Tagged Questions

Rasters are regular grids of values, usually stored in an image-like format.

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1answer
42 views

Scanned Transparent Map Overlay

We have a flat file of 50 Geology maps that have a transparent overlay with faults and drill holes. I have them scanned and georeferenced as TIF images and they will be used in ArcGIS 10.0, 10.1 and ...
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0answers
35 views

Is there a tool for automated quality assurance for vector data captured on raster data?

I wonder whether is any tool(or script) in ArcGIS or QGIS which allows to make an automated quality assurance for vector data captured on raster data? vector data on binary raster:
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1answer
55 views

How to get the absolute raster row / column of rastercell when using ArcObject Raster Cursor?

When using the ArcObject RasterCursor (see snippet below), how do I get the absolute row / column of the current pixel value? IRasterCursor rasterCursor = raster.CreateCursorEx(null); do { ...
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1answer
134 views

How to assign new values to a raster attribute table - by comparing two fields?

I have created a new raster from two raster datasets using combine operation in ArcGIS. The new attribute table has two fields from the input rasters. What I need is, to compare these two fields and ...
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2answers
139 views

Majority filter (minimum mapping unit) in ArcGIS with larger window size

I want to run the majority filter in ArcGIS with a window size of 4 or 5 i.e. greater than the default 3. Is it possible? Or some other command (or tool) which might help me achieve that? thanks!
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24 views

How to Convert Multiple Raster in to NettCDF in Arcmap 10.1?

My name is Paresh Chaudhary and I've worked in the field of Geometics since 2008. I have 30 day by day surface temperature images of MODIS, aqua satellite. Now i want to convert it into a NetCDF ...
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0answers
88 views

Can ArcGIS handle missing values to create a contour map?

I am trying to create a contour map for a waterbody. It turns out that in several locations there is no data. I just don't want to use the missing values as zero in ArcGIS because it would create ...
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32 views

How can I create a multi layer exportable file (.xcf .psd) from multiple raster image in QGIS?

I have many raster file of the same zone but in differents spectral bands. I would like to create an exportable file of a small portion that can handle different layers. So in practice I would like to ...
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0answers
77 views

Are there limitations with gdal virtual raster option?

I am new at Postgis and I'm groping... I pretend to rasterize some weighty vector layers in Postgis, do some map algebra and reclassification with them and visualize intermediate as well as final ...
2
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1answer
43 views

Displaying raster attributes on data driven pages

I have a feature class of 50 properties that are ranked. I have a photo for each property stored in a raster attribute column (in the feature class) called "Picture". I am trying to create a Dynamic ...
3
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1answer
100 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 ?
2
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1answer
103 views

How to reclassify grey scale tiff in qgis

I downloaded a raster image of the sea floor age. The values in band 1 ranges from -32768 to 32767. I need to reclassify it to no. of million of years to make sense of the data. How can I do so? I try ...
3
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1answer
131 views

Model builder - Nesting models to extract raster values to points

Hello! Hopefully a quick question. I have a simple model below that iterates through a folder full of rasters, taking each in turn to extract data values based on a single shapefile of Random point ...
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2answers
197 views

how to convert grid from Saga gis to have raster in Arcgis?

i am new in Saga Gis, i created grid- LS factor (from Rusle equation for erosis) in Saga gis and now i need to "put" it to Arcgis. How can i do this? I tried a lot of possibilities and none of them ...
5
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1answer
86 views

Best Practice for maintaining a “Cleanup Floor”

I do not have a GIS background and was hoping that someone could point me in the right direction as to the best procedure / software to do the following. Starting with a current LiDAR survey, I need ...
5
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1answer
265 views

How to calculate the flood volume using a LiDAR DEM and a HEC-RAS floodplain polygon

I’ve got a vexing GIS analysis problem which is conceptually fairly straightforward, but in reality more challenging to figure out…. Basically, I need to calculate the VOLUME of floodwater within a ...
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62 views

Masking NaN values in raster as transparent in SDL

I have several floating point raster files where nodata values are signified by NaNs. I would like to mask these values as transparent using an SDL style before uploading to GeoServer. However, when ...
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23 views

How to add attribute table to a Raster file in Quantum GIS [duplicate]

I have a raster file, in Quantum GIS, without attribute table but I need to add one attribute table with the information of the pixel values. I can compute the statistics with the histogram but i need ...
2
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1answer
48 views

How do I stop null values from being assigned extreme color values?

I have a raster surface that I kriged in Surfer and imported to Grass GIS but when I view it in QGIS, the null values outside of the interpolated surface take an extreme value and wash out the ...
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3answers
292 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
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1answer
73 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 ...
5
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1answer
163 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 ...
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2answers
140 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.
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1answer
158 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 ...
2
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1answer
36 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 ...
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1answer
137 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
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1answer
201 views

How to convert jpg file to shapefile?

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 ...
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0answers
80 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 ...
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1answer
49 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 ...
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1answer
100 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 ...
7
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2answers
198 views

How to count and rasterize polygon overlaps in ArcGIS?

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
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1answer
87 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 ...
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2answers
63 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, ...
1
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1answer
108 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 ...
3
votes
1answer
102 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 ...
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4answers
292 views

ArcInfo Grid ASCII to ESRI Shapefile conversion

I have an ArcGIS grid ascii file (Ramankutty Cropland at 5 minute resolution) that begins as follows: ncols 4320 nrows 2160 xllcorner -180 yllcorner -90 cellsize ...
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22 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 ...
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0answers
27 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 ...
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1answer
105 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 ...
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votes
1answer
52 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
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4answers
93 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 ...
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votes
2answers
98 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 ...
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2answers
143 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
69 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
68 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 ...
3
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0answers
191 views

How can you convert a Rainfall Isohyet map into Raster so you can determine the precipitation (mm) at any point?

I'm Joanne & I'm a newbie in ArcGIS... I Hope somebody can help me figure this out: Specifically, I have a rainfall map (Isohyets) measured in mm (precipitation)... I wanted to know a particular ...
1
vote
1answer
611 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 ...
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0answers
47 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 ...
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0answers
52 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?
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vote
2answers
125 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 ...

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