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

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How to find the area of raster values within polygon zones?

I'm using ArcGIS 9.3 and I just can't seem to get this right - I've tried tabulate areas, zonal stats, converting to polygons, etc. I'm missing something somewhere. I have a USGS impervious surface ...
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2answers
1k views

How to calculate the area of rasters in QGIS?

I have been working with some rasters and would like to know how to calculate the area occupied by one element of a raster in Qgis.
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0answers
215 views

Problem loading output layer QGIS

Every time I run operations with temporary file output from the graphical modeler, I get the following error message: Oooops! The following output layers could not be open CLIP: ...
2
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2answers
512 views

How to translate (reposition) a raster in Python?

I tried to use QGIS GeoReferencer to translate a raster layer, but somehow failed. It just goes to somewhere unexpected. Now I decide to do it myself, with python. I think some libraries like GDAL ...
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0answers
126 views

Correlation between point feature (disease) and elevation

I have a problem! How can I calculate the correlation between point feature and Dem raster? Hypothesis: disease prevalence in high altitude is more than low altitude. I must do this in ArcGIS 10 and ...
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1answer
515 views

How to eliminate small features in a grid?

(Update) My final goal is to take some logged point data (1 point about every 20 ft or so there are over 15,000 points) and interpolate that point data. Then I would like to convert the interpolated ...
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7answers
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Work flow for georeferencing imagery using open source tools?

Does anyone have a recommendation for a work flow for georeferencing high resolution aerial photography using open source tools? Comparison of user friendliness and robustness between Quantum GIS ...
23
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3answers
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What is Lanczos resampling useful for in a spatial context?

GDAL includes a resampling method beyond the normal mix of nearest neighbor, bilinear, cubic and splines: "Lanczos windowed sinc resampling". I understand that its a convolution filter, but unlike ...
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6answers
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Creating simple image from vector data

Can anyone suggest a quick (and preferably open source) way to create an image from a shapefile. For example, I have a shapefile containing parcel boundaries, I want to create a png file depicting ...
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5answers
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What is Change Detection and how I can perform such analysis with open source tools?

From wikipedia page: Change detection for GIS (geographical information systems) is a process that measures how the attributes of a particular area have changed between two or more time periods. ...
13
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2answers
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How to smooth/interpolate a raster in python using GDAL?

This is my first post so please feel free to critique where necessary. Background: I am developing in Python and using GDAL from OSGEO to manipulate and interact with rasters and shapefiles. ...
11
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1answer
2k views

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 ...
7
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2answers
915 views

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 ...
17
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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 ...
13
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2answers
5k views

Differences between Raster Dataset, Raster Catalog, and Raster Mosaic

I have about 40 scanned, colorful Geology maps that are GeoTiffs. I want to bring them into an Esri FileGeodatabase to lower their size, combine them as one and display them with a mostly transparent ...
11
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1answer
828 views

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 ...
7
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1answer
6k 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') # ...
11
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2answers
14k 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
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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 ...
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5answers
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Finding minimum bounding extent of given pixel value within raster?

I am wondering if there is a way to find the minimum bounding extent for a raster with a particular value. I clipped a raster from a global image and the extent is set as the global extent with a lot ...
8
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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): ...
6
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2answers
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How to extract values from rasters at location of points in R?

My question is about extracting values from rasters at the location of points. With the function extract this is very easy, and the function gives me a dataframe with the values of all the variables ...
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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 ...
6
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1answer
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How to import a raster into PostGIS?

I'm trying to follow the instructions here to load a raster into a PostGIS database: python raster2pgsql.py -s 4269 -I -r *.tif -F myschema.demelevation -o elev.sql I understand that I replace * ...
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2answers
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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 ...
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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 ...
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3answers
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Extract Raster Value into Polygon Attribute

I have Raster Data for a State which has Elevation Data in its pixels. I also have Vector layer which has the 300 divisions of State. what I need is, I want to get the average elevation value of ...
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2answers
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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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1answer
302 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 ...
5
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1answer
846 views

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 ...
5
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1answer
2k views

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
341 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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1answer
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How to store raster data in spatialite?

I want to cache my raster data(large geotiff files) on local database. I thought to use spatialite. I found librasterlite which provide functionality to do that. Can anybody point to some tutorial on ...
4
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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 ...
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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 ...
8
votes
1answer
2k views

GDAL RasterizeLayer Doesn't Burn All Polygons to Raster

I am trying to burn a shapefile to a raster using GDAL's RasterizeLayer. I pre-create an area of interest raster from a different shapefile, given a specific pixel size. This AOI then serves as a base ...
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4answers
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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 ...
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 ...
6
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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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1answer
7k 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 ...
6
votes
3answers
6k views

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 ...
5
votes
3answers
775 views

Finding outliers with wrong Z values in LIDAR data

I have more than 2000 XYZ (only ground points) .txt files and I have to do Quality Control (QC). Let's say I have file, which I converted to multipoint (or even singlepart feature). I have mean Z ...
5
votes
3answers
3k views

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 ...
4
votes
1answer
353 views

Create a point at the highest value in a raster ArcGIS 10.1

I am trying to find the location of the highest value pixel in my Direct Solar Radiation Raster. I can see the extent of the data in my raster but don't know where the highest value pertains to. Is ...
4
votes
3answers
799 views

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 ...
4
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1answer
2k views

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
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3answers
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How to combine information from raster and vector layers?

in QGIS I have 1 raster-layer (elevation) and 1 vector-layer (administrative units). Now I would like to be able to query one of the administrative units and see the mean and min/max of the elevation ...
4
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2answers
1k 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
612 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
384 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 ...