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

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5
votes
3answers
269 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
1k 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
546 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
233 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 ...
3
votes
1answer
337 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
76 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 ...
3
votes
1answer
730 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
209 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
896 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
86 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
71 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
251 views

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

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
115 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
230 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
819 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
1k 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
182 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
vote
0answers
128 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
1k 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
924 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
457 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
2k 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
80 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
84 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
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
2k 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
101 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
144 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
1k 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
218 views

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

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
285 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
397 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
33 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
131 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
90 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
224 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
372 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
94 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
248 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
162 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
14 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
120 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
323 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
323 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.
4
votes
2answers
178 views

How to filter and download 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 ...
1
vote
2answers
416 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
93 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
41 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
3k 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 ...