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

learn more… | top users | synonyms

9
votes
6answers
1k views

seeking “Available Sky” implementations

I'm looking for implementations of an algorithm called "Available Sky". ArcGIS (Spatial Analyst or GRID) is preferred, but solutions in GDAL, SAGA GIS or others are perfectly acceptable. The ...
9
votes
2answers
454 views

Methodology for Hansen classification of Global Forest Watch?

I have just discovered amazing Hansen´s classification about forest loss and re-growth, available at http://www.globalforestwatch.org/, published in Science, 2013 as: Hansen, M. C., Potapov, P. V, ...
9
votes
2answers
1k 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 = ...
9
votes
2answers
1k views

Extract the area of a DEM above where 60% of the region lies?

I have a DEM of a mountainous region. I'd like to extract the areas of the DEM above which 60% of the total DEM area lies. So, essentially I'd like to extract the areas representing upper portions of ...
9
votes
3answers
942 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. ...
9
votes
3answers
2k 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 ...
9
votes
2answers
1k views

GeoTIFFs made in GDAL don't have min/max range when loaded in Arc/QGIS

I'm creating some floating point rasters in GDAL with the GeoTIFF driver. When I load the resulting images into QGIS or Arc the default symbology puts the min at -3.40282e38 and max to 3.40282e38, so ...
9
votes
1answer
534 views

How should I manage PostGIS Raster data with different projections?

I have a requirement to store and manage archaeological geophysics data that is collected as a rectangular array of samples -- a raster image. Each raster will usually 20x20 or 30x30 floating-point ...
9
votes
3answers
465 views

R, rasterVis and RGL: how to prevent reflective surfaces?

I have been experimenting with digital terrain model files in ESRI ASCII grid raster format. Despite zero experience with this type of data I found it very easy to load into R, as per code below. The ...
9
votes
1answer
3k views

Smoothing raster features into polygon

I have raster data representing urbanized areas, which I'd like to trace and convert to a polygon. Using ArcMap's Raster to Polygon tool, I'm able to get something close to that. Unsimplified: ...
9
votes
1answer
717 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 ...
9
votes
3answers
1k views

What Open Source (command line/API) method is there to orthorectify and georeference an aerial image given telemetry data?

How can I take an image and orthorectify it automatically with open source software? The information associated with each image is: camera specs latitude, longitude, elevation of the camera ...
9
votes
4answers
420 views

Identify corrupt shapefiles or rasters via Python or ArcObjects

I'm interested in a way to identify rasters (e.g., ESRI GRID format) or shapefiles that are corrupt that would prevent them from being used in an analysis tool. I have a large number in structured ...
9
votes
2answers
870 views

Scriptable alternative to ArcScan (particularly vectorising lines within tolerances)?

Sadly the answer to Can you access ArcScan from a python script? suggests that it is not possible to script ArcScan from within a python script. Therefore, does anyone know of any alternatives to ...
9
votes
4answers
2k views

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
votes
5answers
4k views

How to modify single Pixel values in QGIS?

I would like to modify a raster (pixel values) in QGIS. The plugins "value tools" can easily provide me with the value of the pixel of my raster. However I don't know how to modify it. I have found ...
9
votes
1answer
605 views

How to grid unevenly sampled categorical data?

I am looking for a method for gridding categorical data. I have extracted from nautical charts and field sheets a collection of points specifying the nature of the surface of the bottom of the ocean. ...
9
votes
1answer
427 views

Efficient raster sampling of billions of polygons (bounding boxes)

How can a raster be computed efficiently (in Python), given a set consisting of billions of bounding boxes (read sequentially from a file), and given that the raster values for each cell should give ...
9
votes
2answers
540 views

What is the correct way to convert a USGS Orthoimage from WorldImage format to tiled GeoTiff for GeoServer?

USGS provides different resolution orthoimage quadrangles in the WorldImage format (*.tif with an accompanying *.tfw world file). Some of these quadrangles can be used by GeoServer (2.1.0 - 2.1.2) by ...
8
votes
6answers
2k views

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
votes
5answers
350 views

How to ensure uniform colour for DEMs?

This is a silly question, but one I've been trying to figure out for a while. I have two Aster DEM tiles, one next to the other. How do I ensure uniform colour for both?
8
votes
2answers
2k views

How to calculate the number of cells with a given value?

I have a raster file where all cells have values between -3 and 7, no data value is -9999. Have can I calculate the number of cells with a specific value e.g. 6? Can I use the calculator?
8
votes
3answers
3k views

GDAL and Python: How to get coordinates for all cells having a specific value?

I've got an Arc/Info Binary Grid---specifically, an ArcGIS flow accumulation raster---and I'd like to identify all cells having a specific value (or in a range of values). Ultimately, I'd like a ...
8
votes
1answer
4k views

Calculating distance to points in QGIS

Is there a way of calculating the distance to the nearest points in QGIS? In ArcGIS there is a function called Euclidean Distance, which can take an input vector or raster, and generate a raster of ...
8
votes
2answers
400 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
votes
3answers
2k views

Determining statistical relationships between rasters using R vs ArcGIS Desktop?

I am trying to analyze how sets of rasters relate to each other using some statistical techniques. As, I don't have much experience using the spatial statistics tools in ArcGIS I was exporting my ...
8
votes
2answers
1k 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 ...
8
votes
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') # ...
8
votes
2answers
6k views

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 ...
8
votes
1answer
5k views

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 ...
8
votes
3answers
4k views

Using polygons to apply unique value to all raster cells within those polygons?

In ArcGIS 9.3, I have a raster file that I would like to "mask" with polygons, giving a single value to all the raster cells that overlap the polygons. How can I do this? Here's a screen shot, ...
8
votes
2answers
710 views

How to create a solar intensity map for a garden plot?

I'm interested in creating a raster surface that depicts the average solar intensity per unit area for a small garden plot. I imagine the inputs into the model would be the following: Plot ...
8
votes
1answer
586 views

Reduce extent of raster processing in ArcPy or ArcGIS Desktop?

I need to reduce the processing extent of my raster by some sort of automatic procedure in python. Currently the borders of the dataset I've been using has anomalies (due to the classification of the ...
8
votes
1answer
3k views

Is there a fast way to copy large raster datasets between File Geodatabases?

Why does it take so long to copy a large raster dataset from one file geodatabase to another? I can copy the entire database in windows explorer in minutes but copying a single raster in ArcCatalog ...
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 ...
8
votes
1answer
1k views

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 ...
8
votes
4answers
2k views

Looking for a fast, open-source raster cost-distance function to use in code

I've been scouring the internet for a fast, open-source cost-distance function that I can embed inside my code. The functionality should basically work like the ArcGIS implementation where I can ...
8
votes
1answer
4k views

How to resample GeoTIFF images to the same resolution?

I have two geotiff images that I would like to resample the same resolution. If I use ArcGIS this would be easy to do. But using QGIS I don't know how to do this. Some help will be very appreciate. ...
8
votes
1answer
640 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 ...
8
votes
2answers
978 views

How to convert a vector boundary to a raster map?

I need to output a PNG file of a raster map overlayed with boundaries present in a vector map. The problem is, the r.out.png script only exports a raster map. My boundaries are in a vector format. ...
8
votes
1answer
139 views

How to improve the display of color images?

I've found some really nice color ramps for portraying rasters, but in ArcGIS and QGIS, they don't seem to be easily usable for a finished product because their complexity causes obvious steps rather ...
8
votes
3answers
2k views

Poor image quality of raster pyramid files in ArcGIS Desktop (no anti-aliasing)?

There are several GeoTIFF files (size ~7000x7000 px) which I try to open in ArcGIS Desktop 10.0. I have already created raster pyramids for them (.ovr files) using geoprocessing tool but their quality ...
8
votes
1answer
1k 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 ...
8
votes
1answer
2k views

How to make a new raster using con() script in Python?

I'm new to Python and have been trying to code a raster calculator style script. Basically, I want to convert a raster that has values 0 to -10,000 into a raster that is populated by 1s between ...
8
votes
1answer
4k 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 ...
8
votes
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 ...
8
votes
4answers
364 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 ...
8
votes
3answers
2k views

calculate area of vegetations in a raster file

How do I calculate area of several vegetation types in a raster (.img file type) image. They are color coded. Am using QGIS (1.8.0) and ERDAS 9.2.
8
votes
1answer
407 views

Where is this raster offset being introduced in the QGIS processing toolbox?

I'm using the (awesome!) processing toolbox in QGIS 2.0 to reclassify some NoData values in a raster from -9999 to 0, but at some point in the process there's an offset of about 0.2 degrees being ...
8
votes
2answers
729 views

Histogram Matching using Python to improve mosaicking process of multiple overlapping rasters?

I am trying to do histogram matching using Python to improve the mosaicking process of multiple overlapping rasters. I am basing my code on that found at: ...