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

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How can I determine which raster attribute covers the highest area of a polygon?

I'm relatively new to GIS and QGIS but I have a problem that I'm not certain how to solve. I searched here for relevant information but found none. (Or, I used incorrect search terms.) My problem ...
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3answers
384 views

Scatterplot, correlation of dependence and r-square between two rasters

I have two rasters of the same region and of same resolution and I want to plot in a scatter plot their values and compute the best - fit line with r-square. Any idea how can I do this on Arcmap or ...
3
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1answer
578 views

Mapnik + OpenStreetMap + Shapefile with Raster Images + Mod Tile + PostGIS

I am new to GIS. I have a Shapefile (.shp, .shx and .pbf). The .pbf file contains path to PNG files located on my machine only. I was able to save the Shp data to PostGis via Shape2Gis tool. Now ...
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3answers
227 views

Gdal: how to get the max and min altitudes of my topographic raster?

Given a .tiff topographic raster image. How to get the altitudes of the highest and lowest point/pixel ?
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3answers
380 views

Where to obtain free 15m ASTER image for New Mexico?

I am looking for a free Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image that will let me to perform NDVI for the pilot crop health/soil moisture that can go as far back ...
3
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1answer
641 views

Why is Orthorectify button not active in Image Analysis Windows in ArcGIS10?

I wanted to Ortho rectify GeoEye HR imagery using existing RPC and IFSAR DTM in Image Analysis. According to ArcGIS Resource center ...
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2answers
453 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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4answers
2k views

How to clip raster image by the extent of each row in a shapefile with ArcGIS 9.3

I'm using Python to clip a raster image by each row in a shapefile with ArcGIS 9.3. I am hoping to end up with one raster image for each polygon row, clipped to the extent of the polygon row. ...
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1answer
75 views

Difference between raster() and readGDAL()?

I am new in working with rasters and after having trouble working with them i'd like to know the difference between those two import functions. for example i did this library(raster) ...
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1answer
449 views

How to create a catchment from a point using a DTM raster in QGIS?

I need to find a better way to delineate a catchment from a given point on a watercourse using a DTM - currently I am either using FEH, or if the catchment is too small using contours to draw ...
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1answer
214 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 ...
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1answer
130 views

PostGIS Raster: Outputting raster into GDAL supported file?

I have import a raster into my postGIS database via raster2pgsql. My raster tiled to 100x100. Now I'm trying to export (output) the raster to GDAL supported file (for example: PNG). Following the ...
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1answer
348 views

Convert multiple Shapefiles in Raster in R(and then plot it)

I'm trying to convert several shapefiles in rasters at the same time. I already was able to read the shapefiles by doing this: library(maptools) shps <- dir(getwd(), "*.shp") for (shp in shps) ...
2
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1answer
2k views

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 ...
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116 views

Raster area (QGIS) problem explained

I would like to know the area that each value in a raster has... The raster I have has values from 2-15 and I would like to know the area that each value is occupaying within my polygon... Thanks! I ...
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1answer
238 views

Obtain normalized raster average per polygon?

I have a raster that contains percentages of total forest killed plus a polygon layer that defines different zones. My goal is to find a good statistical representative that describes the forest ...
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1answer
861 views

Access PostGIS Raster layer through mapserver

I am trying to use a cgi script calling mapserver to display a raster layer that is stored in a PostGIS database. However, only a blank white image is returned and I don't know where the problem is. ...
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1answer
6k views

Convert a Tif raster file to vector shp file in QGIS

So I've been trying to convert a georeferenced Tif raster file into a vector shp file using QGIS. It's seems to complete this but it ends up giving me a feature class that has over 500,000 features, ...
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1answer
1k views

Adding fields to raster attribute table

I have a raster attribute table associated with an IMAGINE .img raster that I build and open with: IGPUtilities utils = new GPUtilities(); IRasterDatasetEdit2 raster = (IRasterDatasetEdit2) ...
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2answers
137 views

Road-construction (alignment) tools

Are there any tools available in any GIS environment for route alignment? To be specific, the tool should take a DEM and road-construction parameters -- distance and gradient, roadfill, drainage ...
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1answer
79 views

Why do the raster band values have different values than the raster statistics?

I am working on a raster file (1 Band). According to the raster metadata, my minimum value is 0 and maximum is 7458. This seems to be confirmed by the Style options that return some category values ...
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943 views

How do I import OS raster tiles into QGIS at the correct scale?

I have some tiles of OS raster mapping and their associated TFW georeferencing files. The GR files are in the same folder as the raster data and have the same names, ie TQ21.tif/TQ21.tfw. In QGIS ...
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409 views

Gdal: How iterate through all pixels of a raster image?

Given a topographic raster image. How to iterate through all pixels of this raster image ? Solution preferably with gdal, in console. Some other libraries/script could be installed. Related: ...
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1answer
154 views

How to correlate raster map and elevation data?

I have been provided with a set of raster maps. Thanks to another helpful user here I have been able to acquire some elevation data for the same region from gis.utah.gov in asc format. Now I need to ...
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2answers
454 views

How to produce a mean raster file based on other raster files? [duplicate]

Possible Duplicate: Tools to flatten the jp2 to a single band (average the bands)? I have a number of raster files from a same area, that coordinates of corresponding pixels perfectly match ...
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605 views

How to add ECW support to GDAL bundled with PostGIS Windows

I'm currently trying the new raster functionalities of PostGIS 2.0 and I successfully imported some GeoTIFF file into PostGIS (although it only find one band so it's all black and white for some ...
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2k views

Merge single band and multi band color images

I do have 2 color images (orthophotomaps). One is only 1-band with color map and second is with 3-bands. How can I merge them with any FOSS tools or ArcGIS? Thanks a million
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2answers
3k views

Get extent of Georeferenced Rasters in Python and output to polygon shapefile

I would like to create a shape file containing the extents of each of the rasters in a directory. Is it possible to capture the extent of a raster using Python? I have tried ...
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97 views

Issues creating slope raster layer from a point layer

I'm trying to create a slope raster layer using QGIS 2.0 on Windows XP. I started with a points layer with the Z elevation attribute. I then used the interpolation plugin to create a DEM. But, ...
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1answer
113 views

How do I convert coordinates to raster (bsq, bil) lookup?

I have a .bil file, which has interleave = bsq in the hdr file. I'm having trouble finding any insight into how I would essentially do a lookup on the file. I have no problem reading a specific ...
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4answers
284 views

How to determine if point is surrounded using raster processing?

I am attempting to improve a currently extremely cumbersome vector/python process for a natural hazard model. At the moment we have a lengthy script which generates distance/bearing lines from a given ...
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2answers
808 views

Python, GDAL and building raster attribute tables

I have an integer raster for which I would like to build a raster attribute table using Python and GDAL. I can create a GDAL raster attribute table in Python as follows: >>> rat = ...
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1answer
3k views

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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3answers
1k views

How to combine 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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1answer
753 views

How to add a band to an existing GeoTiff using GDAL?

This seems like it should be straightforward but I can't for the life of me figure it out. Given an existing GeoTiff containing a single band, how can you add another band to that GeoTiff? Is the ...
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3answers
850 views

Best way to manage large number of geoTiff rasters

I have around 2-3000 1-bit geoTiffs of size 11000x9400. Color 0 should be transparent, and QGis gets it wrong in the first place, so I used a .vrt file to set all the parameters in one single place. ...
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1answer
253 views

Raster smoothing

I am an italian student. I'm using ArcMap 10. For my thesis I need to simulate a debris avalanche, but in my elevation raster the avalanche deposit is included so I'd need to take it off to simulate ...
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3answers
996 views

Creating raster or vector raster from DEM point file?

i have a point shape of 75.000 elevation points in a regular 5 m grid. We now want to create a polygon grid with the elevation points as "centroids". Unfortunately, all attempts to do so fail: I ...
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1answer
2k views

How to rasterize SpatialPolygons in R?

I'm trying to extract the bathymetry values of my area of interest from a world bathymetry raster layer using the 'rasterize' function in the {sp} package. *Edits: I found the 'extract' function ...
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2answers
3k views

Modify raster layer display and symbology properties programmatically with arcpy or ArcObjects

I have over 1500 NITF files that I need to be able to modify the layer display and symbology of programmatically from within ArcMap. I need to set the properties outlined in red below: I've looked ...
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2answers
318 views

Wavelet vs Discrete compression for imagery

What is the main reasons to choose wavelet (jp2, sid, ecw) instead of discrete (JPEG) compression methods for raster data? Lets limit this question to aerial imagery and lossy compression. Why ...
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1answer
2k views

Count number of unique raster pixels in polygon using ArcMap?

I have a polygon shapefile and I want to generate a table of a count for each pixel value in each polygon. My main goal is to find out what pixel is most abundant in each polygon. I am using ArcMap ...
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1answer
431 views

QGIS composer - How can I eliminate striping across transparent raster layers?

I have downloaded QGIS dev version 1.7.0-114 and I have come across some weird behaviour in the composer. I create a map with a hillshade and a transparent DEM ontop of it, pretty standard stuff. ...
6
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1answer
932 views

QGIS WKT Raster Plugin error, what does this mean?

I have been playing with the WKT Raster plugin. I have installed the WKT Raster experimental binaries in PostGIS successfully and followed the instructions in the read me to the letter. When i am in ...
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2answers
1k views

Moving raster to different mapset GRASS GIS

I have a raster DEM that I created in one mapset but I would like to copy it to another mapset for another purpose. Is this possible within GRASS or can I just copy some files over in the ...
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425 views

Create a Raster file out of a ASCII grid file?

im using a special system to do geomagnetic surveys. Its software let me output the information as image files, ASCII or in its own proprietary file format. Now i want to get its information in my GIS ...
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How to extract values from a raster according to Lat and long of the values?

having 12 files with 12 hdrs for one year: these files are raster (projected WGS84,lat long):https://echange-fichiers.inra.fr/get?k=rLSyoavrnifGyH5XrlO samples = 1440 lines ...
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1answer
2k views

How do I average a set of rasters?

How do I average a set of rasters? I have remotely sensed chlorophyll a rasters for several days and I need to get an average of the days represented as one raster layer. I've got QGIS 18.0 with the ...
5
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1answer
263 views

Getting ArcMap to display rasters properly first time

This is a very basic question, but as I've self-taught most of my GIS skills this is still a gap in my knowledge. When I load a .tif raster into ArcMap, most of the time it requires re-exporting to ...
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1answer
1k views

How to reproject a raster in QGIS?

I am a history teacher and I like to make my own maps (I can never find exactly what I want). I am using QGIS 1.8 and Natural Earth data. I want to reproject their cross-blended hypso rasters into ...