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

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791 views

What DEMs does QGIS support? + DEM data sample

I am working on QGIS rasters. I want to know about DEM file formats supported by QGIS. I know that QGIS can read the GDAL supported formats. but what is GDAL supported format ? Does QGIS support the ...
4
votes
1answer
3k views

Convert 32 bit image to 8 bit image in QGIS

I want to convert my images from 32 bits to 8 bits. I'm using otb to calculate texture and the raster output is on 8 bits, I'm going to use this information as a layer stack for my multispectral image ...
5
votes
2answers
387 views

10 GB Raster Aerial Image in Quantum and POSTGIS

I have a problem... I have been successful in uploading the raster in postgis but when I access it through Qgis. it does not open even after several hours. I have 10GB aerial image raster and ...
0
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1answer
4k views

How to convert a bil image into grid in ArcGIS?

I've downloaded RFE data from FEWSNET. It's a compressed file which includes .bil files. Now i want to convert this ".bil image" into a grid to use the precipitation data in an area. I'm using ...
2
votes
1answer
636 views

Split single raster within multiple polygons

I have a raster ('slope') which content only one attribute in the table. On the other hand I have a feature which content several polygons (catchments) in the attributes table. I would like to obtain ...
1
vote
1answer
216 views

How can I turn QGIS into a simple hiking planner?

I'd like to try and turn QGIS into a simple hiking planner. I have found and worked out how to import OS raster mapping at the correct scale and how to add freehand vector lines to the mapping, which ...
1
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2answers
100 views

Adding 'freehand' data to raster mapping in QGIS

Having just worked out how to import raster mapping into QGIS at the correct scale, I'd like to now add useful information to the map like marked routes, labels etc. How can I do this in a 'freehand' ...
2
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2answers
2k views

How do I import OS raster tiles into QGIS at the correct scale?

I have some tiles of OS raster mapping and their associated TFW georeferencing files. The GR files are in the same folder as the raster data and have the same names, ie TQ21.tif/TQ21.tfw. In QGIS 1.8,...
3
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1answer
840 views

Rotating rasters using GDAL Geotransform (and ArcGIS Desktop)

I am working on a GDAL driver for a proprietary grid-format. In some cases, the grids are rotated in order to get smaller file sizes. In my GDAL geotransform array, I do the following (showing a ...
2
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0answers
1k views

Projecting a Raster from WGS84 to planar Equal Area to Calculate Area: How to Select the Cell Size?

I have a broad question on how to calculate the 'correct' cell size for a raster when analyzing an area not at the equator. My goal is to project a land cover raster provided in GCS WGS84 to an equal ...
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0answers
759 views

How To calculate raster land cover inside overlapping buffer zones?

I am working with a raster land cover file that consists of several land cover types (e.g. forest, buildings, grass ect.) in total there is 40 different land cover types. I have 1200 bufferzonen (...
2
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3answers
279 views

How to create a raster from scratch

I realize this isn't a geographic question as I'm not trying to make this into a geographically placed image. But I hope you all will know how to do this. I want to make a raster from scratch. I ...
0
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1answer
61 views

USGS FLT Hdr file interpretation

I have a legacy program that attempts to read USGS 1/3 arcsec data. When I compare results to GDAL, I find that the lat/lon to pixel conversion is off by 1 line. The reason (I think) is because the ...
2
votes
1answer
198 views

Reproject gif.gz raster to WGS84 in QGIS

I am a steep learning curve into QGIS. I have a raster of global fire maps from the modis site: http://lance-modis.eosdis.nasa.gov/imagery/firemaps/firemap.2013221-2013230.8192x4096.gif.gz I would ...
4
votes
2answers
2k views

gdal_calc.py outputs huge files

I think this is a general enough question to apply to more than just gdal_calc, but perhaps not. When I run gdal_calc.py -A map.tif --outfile=deforestation_00-10.tif --NoDataValue=0 --calc="A >= ...
2
votes
1answer
439 views

Can I update the service on ArcGIS for Server programmatically?

There is Windows Service. This service adds user raster data to the Raster Dataset in sde database. The Raster Dataset registred on the ArcGis Server. This Raster Dataset also was publishing on ...
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2answers
668 views

How to georeference a raster based on identical, already georeferenced raster

I have two identical rasters, one has been georeferenced, the other has not. I would like to georeference the second raster automatically using the first one. I do not want to create links by hand and ...
1
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1answer
685 views

identify percentage of raster cells within a polygon

As per the title I want to determine the population inside multiple polygons according to different land use zoning (High Residential, Low Residential, National Parks etc) that's in raster format. ...
0
votes
1answer
271 views

How to delete raster dataset from sde base programmatically

I use sde database, registered with ArcGis Server 10.1. Sde connection is direct. Database container is postgres. There is a raster dataset in this sde base. I can open this sde database ...
0
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1answer
167 views

Rotating raster grids using ArcObjects changes cell size in ArcGIS Desktop?

I am using ArcObjects, namely RasterGeometryProc, to apply rotation on grids. The transformation works fine. However, when looking at the grids properties in ArcGis, the cell sizes has changed. ...
2
votes
1answer
241 views

Change Values of Georeferenced Raster

I am using QGIS to georeference B&W images. I have now done this and would like to set the black surround of the image (as a result of the georeferencing) to transparent but this does not work as ...
0
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1answer
931 views

Polygonize.py: AttributeError: 'NoneType' object has no attribute 'CreateDataSource'

Given a topographic raster tif of an european country where elevations are simplyfied to either 0, either 200. How to create a polygon ? Comment: With the following polygonize.py command: ...
4
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3answers
2k views

Is there a Raster Equivalent of the Split tool?

I have the DEM of a State in ERDAS Imagine (.img) format. I have a shapefile containing the counties of that state. I want to split the whole raster into DEMs of the individual counties. The counties ...
0
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1answer
2k views

How to conditionnally assign a new value to pixels of a raster image?

Given a topographic GIS raster of one country crop.tif: Given a know pixel value such as elevation (z) is +73 : $ gdallocationinfo crop.tif 1 1 -valonly > 73 Given an elevation threshold n = 50 ...
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2answers
659 views

Gdal: How iterate through all pixels of a raster image?

Given a topographic raster image. How to iterate through all pixels of this raster image ? Solution preferably with gdal, in console. Some other libraries/script could be installed. Related: ...
2
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1answer
1k views

How to work with flt & hdr files

I have been working on a vector-based spatial analysis in R using shapefiles. I wish to use some environmental data that is downloadable, however it is only available in raster format (FLT & HDR ...
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1answer
897 views

Gdal: How to get a pixel's value from raster image?

Given a topographic raster image. Given a pixel's coordinate in pixel/lines or geocoordinate. How to get it's pixel value ?
2
votes
1answer
149 views

Revert back from RGBA raster to original 1 band raster cell value

I have a number or single band raster grids that have been converted to RGBA (png). I no longer have access to the orignal single band raster data but have the png files. Is there a way to convert the ...
0
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0answers
100 views

Vector/Raster Intersection - Speedup and replacement for ST_Centroid

I have some raster data which is the altitude above sea level and also some vector data which represents building outlines. What I want to do is grab some buildings outlines and fetch all the raster ...
2
votes
0answers
346 views

How to render a transparent raster layer on top of one or more vector layers with PyQgis?

I been trying to render a map with a 3 vector layers and one raster layer. The idea is that the raster layer should be on top of the other 3 vector layers. The problem is that even when I add the ...
0
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1answer
596 views

How to change rasterlayer color?

I have rasterdataset in gdb. I create layer from this rasterdataset. private static void CreateLayer() { ... IRasterLayer rlMosaicDataset = new RasterLayer(); ...
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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?
3
votes
1answer
8k views

Import PDF to qgis

i have a PDF containing a region of Baltimore city that contains lots of polygons in it. you can download it from here: http://www.baltimorecity.gov/Portals/0/agencies/planning/public%20downloads/...
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vote
1answer
32 views

Searching 'select by color' for raster or map data

I'm planing to create an online map component with which the user can create/draw polygons based on underlying raster data. Is there some library / tool / procedure existing which enables the ...
6
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1answer
1k views

QGis Save Raster as Rendered Image

In QGIS 1.9.0 Master, when you right click on a raster in the Layers Panel and select "Save As", you can select the output mode to be "Raw Data" or "Renedered Image". When selecting the Rendered ...
4
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1answer
1k views

How is slope of a surface in an arbitrary direction produced?

I am currently developing a program that requires that I calculate the slope for each cell in a DEM. However when I try to understand the algorithm to be used I get stuck trying to understand exactly ...
3
votes
1answer
616 views

How to calculate the distance to multiple locations from each cell of my raster?

I'm working with Arcgis 10.1 and Python 2.7.2 How can I calculate the distance to multiple locations from each cell of my raster? I tried euclidean distance but it only provides the distance to ...
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0answers
191 views

QGIS merge rasters error

I've been trying to merge some raster tiles at work and I've been getting an error message saying I don't have the correct permissions. This works fine on my home pc. Any obvious reasons for this? ...
0
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1answer
106 views

Precipitation or snow cover raster data for Scandinavia

I am looking for free precipitation or snow cover data in Scandinavia mountain during the winter 2011-2012. The WorldClim dataset is not enough acute. I would like 500 m scale at least. There is NASA'...
2
votes
2answers
346 views

Convert ASCII Grid Colorized to Raster

I have an ASCII Grid file + .prj file and can visualize this in qGIS. I can colorize it by going to properties and using a Pseudocolor Ramp. However, I want to export this now as a TIFF / Raster. ...
0
votes
1answer
133 views

Integer rasters referring to the same scale

I'm using ArcMap 10. I want to display the area of simulated avalanches. I want this area to be divided in different colors depending on the thickness of the deposit. I managed to do that. But I want ...
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0answers
141 views

convert vector with multiple attributes to multiple rasters

I have a vector polygon feature with multiple attributes/fields. Ultimately, I want to convert it to a raster 'stack,' whereby each of the attributes/fields will be a different band of the raster ...
2
votes
1answer
188 views

Retrieving proportion of pixels in R

I'm trying to retrieve the following pixel statistics: Proportion of zero value pixels: [nº of zero value pixels / (total nº of pixels - nº of NA pixels)] Proportion of pixels smaller than 3rd ...
0
votes
1answer
136 views

Multiple Rasters into PostGIS

This may have been asked before, but A) what software/libraries etc do I need to B) load multiple rasters into PostGIS? I have Python 2.7.5, QGIS 1.9 (latest Weekly Build), PostGIS (whatever the ...
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vote
1answer
245 views

Can't view PostGIS rasters after changing schemas

I have loaded a few rasters into the Public schema of a PostGIS 2.0 database. Using the db manager in QGIS 1.8.0 I can add the rasters to the map canvas. After moving the rasters to another schema in ...
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vote
1answer
112 views

Area surface doesn't match

I have three municipalities with a total surface of 178 sq km. I want to analyze land cover of those municipalities using both LANDSAT images with a pixel size of 30 x 30 meters and SPOT with a pixel ...
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2answers
4k views

Can ArcGIS Desktop stack layers?

I have 7 bands of Landsat and I would like to combine all layers into one layer. Can ArcMap 10 do this like Erdas software can?
5
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2answers
395 views

Creating planes, eg roof surfaces, from LiDAR/DSM data

I am capturing the area of roof tops of buildings from a DSM (derived from LiDAR data) which has not been much of a problem. I can then also derive angle, hillshade and aspect but it is only per-pixel....
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1answer
865 views

How to convert multiple rasters to new raster (mosaic)?

I want to use Mosaic To New Raster in ModelBuilder. I want it to give me multiple outputs because I have multiple folders with a different number of images in each. Below is the model that I have ...
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0answers
232 views

PostGIS raster functions aspect and slope slow

I am trying to compute the raster and slope values from a DGM table (8184 x 5159) imported from tif file tiled in 500x500 tiles. In my query in which I merge the DGM table with a vector (point type) ...