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

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2
votes
1answer
163 views

How to get a message when the map is moved in QGIS?

I want to get a message when every time I move the map. I had: def info(self): QMessageBox.information( self, self.tr( "Info" ), self.tr("info") ) I suppose that used to be something like ...
1
vote
1answer
121 views

Polygon Nodes do not have separate coordinates [duplicate]

I'm attempting to measure the distance of a series of points from a smaller number of polygons. As a first step, I've changed the polygons into points along their border, via the Vector> Geometry ...
1
vote
2answers
115 views

How to make digitization more detailed afterwards with QGIS?

I digitized already two areas, bordering each other on one side. Than I realized, more detail was needed! What do you suggest as a fast way to do so? Adding each time new dots/verteces takes so ...
0
votes
2answers
422 views

I can't export in QGIS a Shape file to PostGis

When I try export a pipe network shape to postgis i get this error: Problema inserindo feições do arquivo: C:/PP/gvSIG_Projects/Shapes/Abastecimento/QGIS_VATROCOADUTOR.shp Ocorreu um erro no banco ...
3
votes
1answer
951 views

How to import QGIS Raster into PostGIS

I have created a IDW heatmap using QGIS 1.8.0 and need to import the raster into PostGIS 2.0.1. QGIS saves the raster layer as a .asc file. How do you import the raster into PostGIS as a Raster? What ...
6
votes
4answers
1k views

How to get features based on their attributes using Python?

How to Get features by their attributes (similar to Iqueryfilter in arcobjects) in Qgis using python? Instead of getting all features and filter it manually, is there any option to use whereclause to ...
2
votes
0answers
129 views

qgis missing menu bar ver 1.8.0-lisboa on ubuntu linux

QGIS emits the following warnings when starting, and fails to display the main menu bar. $ qgis --nocustomization Warning: loading of qgis translation failed [/usr/share/qgis/i18n//qgis_en_US] ...
2
votes
0answers
123 views

Why do most Area Calculation result in 0?

I would like to autocalculate area (acres) for a shape file that is in UTM zone 16 CRS. I have tried the "Vector|Geometry Tools|Add/export geometry columns" and also the field calculator. The first ...
2
votes
1answer
581 views

How to fix erros loading result layers from SAGA functions in Sextante?

Using QGIS 1.8.0 and SAGA When trying to use the IDW function from Sextante SAGA 2.1.0 64bit, I get the following error: Could not load layer: C:/test.tif. This error seems mysterious to me, any ...
1
vote
0answers
119 views

Creating polygons for a choropleth map using PostGIS

I have a grid of points, each with a value to it as shown in the image below. The data was retrieved from PostGIS and rendered in Quantum GIS. The final result should be a polygons of a choropleth map ...
1
vote
0answers
114 views

How to programmatically change an SVG symbol in the Vector Layer?

I'm trying to change the symbol used in a layer via Python. I've been able to tunnel through a vector layer to the symbol layer, but I don't know how to change the symbol it's using. I'd like to ...
2
votes
2answers
508 views

How to create a printable map of labelled markers with OSM background?

I want to create an image of an OpenStreetMap map suitable for printing on A4 at 300dpi. The map needs to have half a dozen markers/points, and each should be labeled with the name of the point. I ...
2
votes
1answer
98 views

How to permanently rearrange the order of features in a Shapfile with QGIS?

I have created a trimmed/clipped map of Europe, the Middle East and North Africa in QGIS 1.7.3 by deleting all the other countries from a world map shapefile. I would like to permanently rearrange the ...
5
votes
3answers
219 views

What is the easiest one click install method for PostGIS and it's entire dependencies?

For someone new to database servers and their dependencies, what is the easiest assured way of installing PostGIS on a machine with no other software beyond what comes with its operating system? I'd ...
2
votes
3answers
770 views

Connnect to PostGIS db using QGIS - when not on localhost

I"m just getting started with PostgreSQL/PostGIS db (v9.2) and I'm wanting to connect to db while not on the localhost using QGIS. I've been able to connect successfully on localhost, however I'm not ...
3
votes
1answer
405 views

Watershed extraction using different DEM tiles

I would like to extract the watersheds for a particular area using QGIS. However, I only have Aster 30m DEMs to work with, each tile covering one degree square. The problem is that I need to use ...
2
votes
1answer
171 views

Writing python plugin: How terminate plugin from script without closing QGIS?

I'm writing a QGIS conversion plugin in python to be able to create Obstacle-files for a model from shapefiles. What I want to do now is just to close the plugin cleanly. This means, to close the ...
2
votes
0answers
225 views

Problems printing OpenLayers Pluggin Maps To Scale

It the print composer I can print all maps to scale and satisfactory. However, when I add the OpenLayer, usually Bing Aerial, to the project I cannot print it out to scale. I click the scale box, ...
1
vote
1answer
69 views

Problem with labels on export/print a map (qgis master) [closed]

As you can see on the images below, the labels on the exported map (right) are much bigger then in the original map (left). Same by pdf, image, and vector - export. Whats the problem? Can I fall ...
2
votes
1answer
505 views

Joining table to shapefile with pyQGIS

Joining shapefiles is a relatively straightforward proess in QGIS using 'add vector join' in the layer properties menu. I can add a csv file as a vector layer, as well as a shapefile, and join the two ...
3
votes
1answer
140 views

How to see print commands through Python Script while programming plugin for QGIS?

This might sound like a silly question. Is there a way that from running a custom plugin made for QGIS that a Python Shell can appear along when the plugin is run, like a debug screen. I'm asking ...
0
votes
1answer
515 views

How to calculate polygon areas in acres or square miles instead of feet?

I have a layer in State Plane NAD83. When I use "Vector|Geometry Tools|Add/export geometry columns" or Field Calculator they both create the area in feet. What if I want acres or square miles? Thanks ...
2
votes
1answer
77 views

Adding a delimited text layer in QGIS 1.8 only imports a fraction of the total rows

I am trying to add a delimited text layer, and I think I've formatted it correctly as a CSV file. There are no errors when I import the data. But even though there are 1300 rows total, only 189 appear ...
0
votes
1answer
67 views

pgRouting:routing problems using reverse_cost

I saw this post:Routing issues with pgrouting, and try the ability of reverse_cost. As the result of this post, if there is only one way to go from one node to another, even though the reverse_cost ...
5
votes
1answer
180 views

Can I edit shapefile while using a definition query in QGIS?

Is it possible to edit shapes while using a "definition query" or "query builder" in QGIS? I'm trying to do this in the same way I used to in ArcGIS. Thanks!
0
votes
1answer
103 views

Can pgRouting work more efficiently?

I use a river network on which has a lot of nodes to test pgRouting, and I run the SQL, searching for the shortest path between nodes. SELECT * FROM shortest_path(' SELECT gid as id, ...
0
votes
1answer
99 views

Is it possible to update layer source in qgis

I've loaded a few shape files as layers in qgis, and I'd like to make a duplicate of the project and all associated shape files into a single directory. However, all of the layer sources are still ...
1
vote
3answers
638 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
597 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
0answers
158 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
133 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
65 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
vote
0answers
119 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
746 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
620 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
votes
0answers
314 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
821 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
votes
0answers
75 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
78 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
vote
0answers
59 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
957 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 ...
3
votes
1answer
86 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
108 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
674 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
188 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
203 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
286 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
105 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
77 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 ...