QGIS is a user-friendly, cross-platform GIS application licensed under the GNU General Public License.

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8
votes
1answer
338 views

Where is this raster offset being introduced in the QGIS processing toolbox?

I'm using the (awesome!) processing toolbox in QGIS 2.0 to reclassify some NoData values in a raster from -9999 to 0, but at some point in the process there's an offset of about 0.2 degrees being ...
8
votes
2answers
312 views

How to create vertical labels in QGIS?

How to create vertical labels (each label in new line) like: 1998 150 pipe name and not horizontal: 1998 150 pipe name
8
votes
3answers
1k 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.
8
votes
2answers
848 views

Can QGIS Read Spatialite Views?

I have a spatialite database I created that spans several years of crime data. To facilitate a real-world scenario where I may simplify the interaction for a user by introducing a View that simply ...
8
votes
1answer
439 views

What version of SVG should I be saving my images with for QGIS? Any particular options I should use/avoid?

I have a illustration in Adobe Illustrator that I'm trying to export as an SVG file and add to my map layout using the Print Composer of QGIS 1.7.3. When I add the image, I get strange artifacts that ...
7
votes
2answers
634 views

Using ArcGIS and QGIS together in multi-user editing environment?

We have a GIS staff of 7, and another group of about 14 who "use GIS" from time to time. We really, really want multi-user editing. Mostly of a large point file, and we're almost never in the same ...
7
votes
2answers
671 views

How to split lines into equal segments with QGIS?

I'm attempting to split a curved (wiggle) line into equal length segments. Have used Grass's v.split which works to a degree but does not provide the output I'm after. v.split will extract segmented ...
7
votes
2answers
404 views

Is there an open source alternative to ArcGIS for Desktop's Integrate tool?

I need to snap about 1000 lines in one layer to the lines in another layer (there are about 5000 lines in the second layer). The lines to be snapped are about 15 map units away from the base layer ...
7
votes
2answers
2k views

How do I use QGIS python console to iterate through simple layer queries and png outputs?

I'm really new to QGIS coding and I'm having a hard time finding (especially) the api classes/functions to carry out actions of the Query Builder window. I'm basically trying to do this: Iterate ...
7
votes
2answers
841 views

How to get correct area calculation using Google Mercator?

i use QGIS with openlayers-plugin and i´ve loaded google satellite as a layer. what i want to do is making a shape-layer (polygon) with the goal to get the area values of the polygons. i´ve activated ...
7
votes
2answers
4k views

Calculate area of intersecting polygons in QGIS

I have two collections of shapefiles: 1 - postal codes, administrative and political areas 2 - various land use categories like parks & allotments, and points like trees I want to produce ...
7
votes
5answers
16k views

How to install Openlayers plugin on Qgis 1.8?

After having installed Qgis 1.8 i am not able to find the Openlayer Plugin. In "the old days" I know I was supposed to check "add 3rd party repositories", but that button has disappeared? I tried ...
7
votes
1answer
4k views

Import polylines and polygons into QGIS from CSV

I'm assuming this is a simple question, though my efforts have not yet found the answer! I want to import a large number of polylines and/ or polygons into one one or more QGIS layers in order to ...
7
votes
5answers
15k views

How to break single polygon into multiple polygons using ArcGIS Desktop or QGIS?

I created voronoi polygons after which I dissolved them on the basis of one attribute. Now there are cases where in for one single attribute "abc" I have3 polygons at different places with same object ...
7
votes
3answers
6k 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?
6
votes
5answers
4k views

Open Source equivalent to Collector for ArcGIS to use with QGIS/PostGIS?

From my reading of the Esri web pages the Collector for ArcGIS is tightly tied to that platform. I would be delighted to learn that I am wrong about this. I have a strong interest in generic mobile ...
6
votes
2answers
423 views

How to generate discrete areas from multiple, overlapping features?

I have a point dataset that I want to append some information from a polygon to. My polygon shapefile contains over 500 features. Whilst each of these features represents individual areas they are ...
6
votes
1answer
725 views

How to call GRASS modules in pyQGIS?

I wish to use a Grass module (v.to.db) in QGis, without the grass toolbox. I tried with the Python console, but to no avail : Using Sextante plugin but obviously it didn't know all the grass ...
6
votes
1answer
4k views

How to measure area correctly?

I have now used my entire evening, but I can't figure out how to make areal calculations (eg. in km2). I have tried the 'field calculator', I have tried the 'measure area' function on the "attributes" ...
6
votes
1answer
355 views

Simulate (Mock) GPS Tracks

I have the following scenario: 1) I need to create GPX files for use in testing of a mobile device. 2) The tracks to be described within will span large distances over long time periods (i.e. it's ...
6
votes
5answers
9k views

How to export/save a layer composition to GeoTiff?

I want to export/save a QGIS composition of raster/vector layers to a GEOTIFF or ECW raster with high resolution (20 000 * 20 000 Pixel).
6
votes
2answers
6k views

How to draw a Circle with a set radius?

I have a site and want to draw an indicative line in a 5km buffer around the centre of the site. So I want to draw a circle with a radius of 5km. I have a tool for drawing circles and ellipses and ...
6
votes
3answers
2k views

How to create a user map from CSV?

I dont even know if QGIS is the right program for what I need.. What I need: I need a program with maps(Denmark to be specific), that I could feed with a database of users through a CSV file.. e.g. ...
6
votes
3answers
974 views

How to place multiple symbols on one polygon centroid?

I am using QGIS for visualizing the health conditions of elderly living in an old age home, some of the elderly have multiple medical device with them and I want to show them on the map. Suppose I ...
6
votes
5answers
5k views

How to load Shapefiles into a remote PostGIS db using command line?

Can we import a Shapefile from a system which doesn't have PostgreSQL installed (client machine) into a system having PostGIS installed? I am getting problem with 'shp2pgsql' and 'psql' since both ...
6
votes
2answers
831 views

How do you calculate lat/lons from a PostGIS table which has a projected coordinate system?

I have a PostGIS table in a projected coordinate system (EPSG: 28355 or MGA94 Zone55). In QGIS (with the PostGIS manager plugin) I calculate a coordinate by performing the following SQL "UPDATE ...
6
votes
1answer
803 views

Altering composer label items in QGIS with Python

I'm only new to QGIS and Python so this may exists already, and hopefully be easy to do. What I'm hoping to do sometime in the future is build a map book generator using QGIS as the base. In order ...
6
votes
1answer
2k views

How to toggle layer visibility in QGIS using Python?

How can I toggle layer visibility in QGIS via Python API?
5
votes
3answers
1k views

Should you switch from ArcMap to QGIS? [closed]

Background: Our group has full ESRI licenses and applications built with ArcDesktop. We are invested in the arc geodatabase itself and will not change that tier. There is a proposal to switch from ...
5
votes
2answers
318 views

Correctly merging DEM rasters and eliminating edge effects

I'm using 10m DEM rasters from the NRCS Data Gateway for a large portion of California. The problem is some strange tiling that appears after merging, but isn't present in the original data (before ...
5
votes
2answers
621 views

how would one get the end points of a polyline?

I am attempting to write a script to get the end points of a series polylines, and then use those end points to create a polygon. I'm not sure which tools to begin to use on this project. I would ...
5
votes
1answer
2k views

QGIS and SQL Server Spatial Tables Performance

I'm trying to get a SQL Server 2008 R2 spatial database up and running to streamline the production of maps using QGIS. Currently I just have a handful of spatial tables (a postcode level point table ...
5
votes
1answer
357 views

Why does ManageR and rpy2 not work in QGIS (1.8.0-Lisboa)?

I have been trying to get R scripts to function and ManageR to work within QGIS (1.8.0-Lisboa). (Windows 7). Python2.7.5. Two problems indicated that R was not working in QGis. First - when I run an ...
5
votes
0answers
515 views

PyQGIS CRS on the fly reprojetion [closed]

As a first step of a pyqgis plugin I'm trying to import several shape files at once. To get them aligned, using the GUI, I'd enable on the fly reprojections and set the project crs to WGS84. I'd then ...
5
votes
0answers
2k views

Loading raster from PostGIS DB into QGIS: succeeded yesterday, fails now [closed]

I have a PostgreSQL(v.9.2)/Postgis(v.2.0.3) database which includes raster layers (added through raster2pgsql). To open them in QGIS (v.1.8.0-Lisboa), the "Add Postgis layer" menu will not work; ...
5
votes
1answer
104 views

Is there a Small Windows install of QGIS?

I am looking to find a faster alternative to ArcReader. I think QGIS might be faster but I was wondering if there was a smaller install without all the GRASS etc for windows. I just want to get a ...
5
votes
3answers
2k views

How to reclassify a float raster?

I have three rasters which represent distance (in metres) from certain things (bus stops, parks, libraries). I would like to reclassify these rasters so that they get integer values based on the ...
5
votes
1answer
1k views

How to deploy a QGIS Python Standalone Application with minimum installation size?

I am trying to create a Standalone QGis Application using python. I was able to create the nice looking shapeviewer application by following the steps here. Now I would like to deploy this in ...
5
votes
2answers
1k views

Does anyone know the proj4 Coordinte Reference System command line for Rectangular Polyconic Gores?

I am a GIS beginner using QGIS 1.8.0 I am trying to transform a world map from the standard WGS84 Coordinate Projection System to a set of rectangular polyconic gores, with a gore count of 12. ...
5
votes
1answer
1k 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
3answers
559 views

Adding a GIS feature to existing database entry with QGIS

I've built a database with postgreSQL with tables, which include geometry columns. When I add some data to my non-geometry columns, I can see them in QGIS when I connect to my database using postgis. ...
5
votes
2answers
3k views

How to change length to 2 decimal places?

I'm trying to work out how to calculate the length of a line to only 2 decimal places in QGIS. When I use the field calculator to create a new field, it doesn't matter what changes I make to the field ...
5
votes
1answer
2k views

How can I Setup Python to recognize QGIS

I want to use QGIS and work with Python out of the console, but I'm having troubles letting the system recognize the paths of some DLLs. Since I couldn't find a good answer on the web, I wonder if I ...
5
votes
2answers
2k views

Where can the GDAL executables be found in a QGIS installation?

I run QGIS 1.8.0 Lisboa on a Windows 7 machine. Yesterday I attempted to install the TauDEM plugin using these instructions: http://lists.osgeo.org/pipermail/qgis-developer/2012-June/020807.html ...
5
votes
3answers
3k views

How to extract POINT from a [LINE|MULTILINE]STRING

I'd like to create a vectorLayer in QGIS to display all the points that form a LINESTRING or a MULTILINESTRING stored in a PostGIS DB. I think that I need to transform all points of LINESTRING (or ...
5
votes
2answers
469 views

Extract certain area of contours/satellite images

I have 2 satellite images (jpeg2000 format) and 2 xyz-files from the same area. I am trying to extract certain region from the area including contour lines and the satellite image in order to import ...
5
votes
0answers
346 views

Can Quantum GIS replace Proprietary GIS? [closed]

I’m an MSc GIS student in the final year of my studies. I’m researching for my dissertation project which is entitled ‘Can Quantum GIS replace Proprietary GIS in large organisations?’ I’m primarily ...
5
votes
1answer
4k views

How to configure QGIS Sextante to use SAGA?

I have been trying to set up SAGA to work using Sextante in QGIS. I have followed the instructions to configure SAGA in Sextante, with the following input in the path for the SAGA folder C:\Program ...
5
votes
3answers
2k views

Add 3rd party repositories button not in version 1.8.0 Lisboa

The available manuals and other help sources all refer to the 'Add 3rd Party Repositories button' in Plugins>Fetch Python Plugins and then the Repositories Tab. My problem is that the installation of ...
5
votes
2answers
5k views

How to create a lat/lon grid in QGIS?

I'm using QGIS. How can I create a shapefile consisting of a grid 0.5° latitude and 1° longitude in size?