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

learn more… | top users | synonyms

2
votes
4answers
7k views

Combine overlapping rasters with priority to values of specific rasters?

I have 5 rasters that cover a large area. I want to combine all 5 into 1 raster. Each raster has data for portions of the total area that none of the other rasters cover. Raster C overlaps A,B and D. ...
2
votes
1answer
326 views

How to best remove rgb values outside of aerial image?

I have just converted RGB-TIF images to RGB-ECW for reasons of space and performance in ArcGIS. However, after the conversion, there are relics outside of the images which are not nodata values but ...
2
votes
2answers
409 views

SPOT NDVI time series

I have 423 spot.vgt ndvi from first April 1998 till 31 Dec 2009. I want to know how to stack these NDVI to have one image for time series analysis? Or better to ask how is it possible to analyze a ...
2
votes
2answers
1k views

GDAL Clipping (hack)

I am trying to use the python script from http://www.sparkgeo.com/labs/2010/07/07/gdal-clipping-hack/ to clip a raster based on many shapefiles. The script is using a mysql database an i would like to ...
11
votes
3answers
2k views

Combining 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 ...
11
votes
3answers
4k 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 ...
11
votes
2answers
2k 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 ...
9
votes
3answers
747 views

Benefits of *.las vs *.xyz or *.ascii when working with LiDAR in ArcGIS for Desktop?

From time to time, we use LiDAR data for modelling in ArcGIS. Previously, we would be supplied either an .xyz or .ascii of the data, but more recently, we are also being provided .las files in ...
9
votes
2answers
556 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
1answer
452 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
752 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
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
624 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 ...
7
votes
3answers
928 views

How do I display a raster “Background Value” as hollow for more than one set of RGB values?

I have two overlapping .ecw layers of the same area, though one is clipped in the middle, with a white edge. When I set the background value to 255,255,255, and define it as hollow, it only hollows ...
7
votes
4answers
4k views

Garmin etrex raster maps support

I currently use an excellent set of printed topographic route maps for mountain biking. I would like to scan the maps, georeference them, and upload the maps to a handheld GPS device. Does the etrex ...
7
votes
3answers
1k 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 ...
7
votes
3answers
8k views

How to add Raster legends in QGIS map composer?

Is there a plugin or method to add legends for raster layers (with a custom colourmap) as an item in the print composer?
7
votes
1answer
934 views

How can I change the class of one pixel in a classified image?

I have a classified image (I did it in ERDAS) with six categories. There are some misclassified pixels (especially high-density urban category). Is there any way that I can choose one pixel and then ...
6
votes
1answer
142 views

Automate Exporting of Rasters Using Renderer in ArcGIS

It is possible to export rasters in ArcMap by right clicking the layer-> Data-> Export: You can then click 'Use Renderer' check box to ensure the image you export uses the current ...
6
votes
1answer
602 views

ModelBuilder: How to extract data by date, export to separate tables and interpolate tables to rasters

I've been using ArcGIS for a couple years, but when it comes to model builder I've only worked with very simple models. I'm hoping someone that is much smarter than myself can help me in building a ...
6
votes
1answer
1k views

Raster data on PostGIS

I need to publish raster and vector data through GeoServer WMS service and I have already chosen PostGIS as datasource to keep vector data. Now I would like to know what is the best practice to work ...
6
votes
1answer
2k views

Creating a mask with transparent pixels in python

I have a geotiff image with pixel intensities ranging between certain values. Lets say bewteen -2 and 2 (the image is normalized). I have a certain threshold which interests me, lets sat 1. I would ...
6
votes
3answers
6k views

Exporting Selected Raster Graphics using ArcGIS Desktop?

I'm having a problem exporting raster graphics using ArcGIS 10. It seems simple enough, but for some reason I cannot get ArcMap to work with me. Here are my steps: Add a raster to ArcMap Open the ...
6
votes
2answers
2k views

Using SearchCursor to access & export values in a raster table

I am desperately trying to export the values in a raster table to a .txt file. I've seen some other folk post about this, but for some reason can't get the code to work in my case. I have a raster, ...
6
votes
3answers
4k views

Insert Raster to MXD using arcpy.mapping (ArcGIS 10)

What i want to do seems simple. But again i can't even find a workaround... I have got a lot of Raster-files (ESRI-GRID) which i need to insert into a layout mxd-file and then export the map to ...
6
votes
3answers
5k views

Resizing image resolution from 1000 m to 250 m in ArcGIS Desktop?

I'm beginner of ArcGIS and Remote Sensing and I have many problems with the procedure. One of them is that I have NDVI images and Soil map. Both are at the different resolution: NDVI is 250 m and ...
5
votes
1answer
97 views

Which is better for measuring actual ground elevation, NED or SRTM?

I know that NED DEM layers are created using mainly Lidar point clouds and that the SRTM derives its data from shuttle-based radar. I have both of these loaded into QGIS and can see that over my study ...
5
votes
4answers
4k views

How to reclassify a float raster?

I have three rasters which represent distance (in metres) from certain things (bus stops, parks, libraries). I would like to reclassify these rasters so that they get integer values based on the ...
5
votes
1answer
3k views

Save Visible WMS layer to file

Is there tool to save currently visible WMS layer to file in QGIS, or some place in QGIS where you can get needed xml to fetch it using gdal ?
5
votes
2answers
2k views

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): samples = 1440 lines = 720 bands = 1 header offset = 0 ...
5
votes
2answers
3k views

How to get an extent for Raster using python

I have to get an extent of a given raster so that I can save it and use the same to clip another raster with that extracted extent. As of now I am stuck in the extent part. import arcpy from arcpy ...
5
votes
3answers
470 views

Create Zonal Grid in R

Suppose I have a n*n raster, and I want to create k square blocks (k can be divided exactly by n*n ) for zonal analysis: for example, when n = 4 and k = 4 a 4*4 raster is create with value 1 1 2 2 ...
5
votes
2answers
1k views

How to enclose clustered points with polygon?

I have a raster with forest (1), no forest (2) data. "1" is represent single/few trees and there is gaps between them. I want to create a polygon around these trees to a forest map. It is not a dense ...
5
votes
1answer
2k views

How do you add a long list of rasters together in Python?

If you have produced a long list of rasters (lets say 50) and want to add them together, is there any shorter way to write in python rather than typing all the inputs, like so: outRas = inRas1 + ...
5
votes
1answer
2k views

Coordinates of upper left corner in the world file?

According to Wikipedia and ESRI last two lines in the world file represent x and y coordinates of center of upper left pixel. Now, if I have a world file like this: 32.0 0.0 0.0 -32.0 691200.0 ...
4
votes
1answer
237 views

Difference between gdalwarp and projectRaster

I am trying to project a Raster. In R there is the projectRaster() function to to this (below a fully reproducibly example) : # example Raster require(raster) r <- raster(xmn=-110, xmx=-90, ...
4
votes
1answer
417 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) ...
4
votes
1answer
1k views

How to read *.adf files into R?

I want to load .adf files into R. The data is from this page: http://www.fao.org/geonetwork/srv/en/metadata.show?id=14057 I tried the following code that I found after some research in the internet. ...
4
votes
5answers
394 views

How to group individual groups of pixels into a single class

I have a raster image with certain pixel groups of equal area. Each group represents a single house. I want all the pixels near a group of houses to have the same pixel value, i.e., I want to name ...
4
votes
1answer
491 views

Problem loading SID to geoserver

I have a folder with .sdw and .sid files I want to server using geoserver. I've followed the instructions here which basically means to install GDAL extensions and binaries on the geoserver machine. ...
4
votes
1answer
344 views

How to create cohesive Spatial Pixels from Spatial Points Dataset

I have a Spatial Point DF spo (covering an irregular shaped area of interest). The data are not on a regular grid due to crs transformation. My goal is a raster with predefined resolution and extent ...
4
votes
2answers
1k views

Spatial query of raster data

I have population distribution data as a raster layer and exposure contours as vector (polygon) layers. What I'd like to do is use the vector layer to estimate the population indicated from the raster ...
4
votes
1answer
1k views

raster2pgsql: Strange error when creating a table

Hi GIS Stackexchange people, When I try to load a asc file into my psql setup, I get a strange error message. I have created the sql input file via raster2pgsql -s 4236 -I -C -M gis_data.asc -F ...
4
votes
2answers
423 views

QGIS Two Raster Data Sets with black line between the two sets where they join?

Where the two Digital Raster Quad sets (topo maps 7.5 Quad) overlap there is a significant thick black line (not a single line but wide and is wider the further south you go on the map). I am looking ...
4
votes
1answer
660 views

Generate centroids for vector polygons based on raster and land-use data using QGIS

Although QGIS has the ability to generate centroids for polygons, I am not sure how to generate centroids based on land-use development using raster data. Here's an example of what I'm trying to do: ...
4
votes
3answers
4k views

How to convert raster data into regularly sampled points?

I am wondering if there's another way to convert raster data (ex: DEM) into regularly sampled points. I've used Raster to Point under ArcToolbox previously, but if the raster data is huge, that's a ...
4
votes
3answers
3k views

Export georeferenced image overlay from KML?

How might one export image(s) from image overlays in a KML file to a standard geo-referenced raster format like geotiff? Use case: NASA's Earth Observatory has a time series of the changing Athabasca ...
4
votes
1answer
2k views

Filtering a raster by pixel cluster size in ArcGIS?

I have a raster image representing islands in a river (see image) created using the following process: 1) Clip a water surface DEM and watershed DEM by a bounding polygon (waters' edge). 2) Subtract ...
3
votes
1answer
134 views

How to add time and elevation dimension attributes to Geoserver rasters?

In geoserver, when I edit a postgis raster layer and click on the Dimensions Tab, I can't enable either of the Time or Elevation dimensions. The following message appears next to each of the ...
3
votes
3answers
934 views

Unable to read raster into R: 'TIFFReadDirectory:Failed to read directory at offset'

I'm getting a weird error when trying to read a raster into R. >r <- raster('myraster.tif') Error in .local(.Object, ...) : TIFFReadDirectory:Failed to read directory at offset 2606110 ...