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

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grib2 to raster? (grib2 -> raster2pgsql -> PostGIS 2.0 -> GeoServer)

I'm looking to implement import of US National Weather Service data for doing various sorts of models (www.soils.wisc.edu/uwex_agwx if you're curious about what we're doing with the data). The ...
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2answers
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How to vectorize a Raster-Classification? (qgis, grass)

I classified my raster-DHM into elevation levels using colormap. Its not a "real" classification, just a colormap. So I cant vectorize the classes to get polygones for every class. Whats the best ...
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1answer
1k views

Get a pixel value

How can i do this operation: I want to get a pixel value fro the satellite image (Landat, GeoTIFF, 7 bands) using qgis-python. What operators should i use? (for example in qgis's Python Console) ...
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2answers
17k views

How can I join several raster files using QGIS?

I'm new to QGIS. How can I combine multiple raster layers into one layer? The raster images are of different areas with very little overlap. The goal is to bring numerous town plats into one project. ...
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2answers
947 views

Are there GIS tools for simulating landscape fragmentation?

I am currently looking for any GIS packages (or add-ons) that allow the simulation of landscape fragmentation on raster data. Maybe also other software than GIS tools? Does anyone of you have had ...
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4answers
4k views

How to install “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 ...
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2answers
280 views

Configuring a WorldImage data store starting from a folder containing tif and tfw files

i have a folder of tif and tfw files and i'd like to show the raster in a map using geoserver. Even reading the geoserver tutorial for this kind of datastore ...
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3answers
445 views

In what data format should I export a (lat,long,alt) or (x,y,z) grid to be compatible with the largest number of GIS software?

I am new to GIS and developing an application that generates a 3D grid with (latitude, longitude, elevation) or (x, y, z) metric triplets, and I would like to add an exporting feature that ensures ...
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298 views

Raster calculation confusion

I need to do some raster calculation, I've been trying to make it work but I am not sure everything is working properly. I need to apply a formula, but I am unsure if I am doing it properly. The ...
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143 views

identify the fraction of raster cells and listing all the cell values in every polygon

In Arcgis 10 I have a netcdf file that maps the fractions of cropland in the world from 1700 to 2007. I extracted the years that i needed as raster layer format (continous data from 0 to 1) and now, ...
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1answer
349 views

Multishading: bring them together to one Raster-Image

I made a multi-hillshade with 4 different light-directions and colors and stacked one above the other, each with its own transparency. Now I want to "save" the result in one raster-image. Whats the ...
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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 ...
3
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1answer
706 views

Cell calculations; QGIS,GRASS,GDAL,SAGA

I recently asked a question about trying to calculate the slope over distance (manually) using QGIS, but then I came up with another way of solving the problem, but I would have to get some help for ...
4
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1answer
2k views

ArcMap, Make Grids and Graticules Layer example

I'm trying to use the Make Grids and Graticules Layer tool in ArcMap (have a ArcInfo license). I'm looking for a basic example like in North America. eg. 1.)Start with empty map 2.) Set data ...
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1answer
199 views

What are strengthes and flaws of using grid-cell analysis in GIS? [closed]

I'm going to use grid-cell analysis. What are the strengths and weaknesses?
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2answers
883 views

Calculating slope over distance from raster

I am sitting with an elevation raster, trying to produce a calculation for slope angle. I have a cell size of 2,-2 and I am trying to figure out how to calculate cell value difference between adjacent ...
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1answer
279 views

managing .adf's in QGIS or SAGA?

I have a few .adf's that I aquired from a fellow using ArcGIS (as I understand, this format is a specific ArcGIS format). I can open it up in qgis but their relative geographic position is off, seems ...
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1answer
2k views

How to generate smooth contours from cropped raster?

I’m trying to create contours from a raster layer in QGIS. On my first attempt, I cropped my raster layer in Photoshop and reimported it, but it lost coordinate data I think. I made the contours ...
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8k 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 ...
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2answers
1k views

How to calculate a new raster based on nodata values from original raster, in QGIS?

I'm using the raster calculator from core in QGIS and I need to generate a new tif raster file (mask) from the nodata values of another tif raster file. I tried isnull(), but no luck. Any one can ...
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2answers
9k views

How can I calculate the number of raster pixels within polygons?

I have two layers, flood area (flood.img) as a raster and flow direction as polygons. Would you please help me in calculating the number of pixels in each flow direction polygon? I want to get the ...
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1answer
336 views

Raster format with rotated cells - no resampling

Is there any way to rotate a raster w/o resampling? I am aware that rasters are always 90 deg perpendicular grids, but is there any file format or methodology that allows for a diagonal raster - one ...
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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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2answers
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Reclassify raster values of 9999 to NoData, leaving all other values alone, in ArcGIS Desktop?

I have a raster in ArcGIS which has a number of cells with the values 9999, showing that the data could not be generated for that cell. I want to convert all of these 9999 values to NoData, so that ...
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1answer
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How should I correctly exaggerate a hillshade raster (ArcGIS10, Spatial Analyst)?

I once wanted to generalize a high resolution raster and instead of MEAN i accidentally selected the default SUM technique, using a cell factor 5 (Lidar DEM is 1m resolution). When I used this result ...
4
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1answer
366 views

Can I create a legend of a map that I had get from a WMS?

Can I create a legend of a map that I had get from a WMS? Can I create a legend of a raster map with Qgis version 1.7.4, or only with the 1.8 version?
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4answers
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problem in raster data with arcmap 10

I have a problem when trying to load raster data (a TIF) in ArcMap. ArcMap 10 instantly shuts down and the well known window appears "ArcGis Desktop has encountered a serious application error and is ...
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519 views

Adding noise to a raster

I want to add some fine-grained noise to a raster in an automated python process (i.e. I do not want to use Photoshop or GIMP). I looked at PIL, but unless I'm mistaken, it doesn't seem to have any ...
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2answers
619 views

How do I create a negative to positive value raster with neutral 0?

I have a raster layer with a band with values from -137 to 9229. I want to create a color scheme showing how far from 0 the positive numbers are in one color, and how far from zero the negative ...
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1answer
196 views

can't generate/display signed float values using python/gdal

I'm trying to create a raster with signed float values as the pixel values and display the results in MapWindow on windows. What is the proper gdal band type to use? I've tried both gdal.GDT_Byte ...
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146 views

Display Rectangular Data Grid

I'd like a Linux program which displays ASCII ArcGrid files (NxM rectangular ASCII data grids which may have either integer or floating point values). There is no practical upper or lower limit to ...
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1answer
703 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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Determine direction of rivers, which villages lie upstream and which downstream

I want to determine which villages lie upstream and which villages lie downstream big cities built on the side of rivers in Indonesia. I have the .shp file of villages and cities, the .shp file of all ...
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1answer
174 views

Change ellipsoid reference for altitude in a DEM

I have DEM data stored as RGF93 (Lambert-93) for lat/lon and NGF-IGN69 for altitude. I'm trying to change the reference ellipsoid for the elevation data (ultimately to NTF, but WGS84 would be fine to ...
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Get Raster Values from a Polygon Overlay in Opensource GIS Solutions

I have two layers. A polygon-shape-layer with many tiles and a raster-layer containing CORINE 2006 land cover with many categories in a colourmap. I want to obtain for each polygon in the shapelayer a ...
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914 views

Why is my mosaic of rasters a big, black rectangle?

I downloaded NED rasters from USGS, and I now want to mosaic all of the rasters into one. I used the Mosaic to New Raster tool, but the output is a big, black rectangle. Am I missing something? I feel ...
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1answer
435 views

Get raster field names in R

Does anyone know how I can extract the raster field names (VALUE, COUNT and other existing field names on a categorical raster file) in R? I am using the raster package to load the raster files.
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How to Clip a Vector File based on certain Raster Values?

I need to clip a vector file based on certain values of a raster (Slope > 2%). I can´t find a direct way to do it. Trying to vectorize the raster first didn´t work. Is there any tool (ArcGIS or ...
4
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3answers
968 views

Is there a “Tabulate Area” function in QGIS?

I have a raster file about land usage in northern italy (crops / urban areas ecc..) I have defined some buffer zones around some given points of a vector layer and I'd like to calculate the % of ...
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1answer
573 views

Preventing an Openlayers WMS layer from updating on zoom-change

I'm using openlayers to overlay a raster. When I zoom out, the overlaid layer expands to cover a larger area than was originally requested. I want the tile to be fixed to a particular boundary, and ...
2
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1answer
392 views

When creating a new raster, how to determine a raster's upperleftx, upperlefty?

I'd like to create a raster from point data, averaging the point data over a given area and placing the results into a given pixel/cell. With each pixel/cell as 50m x 50m. I'm new to this and have a ...
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4answers
8k views

How to calculate raster statistics for polygons?

how can I calculate sums, averages etc of raster-points (multi-band) per polygon of a vector-layer. I was told that this is called "zonal statistics". I tried that with QGIS first. There is a way to ...
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1answer
94 views

Which raster-format stores Missing, Strings, Variable Names, Multiple Bands

still looking for the ideal raster-format :-) GeoTiff stores: - projection/coordinate-system etc numerical values missing values multiple bands It does not allow for: variable-names. It just ...
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1answer
477 views

What are some examples of model-based upscaling of raster data?

Remotely-sensed raster data may be too fine-grained for many purposes. A typical approach to coarsen the grain is to upscale by reducing the resolution. If the data are continuous (e.g elevation, ...
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1answer
591 views

What are the rules that the Gdal rasterize function follows to allocate a value to a cell?

How does the rasterize tool decide which value to represent when a cell covers an area which inclueds different values? I need it in this case for polygons but would like to know for lines and points ...
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629 views

How to extract cell values from a raster file with Idrisi Taiga?

I need to convert raster cells into points. I use Idrisi and I need to generate a table containing xy (coordinates) and z (cell value).
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5k views

How to visualize grd files in QGIS?

How to visualize grd files in the software QGIS?
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2answers
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Coordinates of raster image from .TAB file

I have got a raster image (tif) from a mapping site and an associated .TAB file. I am trying to correctly map it into CAD/3d model - which I know is set up to the correct coordinates. The .TAB file ...
2
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1answer
172 views

Creation raster image from interpolated image

I have interpolated temperature data that I have. This image's max and min values are 11.9 and -1.7, respectively. And then I exported this image to raster using 'export to raster'. But the max and ...
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1answer
450 views

Why can't r.patch find the rasters?

I have elevation rasters which loaded just fine in a GRASS session. They represent adjacent areas, so I want to meld them into one raster. I ran r.patch using the GRASS GUI, and it would only accept ...