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

learn more… | top users | synonyms (1)

6
votes
0answers
336 views

What is the correct syntax for using gdal_rasterize with a PostGIS datasource [closed]

I have a multipolygon layer in PostGIS and I would like to use gdal_rasterize to generate a raster. I cannot find the correct syntax to specify PostGIS as the data source. $ gdal_rasterize -a ...
5
votes
4answers
707 views

Find the best path along raster

I've just posted a question to StackOverflow about the best way to go about finding the best path on the raster below (where whiter pixels are 'better'), but have realised that it might actually be ...
5
votes
3answers
2k views

resize image resolution from 1000 m to 250 m

I'm beginner of ARCGIS and RS. I have many problems with the procedure. One of them is I have NDVI images and Soil map. Both are at the different resolution: NDVI is 250 m. soil map is 1000 m. So I ...
5
votes
2answers
436 views

Disaggregating aggregate GIS data using remote sensing

I haven't really done much with remote sensing imagery. I have census data for an area, and a TIFF raster image of the area. I'm sure this is possible, is there a simple way to disaggregate the ...
5
votes
2answers
508 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?
5
votes
1answer
2k views

Calculating distance to points in QGIS

Is there a way of calculating the distance to the nearest points in QGIS? In ArcGIS there is a function called Euclidean Distance, which can take an input vector or raster, and generate a raster of ...
5
votes
3answers
711 views

What is a simple binary raster storage format which ArcGIS can read?

I have a C++ program that manipulates raster digital elevation models. I have been using ArcGrid ASCII format for results. It is simple to code and gets the job done, but it necessitates a decimal ...
5
votes
3answers
3k 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 ...
5
votes
3answers
584 views

Is it possible, in QGIS, to create buffers with a set radius, but with individual values taken from the attribute table?

I am looking to create an output that consists of an 11KM buffer around a number of discrete points, where the buffer has a value defined by a column in the data sets attribute table. Is this ...
5
votes
2answers
931 views

Creating a multispectral image from scratch

I want to make a multispectral image from cero to do some tests on it. Something really simple like 5 completely uniform bands with salt and pepper noise on them or a square of different values at the ...
5
votes
3answers
103 views

Please help me identify this CRS. How could I identify this myself in the future?

I'm trying to georeference this map, but I don't recognise the CRS. It is for a region of Tanzania. Here is the image on imgur in case Stack Exchange compresses the image. How would I go about ...
5
votes
3answers
654 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
3answers
4k 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?
5
votes
2answers
2k views

How to set the value of a pixel based on its current value?

I am attempting to set the value of a pixel based on its current value. I am using the Raster Calculator in Quantum GIS dev 1.7 trunk. For example, if the value is 0, I want to set it to 255. Based ...
5
votes
2answers
1k 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. ...
5
votes
4answers
371 views

What satellite imagery would help to show spring locations?

I've got lots of tiny streams on a hydrography shapefile. Historic texts indicate that certain ones have headwaters at "sources" or springs, and I want to try to find these. Browsing the historical ...
5
votes
1answer
2k 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 ...
5
votes
2answers
1k views

How to return raster values based on polygon (shapefile) boundaries in QGIS?

How to return raster values based on polygon (shapefile) boundaries in QGIS? Is this an elementary question, because I am finding it hard....... Ideally I would like a neat workflow as I am likely to ...
5
votes
3answers
2k views

Creating a raster surface of overlaps from vector polygon shapefiles?

Basically what I'm trying to do (in ArcGIS 10) is to compare three vector files in order to create a 'comparison' raster layer. I tried using Data Comparison (under Data Management tools) but it ...
5
votes
4answers
3k views

Quantum GIS and ECW images?

How might I enable Quantum GIS to read ECW imagery? At the moment I'm mostly concerned about this on Ubuntu 10.4 amd64, but I also use WinXP & Win7.
5
votes
1answer
588 views

Identify Polygons on raster image

I have OS street view mapping as raster images. Is it possible (without the obvious of tracing each dwelling) to identify all polygons on each tile. To clarify, My ultimate aim is to produce a ...
5
votes
2answers
263 views

Raster calculation confusion

I need to do some raster calculation, I've been trying to make it work but I am not sure everything is working properly. I need to apply a formula, but I am unsure if I am doing it properly. The ...
5
votes
2answers
4k views

How to clip a vector feature to the extent of an existing raster dataset using arcpy

I have a clipped raster dataset with polylines (from the contour tool) overlayed (see attached). I am trying to clip the polylines to the extent of the raster dataset, which seems simple enough, but ...
5
votes
2answers
160 views

Distortion of equally sized world tiles

My question is related to this: http://stackoverflow.com/questions/7927863/location-data-format-for-adehabitat-package I have a relational database with 'world tiles'. Each tile has a side length of ...
5
votes
2answers
4k views

Interpretation of ArcGIS Kernel Density legend parameters

In ArcMap 9.3 I've used Kernel Density to map various incidents, but the resulting shapefile doesn't display any units of measurement. Is there a good, not-to-technical source that would explain in ...
5
votes
5answers
5k views

How Do You Remove No Data From A Raster (.sid)?

I have an Image.sid that has a white border which is No Data. I've tried using Clip Raster Tool with no success. I've also changed the symbology value for No Data to be transparent. I'd like to ...
5
votes
2answers
197 views

Raster: mosaic first, or project first?

I have a thousand raster tiles in un-projected decimal degrees from which to build a seamless mosaic in a metres-based coordinate system. The final image will be about 70,000px by 50,000px. Which is ...
5
votes
1answer
169 views

Getting ArcMap to display rasters properly first time

This is a very basic question, but as I've self-taught most of my GIS skills this is still a gap in my knowledge. When I load a .tif raster into ArcMap, most of the time it requires re-exporting to ...
5
votes
1answer
812 views

How to keep spatial reference using arcpy.RasterToNumPyArray?

I am using ArcGIS 10.1, and want to create a new raster based on two preexisting rasters. The RasterToNumPyArray has a good example which I want to adapt. import arcpy import numpy myArray = ...
5
votes
3answers
293 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
1answer
852 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
4answers
1k views

How to generate a world file with rotation

I`m writing code to geo reference some images that I get with a rc plane. I have the central coordinate of the image because its atached to the center of the plane. But I have problems when I open the ...
5
votes
1answer
306 views

Unknown Coordinate System on old drawing

I work with many old civil engineering documents, and occasionally I'll need to georeference one which has coordinates pairs listed at many given points but does not list which coordinate system these ...
5
votes
2answers
2k views

How do I calculate a weighted centroid with respect to a raster, e.g. population weighted centroid

In ArcGIS 10.0, how do I calculate the weighted centroid of a collection of polygons, where I want the weight to be a raster layer. In particular I am using a raster of population counts and would ...
5
votes
1answer
172 views

Terminology problem - Raster vs Grid vs Lattice

I have a question about GIS terminology - what is the difference between grid and raster and grid and lattice - in theory?? I thought, that raster is regular network and value is in the cell and the ...
5
votes
2answers
79 views

How to automate creation of toe of slope from DEM?

I was looking for an automated process to "identify" the toe of a slope from a DEM and ran across this ESRI thread and technique: I am at Step 7 but have no idea how this is accomplished. I get it is ...
5
votes
1answer
264 views

Georeferencing a jpeg in QGIS but the scale is way off

I've gone through the really helpful walk-through(s) of how to georeference a jpeg in order to make it a layer, but after inputting the coordinates (either by typing in actual coordinates or clicking ...
5
votes
2answers
667 views

How to batch import GDAL supported raster files into GRASS?

I am trying to import some GDAL supported raster files into a binary raster map layer using the r.in.gdal module from QGis Grass tool. As I have multiple files to import, I would like to batch import ...
5
votes
1answer
4k 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 ...
5
votes
2answers
1k 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, ...
5
votes
2answers
960 views

Where are imported Mosaic Dataset images stored on ArcSDE server?

I am trying to learn more about Mosaic Datasets and specifically how they interact with ArcSDE (SQL Server 2008). I read in How raster data is stored in a geodatabase that "...In the case of the ...
5
votes
1answer
408 views

How to create a field with a specified slope projecting from a 3D polygon

Im trying to figure out how to create a elevation raster from a known location (3D polygon) that projects at a specified slope (1%) for a specified distance(1-2 km). Does anyone have any idea how to ...
5
votes
2answers
114 views

filling up a depression to create new surface

A collegue here has a problem I cannot help with. She has the surface (as raster) of a landslide release area (from AFTER the slide) and wants to calculate the calculate the theoretical/approximate ...
5
votes
1answer
741 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
1answer
94 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), ...
5
votes
1answer
972 views

How do I average a set of rasters?

How do I average a set of rasters? I have remotely sensed chlorophyll a rasters for several days and I need to get an average of the days represented as one raster layer. I've got QGIS 18.0 with the ...
5
votes
2answers
334 views

In ArcGIS 9.3, how do I eliminate the slivers of missing data between polygons?

I am editing a single-band .tiff file in ArcGIS 9.3. I started with an image that I had to georeference, but unfortunately, the image had these little slivers of missing data between the data cells. ...
5
votes
1answer
499 views

How to reproject a raster in QGIS?

I am a history teacher and I like to make my own maps (I can never find exactly what I want). I am using QGIS 1.8 and Natural Earth data. I want to reproject their cross-blended hypso rasters into ...
5
votes
6answers
3k views

How can I align two non-coincident equi-resolution raster grids?

I have two rasters: a digital elevation model (DEM) and a Landsat band. The grid resolution of both is 30 m, but the grids are not coincident (see image: the dark raster on top is the DEM; the light ...
5
votes
3answers
836 views

Kriging points in a raster in R

I wonder if there is a way to interpolate xyz points in a raster within certain bounds using R?. In arcgis this is call interpolation with barrier. i wonder if there is something similar in r?. I ...