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

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Random sampling of raster using R

Is there a straightforward way of randomly sampling a raster so that the output of the process is a raster? I'm using an example that I found on the r-sig-geo list and I have also tried the ...
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2answers
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Extracting roads out of Landsat raster images

For a study into the expansion of road networks in the rainforest I am trying to extract roads out of Landsat images. We already have sharp and cloud-free composites on which the roads are clearly ...
8
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1answer
8k views

Converting a polygon into a raster using R

I'm trying to convert a shapefile into a raster within R. My approach is to read in the raster as follows: library(rgdal) # Loads SP package by default demo <- readOGR('F:/data/', 'shapefile') # ...
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2answers
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What resampling technique should be used when projecting aerial photos?

I'm doing some time-intensive projecting of aerial photos, and I'm curious - what resampling technique is best to use on aerial photos? In ArcMap, my options are NEAREST, BILINEAR, CUBIC, and ...
11
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1answer
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Method to shade or overlay a raster map to reflect time of day and ambient light

I have a daytime raster of my study area. I have 20+ counters in the study area that count "stuff" with a timestamp. Using PyEphem I determined the type of ambient light for each collected data ...
8
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1answer
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Best Way to Handle Many Raster Files in QGIS?

I have a project with a large number of raster files, but it is becoming very slow. I wonder which is the best way to handle all this. I'm simply georeferencing these files creating .wld file (geoTiff ...
6
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3answers
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Raster: How to get elevation at lat/long using python?

I was wondering if anyone has some experience in getting elevation data from a raster without using ArcGIS, but rather get the information as a python list or dict? I get my XY data as a list of ...
5
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2answers
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r - increase speed of crop, mask, & extract raster by many polygons

I'm extracting the area and percent cover of different land use types from a raster based on several thousand polygon boundaries. I've found that the extract function works much faster if I iterate ...
3
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1answer
495 views

Random-Forest Classification of 10cm Imagery for species-distribution in R (no point-shapes)

I'm actually trying to classify 10cm-resolution images with the RF-package. I do this to separate some species in the forest, seen on my images. While I was searching for an answer, I found the ...
13
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5answers
842 views

Dikes extraction from DEM

I do have DEM of 1x1 meter and original LiDAR point cloud in .las, that DEM is made of. I need to extract river dikes (highest points of the dikes) to vector feature (point, polyline). Any idea for ...
12
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6answers
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Rasterfile clipping error: Cannot compute bounding box of cutline

I have a raster file and want to clip it, a vector file is supposed to be the mask layer. I use the most obvious method (Raster->Extraction->Clipper). No matter what I do, I get this error (see pic): ...
11
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2answers
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How can I improve my Georeferencing results?

Background This is my second question related to georeferencing naked raster maps in order to re-visualize them on different coordinate systems and in conjunction with other data layers. The previous ...
7
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2answers
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Splitting raster into smaller chunks using GDAL?

I have a raster (USGS DEM actually) and I need to split it up into smaller chunks like the image below shows. That was accomplished in ArcGIS 10.0 using the Split Raster tool. I would like a FOSS ...
6
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2answers
2k views

creating a raster of the residuals of a regression between two rasters

I am trying to create a raster of the residuals of a regression between two rasters. i.e. I would like to carry out a regression of one raster against another of the same extent and plot the residual ...
6
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2answers
1k views

Creating shapefile of satellite image footprints?

I'm looking for a tool or a workflow to compute satellite image footprints, for a large number of images across directories, and produce a shapefile. Ideal work flow would be: fire up tool point to ...
5
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3answers
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How can I specify the CRS of a raster layer in pyqgis?

I manipulating netcdf raster data from the QGIS python console. The metadata of my netcdf file does not provide the Reference system. However I know it is 'EPSG:4326' I am writing a python script to ...
3
votes
2answers
5k views

How to convert .geotiff --> .tiff?

How to convert .geotiff files to .tiff files (ordinary plain images)? Basically, I have cropped the image to a rectangle of interest and knowing its left-lower location and having chosen the pixel ...
9
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3answers
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How to reclassify a very large land cover dataset?

Consider the NLCD2001 Land Cover dataset for Alaska (download link). I need to reclassify this dataset so that only pixels of value 41, 42, and 43 are preserved; all other pixel values should become ...
7
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0answers
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Loading raster from PostGIS DB into QGIS: succeeded yesterday, fails now [closed]

I have a PostgreSQL(v.9.2)/Postgis(v.2.0.3) database which includes raster layers (added through raster2pgsql). To open them in QGIS (v.1.8.0-Lisboa), the "Add Postgis layer" menu will not work; ...
7
votes
1answer
357 views

How to create points around edge of viewshed results?

Is there a tool or module, or multiple tools, in ArcGIS that will allow you to automate the creation of points around the outer edges of a viewshed? What I am trying to do is gather data about the ...
7
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7answers
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How can I align two non-coincident equi-resolution raster grids?

I have two rasters: a digital elevation model (DEM) and a Landsat band. The grid resolution of both is 30 m, but the grids are not coincident (see image: the dark raster on top is the DEM; the light ...
6
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2answers
157 views

How to speed up this script in QGIS?

I am a new in PyQGIS, I want to create a Point layer from a raster layer. In table of point layer created, there is 3 fields by name of "X_coord", "Y_coord" and "Azimuth", each point in Point layer ...
6
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1answer
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Python equivalent of gdalbuildvrt

Is there a way to perform the same task as the gdalbuildvrt utility using GDAL Python bindings? So far I have not found any way to do this other than creating a vrt of a single dataset and manually ...
6
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1answer
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Loading a raster using QGIS into a PostGIS2.0 enabled database

Following on from my attempt to install a postgresql 9.1 db with postgis 2.0 on windows 7, I am trying to figure out how to load a raster. I have successfully loaded a shapefile, and am trying to do ...
5
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1answer
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How to extract pixel value counts from a raster in QGIS?

How does one go about obtaining a summary of the counts of cell values within a raster in QGIS? I know QGIS is doing this, in order to provide the summary statistics and histogram in the properties of ...
5
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3answers
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Loading raster data to postgis

I'm a newbie in GIS technology and need some help in loading a rainfall radar raster data into PostGIS. The raster image is shown here: What I need is to store in the database the radar ...
5
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2answers
3k views

How to Merge Raster Datasets of Different Resolutions?

I have two DEMs in .tif format and I am looking to merge the two. The main problem with merging these are that they are different resolutions (one is 10m and one is ~20m). Also, another problem with ...
5
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1answer
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Why does QGIS's Clipper tell me “Computed -srcwin falls outside raster size” and how do I address it?

I'm trying to clip a heightmap to a small area that I'm interested in. When I attempt to use Raster > Extraction > Clipper I get an error dialog with the message ""Computed -srcwin falls outside ...
5
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1answer
382 views

Unknown Coordinate System on old drawing

I work with many old civil engineering documents, and occasionally I'll need to georeference one which has coordinates pairs listed at many given points but does not list which coordinate system these ...
4
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2answers
376 views

Combine raster values for overlapping cells of multiple rasters

How do I combine the values of cells for 3 rasters for cells where they overlap. I want the output raster to cover only the area of the overlap for the 3 rasters and the output cell values to be a sum ...
4
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1answer
134 views

Why are raster z-values changed when reprojecting?

I have raster data with height values (z). When I try to reproject/warp the raster to Gauss Kruger 3, the z-values are changing (several meters). (The data is already GK3, but I have to reproject ...
4
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3answers
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How to speed up Postgis raster layer display in QGIS?

i've been importing some digital orthophoto geotif files into postgis 2.0.1 via raster2pgsql tool (i also made 3 levels of an overview table - pyramid). Then i tried to import the layer into qgis via ...
2
votes
1answer
117 views

Counting overlaps between raster files using ArcPy?

Would it be possible to simply detect and count overlaps between raster files, i.e. not polygons against rasters, using arcpy? By default I don't have the spatial analyst extension for ArcMap 10.1 but ...
9
votes
2answers
5k views

How do I layer stack rasters in QGIS?

I have some multi-spectral data, where the individual bands are separate Raster files. How do I layer stack these rasters so that I get one raster with 3 bands instead of 3 different rasters? This ...
8
votes
1answer
10k views

How to crop raster layer?

Can anyone tell me how to crop a raster layer in QGIS? I want to make contours from a section of a layer, and including the whole layer will create far more data than I need and slow down the ...
7
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5answers
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Continuous color band for a raster legend in QGIS composer legend

I'm looking for a way to insert continuous colour legend for a raster layer. I managed to create discrete symbols with values along the bar, but I would like to have a continuous bar with some values ...
7
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4answers
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Installing 1-band color raster color table?

I would like to use the "1-band raster colour table" extension. I'm using QGIS Wroclaw 1.7.4. In the plugin installer I can't find this extension, even I quote for third party extensions thing. Does ...
7
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3answers
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Creating a raster surface of overlaps from vector polygon shapefiles?

Basically what I'm trying to do (in ArcGIS 10) is to compare three vector files in order to create a 'comparison' raster layer. I tried using Data Comparison (under Data Management tools) but it ...
6
votes
2answers
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How to make RASTER from irregular point data without interpolation

I was trying to make a raster image from an irregularly spaced point database. The data looks like- > head(s100_ras) x y z 1 267573.9 2633781 213.29545 2 262224.4 2633781 ...
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4answers
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How to sum up pixel values in QGIS?

I need to know the value of the sum of all pixels in a raster. However, in the Statistics section of the Metadata tab in Properties, under Sum of All Cells it always indicates 0.00. I have tried with ...
6
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3answers
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Clipping a raster using a polyline or polygon

I have a large raster created from values that cover the whole United States and Alaska which are both polygon and polyline features, this raster was caluclated using Spatial Analyst IDW ...
4
votes
1answer
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In ArcGIS 9.3, how do I split a 3-band raster (.tiff) file and summarize the band values?

Using ArcGIS 9.3, I would like to make a new, single-band raster file that includes only one value: a summary of the three existing bands. The composite band is currently a composite .tiff file. ...
4
votes
2answers
2k views

Calculating Net Primary Production (NPP)?

When I calculate Net primary production (NPP) for a local scale, what kind of software should I use? I always use ENVI, ERDAS IMAGINE, ArcGIS for Desktop and IDRISI. Is it possible to use these ...
4
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1answer
657 views

affine transformation on geotiff

I have a bunch of geotiffs stored in a PostGIS DB that i am mounting on my OpenLayers map. They all have the geoTransform information in them. I just want to know how i can mount them on my ...
3
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1answer
119 views

Processing large amounts of Rasters in R

I have 6500 processed and clipped rasters that indicate snow levels on a daily basis in the northern hemisphere. I need to create a raster that represents a sum of the snow for the season. The winter ...
3
votes
1answer
2k views

Re-project raster image from Mercator to Equirectangular

I have a raster image of the world map in Mercator projection, square 1:1 format. I want transform the image into an Equirectangular projection accurately. I assumed from my research that GDAL would ...
3
votes
2answers
779 views

How to translate (reposition) a .tif raster layer?

I'm starting to use QGIS for my thesis (environmental physics) and have to admit I'm pretty ignorant about it - I've always used Mathematica or Matlab. My problem is: I have a raster layer, in .tif ...
3
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1answer
540 views

Area precipitation using IDW

I'm having the following problem with IDW automation. I have a catchment and several gauging stations measuring daily precipitation amounts. I would like to interpolate the precipitation amounts from ...
3
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1answer
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How to Calculate Utilization Distribution Overlap Index (UDOI) in ArcGIS Desktop?

I was wondering if any of you happen to have any information on how to calculate the Utilization Distribution Overlap Index (UDOI) in ArcGIS 10? If I understand it correctly the UDOI takes two kernel ...
3
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2answers
570 views

Determine density or cover from a raster layer that has been clipped by a polygon

I am a very new GIS user using ArcMap 10. I have a raster layer of tree canopy that I have clipped so that the layer is in a polygon that is a circle with a 2km radius. I have done this for four ...