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

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23
votes
2answers
2k views

How to represent trend over time?

I have a time series of rasters where the cells of each raster represents some value at a certain time. I'd like to generate a map that highlights the magnitude of positive or negative trends in this ...
2
votes
1answer
107 views

What is No Data Value?

I'm looking at the transparency window of the layer properties of my "Heat map". How does the No Data Value effect a raster layer. I'm assuming an initial setting of -9999 sets it out of the way, so ...
6
votes
1answer
3k 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 ...
3
votes
2answers
962 views

How to calculate the area of rasters in QGIS?

I have been working with some rasters and would like to know how to calculate the area occupied by one element of a raster in Qgis.
1
vote
1answer
485 views

What are Bands, Dimensions, and Histograms in QGIS?

First; I can see a band as synonymous with a channel in an image editing program like GIMP, is this correct? If so then bands play the role of color mixing and masking. Are there any other ...
3
votes
1answer
77 views

What defines a Class in the Heat map plugin?

What defines a Class in the Heat map plugin? As in: "Black holes like that are usually caused by raster values exceeding the range of the color ramp. Try adding another class with a higher associated ...
8
votes
1answer
563 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 ...
3
votes
1answer
1k views

How to convert jpg file to shapefile? [duplicate]

I am developing a GIS application like this: By now my steps are: I have got a jpg file, 5040 x 8179 dimension. In this map, the roads, rivers, towns etc. are marked. I am using .Net to develop ...
3
votes
0answers
145 views

How does Zonal statistics handle pixels that are on the border of the polygon?

I am using the plugin zonal statistics to calculate the sum of the raster cells within polygons. How does this plugin handle pixels that are on the border of the polygon, are those cell values ...
1
vote
1answer
106 views

Problem loading raster to PostGIS using QGIS

I am having trouble loading a raster (.asc) file to PostGIS 2.0.1 using the plugin Database - PostGIS Raster - Load raster to postgis in QGIS 1.8.0 on Win Vista 64 bit. I get the following error ...
1
vote
1answer
232 views

Qgis - Raster clip Problem

I tried to use the Raster (Extration) tool "clipper" and I always get this error log: What is my problem? Fehler bei der Ausführung von Python-Code: Traceback (most recent call last): File ...
11
votes
2answers
2k 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 ...
2
votes
1answer
145 views

filter / generalize elevation points on the basis of some conditions

I wanted to generalize many elevation points in a rectangular area (about 700 square km). I need to take about 3 points for square km. These points must satisfy some conditions: One of these ...
1
vote
2answers
320 views

Getting 2147483647 and -2147483647 as min and max output for point to raster, polygon to raster, and feature to raster tools

No matter which feature to raster tool I use (feature to raster, point to raster, or polygon to raster), I am getting a raster output whose min and max values are 2147483647 and -2147483647, ...
2
votes
3answers
389 views

Stuck in loading raster to PostGIS

I am running running Mac OS X (10.7.5), PostgreSQL (9.2) and PostGIS (2.0.2) (installed via Postgres.app). The PostGIS extension seems to work perfectly with vector and raster layers. Once I enable ...
2
votes
3answers
508 views

Raster dataset doesn't exist error

Dataset exist and I am able to get statistics from ArcGIS python window. But it failed as a script with error: ERROR 000865: Input raster: C:\temp\ras does not exist. I have tried following ...
3
votes
1answer
180 views

Reclassification of environmental values

I've started to use Qgis recently. I have a logical question. I'm trying to reclassify a raster. The values in the raster are depths, obtained by an interpolation. The original depth values (of the ...
0
votes
0answers
30 views

Polygonize Raster to Vector Error [duplicate]

I have a problem when I am trying to Polygonize (Raster To Vector). I have a Corine map with 44 different land uses. I run a query and I save the selected areas with Bands 0 and 1. Now I am trying to ...
0
votes
1answer
44 views

Isolate And Save Raster Features From Existing Multivalue Raster Map

I have Cyprus Corine map with 44 different types of land use. I want to run a raster calculator query or any other way to isolate the areas with codes 10 to 22 and 26 to 34, all other values 1 to 44 ...
0
votes
2answers
451 views

How do you use 'reclass' in GRASS?

It could be user error, but for some reason, the reclass tool is just hanging and hanging... QGIS 1.8 Compiled against GDAL/OGR 1.9.2 Ubuntu 12.04.1 Running the tool from the Sextante toolbox Input ...
1
vote
1answer
97 views

Sextante (SAGA) “Normalisation” problem

I don't understand the SAGA-module "NORMALISATION". In SAGA Gis I just can define one MIN and one MAX value. In QGis I have to define 2 of both. How to handle that exactly?
3
votes
4answers
180 views

Combining UK OS Historic Digimap Tiles

I'm assisting a retired user in combining a large number of raster tiles downloaded from Historic Digimap http://edina.ac.uk/digimap/description/historic_overview.shtml into one project in qgis. I'd ...
4
votes
2answers
211 views

How to create a colormap where colors diverge at value 0 in QGIS?

I calculated a raster as difference of two other rasters. Now I want to create a colormap where one colour represents negative values and one colour positive ones. The two colours should become ...
0
votes
2answers
913 views

Digitizing from OpenLayers Plugin in QGIS, or create raster?

Is there an easy method for digitizing from a layer added from the OpenLayers pluggin. As i cannot snap to it or use it as raster so the entire map does not load? two separate issues there.
3
votes
1answer
194 views

Difference between gdal versions in reading raster on two machines?

I am using raster data from Afripop.org and using the R package raster (raster_2.0-41) to do all my computation. Everything has been working out just fine until I tried sending some jobs to a remote ...
6
votes
1answer
188 views

weighted mean across rasters in R

I have 2 rasters. One raster (bio1) contains temperature information across a continent. The other (sp) contains, for each cell, a probability of occurrence for a species. I would like to calculate ...
2
votes
0answers
828 views

How to convert Rainfall Isohyet map into Raster to determine precipitation (mm) at any point? [closed]

Specifically, I have a rainfall map (Isohyets) measured in mm (precipitation)... I wanted to know a particular value (precipitation) at any point between these lines... How can I do this? Do I have ...
1
vote
1answer
3k views

reclass, raster calculator

I'm trying to apply seperate equations for different land types. I have created a raster containing only the land type I'm interested in. I then reclassed the values to '0'. My plan was to use the ...
1
vote
0answers
57 views

How to clip Raster using multiple polygons and Python? [duplicate]

Possible Duplicate: clipping a raster by multiple datasets or polygons I have polygon layer and DEM and I want to write a program using python to cut the raster into multi-raster based on ...
3
votes
1answer
160 views

How I can incorporate results of histogram stretching into georeferenced image?

I have one channel 8 bit raster and when I open it in QGIS with histogram stretching "on the fly" it looks fine. How I can recalculate original raster accordingly changed histogram?
1
vote
2answers
545 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 ...
4
votes
3answers
2k views

How to extract raster values and create new raster in Qgis?

I want to extract certain values of a raster image in order to create a new raster which then should only contain the extracted/chosen values. How to do this in QGis?
8
votes
1answer
536 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 ...
3
votes
1answer
183 views

ArcGIS Raster Symbology - Break contour at 0

In ArcGIS 10, how can I break raster symbology (stretched) at a particular value (i.e. 0). For example, I have a DEM representing both topography and bathymetry and I want a break at the 0 m contour ...
6
votes
2answers
276 views

Breaking apart a polygon layer by unique values, creating many new layers

I have a large dataset of habitat information that I need to calculate distances from animal locations to the closest polygon of each habitat type. The way to do this, that I understand, would be to ...
1
vote
2answers
164 views

Put color for raster data(aspect.tif) on QGIS1.8.0

I create aspect.tif from DEM file. I could put the values(0 to 360)from contrast enhancement. I could set color from color map(freakout or Pseudocolor). In here, the data is shown by only 4 colors. I ...
1
vote
0answers
192 views

How to use GDAL to burn a selected value from one raster into another?

I think this should be a relatively simple process, but I'm not quite sure how to approach it. I have a shapefile containing 1000's of polygons. I also have 19 rasters. All of the polygons fall ...
2
votes
1answer
81 views

How to visualize the water equivalent between two raster layers in arcmap 10.1?

I do have two raster layers (interpolated with Empirical Bayesian Kriging), that show the elevation of a glacier in April, and September. I want to show the change in elevation between the layers in ...
4
votes
1answer
132 views

Why does the added raster layer have strange edges?

I'm using Geoserver in conjunction with the google maps API to add a raster layer onto a map. It loads fine, however there's some strange problem with opacity at the edge of the layer where you can ...
3
votes
1answer
561 views

Importing grib, grib2, netcdf to PostGIS

According to grib2 to raster? (grib2 -> raster2pgsql -> PostGIS 2.0 -> GeoServer), it seems like that grib2 can be treated as raster directly. Is it the so called "standard" way? How about ...
1
vote
2answers
356 views

ArcPad Raster Not Displaying Correctly

I have a hillshade that I would like to use as a background in an ArcPad 10 map. I get everything set how I want in in ArcMap and when I export the map to use on my Trimble the hillshade doesn't show ...
1
vote
1answer
150 views

cannot print listRasters

I'm trying to run this very simple script to check a problem in another more comlpex one. import arcpy arcpy.env.workspace= 'C:\\Users\\Umberto\\Desktop\\Prove_Script\\Karakoram\\temporary_01' rst= ...
4
votes
2answers
921 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):https://echange-fichiers.inra.fr/get?k=rLSyoavrnifGyH5XrlO samples = 1440 lines ...
4
votes
3answers
148 views

Where can I find decadal climate and ocean data for Europe?

I would like to find decadal climate and ocean data for Europe that I can download and use directly in ArcGIS. Specifically, I am looking for mean annual temperature, sea surface temperature, and ...
5
votes
1answer
99 views

What GIS software is required to export a GIS map as a hi-res raster image?

I am looking for some (preferably free) GIS software that will enable me to export multi-layered world maps (made up of shape-files and kml files and so on) as hi resolution (21,000 pixels wide), ...
1
vote
1answer
243 views

How to add multiple rasters to a layer file?

I'm trying to make a .lyr file to bring into ArcMap with arcpy.mapping. I can bring a single raster into a .lyr with the script below. I'm unsure how to proceed to get multiple rasters from the same ...
2
votes
2answers
3k views

How to georereference a TIFF file which has already a spatial reference?

I have a TIFF file of Poland and a self drawn vector map of Poland. The vector map has no spatial information. I am intending to reference the TIFF exactly to the shape of the self drawn map. My ...
4
votes
1answer
228 views

Use csv file as raster file and stitch them together

I'm having an issue trying to stitch together 100 32bit Tiff files (coming from thermal imagery video and extracted as 32bit Tiff). I used Hugin to mosaic the pictures extracted from the video which ...
3
votes
1answer
231 views

shortest distance between a raster and another raster

i am using arcgis 10.1 i want to calculate the shortest distance between a raster and another raster. i have a bathymetric raster and an underlying fault plane raster. for each bathy raster cell, i ...
4
votes
1answer
253 views

How can I avoid reprojection gaps when merging DEM rasters?

I have two raster DEMs in same resolution I want to bring together. I was using the merge-function in SAGA, GRASS and QGIS but I always get the following result: What do I need? Where could the ...