROI, but the ROI polygon that the plugin creates appears in a different part of the image ...
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21 views

How does `ST_Union` treat NULL values in a raster?

My question is about how ST_Union of rasters containing NULL values are handled. For example suppose I have two rasters that intersect but the values of the intersection are NULL in one of the ...
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37 views

Zonal Statistics for multiple rasters

I'm trying to create a timeseries of raster data (one layer per year) by polygon (Administrative regions). Is there any way in QGIS to perform Zonal Statistics for multiple years (without having to ...
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44 views

When subtracting two raster with different cell sizes using raster math, what value is used for smaller cells?

After reading the answer to a similar question (What will happen if we subtract two raster with different cell size using Raster Calculator?), I am still left with a question. When the raster with ...
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21 views

Selecting all pixels above a given value in a raster in PostGIS

I have a raster with one band whose value represents the date of the occurrence (a sequential integer). This raster file gets updated regularly, and each time that happens, I need to run a process ...
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28 views

Merge raster tiles in PostGIS

I have several raster tiles that are adjacent and non-overlapping, so they form a mosaic. I am trying to merge two adjacent rasters using PostGIS but am getting an error that they do not have the same ...
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52 views

SRTM DEM and satellite DEM fusion

I have a SRTM DEM and a DEM derived from satellite (Cartosat). Both the DEMs are registered perfectly. Now I want to carry out a DEM 'fusion' process to derive a higher quality output DEM. I am not ...
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19 views

Transforming climate text data to raster in ArcGIS Desktop?

I have climate data in text files with no header in the format below from Udel's climate program. Each row has a lat, lon, and a temperature for each month (14 columns total) from 1900-2010. I need ...
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45 views

Remove Frame Border from USGS scanned images in ArcGIS

I have a couple of USGS scanned maps like I want to remove the frame border from these images so that I can use them in ArcGIS. Is there algorithm or python script that I can run to remove the ...
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19 views

Second order rectification display problems

I'm using GRASS 7.0 to geo-rectify oblique images taken from a fixed altitude and using RTK-GPS data as a GCP (as a vector file) for the process. The survey area is very small and flat, so I'm not ...
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21 views

How to best import a US Map Schematic?

I would like to use the following wiki US Map schematic as a background to my map work. (http://en.wikipedia.org/wiki/File:Blank_US_Map.svg) It is a .svg file, and GeoReferencer is unable to import ...
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55 views

Point to raster: QGIS vs ArcMap

I have an equidistant point grid (0.5m) and created a raster from it in QGIS and ArcMap, with different results: QGIS: Raster -> Conversion -> Rasterize Result: raster, with points in the top left ...
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62 views

moving window regression on raster stack in R

I want to perform a moving window regression on every pixel of two raster stacks representing Band3 and Band4 of Landsat data. The result should be two additional stacks, one representing the ...
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How to create a map series of different rasters (same location, same legend)?

We have hundreds of raster images at the same location (same dimensions, pixel size, projection, etc.). We would like to display each one in its own map using the same legend with the same vector ...
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34 views

Extracting area from DEM Raster?

After applying constraints to the DEM I polygonised the raster (using GRASS r.to.vect.area) The result is shown below with a lot of vector with resolution = [30 * 30] Is there any solution to make ...
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58 views

Convert polygon to raster and give value to null cells

Is there a way to convert polygon features to raster while also populating null cells with a specific value? As in, can I create a raster from a polygon shapefile and have the tool populate all null ...
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41 views

Combining information from one raster with another raster

I have two rasters, A and A1. Raster A is the image below that is greenish and has the following attribute table: The table has two fields that I need: Value and class_name Raster A1 is the ...
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46 views

Modifying DEM elevation data in QGIS using a polygon

I've tried searching through the existing questions but am struggling to find a succinct answer to what I am trying to achieve. For background, I am running a flood model in TUFLOW to help support a ...
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31 views

In ArcSDE, SQL Studio Manager 2012, How to get pixel data using a point layer?

I was using 'where' and 'ST_Intersects' with polygon data to get values 'under' my point layer. Example: Select rd.[FORESTNAME] as Forest, Count(Distinct morel.[OBJECTID]) AS Observations From ...
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37 views

How to check if a file is a valid raster image?

How to check if a file is a valid raster image? Valid in the sense of not being corrupt, the file record is complete. The GIS corollary to "zip --test somefile.zip" to test if an archive's integrity ...
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44 views

Landsat Data to Map Slums in India

I am working on a project to answer the following geographic question: How much have slum areas increased in Mumbai, India, since the 1970's (or earliest data). I have downloaded LandSat imagery and ...
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77 views

How to avoid “Unable to compute a transformation between pixel/line”?

I am trying to re-project from Equi-rectangular to the NASA global EASE grid (Equal Area Scalable Earth) grid 1383 586 with a ~25 km cylindrical projection (ESPG=3410). The file is provided as HDF5. ...
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Where to find QGIS geoprocessing results?

Is there a way to access in QGIS 2.6.1 something like the Geoprocessing Results window found in ArcGIS? The History and Log window in QGIS appears to show the geoprocessing results from SAGA, OTB ...
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25 views

QGIS - r.* commands not found

I'm very new to GIS and have recently installed QGIS on my mac desktop computer, running Yosemite 10.10. I'm working with DEM data for stream network extraction, but the majority of grass raster ...
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86 views

How to OCR topographic maps

I have old topographic maps that i have scanned and converted into pdf in Actobat XI 11. I need this pdf to be text-searchable (not mere image). To do this i tried text recognition in acrobat but it ...
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57 views

QGIS - quickly style categorical map

Example situation: a raster map that denotes various provinces in a country, each indicated with a unique value. Goal/question: quickly (for 'preview' purposes, not making a publishable map) assign ...
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22 views

Calculating Autocorrelation in Different Zones

I'm an intermediate-ish user of ArcGIS 10.2 (win7 pro, hardware robust enough to handle very large datasets and computationally intensive analysis) with perhaps a simple problem that's evading me ...
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39 views

How legitimate is smoothing raster data that has been converted from polygons?

I am interested in applying this methodology to census block data after conversion from a raster: http://rutgerscps.weebly.com/uploads/2/7/3/7/27370595/censusdatasmoothing_brief.pdf Basically, the ...
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65 views

GRASS GIS r.walk issue

I have been playing around with GRASS GIS to do a simple cost analysis of getting from point A to point B. I have a DEM clipped to the study area, a raster containing the friction costs, as well as ...
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73 views

Add Surface Information alternatives in QGIS?

Is anyone aware of a single tool or possible routine of tools in QGIS (2.6) which emulate the results of the ESRI 3D Analyst tool 'Add Surface Information'? I have several polygon shapefiles (some ...
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39 views

Extract by mask/copy raster a RGBA (4bands) raster results in a greyscale image in photoshop discarding all RGB composite info

I used a polygon Shapefile to extract by mask (ArcGIS) the sea area from a RGBA (4 bands aerophoto) raster. The Extract by Mask caused up-sampling from 16 bit (my raster's initial pixel depth) to 32 ...
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119 views

Performing Maximum Likelihood Classification in R

I'm trying to perform maximum likelihood classification of landsat imagery using R, I have been searching for a package that implements it but so far I haven't found it. What is the easiest way to ...
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63 views

Calculate surface map from PostGIS

We need to create surface maps from the website. The data is stored on PostGIS (2.1) as a table of Point geometries with a field indicating a thematic value. The optimal solution would be to produce ...
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54 views

ArcGIS Split Raster tool results in black rasters

I have a rather large raster that I am trying to split into small tiles in PNG format to upload to Autodesk Infrastructure. I came across the Split Raster tool and thought it would do exactly what I ...
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44 views

Problem with QGIS raster interpolation from a point shapefile after duplicating the shapefile

Let me explain a problem I had with QGIS to see if somebody else has experience it. I created a raster from a point shapefile through the Raster-> Interpolation menu with no problems. After that, I ...
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57 views

Does interpolation create a vector or raster?

I have been reading about interpolation and am trying to understand whether interpolation results in a vector or raster. Say I have a layer of points and I am interested in creating a raster that fits ...
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OpenLayers/Geoserver - can I create a tiled, zoomable raster layer?

Still a relative newbie with Geoserver and OpenLayers. Developing an application with Geoserver in the back, OpenLayers (3.0) in the front. I have a requirement to display imagery on top of a base ...
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84 views

Add Rasters to a new GDB/Mosaic Dataset in ArcGIS ModelBuilder

I'm attempting to add rasters to a new mosaic dataset in a new file geodatabase, all in the same model. However, the Add Rasters To Mosaic Dataset tool does not recognize the NewMosaicDataset or the ...
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24 views

How do you symbolise a 32-bit raster in ArcObjects?

For rasters that are ABOVE 16-bit - you cannot apply a colormap - so what is happening when you symbolise in ArcMap a 32 bit raster, it's certainly possible. I'm trying to emulate this funcitonality ...
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29 views

Worldfile incorrect? Puzzler: all resources supplied!

Trying to manually create a worldfile for gif images of surface currents supplied by the navy here. I have QGIS and am decent at using it but the world file tool is failing without error on me (even ...