Rasters are regular grids of values, usually stored in an image-like format.
2
votes
1answer
698 views
Adding fields to raster attribute table
I have a raster attribute table associated with an IMAGINE .img raster that I build and open with:
IGPUtilities utils = new GPUtilities();
IRasterDatasetEdit2 raster = (IRasterDatasetEdit2)
...
1
vote
1answer
99 views
How to correlate raster map and elevation data?
I have been provided with a set of raster maps. Thanks to another helpful user here I have been able to acquire some elevation data for the same region from gis.utah.gov in asc format. Now I need to ...
1
vote
2answers
2k views
Get extent of Georeferenced Rasters in Python and output to polygon shapefile
I would like to create a shape file containing the extents of each of the rasters in a directory. Is it possible to capture the extent of a raster using Python?
I have tried
...
1
vote
2answers
5k views
How to calculate Raster Area per Polygon?
In ArcMap, I have a raster file that contains 6 classes of landcover and a shapefile that is the census data (OA boundaries and their population).
I want the area of each class in each OA? For ...
8
votes
3answers
573 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.
...
7
votes
7answers
608 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 ...
6
votes
2answers
274 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.
6
votes
1answer
152 views
Finding largest number of observations within a given radius
I have the following problem: Given the location of insured properties (say houses with fire insurance), i have to find the largest sum of insured values which fit into a 300m radius. Now, my first ...
6
votes
1answer
720 views
QGIS WKT Raster Plugin error, what does this mean?
I have been playing with the WKT Raster plugin. I have installed the WKT Raster experimental binaries in PostGIS successfully and followed the instructions in the read me to the letter.
When i am in ...
6
votes
7answers
2k views
Extract raster values at points
How can I extract values from a raster by points. I prefer not in Arcgis. I prefer in Qgis or Mapwindow or other open source gis.
5
votes
3answers
2k views
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 ...
5
votes
1answer
500 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 ...
5
votes
1answer
436 views
Why do TIF loaded into PostGIS lose their colormap?
I have successfully loaded a TIF image (using raster2pgsql) into my PostGIS 2.0.1 database. I can load the raster image into QGIS and it displays in the correct space. However, it has lost all colour ...
5
votes
1answer
596 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 ...
5
votes
2answers
233 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 ...
5
votes
3answers
380 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 ...
5
votes
1answer
335 views
QGIS composer - How can I eliminate striping across transparent raster layers?
I have downloaded QGIS dev version 1.7.0-114 and I have come across some weird behaviour in the composer.
I create a map with a hillshade and a transparent DEM ontop of it, pretty standard stuff. ...
4
votes
2answers
249 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
2answers
141 views
Wavelet vs Discrete compression for imagery
What is the main reasons to choose wavelet (jp2, sid, ecw) instead of discrete (JPEG) compression methods for raster data?
Lets limit this question to aerial imagery and lossy compression.
Why ...
4
votes
2answers
297 views
How to fix a raster with wrong Eastings?
I get an error when trying to warp a tif file in QGIS:
ERROR 1: Too many points (35721 out of 35721) failed to transform, unable to compute output bounds.
I am using QGIS 1.7.0 Wroclaw with gdal ...
4
votes
2answers
735 views
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 ...
4
votes
2answers
282 views
What generation of the MrSID format is supported by ArcGIS 9.3?
This is probably old news to some, but I just learned that MrSID (.sid) files have different 'generations' of file formats - so there are MrSID Generation 2, Generation 3, and Generation 4 files. ...
4
votes
1answer
571 views
Can QGIS resample Rasters during display?
When I was using ArcGIS a user could resample a raster during the display (I think via layer properties under the display tab). This would smooth the appearance of the raster so it wouldn't appear ...
4
votes
2answers
2k views
Modify raster layer display and symbology properties programmatically with arcpy or ArcObjects
I have over 1500 NITF files that I need to be able to modify the layer display and symbology of programmatically from within ArcMap. I need to set the properties outlined in red below:
I've looked ...
3
votes
1answer
127 views
An error in raster calculator in Arcgis
I wrote and ran this formula in raster calculator in ARCGIS. But the following error gets me into trouble. Does anyone have a suggestion to overcome this? Here is the formula I wrote and the error ...
3
votes
1answer
80 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 ...
3
votes
2answers
308 views
Exporting DEM-derived rasters to CSV from QGIS?
I have been able to import into QGIS a set of raster topographic maps and the associated DEM raster maps. It registered the two for me. From there I have calculated the associated slope raster map. ...
3
votes
1answer
578 views
ArcGIS 10 trouble displaying raster correctly
I think I've come across a Bug in ArcMap 10 in displaying rasters. This particular model comes from the USGS GAP Species dataset with metadata hosted here. I'd like to know if anyone else has ...
3
votes
1answer
2k 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 ...
3
votes
5answers
856 views
When a raster is clipped to a polygon with Python, why does it still take on the extent of the entire shapefile?
I am clipping a raster image to each polygon row in a shapefile in ArcMap 9.3 using the Clip tool (Data Management) in Python with Clipping Geometry set. While the clipped raster successfully depicts ...
2
votes
1answer
90 views
How to calculate volume from a raster file?
I have a raster file containing the depth of water. I need to find the volume of water using that raster file. I need to find the area of each cell and multiply with the depth. How can I do it in ...
2
votes
1answer
56 views
Create raster distance around a single point feature class
Okay, so I'm relatively new to ArcMap and I'm trying to use the Fuzzy membership for suitability test. I have a single point feature class that I wanna use for this analysis. I know that in order to ...
2
votes
1answer
165 views
Querying PostGIS Raster with MultiPoint
For one of my projects using PostGIS 2 I have a table with GPS tracks (igc_files). It holds records including a MULTIPOINT() column that has about 1,000 points for each record and a column that has an ...
2
votes
2answers
492 views
How to speed up Postgis raster layer display in QGIS?
i've been importing some digital orthophoto geotif files into postgis 2.0.1 via raster2pgsql tool (i also made 3 levels of an overview table - pyramid). Then i tried to import the layer into qgis via ...
2
votes
1answer
231 views
Recreating A Lat/Long Grid Using a Specified Formula
I'm trying to recreate the Gridded Mercury emissions 2000 (0.5 x 0.5 degree grid) designed by the Arctic Monitoring and Assessment Programme. The file is in ASCII format, but without any coordinates. ...
2
votes
3answers
542 views
Batch script converting and resampling orthophotos
I would like to convert more than 300 orthophotos produced at scale 1:8.000 with a pixel size of 0.8m X 0.8m from Ecw format to Tiff format and after resampling pixel values.
My aim is to batch ...
2
votes
2answers
2k views
How to export a raster layer for external processing?
Is there a way to export all values from a raster to for example a cvs or other textfile or dbf or xls and later import (changed) values from that file back into the raster? For vector-files this is ...
2
votes
0answers
133 views
How to sort entries in raster legend?
How do I reorder the Value field in a raster? There is no up or down button in it.
2
votes
1answer
260 views
Two rasters created from the same polygon have different extents?
My problem is that i am trying to export some rasters to Rockworks so that i can create a sand layer from them. Rockworks requires the grid files i use to have the exact same XY co-ordinates.
So i ...
2
votes
2answers
810 views
Converting google map api coordinates into meters
How would I go about converting the results of my map bounding box into meters within javascript?
For example, if I have the coordinates 51.52366625446907, -0.07467269897460938 decimal degrees, can I ...
2
votes
1answer
2k views
How can I compute raster pixel width and height given raster bounds, row count, and column count?
Restated, how do I convert arc degrees to meters? For example, I have an elevation data raster that has the following metadata:
WEST LONGITUDE=64.97798789° E
NORTH LATITUDE=33.02003415° N
EAST ...
1
vote
0answers
41 views
Feature to Raster Conversion Results in Empty Raster [closed]
I have a simple shapefile with one feature in it with a single value (of 1). I am trying to run a Euclidean Distance on that feature, but I get "invalid parameters" errors.
So I tried to convert the ...
1
vote
2answers
127 views
Why is Format of output data grayed out on Save As dialog for Rectify?
I started georeferencing and I could not save my new "rectify" file, I don't know if is because of the raster or I did something wrong. Then I find out that my control layer is not accurate, it ...
1
vote
0answers
51 views
jagged edges in mosaic DEM
I encounter edge issues when trying to mosaic USGS NED DEMs in ArcGIS 10.0.0. After projection and aggregation, I attempt arcpy.MosaicToNewRaster_management(). I've reproduced the same results using ...
1
vote
0answers
205 views
How to reproject a raster in QGIS? [closed]
I wanted to reproject raster file from UTM to decimal degree in QGIS version 1.7.1 or 1.8.0..
I could reproject one raster file before in QGIS Version 1.8.0. I have tried again, but now we cannot ...
1
vote
2answers
152 views
Cannot get arcpy.MosiacToNewRaster to work with list
Below I have a snippet of a much larger code that I cannot get to work and I am not sure why. It seems that I always have trouble using arcpy functions with rasters. Can anyone help me get this code ...
1
vote
1answer
344 views
Filtering a raster by pixel value with GDAL
I have downloaded Globcover data in GeoTIFF format. I want to create a new grid which only has values where the Globcover data (the only band in the TIF file) has one certain value (==190).
Can I do ...
1
vote
1answer
1k views
Convert a Tif raster file to vector shp file in QGIS
So I've been trying to convert a georeferenced Tif raster file into a vector shp file using QGIS. It's seems to complete this but it ends up giving me a feature class that has over 500,000 features, ...
1
vote
1answer
255 views
How to convert SQL Server Rasters to ASCII Grid?
I have 25km by 25km squares of the world in a relational database. Each square has coordinates for the top left and lower right corner as latitudes and longitudes. Each square also has an index ilat ...
1
vote
2answers
1k views
How to set cell size for vector to raster conversion in QGIS GRASS plugin?
I'm converting a vector (loaded in GRASS plugin in QGIS (1.7.0.-wroclaw) and would like to convert this to a raster with a defined cell size. At the same time I need a value from the attribute tabel ...
