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

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2k views

How to find the watershed area for each point in the river network using DEM?

Update#1: Thanks, Micha, I have followed your instruction and successfully use the modules in GRASS. I use r.watershed to get the basin raster and the drainage line: and I use r.water.outlet to get ...
2
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1answer
1k views

How to apply a graduated renderer in pyQGIS?

Just trying to run the following code already given in the pyqgis cookbook to create graduated colors symbology (as in example with 2 classes) I define the source info for the shapefile but when I ...
2
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1answer
2k views

Is it possible to place a point at a coordinate in QGIS?

Is it possible to place a point at a coordinate in qgis? I have a map, using irish grid reference and wish to place a point at an exact 6 digit coordinate. Is it possible to do it. Previous to this ...
2
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1answer
735 views

QGIS identify features button issue

Is there anyway to get the Identify Features button in QGIS to automatically select a layer and provide the information without having to highlight it first in the layers TOC? MapInfo and ArcGIS ...
2
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1answer
1k views

encoding problem with QGIS 1.8 and CSV import

I have following problem with QGIS 1.8. Lisboa (standalone installer, Win 7 Pro 64bit) - I import CSV - text in CP1250 separated with ";" and using "," as decimal separator. I correctly set the ...
2
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1answer
1k views

How to create a grid constrained within a polygon in QGIS?

In QGIS I have created an irregularly shaped polygon. I can create a grid based on the maximum extents of the polygon via Vector>Research Tools>Vector Grid. However, what if I need the grid to ...
2
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2answers
492 views

Which labelling tool/engine in QGIS will be supported in the long term?

Why does QGIS appear to have two labelling tools? (Note this is not new and old symbology, but that...) there are two different GUIs, one in the toolbar (which gives the Data Defined Settings option) ...
1
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1answer
158 views

What is the purpose of some functions and files in QGIS Python plugins?

I'm just trying to understand the architecture of a QGIS Plugin created with the QGIS Plugin Builder, as well as the workflow and the linkage among generated files. If possible, I'd prefer a diagram. ...
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1answer
156 views

How to use the MMQGIS plugin through the Python console?

I know how to make Hub Lines using the GUI, I want to know how to do the same using the Python Console, a tutorial would be great. Thank you
1
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1answer
429 views

How to add the attributes of selected features to my new layer in pyqgis

I am trying to create a layer from the selected points coordinates. I am drawing a circle to the coordinate of selected points. I also need to add initial attributes of my selected features to my new ...
1
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2answers
666 views

Does QGIS attribute edit form support “relationship” data?

Consider I have a geometry table having one-to-many relationship with a no-geometry table. When I create a feature (geometry), I would like to be able to add the relative no-geometry table data in the ...
1
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1answer
199 views

How to set the path to shapely?

I am using QGIS 1.8.0 on Mac OS 10.8.3 with python 2.7. Thanks to other threads in the forum, I have successfully installed shapely here: ...
1
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3answers
1k views

export 3D data dxf file

I'm trying to export a DXF file from Qgis1.8.0 Lisboa and can not have a 3Dfile in Autocad! Or micristation. It results always in 2D file. How can I export height data from a shape file in Qgis? ...
1
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1answer
404 views

Find closest point from origin in QGIS and display measure line in composer

I have a location point. there are several constraints areas surrounding the point. Is there a way to calculate the closest point of this constraint from my point and to display the distances as a ...
1
vote
0answers
565 views

Why is my .csvt not recognized? [closed]

I am trying to associate a .csvt file with a .csv file, so QGIS doesn't insist on calling all the fields text strings (thereby preventing the use of graduated symbols). I used the syntax described by ...
1
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1answer
5k views

Opening TIFF DEMs in QGIS

I have files, in Tiff format, downloaded from ASTER-GDEM. Can I open this file with QGIS? If yes, how? Thanks in advance
19
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3answers
6k views

Optimal video cards for GIS programs

I recently purchased a Dell XPS-8300 (i7-2600|16 GB DDR3 RAM|64-bit Windows7) which I intend to use primarily for GIS programs. I bought a refurbished model because it was much cheaper and because I ...
16
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2answers
3k views

Does QGIS have the equivalent of ArcGIS's Layer (*.LYR) file?

Using ArcMap, it is possible to add a dataset (eg a shapefile) to the map, and configure the layer's properties (such as the symbology, table joins, switching some attributes off in the Identify ...
12
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2answers
542 views

How to clean such a bad shapefile for routing ?

I am trying to clean a shapefile to make it usable for routing with pgrouting, postgis, postgresql. Here an intersection, it seems to be connected but when we zoom …. It is not: Same here : ...
9
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1answer
403 views

How to auto-generate map images with different styles in QGIS?

I have got a simple map in QGIS, containing only 1 layer which consists of 10+ features. Now I need to (programmatically) generate about 200 different JPEG map images of the same area. Each map should ...
8
votes
1answer
351 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
327 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
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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
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2answers
871 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
440 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
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2answers
677 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
717 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
419 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
861 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
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1answer
5k 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
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2answers
7k 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 ...
7
votes
5answers
16k 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
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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
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5answers
5k 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
1answer
7k views

How to enable “snapping” in Quantum-GIS while drawing polygons?

I tried to draw polygons in qgis-1.7.0 and I somehow can't find or failed to find the "snapping" option. I'm used to ArcGIS-10.0 where you have some snapping options, like placing points of polygons ...
6
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2answers
430 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
760 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
368 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
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
1k 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
840 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
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1answer
815 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
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1answer
2k views

How to toggle layer visibility in QGIS using Python?

How can I toggle layer visibility in QGIS via Python API?
5
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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
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2answers
369 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 ...