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

learn more… | top users | synonyms (1)

10
votes
2answers
2k views

Intersecting a raster with a polygon using PostGIS - artefact error

I'm using PostGIS2.0 to do some raster/polygon intersections. I'm having difficulty understanding which operation I should use, and what the quickest way of performing this is. My problem is as ...
10
votes
3answers
2k views

How can I mosaic images in ArcMap without it affecting the colour?

This is 4 images (NE, SE, NW, SW) sections of imagery. They have some overlap between them. Working with 1m 3-band orthoimagery. Different parts are sometime flown at different times/sources hence ...
10
votes
2answers
687 views

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 ...
9
votes
7answers
5k views

How to get raster image as array in Python with ArcGIS

When starting to work with Python and ArcGIS 9.3, I assumed there would be a simple way to get a raster image into a Python array so that I can manipulate it before storing it back as another raster ...
9
votes
2answers
9k 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. ...
9
votes
3answers
3k views

Best method to aggregate 1m DEM mosaic to 10m DEM

I have a mosaic of a 1m LiDar derived DEM. I need to output a subset of the data as a 10m DEM. I am currently using the aggregate tool in ARCGIS 10 to produce a mean value for each new 10m pixel. ...
9
votes
2answers
1k views

How to count and rasterize polygon overlaps in ArcGIS Desktop?

How do you take a vector layer with overlapping polygons and turn it into a raster where each cell counts the number of polygons containing that cell? We are looking at polygons of fire burn areas ...
9
votes
5answers
1k views

Multicriteria Analysis : how to?

I have to do a multi-criteria analysis to answer the question : "which is the best lot to develop". A few of the criterias are : distance of the nearest bus stop (point layer with bus stops) ...
9
votes
1answer
381 views

How do I randomly alter a raster map of habitat types?

I have a raster of habitat types for a specific area in Scotland. I need to create future habitat scenarios with changes in habitat to assess the population viability of a bird species. For example, ...
9
votes
2answers
3k views

Difference between Geoserver stores: ImageMosaic, WorldImage, ImagePyramid

What are the differences between the Geoserver stores ImageMosaic, WorldImage, and ImagePyramid? I noticed that ImagePyramid is no longer included in the latest Geoserver. Is one of these more ...
9
votes
2answers
1k 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?
9
votes
3answers
2k views

How to get hypsometric curve from elevation data?

I have my elevation data but cannot make an attribute table from it and so I'm not sure how to get any of that data into a table in order to make a hypsometric curve.
9
votes
3answers
629 views

Creating raster by randomly choosing cell value from multiple overlapping rasters?

I'm using ArcGIS Desktop 10 with its Spatial Analyst extension. How do I combine multiple rasters into one, always choosing randomly from the values of overlapping cells? I have an image that may ...
9
votes
1answer
4k views

Raster legend in R: how to colour specific values?

I have an elevation model plotted in R r <- raster("example.dem") plot(r, col = topo.colors(20)) Some of the values are below sea level (0), and I'd like to have those display in red. How can ...
9
votes
1answer
3k 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 ...
9
votes
2answers
1k views

What to do with -3.4e+38 nodata values?

I am trying to process some bioclimatic raster files, such as can be downloaded from http://www.worldclim.org/current (bioclim set). They seem to have nodata values set to -3.4e+38 according to QGIS ...
9
votes
2answers
682 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
4answers
194 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 ...
9
votes
4answers
956 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
2answers
623 views

Scriptable alternative to ArcScan (particularly vectorising lines within tolerances)

Sadly the answer to this question suggests that it is not possible to script ArcScan from within a python script. Therefore, does anyone know of any alternatives to ArcScan (either within ArcGIS, or ...
9
votes
1answer
354 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
431 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
5answers
300 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
5answers
795 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
7answers
11k views

Get boundary of raster image as polygon in ArcGIS 10

I have a rectangular raster image in ArcGIS. My question is: how can I produce a polygon which is just the extent of the raster image? That is, I want to have a polygon layer with a single ...
8
votes
3answers
4k views

How to find the locations of the highest values in a raster?

Using ArcGIS 10, I have a raster where I would like to find the pixel with the maximum value in the raster and return its location (center of pixel) in decimal degrees. I would like to iterate through ...
8
votes
2answers
420 views

How to add different sized rasters in GDAL so the result is only in the intersected region

I'm writing a Python method that adds two rasters and generates a single raster output. For reasons beyond my control, the extents of the input rasters are different, but they do overlap. Is it ...
8
votes
2answers
3k views

How to fully load a raster into a numpy array?

I have been trying to check my filters on DEM raster for pattern recognition and it is always resulting in missing last rows and columns(like..20). I have tried with PIL library, image load. Then with ...
8
votes
2answers
709 views

Resample binary raster to give *proportion* within new cell window

I would like to go from a binary raster of forest/non-forest at 30m resolution to a raster at 240m resolution with the value of each cell being the proportion of that cell forested - i.e. the data ...
8
votes
3answers
2k views

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 ...
8
votes
2answers
2k views

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 ...
8
votes
2answers
1k views

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 ...
8
votes
1answer
2k views

How to reproject a raster file in QGIS with datum transformation?

I want to reproject a tiff raster file from projection A (ETRS89/UTM Zone 32) to projection B (DHDN/Gauss-Kruger zone 2). The two projections have a different datum so I have to use a datum ...
8
votes
2answers
565 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 = ...
8
votes
1answer
1k 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
3answers
11k views

How to convert a vector layer to raster?

In qgis in the raster menu there is an item "convert vector to raster". This behaves strangely - I do not understand how it is supposed to work. I can select a vector file, an attribute and an ...
8
votes
2answers
933 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 ...
8
votes
3answers
764 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. ...
8
votes
1answer
719 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
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 ...
8
votes
2answers
749 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
4answers
1k 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
458 views

Calculating distance from points to different class in raster

I am looking for some advice on how to calculate the distance from a point to a different class of a raster. Specifically, I have observations (points) of animal use overlaid on land cover data. For ...
8
votes
1answer
377 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 ...
8
votes
1answer
383 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
948 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
3answers
844 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
4answers
375 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 ...
8
votes
3answers
232 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 ...
8
votes
1answer
266 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 ...