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

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11
votes
1answer
813 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 ...
3
votes
4answers
2k views

When labelling polygons, not all labels are displayed - QGIS 1.7.0

I am trying to create a simple map of Mexico showing the state polygons and their label. The state shapefile is from here, and the specific file is the first one from the top (Áreas Geoestadísticas ...
4
votes
2answers
8k views

How to change projection and show latitude / longitude in QGIS?

I am new to QGIS and pretty ignorant with the subject, but I want to be able to see the latitude / longitude of a point (with a mouse click) in Quantum GIS. I imported a shapefile (roads of finland ...
8
votes
3answers
842 views

Best way to manage large number of geoTiff rasters

I have around 2-3000 1-bit geoTiffs of size 11000x9400. Color 0 should be transparent, and QGis gets it wrong in the first place, so I used a .vrt file to set all the parameters in one single place. ...
5
votes
1answer
1k views

How to create a polygon from other polygon boundaries?

I want to write an algorithm that creates a polygon inside a hole made by a set of other polygons. It's something like a flood fill and it's like the "boundary" tool in Autocad. The image shows an ...
3
votes
5answers
4k views

How to redefine the nodata value into zero in QGIS?

I have an image which i cliped with an AOI polygon. The contour area was set to pixel value = 0 and I have a nodata value of -32768. I want to redefine the nodata value into zero. I used to do this ...
2
votes
0answers
250 views

RT Sql Layer plugin giving an error [closed]

I am trying to use the aforementioned plugin with QGIS 1.7 and Postgres 9.0/PostGIS 1.5. Added a PostGIS spatial layer w/out a problem and then clicked on the RT Sql layer button which displayed the ...
7
votes
1answer
1k views

Is there any 'Auto-complete polygon' tool in QGIS?

Is there any 'Auto-complete polygon' tool in QGIS, similar to the one existing in ArcGIS?
7
votes
1answer
3k views

How to delete fields in QGIS?

When is the option to delete field in an attribute table enabled in QGIS? I'm in editing mode and still am not able to delete a field...
3
votes
1answer
1k views

How to update only a single vector layer in QGIS map canvas?

I want to update a single vector layer as I am working on 8 vector layers and they are getting fast data from serial port so for updating I use mapCanvas().refresh() which refresh all the layer and I ...
12
votes
2answers
9k views

How to join external tables with a shapefile's attribute table in QGIS?

I need to join a .csv table into an attribute table of a shapefile. I wanted to do this with QGIS and i don't seem to find anyway of doing it. I know that the mmqgis plugin does it, but my shapefile ...
0
votes
1answer
305 views

QGIS 1.6.0 problem during printing & export to PDF

When trying to print or export my map to pdf something happens to my document. When trying to print, the outcome always results in the printer producing a solid grey rectangle, and when I try to ...
2
votes
0answers
454 views

How to read a .GPB file in C#?

I have a .GPB file, I need to extract the common GPS data from it but I don't find a clear structure that specify the contents of that file. as a sample record from file 00000260 02 11 A9 61 E7 96 ...
1
vote
3answers
1k views

How to count pixels of a raster in polygons using QGIS?

I need to compute some statistics of the pixels of a given raster that are coincident to the polygons of a vector file. Is there a simple and effective way to do this in Quantum GIS or similar?
8
votes
4answers
3k views

Is there a way to concatenate fields in field calculator of QGIS?

Is there a way to concatenate fields in field calculator of QGIS? (e.g. hectares + ' ha')
7
votes
4answers
3k views

How to identify and eliminate overlaying polygons in Quantum GIS?

I have a shapefile with polygons and now, not sure why, most of the polygons became duplicated and overlaid, i.e. when i click to selected one, i get two selected... How do i identify those polygons ...
5
votes
1answer
1k views

How to draw or edit curved lines in free GIS?

I'm searching informations about drawing simple curved arrow lines into free GIS like QGIS, in this problem data geometry is CIRCULARSTRING ( a type which exists in latest postgis version) It seems ...
5
votes
1answer
4k views

qgis to local postgis connection - fails

It seems pretty clear I cannot connect to a local postgresql installation out of QGIS. This is my first experience with PostGIS. I am using PostgreSQL 9.0 on a win7 machine. I can see the successful ...
6
votes
1answer
4k views

How to create a point along a line given distance

I have been given a non-spatial database which contains the names of lines which I have a shapefile for. The database also has names of points and the distance of each point from the origin along the ...
7
votes
3answers
1k views

When i'm in editing mode in QGIS, how do I make the selection color transparent?

...because i need to split a polygon and i want to see the layer underneath it. But I have to select the polygon in order to cut it, and when i do that it turns yellow!
13
votes
1answer
2k views

How to have a drop down list for feature editing (attributes) in Quantum GIS?

I'm editing a lot of polygons of a shapefile in QGIS and i need to classify them, so i have to write the classes a repetedly a lot of times. In ArcMap there is an option to have domains set for the ...
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 ...
2
votes
2answers
462 views

Error when setting projection of a tif file in QGIS. Any ideas to solve this? [closed]

I get this error when trying to define a projection for a tif file in QGIS: ERROR 1: Too many points (3249 out of 3249) failed to transform, unable to compute output bounds. How do i work this out? ...
15
votes
1answer
2k views

Voronoi polygons that run out to infinity

I have been working on implementing the voronoi.py script (Bill Simon's translation of Steve Fortune's code). According to the QGIS link it is basically the same code that I am working with, but the ...
1
vote
1answer
235 views

What is the shell command for the tool 'simplify geometry' in QGIS?

I was wanting to batch the tool 'simplify geometry' for a set of shapefiles, in the osgeo shell.
1
vote
1answer
797 views

Last edited information missing when used QGIS - Dxf to Shp

I am doing as constructed drawings which require the information to be in a GIS system and more specifically drainage as constructed drawings. I must have a separate file for Pipes and Pits. First I ...
2
votes
2answers
396 views

Shapefile CRS changed after exporting from QGIS. Are they equivalent?

I added a shapefile as a vector layer in qGIS 1.7 so that I could join in additional attribute data (not geodata) from another DBF file. The Shapefile that I added has this CRS (as far as I can tell ...
7
votes
2answers
2k views

QGIS and Raster Mapping in 'Seamless' layer

I would like to use Ordnance Survey base mapping in QGIS. I would like to set up something like a seamless table in MapInfo. I think that the equivalent in QGIS is a Virtual Raster Table. The files ...
2
votes
4answers
4k views

Export to new projection in QGIS 1.7

Suppose I have layers A and B. I don't know their projections but by the looks of the map I know they are not the same. In QGIS 1.6 I would use one of my favorite features: Vector> Data ...
6
votes
2answers
4k views

Using Field Calculator in QGIS to update columns with centroid coordinates

In QGIS I would like to update two columns with the centroid easting and northing of my polygons. I am using the field calculator. I have tried using $x and $y but this only seems to work for points. ...
4
votes
2answers
325 views

Total newbie. Creating map from aerial photo of golf course in QGIS

I have a aerial photo in tif with a tfw file of the golf course that I work at. I would like to create vector data of different features on the course such as greens fairways tees, etc. to calculate ...
14
votes
4answers
6k views

How to join attributes from nearest point in QGIS?

I have two layers with points, call them A and B, each with different attributes. For each point in A I want to join all the attributes from the nearest point in B. Ideally this would also include ...
23
votes
5answers
5k views

How to identify clusters in vector point data?

I have a vector dataset of rural broadband data-points (how fast, etc.) and I'd like to explore if there are clusters of points with similar characteristics, and to plot polygons encompassing them. ...
0
votes
2answers
1k views

QGis import partial PostGIS layer using query builder

I'm sorry, but I'm terribly new to the GIS scene (and PostGIS & QGis). I have loaded a whole bunch of OpenStreetMap data into a PostGIS database and successfully drawn a map using Mapnik. Now I ...
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 ...
3
votes
2answers
3k views

How to Zoom in QGIS Print Composer Without a Scroll Wheel

I am attempting to print a simple map from QGIS in portrait orientation. When I use the "Add New Map" tool it brings the map in at an extent which matches my original data frame if I were to use ...
1
vote
1answer
409 views

Python console not loading with QGIS1.7-Ubuntu 10.04.2 LTS lucid,

Any tips on how to get the Python console working on Q-GIS (Quantum GIS)? (Its not working from the software's menu.) System: Python 2.6.5 QGIS1.7 OS Linux: Ubuntu 10.04.2 LTS lucid Error ...
22
votes
7answers
22k views

Removing small spaces (slivers) between polygons?

I have a set of polygons representing administrative districts. The districts were digitized by hand, and there are small spaces (slivers) between polygons where the polygons should be touching. How ...
3
votes
2answers
762 views

Overlaying GPX data on rasters in QGIS

I have a series of raster map images that I would like to use in QGIS and overlay some simple GPX routes over the top to produce a custom map image. This is all quite new to me so please bare with ...
2
votes
2answers
2k views

Problem reprojecting data from personal geodatabase using QGIS

I have a dataset in the form of a personal geodatabase (mdb) and am interested in using certain feature classes for further processing. My problem is - I am using USGS data orthoimagery which comes ...
9
votes
5answers
10k views

How to join multiple records to single feature?

apologies for what I'm guessing is a really easy problem to solve. GIS user, not programmer here. I'm trying to create a join/relate in QGIS where I have a shapefile of buildings and to that I would ...
6
votes
1answer
798 views

How to force QGIS Centroid Fill inside the Polygon?

I would like to use a centroid fill to enable me to place a letter inside a polygon. The advantage of using a centroid fill is that it also shows up in a legend, whereas labelling the layer would mean ...
6
votes
1answer
802 views

Vector Legend item names in QGIS Map Composer

Is it possible to get the text for a legend item to go over multiple lines? I have some long item names and I have a set legend width that I have to use. Without being able to make the text go over ...
5
votes
2answers
277 views

How to deal with multitype data sources in QGIS?

Today I was trying to import a DXF to Qgis, the result is that qgis displays everything LINES and POINTS but it only displays options for the POINT objects. When I try to export to a shapefile, it ...
2
votes
3answers
472 views

Has QGIS 1.7 been released as a stable version yet? [closed]

Has QGIS 1.7 been released as a stable version yet? I see on the QGIS site the windows download on the is still referring to 1.6 and the OSGEO4W install has 1.6.0-7 as the stable release. I had seen ...
25
votes
2answers
9k views

How to style beautiful road maps with QGIS?

I am trying to design a beautiful map using Qgis. As I'm a software developer not a designer, I was hoping that this will be easy, but it isn't! There is a similar question here Qgis tutorials and ...
5
votes
1answer
1k views

QGIS Data Management: How to calculate Standard Deviation?

does anyone know of a way to find the standard deviation of an attribute lying within any given polygon? The plugin dialog "Join Attributes by Location" gives only the options Mean, Min, Max, and Sum. ...
4
votes
2answers
279 views

How can I make my data efficient and “light” to do 3D Visualizations in Google Earth?

As a test run, I'd like to visualize population on census blocks for a few states (New England for example). I assume that the kml to do this will be huge, when you factor in the census boundaries and ...
3
votes
1answer
798 views

How to Solve the error - “Python Plugin is Broken”?

I tried following the steps to build a python plugin for QGIS. (step 3 is where I am stuck at) 1) I used the Plugin Builder plugin to build the initial set of files. I call my plugin ...
1
vote
1answer
333 views

How to get a composition name in Qgis python console?

In Qgis python console: I want to populate a list with compositions names, like in Composer Manager, but I can't figure out how to get the names (titles). So far: composerlist = ...