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

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Snap mean coordinate to layer in QGIS and creating MCs for multiple shapefiles

1: I wish to create a mean coordinate for a group of points. However, I would like the new point to be snapped to the nearest point from the set of points used to generate it. How might one go about ...
3
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1answer
2k views

PyQgis question: How to change or set active layer?

Developing a qgis plugin, I found that if no layer is selected in the Layers panel I can iterate over all layers and do anything to them, but "activate" them. Could someone give me a hint please? ...
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1answer
183 views

Why does the “Dissolve” tool in QGIS create an empty layer?

I have a shapefile containing cadastral data. I would like to dissolve the polygons using my field "OwnerName". My goal is to get one polygon per landlord's name. When I use the "Dissolve" tool, QGIS ...
4
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1answer
556 views

Can Spatialite SQL statements be issued with a python script in QGIS?

In my previous scripting environments (ms-access and Manifold GIS), it was possible to create and execute SQL queries from withing VBA or VB Script procedures. This is really useful for things such ...
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1answer
133 views

how can i install Semi-Automatic Classification plugin manually?

I try to install with Fetch Python Plugins. But fetch python plugins show only those which are installed? can i install manually when direct installation failed repeatedly?
4
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2answers
2k views

How to merge TopoJSON features?

I currently have a coordinate based map of the US and it's states for topojson (https://github.com/mbostock/topojson). The coordinates are a JSON array (as topojson works), data looks like this: ...
2
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0answers
138 views

Convert pixel value histogram to table

I am working in QGIS 2.1 with the National Land Cover Database 2006 land cover layer. It is a raster layer with pixel values corresponding to different land cover types. I have clipped this raster to ...
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1answer
122 views

Can't get the openlayer plugin to operate [closed]

I can't get the openlayer plugin to run. I've got QGIS V1.8 on Windows 7. I've tried various repo's recommended on different sites; http://plugins.qgis.org/plugins/plugins.xml & ...
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2answers
219 views

How to determine the location that has the most intersections with other polygons in a certain distance/buffer?

I have a very scattered map with a lot of very differently shaped polygons. Now I want to determine the location where a circle polygon of a certain size intersects the most surface of these scattered ...
2
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1answer
72 views

Why does Fetch Python Plugins responded with only the installed ones?

I use QGIS 1.8. Whenever I demand to install plugins through Fetch Python Plugins it displays only those the already installed. I couldn't find for example; point sampling, group stats and photo2shape ...
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2answers
816 views

Intersection between points and polygons in QGis

I have the following problem. I have a shapefile of points and a shapefile of polygons. I want to know WHAT points (not how many) fall inside EACH of the polygons of my multipolygon shp. I thought ...
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2answers
1k views

Deleting points that fall outside a polygon

I have a polygon that is my region of interest. I also have a database of observation points that I have imported into QGIS as a points layer. I'd like to exclude all the observation points that ...
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1answer
471 views

What's the correct transformation for Lambert Conformal Conic for Mexico?

I have a shp archive without the .prj file. I don´t know the proyection of this shp, but I think it is in lambert conformal conic. Can anybody helpme to proyect this shp? i´ve tried to proyect it in ...
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1answer
280 views

How to install two versions of Qgis on Ubuntu 12.04?

I would like to run multiple versions of QGIS on Ubuntu 12.04. Can I do that, and how if so?
5
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3answers
483 views

Best practice in writing automated tests for QGIS plugins

I'm looking for some best practice advice on writing automatic tests for QGIS plugins written in Python. I have written tests for Python scripts in the past using PyUnit (the unittest module), but ...
0
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1answer
296 views

qgis — style edges of layer shapefiles to have thicker borders

I have two layers I'm working with here, both of North Carolina. One is "townships" the other is "counties". I want the counties shapes to have thick edges with no fill-in color. I couldn't find ...
3
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2answers
472 views

Can QGIS use a non-spatial Oracle Database?

I'm building my first plugin in qgis, that needs to read some coordinates from an oracle database (not oracle spatial database) and create a shapefile with this points. I'm searching but only find to ...
2
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2answers
326 views

How to save colour (color) ramps in QGIS

This strikes me that it should be simple, but efforts in QGIS and research here and elsewhere are not providing a solution. I have a (vector) map which I have to mark out in colours according to the ...
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2answers
526 views

How to find and replace all null values in multiple columns?

To find and replace all null values in a specific column I am using: case when "myColumn" is NULL then '99999999' else "myColumn" end But how can I use the QGIS calculator to find and replace all ...
4
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0answers
370 views

How do I install Orfeo toolbox and Qgis 1.9?

I'm having a lot of trouble getting Orfeo toolbox and Qgis 2.0 working. I followed the qgis wiki instructios, added the ppa, installed qgis 1.9 (it's beautiful, great work!). But when i tried to ...
2
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1answer
294 views

QGIS Georeferencer, unexpected transformation, and GCP placement

Im trying to get the sample map which i believe to be EPSG:3112 into QGIS and geo referenced. In my screenshot, on the right is the raster in georeferencer with the points i have added. On the left is ...
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1answer
175 views

Can SQLite and SpatialLite files be linked

Coming from a ms-access background, it is common to split up larger applications into several database files. An ms-access database can then access data that is in another database via a linked ...
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2answers
116 views

How can I delete dangling paths after merging features

In my previous question I've asked how to can I merge different polygons while converting to GeoJSON and TopoJSON. After a day of researching I've realized that, rather trying to do it command line, ...
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2answers
206 views

Integrate grid and polygon of municipalities keeping the biggest municipality per cell with QGIS (or another)

I have a 9x9 grid and a polygon of municipalities of an extensive area of Brazil. My goal is to have a field indicating the biggest municipality per grid cell. I've been trying with intercept without ...
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0answers
211 views

Personal Geodatabase not recognized as valid datasource in the last QGIS Windows Weekly build (64 bits)

I was using Personal Geodatabases in QGIS without any problem but it's stopped to work since I installed the last 64 bits weekly build for Windows (1.9.0-35-Setup-x86_64). I'm now receiving an ...
5
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2answers
1k views

Reduce the resolution of a shapefile in R (or QGIS if necessary)

I'm using shapefiles of history U.S. state boundaries from NHGIS to make maps in R. These shapefiles are much higher resolution than I need when making maps at the scale of the country: over 2 million ...
0
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1answer
192 views

Calculate attribute height of point data

I have an x (easting), y (northing) and z (height) values associated with my point shapefile. I would like to calculate the z values from the DTM I have - how do I do this in QGIS? I am fairly new ...
3
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1answer
2k views

How to load a NetCDF-file into QGIS using Python?

I have a CF-conform NetCDF-file which can be loaded into Quantum GIS (Version 1.8) by using the "Add Raster Layer"-button and subsequently choosing the file and the raster layers of interest. This ...
2
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1answer
115 views

How to drill down through multiple polygons/points in QGIS?

I have a layer that has multiple polygons sitting on top of each other, is there a way to easily scroll through those polygons that overlap each other? Thanks
3
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2answers
617 views

Which Windows OS is supported?

Please can you tell me which Windows OS Quantum Desktop supports. i.e. Windows 7, XP, Vista etc.
3
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1answer
293 views

QGIS Arch Linux compilation error

Just pulled QGIS from git and am trying to compile it, here's the relevant error: [ 89%] Building CXX object python/CMakeFiles/python_module_qgis_core.dir/core/sipcorepart3.cpp.o In file included ...
2
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2answers
188 views

How to extract coordinates from a coastline layer?

I have downloaded QGIS and the Natural Earth base maps. I'd like to somehow get a list of coordinates of a selected coastline. I've got the 10m_coastline layer selected to what I want but can't see a ...
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1answer
109 views

Add image from my computer for background in Print Composer?

Add image either by dropdown or icon does not produce any kind of dialog box where I could upload an image. Item properties is checked and showing in the right hand panel, but it's blank (no options ...
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1answer
208 views

opening older 9.x Esri .gdb in QGIS?

I want to open an Esri .gdb with QGIS. I have adjusted GDAL and it works fine with an example .gdb provided on another thread on the topic. I still cannot open the .gdb of interest to me and suspect ...
0
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1answer
59 views

How to generate raster from vector in QGIS with resolution matching existing raster?

Is there any way to use open source tools (preferably QGIS) to rasterize a vector to create a raster with the same coordinates and resolution as an existing raster? I know that the map size can be ...
2
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2answers
631 views

How can I create a vector layer in PyQGIS from a table without geom column?

In QGIS I've got a Spatialite database containing tables without a geometry column. With the QGIS GUI it is perfectly possible to add such a table as a 'Spatialite vector layer'. But how to do this in ...
3
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1answer
567 views

QGIS Shapefiles have the same CRS but dont line up. (Census Tiger Data & State Data)

I have the Census Tiger data for Oregon from http://www.census.gov/geo/maps-data/data/tiger-data.html Then the bottom one of 2010 Census Population & Housing Unit Counts — Blocks. The shp ...
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1answer
1k views

Export all visible layers in map view window to DXF (as one)

I'm looking to find a way of exporting all that is visible in the map view window to a dxf file. That is to say, multiple features from multiple layers, all at once. Can this be done?
0
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1answer
194 views

Extracting “derived” data [duplicate]

Rookie Question! I have a shapefile in QGIS 1.8.0 of a country with 20000 divisions. I need the area of each division, but this is not a given attribute. When i click on a district, the "Identify ...
4
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2answers
416 views

How do I snip/split polylines at chainages?

What is the best way to snip/split lines at chainages? E.g I have a csv with the uniq ID of the polyline item and a start and end chainage. I want to extract the lines between the chainages stated. ...
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0answers
95 views

level of spatial aggregation of polygons

I am looking for a method that allows me to obtain the spatial aggregation of polygons for each cell of a grid with 10kmx10km resolution. In each cell (10kmx10km), I want to be able to consider that ...
2
votes
2answers
1k views

QGIS: when using composer to save as image the image has a shift of about 50m [duplicate]

im using qgis 1.8.0; i have two layers turned on, 1 the google earth hybrid layer from the open layers plugin and a shapefile of my own making. i set on the fly projection and everything looks spot ...
3
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3answers
2k views

How to group and count attribute data?

I have a problem with group same data to count it. for example, i want to group same code to one and count them. i can do it when i use MapInfo (Pic 1) but i can't in QGIS. (Pic 2: i can classify ...
0
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1answer
123 views

Why does my buffer take up the entire screen?

I am using QGIS. I am aware there is a similar question here but the solution (changing the layer CRS) is not working for me. I cannot change my CRS as I am using information for the entire ...
2
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0answers
118 views

Displaying DEM raster in QGIS

Using Raster>Analysis>DEM to display hillshade produces the message "gdaldem.exe had stopped working" so I asked the community. I'm new to QGIS, and I now realise after a little experimentation that I ...
2
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1answer
115 views

Is it possible to destroy a spatial index?

QGIS 1.9 Is it possible to destroy a spatial index? I am noticing that if I generate a spatial index on a set of polylines (within a plugin), split one of the lines, and then recreate the spatial ...
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2answers
124 views

Counting raster points within boundaries in another layer?

I know this question is similar to some out there, but I have tried all the 'solutions' and none of them are working for me. I am using the latest version of Qgis. I have a raster layer with ...
2
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1answer
48 views

Placing TIF image on the top of WMS layer

How to place TIF file on the top of WMS layer in QGIS? When I import TIF file, it has different coordinate system, and it is placed far from WMS layer, but I want to put this TIF layer on the top of ...
1
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1answer
122 views

How do I include libfcgi files when installing QGIS on SUSE Linux?

I'm using SUSE Linux Enterprise Desktop 11 SP2. When I try to install QGIS from YAST, it seems that the package "libfcgi.so.0" and "libfcgi.so.1" are missing. Is there anyone else that has experienced ...
2
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1answer
600 views

How to save data from QGIS 1.8 to PostGIS without shapefile intermediate?

Is it possible to save data directly into an existing PostGIS database from QGIS without having to first save it as a shapefile? I know about the SPIT plugin but that requires a shapefile. I want to ...