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

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3
votes
1answer
707 views

How to hide/show QGisVectorLayer from Python code?

Once created a layer, how can I hide/show it? I can enable/disable rendering of a specific layer by selecting the checkbox through QGIS, but I need to do it programmatically from python code. How can ...
1
vote
2answers
101 views

How to draw a closed line in QGIS1.8?

I want to draw a closed line in QGIS1.8,but I don't know how to make the last point coincide with the first point.What am I supposed to do?
1
vote
2answers
2k views

How to fix QGIS PyQGIS package?

I have a broken package that is preventing QGIS from loading python plugins, updating itself, or even un-installing. The main symptom of this problem is the following message that appears when QGIS ...
1
vote
3answers
545 views

Scripting (with) WPS?

As far as I understand WPS (web processing service) can be used to execute geospatial operations on the server side. Is it possible to create scripts with WPS? For example something like: 'check in ...
1
vote
2answers
171 views

information from a shapefile to another shapefile

I am very new to GIS and learning by myself so what I'm about to ask is possibly quite basic. I am using QGIS. I have a shapefile, which categorizes areas (land cover) by numbers (corresponding to ...
5
votes
2answers
887 views

How to recreate unique reference number with QGIS or PostGIS?

I have a shp file with about 500 odd records in it. It has an ID field but I want to add in a new field with a unique reference number. Can I use the field calculator to generate a unique reference? ...
3
votes
1answer
92 views

Is it possible to create DEMs from ORT format in QGIS?

I recently requested DEMs for my area of interest. The data has however arrived in ORT file format - how do I create DEMs from this data in QGIS? When I open the files in Notepad there are three ...
3
votes
1answer
372 views

How to emulate the modulo operator in a style rule?

I have SHP layer loaded in QGIS. It consists of lines with attribute column z, containing integer value associated with line elevation in meters. Lines are drawn at 10 meter increment, and I want to ...
4
votes
1answer
6k views

How to do a simple find and replace in QGIS field calculator?

I'm trying to replace selected string values in an attribute table, eg. "Text1" for "Text2" (QGIS 1.8.0), patriculary for those rows with NULL values. I have been trying to use the replace expression ...
0
votes
2answers
176 views

Why does a track point layer attribute table have no positional information?

I imported a track log in GPX format to QGIS. The track had two layers, the track points and the track, a smooth line joining the track points. Why does the attribute table for the track points have ...
3
votes
1answer
2k views

Import GPX file to QGIS and correct apparent CRS problems

I am using Easy Trails software on an iPhone to output a gpx file of a walk. When I import the file (import vector layer) to QGIS, into a project with OSGB information and the correct CRS for OSGB ...
1
vote
1answer
483 views

How to convert images from the South African co-ordinate system to WGS84 lat/long?

I have a number of orthophotos for an area in South Africa, but they are projected in the South African co-ordinate system which measures a location in meters from a central (uneven) meridian. These ...
4
votes
3answers
2k views

What's the easiest way (style wise) to publish my MapInfo map as WMS?

I've downloaded data for my country from OSM and let a GIS expert to style it for me in MapInfo pro. (I have TAB files and .wor - workspace). When I tried converting them to SHP (for QGIS) I've ...
3
votes
1answer
151 views

Points warped when exporting to shape

I have recently purchased a Trimble GeoXH (used) and have done a few surveys. I have done differential correction in Trimble Pathfinder Office and all points seem fine. When exporting to shape and ...
3
votes
1answer
2k views

How to get attributes of overlaying polygon layers by a spatial query?

I am new to QGIS and would like to merge selected data/attributes out of the attribute tables from overlaying vector objects on different vector layers without creating new additional layers. Is ...
2
votes
0answers
197 views

How can I map polygon value distribution?

I'm surveying an area and have a z-value attached to each polygon. In comparison to the area I'm studying the polygons are quite small. What I'm trying to do is show the distribution of this value. ...
1
vote
1answer
273 views

Merging data in Quantum GIS

I have a set of postcode boundary data that currently goes down to the most detailed level possible, like this: AB1 2CD I would like to 'simplify' the data so that it just shows the first part of ...
13
votes
3answers
1k views

Why Do Colors Look Darker When Printed on Paper?

I made a map with a terrain-colored relief-shading in the background. I then exported them as PDF from Print Composer in QGIS. But when I print the PDF onto paper: the shaded-relief color in the ...
5
votes
1answer
648 views

How to emulate a specific vector grid in QGIS?

I would like to analyze data included in a pdf file. The file contains information on characteristics of 16km grid cells for a specific study area. The file also includes a map displaying the grid. I ...
0
votes
1answer
802 views

How to fix crashes after update to Ubuntu 12.04?

Some weeks ago I had updated Ubuntu at the 11.10 version, but I had started having problems with QGIS 1.8: I installed the program and launched it, but it didn't open and crashed continuously. I ...
1
vote
0answers
289 views

How does QGIS execute Python plugins?

I am trying to run a python script from within a python plugin. The script runs a CGIHTTPServer in a separate thread. It works as expected when executed from the command line and i can issue requests ...
2
votes
2answers
606 views

How to import qgis.core to python IDLE?

I try to follow the step in How to import qgis.core to python app? to import qgis.core with Python Shell. But when I type set PYTHONPATH=C:\Program Files (x86)\Quantum GIS Wroclaw\apps\qgis\bin it ...
2
votes
2answers
662 views

How to create a “Datum-less” projection in QGIS?

I want to use QGIS to do some georeferencing and image registration. On ArcMap10 I can define an "Unknown Projection", basically a default metric grid, and use it as a grid for georeferncing. In QGIS ...
6
votes
1answer
517 views

Generalize large polygon-file

I have a large polygone file with landuse information (6 classes). Its vectorised from a raster classification so the polygons are all angular. Any of my tries to generalize with v.generalize (sneaks, ...
0
votes
1answer
377 views

QGIS Crashes when selecting > Settings>Project Properties

I am new to QGIS and this forum but have not found a related problem with a solution. Running Quantum GIS 1.8.0, on Windows 7 Pro Running the software, the first action I would normally take on a ...
2
votes
1answer
304 views

How to align labels using Label toolbar?

I'm worried I'm missing something terribly obvious here: how do you set the alignment (left / centre / right) for feature labels? I'm referring to QGIS 1.8, and using the 'Label' toolbar, rather than ...
11
votes
2answers
2k views

What to do with -3.4e+38 nodata values?

I am trying to process some bioclimatic raster files, such as can be downloaded from http://www.worldclim.org/current (bioclim set). They seem to have nodata values set to -3.4e+38 according to QGIS ...
4
votes
2answers
565 views

Why are “capture line” etc not available?

I have a question about QGIS which I just started using. I loaded a shp file and want to edit different elements, but the tool for drawing a new line or adding new points does not appear. I can add a ...
2
votes
1answer
343 views

Why shapefile loaded in canvas always appear in random color?

I created the simple frame .UI file, compiled with pyuic4, and tried the ShapeViewer.py to load the shapefile "world_borders.shp". However, the map is always loaded in different random colors every ...
1
vote
1answer
345 views

QGIS Python error on OS X while trying to simplify shapefile geometries

I am trying to reduce the file size of the shapefile by simplifying geometry in QGiS on OS X. But I get the following error... An error has occured while executing Python code: Traceback (most ...
3
votes
2answers
427 views

How to generalize polygon attributes in a regular polygon grid?

I'm trying to generalize the attributes of a set of polygons(let's say they're census blocks with a population property) into another, overlapping set of polygons(let's say it's just a grid with no ...
1
vote
0answers
30 views

qgis projections from Michigan's CGI data [duplicate]

Possible Duplicate: How to reproject from Michigan Georef to WGS84 in QGIS? I'm importing shapefiles into QGIS. These files were created by the state of Michigan, primarily to be used in ...
2
votes
2answers
3k views

How to fix missing ippj-5.3.dll error in QGIS?

I try to install OSGeo4W but when I tried to run it appeared an error message about ippj-5.3.dll is missing... does anyone know what happen?
2
votes
1answer
404 views

Warning: QNetworkDiskCache::prepare() unable to open temporary file

When I run qgis 1.8.0 on Linux and load a WMS layer from a remote server I get messages (in terminal) saying Warning: QNetworkDiskCache::prepare() unable to open temporary file Downloading tiles ...
2
votes
0answers
159 views

How to geocorrect in qgis?

I need to fit a utm wgs84 tiff raster to a topomap in the same projection. I use GCP and it invariably fails. The first raster uncorrected rater superimpose well, the "geocorrected" raster is ...
4
votes
2answers
471 views

How to add a geometry to an existing feature that was created with NULL geometry?

I have a simple SpatiaLite geodb loaded in QGIS with one table. There is a POINT geometry field and some alphanumeric data. In some cases I can record data about a specific site, but the coordinates ...
2
votes
1answer
3k views

Using clip tool in qgis - contours to exact map area

I am using QGIS. I am trying to clip contours and water vector layers to the exact size of my map (polygon layer). Sometimes it works; sometimes the program crashes before completion (at the same ...
4
votes
1answer
570 views

How to use scale -rule based renderer in QGIS?

I wish to render a shapefile of builindings such that at scales below 1:5000, they have a border, and above 1:5000, they do not have a border. For this, I went into layer properties, selected ...
7
votes
2answers
140 views

How do you obtain the execution times of processes in qgis?

I am working on QGIS. I need to determine how much time QGIS needed to finish a specific task. I have been unable to get execution times for the processes. What is the proper way to get processing ...
1
vote
0answers
23 views

Retaining original thematic colors in a USA source shapefile [duplicate]

Possible Duplicate: Adding Layerfiles (.lyr) to Qgis New to QGIS and need a lot of help! I am using QGIS with MAC - I have downloaded a USA thematic map but when I open it in my system it ...
3
votes
1answer
393 views

Labels with white (or other color) background

I tried to give my labels somekind of box and a backgroundcolor (or boxcolor) in QGIS, but i couldnt find the right option. My labels are not readable because my layers are too dark. I found offset ...
5
votes
3answers
4k views

How to style points in QGIS based on multiple attributes

While trying to find a useful way having earthquakes displayed, I noticed that it isn't that easy to manage. I'd like to be able to recognize the "Magnitude", "Date", and "Depth" from the style of ...
3
votes
2answers
710 views

How to create a standard deviation map from three rasters in QGIS?

I have 3 normalised (0-100) raster maps. Is it possible to get a map which shows the standard deviation? I'd like to see the areas with smaller and higher std deviation. Thank you!
5
votes
1answer
2k views

How to remove a vector QgsVectorLayer from QGis python plugin

I managed to add QgsVectorLayer in QGIS through a python plugin, for example: vl = self.iface.addVectorLayer(uri.uri(), layerName, self.dbConn.getProviderName()) But how can I remove it?
2
votes
0answers
11 views

updatation query along a point [duplicate]

Possible Duplicate: GIS QUERY on point and buffer All, I have a PostGIS/Postgresql DB that has one table in it. One with point geometries and the other that represents buffer as polygons. ...
2
votes
1answer
950 views

How can I fix QGIS PostGIS Manager error 'shp2pgsql' is not recognized?

I have QGIS 1.8.0 installed via OSGeo Installer and work on win 7. All I need is to upload the shapefile to the database via this plugin. Unfortunately I am receiving an error: Something's wrong: ...
4
votes
3answers
106 views

GIS QUERY on point and buffer

I have a point table and the buffer geometry is created around the point. I have defined the if the point is within the buffer_distance then its value is =1 and if it is outside the buffer its value ...
2
votes
1answer
844 views

How to improve OSM layer resolution in OpenLayers plugin while exporting?

I'm having trouble with the OpenLayers Plugin exporting a map to a png or pdf file: The output resolution of the exported osm-layer is very, very poor. Zooming to 100% in the png file shows big ...
2
votes
1answer
112 views

Error message 'Module qgis.v.kernel.rast.py not found'

How do I repair this error in QGIS: The error message was received whilst trying to run v.kernel from the modules list. I can however run v.kernel from the GRASS shell. A while ago, I installed ...
0
votes
0answers
56 views

Point to Polygon [duplicate]

Possible Duplicate: Create new polygon layers from postcodes latitude & longitude I'm running QGIS 1.8.0 I have a list of points that I need to convert to one polygon. So far I have ...