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

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R: Download a large DEM, change projection, and adjust to smaller scale

This is a process that takes just a few seconds in GIS software. My attempt to do it in R uses a large amount of memory then fails. Is there something wrong in my code, or is this just something R ...
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Manipulate .asc files in qgis

I have an .asc file and I want to import in QGIS. The standard way to open it is from "add Raster layer" ("import Raster Layer"), there is another way? I know is strange that ask but I need it. And I ...
6
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234 views

Transforming geostationary satellite image to lon/lat

The ICARE Data and Services Center distributes the SEV_AERUS-AEROSOL-D3 product in HDF5 format (http://www.icare.univ-lille1.fr/archive/?dir=GEO/MSG+0000/SEV_AERUS-AEROSOL-D3.v1.03/). The main ...
6
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2answers
807 views

How to decide how to “stretch” raster imagery?

I have to symbolize a digital elevation model. ArcMap offers many different setting for stretching the symbology which all give widely different results. Some stretch methods symbolize the data so ...
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2answers
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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 ...
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5answers
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Is there a way to clip an image with the basic ArcView package (9.3)?

Is there a way to trim a geo-referenced air photo to an irregularly shaped boundary? I tried the clip tool shown in my attachment, but it didn't work. It looks as though the output extent field ...
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2answers
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How do I calculate a weighted centroid with respect to a raster, e.g. population weighted centroid

In ArcGIS 10.0, how do I calculate the weighted centroid of a collection of polygons, where I want the weight to be a raster layer. In particular I am using a raster of population counts and would ...
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1answer
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Convert ESRI Shapefile to Raster using R - biggest polygon area to raster cell value?

I want to create a raster from an ESRI shapefile. Multiple polygons may exist in one raster cell. If so, I want to assign the attribute variable which occupies the biggest area of the raster cell. If,...
5
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1answer
277 views

parallelization of raster mosaic

I would like to create a raster mosaic of the national USGS NED 30m DEM (~50 GB). I'd like to leverage parallel processing using python multiprocessing module where possible. I'm using ArcGIS 10.0. My ...
5
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1answer
699 views

How can I create a pollutant dispersion raster in QGIS?

As my previous questions have indicated, I am working on an air quality problem where I have a dataset of industrial emissions that consists of a location (long, lat), and an annual volume of ...
5
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3answers
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What is a simple binary raster storage format which ArcGIS can read?

I have a C++ program that manipulates raster digital elevation models. I have been using ArcGrid ASCII format for results. It is simple to code and gets the job done, but it necessitates a decimal ...
4
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1answer
432 views

Raster to vector with gaps in Landsat ETM

I need to find size of water area from a raster (jpg) using QGIS 1.8.0-Lisboa. The raster is a Landsat image with gaps of data in it. I used Polygonize, but the output file shows wrong polygon size ...
4
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2answers
289 views

Measuring distance to roads using raster data in ArcMap?

I am using ArcMap 10.1 on a Windows x64 system. I am trying to analyse the driving force of urban land use land cover changes. I have 7 raster files represents distance to roads, distance to river, ...
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3answers
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using Python to calculate NDVI, output as a Geotiff

I need a script that can calculate NDVI from two separate input Geotiff files, then output the results as a Geotiff. I wrote following script, most of which is borrowed from various on-line sources (...
3
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1answer
907 views

How to speed up band math in R 'raster' package?

I have some GeoTiff rasters with over 100 bands in total, but they are not huge: resolution is about 1200x600 and total size is less than 7 mb. I'm trying to do a simple NDVI calculation: raster <-...
3
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1answer
497 views

How to cope with imprecision in floating-point grids?

I have a floating point grid/raster and will want to make all values rounded to the nearest tenth. I have converted to integer (added 0.5 for rounding), but the final floating point output grid is ...
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2answers
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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 ...
12
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3answers
342 views

What practices are available for modelling land suitability?

I currently use a "classic" raster based approach of dividing a study area into cells. All input layers are converted to rasters at the same cell resolution and given a suitability rating. A final ...
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2answers
5k views

Grid vs TIF vs IMG

As the title suggests both of the above three formats are raster files. In ArcGIS, apparently there's no difference between them. So what's the difference between these three formats?
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4answers
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How to “clean” and vectorize a raster map?

I'd like to make use of a geological map as shown in the example below, which is only a pretty small and downsized part of the map, so editing/redrawing doesn't seem to make sense in the end. My idea ...
9
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2answers
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Converting point data into gridded dataframe for histogram analysis using R?

I am very new at using GIS data and only modestly experienced with R. I've been reading about how to analyze spatial data using the spatial-analyst.net PDF book, so I'm not completely lost, but I ...
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1answer
760 views

How to view a 155 MB raster stored in PostGIS?

I am using the following command to load a raster into a postgres database: raster2pgsql -I -C -e -Y -F -s 3086 -I -C -M myraster.tif myraster -F -t 30x30 | psql -U postgres -d database -h localhost -...
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4answers
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How can I export raster data from Arcmap to an R *.grd file format?

I want to work with raster data in R, but I have problems exporting my raster dataset from ArcMap. By "export data"/GRID I get a file with an *.aux extension. What I need is *.grd. Can anybody help ...
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594 views

More accurate way to calculate area of rasters

In my daily work, I am constantly asked to calculate areas of global raster datasets in geographic projection at 30 arc second resolution. These datasets are normally the result of a Combine operation ...
8
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1answer
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How to apply a Majority filter in GRASS GIS?

I was wondering if someone could help me write a majority filter for GRASS GIS. I have this map (see below) which I need to run a filter over to make the red areas a bit more dominant. I know I can ...
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4answers
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How to generate a world file with rotation

I`m writing code to geo reference some images that I get with a rc plane. I have the central coordinate of the image because its atached to the center of the plane. But I have problems when I open the ...
6
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2answers
644 views

Raster to Vector

I want to map out moisture availability using satellite image but I do not know how to convert the raster image to a thematic map with limiting boundaries like state boundaries. I am using ArcGIS 9.3 ...
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2answers
403 views

Breaking apart a polygon layer by unique values, creating many new layers

I have a large dataset of habitat information that I need to calculate distances from animal locations to the closest polygon of each habitat type. The way to do this, that I understand, would be to ...
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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 ...
6
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1answer
228 views

What is the best raster format for large NoData areas?

Is there a good raster format for dealing with a large number of NoData cells? I do a lot of flood modeling and mapping, and recently I've been using rasters to show predicted flood depth and/or ...
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Rasterize a vector layer in PostGIS

Related to this question asked here on gis.se and this thread on postgis-user, has anyone worked out a good solution for in-database rasterization of a vector layer using PostGIS? It sounds like the ...
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How can I Destripe Landsat Images?

I am working with Landsat 7 ETM+ SRC-off imagery. I'm doing some land-cover classification for a place in Kenya. My problem is the no-data stripes in the image. Is there a way in which I can ...
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1answer
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Convert 32 bit image to 8 bit image in QGIS

I want to convert my images from 32 bits to 8 bits. I'm using otb to calculate texture and the raster output is on 8 bits, I'm going to use this information as a layer stack for my multispectral image ...
4
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1answer
921 views

Raster data array output flipped on x-axis using python/gdal?

I'm trying to create a raster using the python gdal libraries and I've gotten to the point where data is being output, but the output data is flipped on the origin point's x-axis. I know I must be ...
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2answers
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Converting shapefile to raster: Character attributes

I've got a shapefile that I would like to convert into a raster, but the trick is that the attribute I want a raster version of is character data. I'm familiar with geoprocessing using GDAL (in the ...
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4answers
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Combine overlapping rasters with priority to values of specific rasters?

I have 5 rasters that cover a large area. I want to combine all 5 into 1 raster. Each raster has data for portions of the total area that none of the other rasters cover. Raster C overlaps A,B and D. ...
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3answers
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How to Export Raster with same classification colors seen in ArcMap?

I have a single band raster, but i like to export it with the same colors as in Arcmap. Any help please.
3
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1answer
348 views

how to square the pixels of a GeoTiff

I have a GeoTiff that has been supplied to me with non square pixels (I suspect due to reprojection to lat lon at some point). However the next step in my processing chain requires a Arc ASCII grid as ...
3
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1answer
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How to assign CRS to RasterLayer in R

I have a layer with coord. ref. : NA. How can I assign coord. ref. : +proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0 to coord. ref. : NA? class : RasterLayer dimensions : 127,...
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1answer
347 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 ...
3
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2answers
514 views

Need to clip raster based on field name in ArcGIS 9.3

Is there a way around for me to batch clip a raster using a field name to create output a raster layer ? Much like using Split tool but it is for a vector. How about that for the raster side ? Going ...
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3answers
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How to extract X Y coordinates and RGB from pixels using python in QGIS?

I'm trying to white a Python plugin in QGIS (2.2) to get, for each pixel of a raster image, its X Y coordinates, as well as, its RGB (3 bands) values. At first I opened the raster file using: rlayer =...
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2answers
331 views

How to automatically calculate maximum cell values contained within polygons?

I've got a dataset made up of a large range of polygons (about 70 or so) which represent structures. I also have raster layers which detail a flood depth across an area. The floods depth raster has a ...
3
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1answer
583 views

1m cell size equivalent value in decimal degree

I'm doing re-sampling pixel size in ERDAS 2014,I'm using input image(Indian terrain) in GCS_WGS_84 projection. Now I have to keep out put cell size as 1m,what is the 1m equvivalent value in Decimal ...
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1answer
354 views

How to best remove rgb values outside of aerial image?

I have just converted RGB-TIF images to RGB-ECW for reasons of space and performance in ArcGIS. However, after the conversion, there are relics outside of the images which are not nodata values but ...
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2answers
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Changing color of raster images based on their data values - gdal

Let's say I have 1 band raster images with Gray Color Interpretation and I want to change their color based on their data values. Data values -1, will be Blue, -0.5 will be Light Blue, 0 will be ...
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2answers
431 views

SPOT NDVI time series

I have 423 spot.vgt ndvi from first April 1998 till 31 Dec 2009. I want to know how to stack these NDVI to have one image for time series analysis? Or better to ask how is it possible to analyze a ...
2
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2answers
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GDAL Clipping (hack)

I am trying to use the python script from http://www.sparkgeo.com/labs/2010/07/07/gdal-clipping-hack/ to clip a raster based on many shapefiles. The script is using a mysql database an i would like to ...
12
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3answers
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Combining corner-touching polygons into a single feature

I have created a polygon layer from rasters, and only have a single classification ID (and calculated acres) for each polygon. I would like to "dissolve" all touching features into larger, individual ...
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2answers
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PostGIS raster value of a lat/lon point

I have a tiff raster in my PostGIS 2.0 database. I want to get the value of the raster at a specified lat/lon point. I have: postgresql-9.1 postgis-2.0-svn with raster support a raster imported ...