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

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1
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3answers
727 views

QGIS 1.8 startup crash - looking for a log file

I have a problem with QGIS 1.8 with OSGEO4W installer (windows 7 - 64 bit). QGIS crash on startup, it shows the splash screen and then nothing. I have updated from an old 1.7.4 QGIS version. I have ...
5
votes
1answer
765 views

Speed of editing attributes in QGIS from a Python plugin

I'm trying to edit the value of an attribute for each feature in a layer using a QGIS Python plugin. I've found that doing this outside of editing mode is much slower than while editing (even ...
1
vote
1answer
186 views

How can I map data points to OpenStreetMap (OSM) line data?

my goal is to filter measuring points of vehicles by mapping them to streets. So I could filter out all the false data located in fields and rivers and so on. I imported my data into a PostGIS ...
1
vote
1answer
155 views

pgRouting:how to use reverse_cost?

I add a new column, naming it "reverse_cost", and give it the same data in the shape_leng column. But as I run the shortest path algorithm in pgadmin, I got an error message. here's my sql code ...
0
votes
1answer
66 views

Font Issues Upon Export From QGIS 1.9

I'm using QGIS 1.9.0-Master, code revision 1570240. I know I shouldn't be using it for 'production' but I'm working on a map layout, and all of the new composer features are very helpful! As of the ...
1
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0answers
123 views

I can't connect QGIS with postgresql

I can create a connection to the database in qgis and the test connection is successful. However when I actually connect to the database to export shape files I get the following error: the ...
1
vote
1answer
884 views

How to dissolve polygons and aggregate their data in QGIS? [duplicate]

I have a shapefile (one layer) with my country but I have a problem. It is divided into 4 entries (prefectures), and I want it as one, not 4. Also, there is a table with some data, and I want to ...
3
votes
2answers
766 views

Problem loading PostGIS (Postgres) View layer in QGIS

Why is Postgres user XX via command „Add PostGIS Layers“ in QGIS enabled upload only View tables which owns? Or how to achieve it to the user XX via PostGIS can load View table which owns the user YY? ...
2
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0answers
370 views

Principal Component Analysis in QGIS

How do I go about to perform a band ratio and Principal Component analysis in QGIS? I need to derive principal components from ratios of landsat TM bands .
0
votes
1answer
1k views

How to georeference PNG images using QGIS? [duplicate]

How can I georeference png images using QGIS, running on OSX? I've looked at ExifTool, and the plugins GeoTag and Import Photos + Photo2Shape. These tools (and other answers) as far as I can tell ...
0
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0answers
78 views

Developing QGIS Plugin on windows [duplicate]

I have developed a small plugin which acts as a plugin for QGIS. On linux, QGIS (customized) as well as the plugin were built using QT creator and worked well. Same code I am trying to port on to ...
3
votes
1answer
80 views

What is displayed when I am using a geographic CRS for my project

I understand that each geographical dataset has a CRS, and that in order to overlay them, you need to either make sure that all datasets use the same CRS, or re-project some of them (or use on-the-fly ...
1
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0answers
60 views

Purge Layers from QGIS [duplicate]

I have created numerous databases from a base source and merely added and removed various layers then saved as a new project. There were more layers common than not in common in each project. However ...
5
votes
2answers
1k views

How to avoid creating corrupt Shapefiles during Editing?

I have one of my GIS technicians digitizing some lines in QGIS in shapefile format. I don't know how he did it (and neither does he), but somehow the shapefile became corrupt. It was creating random ...
4
votes
1answer
93 views

Is there a Small Windows install of QGIS?

I am looking to find a faster alternative to ArcReader. I think QGIS might be faster but I was wondering if there was a smaller install without all the GRASS etc for windows. I just want to get a ...
1
vote
0answers
123 views

Qgiscloud upload problems

Uploading a map to Qgiscloud seems to work fine. But uploading data presents two problems. Qgiscloud complains that my version of OGR/GDAL is outdated. And if I try to upload data, qgis complains that ...
3
votes
2answers
847 views

How to find the middle point of a line in QGIS

I am trying to locate the coordinates of the middle point of a line feature in QGIS. I tried searching online but can't seem to find an easy way to do this.
1
vote
1answer
205 views

How can I change SQL query through a layer of an action (python)?

I have three layers from three diferent database tables. When I click in other layer I want to change (with an action) the query of that three layers. How can I do that? Thank you
2
votes
2answers
235 views

Capitalizing The First Letter Of Each Word In Attribute Field

Does anyone know of a way to capitalize the first letter of each word in a field in an attribute table? I am doing this in QGIS. I know of field calculations to change all the words to Lower or ...
1
vote
1answer
327 views

Aggregate points with same values to polygons

I have a shapefile with 2M measurement points (each measurement point has a resolution of a 1/10). How can I aggregate points around each other if and create polygons out of it? They do not have to ...
0
votes
0answers
29 views

Exporting QGIS attribute table to excel [duplicate]

I have a million rows in the attribute table, with lat/lon columns that I want to export to Excel. Selecting all the rows causes QGIS to crash. Is there another way to do the export? The million rows ...
0
votes
0answers
115 views

gdal_merge.py aligns incorrectly at the seam of two GeoTiffs

I am trying to merge four GeoTiffs from the National Elevation Dataset (EPSG: 4269) into a 2x2 DEM using gdal_merge.py. For some reason, when it merges the upper two NED rasters, gdal produces a seam ...
0
votes
0answers
79 views

QGIS very slow startup on Mac

I am experiencing startup times of c5 minutes (!) for QGIS 1.8 on my Mac Mini with 2.4GHz processors and 8G RAM. I have just 4 python plugins and only a handful of shapefiles/data layers so I can not ...
2
votes
3answers
194 views

How to minimize the number of nodes in a polygon?

I'm building a web application that will be transferring polygons from server to client. Initially, the shapefile is coming from an external source that I have no control over. Often, I find polygons ...
1
vote
1answer
292 views

How to save a joined spatialite table when each table contains PKUID fields?

QGIS 1.8.0 -- QSpatialite 6.0.7 -- Windows XP I have spatialite tables joined together that I need to save as a single table, but an error-message says that QGIS can't save the table because there ...
1
vote
1answer
88 views

How to reopen a plugin-window in QGIS?

I am currently taking my first steps in playing around with programming a plugin in python 2.7 for QGIS 1.8. While my plugin does what it should, I would like to make it more userfriendly. At the ...
2
votes
3answers
208 views

How to classify shapefile data into groups?

I have a map with a shp file containing information on land use. The attribute table has over 10,000 rows. I need to classify this information into 6 groups to represent 6 colors on my map. I know ...
2
votes
1answer
149 views

GPL License - App only uses QGis components as a GIS display

I'm still not clear on QGIS licensing ... I am contracted to write a system that has nothing to do with GIS and GIS analysis, but goes around managing animal tags, and I want to use QGIS to draw on a ...
0
votes
0answers
13 views

Sextante Modeler Error “global name os is not defined” [duplicate]

I want to generate a model whic reclassify radter values. So i added Saga reclassify grid values tool to Modeler and saved the model. When i run the model i got this error both on Ubuntu OSgeolive 6.0 ...
0
votes
1answer
116 views

In QGIS can I show just the lines in a Postgis query? How can I do that?

I have three tables in Postgresql, each table with one layer of lines. I want to show the path of an initial line to another final. Is it possible executing a SQL query? Thanks My three tables are ...
0
votes
2answers
276 views

Why is QGIS reading in my CSV numeric data as string data, and how do I change it? [duplicate]

QGIS keeps reading in my numeric data from .csv files as string data. This means I have to figure out how to read it in with the proper data type, or convert it back to numeric inside of QGIS, ...
2
votes
3answers
233 views

How to delete polygons less than a certain area?

I'm trying to delete all polygons with an area smaller than a certain give value. Is this possible in qgis? The goal here is to delete all the islands off a map.
3
votes
2answers
156 views

Why is it so hard to download only a part of OSM data by attribute tag?

Is there any online service that allows to download only one thematic layer of the OSM data for a specific geographic region? For example all objects related to vegetation (trees, grassland,...), but ...
0
votes
2answers
307 views

SAGA, GRASS Raster values to null

I want to make the cells which values "1" to null in QGIS with Grass or Saga tools (exactly Saga).
0
votes
1answer
88 views

Is it possible to export an image that can be zoomed-in on?

I am using QGIS on a Mac. I would like to export my map so that the viewer can zoom in on it, just as I view the map on my QGIS canvas. I am not sure how to word what I want. If you see the map ...
0
votes
0answers
39 views

Print Composer doesn't display my map! [duplicate]

So I have created a map that I need to share with my coworkers. When I open Print Composer and add map, my map does not appear in the rectangle that I create. It is just blank. I try updaing the ...
8
votes
5answers
2k views

What is the best free web GIS browser?

Hi I have created several projects for several different clients. Each project has OS maps, shapefile layers from Government Bodies, Shapefile layers created, AutoCAD dxf loaded in (in various ...
2
votes
2answers
164 views

merging layer stored in PostGIS

I have a bunch of layers stored in PostGIS that I want to merge. I have spent quite some time investigating various approaches but I ket tripping over getting the GIDs to update properly. In the end ...
1
vote
0answers
489 views

Line to Polygon via Polygonizer in QGIS

My question is in the same vein as this one. I'm attempting to convert precipitation lines (Precipitación Media Anual) to a polygon for Mexico in QGIS using the Polygonizer plugin. After running the ...
0
votes
1answer
239 views

QGIS Trace Tool; Error

I have installed the traceDigitize tool from the experimental repository in QGIS 1.9.0 Lisboa. My understanding of the tool is that you have to: Add 2 layers to QGIS Desktop. My empty shapefile to ...
2
votes
2answers
192 views

How to determine the coordinates of the corners of the raster layer

How can we determine the coordinates of the corners of the raster layer? The image opens function QgsRasterLayer.
8
votes
3answers
864 views

Howto setup and use a remote GIS workstation (QGIS,GRASS,PostGIS)?

I'm using QGIS (and sometimes GRASS and PostGIS) on my 2009 MacBookPro for my thesis project. I was wondering (during an endless batch generalizing in QGIS) if I can set up a server so I can work from ...
1
vote
1answer
70 views

Is there any “proper” way of setting the viewport for QGis Time Manager?

I'm working on video visualisation for some geo data. Everything works fine for me except the viewport that the time manager plugin is using for image frames. It makes image frames size of actual map ...
9
votes
1answer
283 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 ...
2
votes
2answers
425 views

How to calculate area in sq km of an ellipsoid shapefile

In QGIS, I often find myself setting up projects with an ellipsoid coordinate system (e.g. WGS84) so that the resulting maps have lat lon scales, etc. Often in these projects I also need to do some ...
3
votes
2answers
2k views

How to reclassify a float raster?

I have three rasters which represent distance (in metres) from certain things (bus stops, parks, libraries). I would like to reclassify these rasters so that they get integer values based on the ...
0
votes
1answer
78 views

Full Easting and Northing coordinates values cannot be encoded in GRASS r.water.outlet in SEXTANTE-QGIS

The Easting or Northing coordinate parameter accepts only 5 digits. The Easting and Northing values for my outlet are 6 and 7 digits long (integer). How can they be encoded in r.water.outlet? Can ...
3
votes
0answers
353 views

Error in uploading data in QGIS cloud

I want to publish my .shp file using QGIS Cloud plugin. I signed in to qgiscloud.com (free). On create new database it will auto create dbname='fbeudp_mfaphk' user='fbeudp_mfaphk' ...
2
votes
0answers
103 views

Raster area (QGIS) problem explained

I would like to know the area that each value in a raster has... The raster I have has values from 2-15 and I would like to know the area that each value is occupaying within my polygon... Thanks! I ...
1
vote
2answers
217 views

Qgis 1.8 is not recognizing sdw file

I'm running qgis 1.8, and trying to load a sid file into my map. It imports fine, but seems to ignore the sdw file that comes with it, as the raster shows up without any apparent georeferencing. Is ...