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

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11
votes
1answer
821 views

Snap line layer to network in QGIS or PostGIS

I have GPS data I've taken of bus routes, and now I'd like to snap it to my road network. Both layers are line layers in a PostGIS DB. I'd like to use either QGIS or PostGIS, but if I have to go with ...
11
votes
2answers
354 views

How to sort by multiple fields at the same time?

Is it possible to sort multiple fields at the same time in QGIS? For example, I'd like to sort a table by state name, and then within each state, sort by county name. This would be the same as the ...
11
votes
1answer
596 views

How to create text labels with background boxes?

I'm trying to create some custom labels for point features in a QGIS point vector layer, and I want to write a python plugin to do it. We need our labels to be presented with color tinted rectangles ...
11
votes
1answer
936 views

How to define Winkel Tripel in proj 4.8.0?

I have QGIS with proj 4.8.0 installed. I'd like to add Winkel Tripel projection which seems to be defined as +proj=wintri But that definition string does not work. Is this a bug in my proj version, ...
10
votes
4answers
1k views

How to model a graveyard - one point per deceased or one per grave? [closed]

This is a continuation of my previous question about our project on how to economically get away with the implementaion of a graveyard in a GIS system… On the graveyard we can find Regular ...
10
votes
7answers
11k views

How to merge lines with slightly different endpoints in QGIS?

In QGIS, I have two lines. The endpoints are near each other, but not quite aligned. I'd like to turn the two lines into one, with the two endpoints merged into midpoints. The closest I've been able ...
10
votes
4answers
4k views

How to export shape file to SpatiaLite

I have a shapefile with one layer. I can open it with QGis. Now I want to convert this shapefile or layer to Spatialite database. How can I do it? Is it possible to do with QGis?
10
votes
5answers
589 views

Database versus Files for Solo Developer

I'm just getting started in GIS and am interested in using it to create maps of mountain biking trails in my area and nearby. I've been learning QGIS and have made enough progress to generate a decent ...
10
votes
3answers
5k views

How to create polygons with straight lines and right angles in QGIS?

I am running QGIS 1.7.0 on Mac OS X 10.6.8. When creating a polygon, how do I do it so that the lines are straight (90, 0 degrees, etc.) and when I create corners they can be right angles? For ...
10
votes
2answers
893 views

How to link dataframes in ArcGIS or QGIS?

The below image shows a layout in ArcGIS 10.1 with four dataframes. Each dataframe is of the same geographic area, although they are different images. For example, the top left image is a 1989 DOQ, ...
10
votes
2answers
3k views

Running QGis from flash drive

How can I setup a portable QGis to run from a flash drive / USB-Stick? In the userguide for QGis 1.7 Wroclaw there is only mentioned the option of "--configpath". But to me it is not clear how to deal ...
10
votes
5answers
2k views

Multicriteria Analysis : how to?

I have to do a multi-criteria analysis to answer the question : "which is the best lot to develop". A few of the criterias are : distance of the nearest bus stop (point layer with bus stops) ...
10
votes
1answer
6k views

Understanding QGIS buffer tool units?

I have been trying to figure this out for a couple weeks now and have had no luck getting the buffer tool to accept anything but degrees as units of measure. I have found lots of stuff saying the ...
10
votes
3answers
14k views

How to import coordinate data from excel into QGIS?

I have an excel file containing data collected over many years as latitude and longitude coordinates for archaeological sites - how can I import it into QGIS as a new layer?
10
votes
2answers
579 views

Can I add an ArcToolbox tool to QGIS?

I have been using a publicly available tool in ArcGIS called SPreAD-GIS. It is a series of python scripts that are "implemented as an ArcGIS toolbox" (with tbx file). I am new to QGIS. Is there a ...
10
votes
7answers
8k views

How to georeference a vector layer with control points?

I have a non-georeferenced vector layer that I need to be georeferenced. With raster layers the task is easy and straightforward, but I have no idea what should I do with my vector layer. I have a few ...
10
votes
1answer
4k views

How to display geoJSON from an URL in a layer?

I am looking for some type of plugin or code which would allow me to add a geojson URL, define the areas to input the lat/long variables from the visible Qgis canvas map and call/render the results ...
10
votes
3answers
5k views

How can I iterate over map layers in QGIS python

I'm having trouble figuring out how to iterate over map layers. I can access the currently highlighted layer in the table of contents via iface.activeLayer() but I want my code to operate on all ...
10
votes
5answers
11k views

Can QGIS read an ODBC connection?

I have a co-worker who manages a large MS Access database that contains X & Y fields for various locations he tracks. We have previously exported the data to CSV and used the QGIS Delimited Text ...
10
votes
2answers
4k views

Is it possible to create Thiessen polygons around nodes in QGIS?

Is it possible to create Thiessen polygons around nodes in QGIS? e.g. http://en.wikipedia.org/wiki/Voronoi_diagram
10
votes
1answer
3k views

OpenLayers Plugin Error: latitude or longitude exceeded limits

I'm aware the 'traceback' OpenLayers plugin error has been dealt with before, so apologies for raising the issue once again. Unfortunately for me, the solutions posted were way over my head, e.g. ...
10
votes
5answers
3k views

How to identify duplicate attributes in a field?

I have a point shapefile with thousand of points. It has an ID code field that supposed to be unique. Every now and then the data entry clerk wrongly type the id creating duplicates.Right now I'm ...
10
votes
1answer
703 views

Is there a way to add system date in print composer?

Is there a way in the Print Composer of QGIS to create a label that will automatically update the date (systems date) instead of having a label that you have to manually have to update?
10
votes
3answers
518 views

How can I parallelise embarrassingly parallel GIS operations in QGIS python?

A common requirement in GIS is to apply a processing tool to a number of files or apply a process for a number of features in one file to another file. Much of these operations are embarrassingly ...
10
votes
3answers
338 views

From polygon to continuous measure of diversity?

First of all; I have tried to find a similar question, without success. Maybe it's because I'm quite new to GIS and I don't really know what exactly I'm looking for. If someone points me to a similar ...
10
votes
1answer
665 views

How to render a table with mixed geometry types in QGIS?

I created a table with geometry type "GEOMETRY" AND inserted data of point, line and polygon type. My question is how to show this spatial data Qgis not supporting for geometry type "GEOMETRY".
10
votes
2answers
2k views

How to compute parameters for QGIS Affine transformation?

I have a vector floorplan (DXF) that I've added to a blank project in QGIS using the Dxf2Shp plugin. I've been reading tutorials and StackExchange threads, but I can't seem to find out how to ...
10
votes
2answers
2k views

How to buffer a line with different distances for left/right sides

How can I buffer a line in QGIS using one attribute for the left side of the line and one attribute for the right side of the line? I am trying to buffer a river with its bank width, which is ...
10
votes
1answer
648 views

How to convert fake donut holes in polygons to real ones?

I have this problem where I have to import shapefiles into our system which must be geometrically valid, but the software that everyone uses to produce them seems to output files where every polygon ...
10
votes
2answers
3k views

How to get FGDB support in GDAL 1.9 without compiling?

I was hoping that I could use the 'master' (nightly-build) version of QGIS to get fgdb support without compiliing (I'm not a developer and frankly have wasted days of productive time trying to get ...
10
votes
2answers
2k views

What is the standard Mercator projection?

I'm using QGIS in order to re-project a shapefile I have into "Mercator" so that something like protoviz understands my co-ordinates. Protoviz tells me "Mercator" ...
10
votes
1answer
1k views

Is there a way to access QGIS plugins in Python?

Is there a way to access QGIS plugins in Python? I'd like to write a script to do some geoprocessing, and I'd like to use the clip, regular points and convex hull tools in fTools, as well as the Road ...
10
votes
1answer
336 views

How to find the buildings (polygons) a user can see from a given location (point) and orientation (angle range)?

I would like to retrieve the set of buildings I can see from a given location (point -lat,lng) and orientation (interval of angles) + certainly with a given depth (e.g. 100 meters). Ideally I would ...
10
votes
2answers
501 views

How to perform repetitive tasks in QGIS?

I am trying to do a treatment on many feature files, so I would like to automate it. In fact, I have one shapefile with the spatial distribution of some species, and one with vegetation type. I ...
10
votes
1answer
745 views

Is there a detailed description on the .qgs file structure somewhere?

Is there a detailed description on the .qgs file structure somewhere? I checked here: http://mrcc.com/qgis.dtd ("The requested URL /qgis.dtd was not found on this server.") and here- ...
10
votes
1answer
474 views

What is the best way to represent bridges using a point vector layer in QGIS?

I'm working on a hiking/biking maps of trails in the woods which sometimes have bridges that need to be shown on the map. I'm trying to figure out the best way to capture and represent them using QGIS ...
10
votes
2answers
2k views

How do you display related records in QGIS?

Coming from an esri background I have always used relationship classes in a gdb to display records related to a feature. Eg. Relate 1 survey point to many documents, photos etc. Does any one know how ...
10
votes
1answer
180 views

Automated detection of tracks

Given an area with depressions in open area from; say all terrain vehicles driving on soft surface. The vehicles will cause parallel depressions (paths) of about 10-20 centimeters in depth and around ...
10
votes
2answers
603 views

How to build a minimum convex hull crossing the 180 degrees line?

I've been building convex hulls for species that inhabit the Indo-Pacific (~ from 20 to -65 degrees of longitude). The problem I've encountered is that for the species that can be found on both sides ...
10
votes
3answers
2k views

How to prevent text labels from overlapping other markers?

Is their a way within QGIS to prevent text labels from overlapping icons used to label a point layer? In the example map shown below, there are two layers: Roads layer which is labeled using the ...
10
votes
1answer
406 views

Is it possible to edit layers from a FGDB - File Geodatabse in QGIS?

I think I've found the answer (you can't edit FGDB's) but there seem to be few reports around that it is possible to edit FGDB files in QGIS. Can anyone advise if it's possible to setup QGIS ...
10
votes
1answer
519 views

PyQGIS file lock release

I was wondering what triggers the release of file locks in pyQGIS? I am trying to delete a few data sources (used temporarily) by calling QgsVectorFileWriter.deleteShapeFile, but I have to quit QGIS ...
10
votes
2answers
1k views

How can I improve my Georeferencing results?

Background This is my second question related to georeferencing naked raster maps in order to re-visualize them on different coordinate systems and in conjunction with other data layers. The previous ...
9
votes
2answers
8k views

How to add Direction and Distance to attribute table?

anyone who can help. i just want to add direction (Bearing: i.e N 25 35 E) and Distance (Length: 125 meters) as my new field in polyline/line data. is there a plug-in to generate these fields? i tried ...
9
votes
2answers
6k views

Converting point sets to polygon boundaries

I'm trying to convert sets of points to their respective polygon boundaries. I think this is something like a Voronoi diagram or Convex Hull, but not quite. I'm sure there's a technical term for it, ...
9
votes
4answers
6k views

Tutorial on how to model flooding using data from gauging stations along rivers in QGIS?

Can someone please direct me to a tutorial where I can learn more about how to model flooding using data from gauging stations along rivers using QGIS?
9
votes
4answers
8k views

How to calculate raster statistics for polygons?

how can I calculate sums, averages etc of raster-points (multi-band) per polygon of a vector-layer. I was told that this is called "zonal statistics". I tried that with QGIS first. There is a way to ...
9
votes
1answer
1k views

Is it possible to show our custom message in QGIS Status bar using python?

Is there any way to show our custom message in Qgis Status bar using python? Just like in arcgis "IApplication.statusbar.message(0) = "Please wait..." like that is there any option to show ...
9
votes
6answers
7k views

Rasterfile clipping error: Cannot compute bounding box of cutline

I have a raster file and want to clip it, a vector file is supposed to be the mask layer. I use the most obvious method (Raster->Extraction->Clipper). No matter what I do, I get this error (see pic): ...
9
votes
7answers
10k views

How to copy attributes from one polygon layer to another?

I have a problem that I can't seem to get my head around. I have two polygon layers: Polygon A - is a subset of polygon B with the same fields and has identical polygons to Polygon B Polygon B - has ...