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

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3
votes
3answers
1k views

Obtain all elevations points from a raster DEM

I need to obtain all elevation grid points from a raster DEM. I see the steps required as: Read in raster DEM (Arc Info Binary Grid format). Create subset area using Points2One (see triangle area ...
2
votes
1answer
326 views

Combining polygon geometries with python and QGIS segfaults

I am trying to combine polygons, using Qgis 1.8, and every time I run this script in the python console, I get a segmentation fault. Here is the script: from PyQt4.QtCore import * iface = ...
0
votes
0answers
36 views

How to change value of an Line edit dynamically

I create a form in QT4 and compile with pyuic4. it create an form.py I want to modify the value of the line edit dynamiclly with code. I put this code in the form.py but never happen: ...
0
votes
1answer
90 views

Make many lines in one layer (Python)

I what to create many lines with this code: v_layer = QgsVectorLayer("LineString", "cable", "memory") pr = v_layer.dataProvider() seg = QgsFeature() ...
0
votes
2answers
924 views

How to Join Attributes by Location in QGIS 1.8.0

I have a points layer with site attributes and a polygon layer with region attributes. I'd like to join the names of the regions to the point site locations using QGIS 1.8.0., on Windows XP. ...
0
votes
2answers
83 views

Python to get ids from shp dont return all records

I have some Python code to get the ids and georeference from a shapefile: canvas = qgis.utils.iface.mapCanvas() allLayers = canvas.layers() nos = QgsFeature() for i in allLayers: if ...
8
votes
1answer
271 views

How to automatically reduce polygon size?

I am working with two polygon layers (counties & states) which I will 'intersect' to find which counties are within which states. Due to data inaccuracies I have to change all county polygons and ...
0
votes
1answer
100 views

How to convert geometry of SHP to decimals

I try to create a line with two points. These points are obtained in a SHP layer. How can i convert that points to decimals? Thank you
2
votes
1answer
166 views

How to clip roads to exclude those within a flood zone?

I have OSM road network data in QGIS along with a shapefile showing the possible extent of a flood. My question is: is it possible to exclude all of the roads that are in the flood zone (so as to ...
5
votes
2answers
641 views

Calculating distance and/or time taken to travel from population centre to nearest hospital in QGIS

I'm trying to find out how long it would take to travel by car from each of the Lower Layer Super Output Areas (LSOA) in Norfolk, England to the nearest Hospital (or just what the distance is and I ...
0
votes
2answers
476 views

How to display data from a feature?

I want to display data based on the feature currently selected/clicked on. I am following a tutorial from http://www.qgisworkshop.org/html/workshop/plugins_tutorial.html. It initially shows you how ...
0
votes
1answer
267 views

How to use expression in QgsVectorlayer label by using python?

how to show the two field values as a label on features. I have done it for a field called "ErrorDescr" with this i need to show another field values. Other field is "MarkerId" ...
0
votes
1answer
83 views

trace a transmission line for a certain distance

I’m looking for a way to easily trace a transmission line for a certain distance. Here is the scenario that I am working with. We have an issue with our transmission line; our OMS tells us that there ...
-1
votes
1answer
127 views

How to change windows can't find D:\Program [closed]

Today, I setup QGIS. When I run msys, it appear 'windows can't find D:\Program'. Why? Thank you!
1
vote
1answer
67 views

looking for datum to georeference maps of 19th century Maine

I am trying to georeference 3 (1840, 1844, and 1877) northern Maine maps. I really am not able to find which datum to use. Can anyone point me to a list of historic and regional datums? thanks
1
vote
2answers
258 views

Easy Custom Labeling plugin does allow to save?

I use the Easy Custom Labeling plugin chose positions of the labels and safe the layer and project for continuing later. When opening again the project, the layer opens but without any objects inside. ...
4
votes
1answer
110 views

How to select behind feature which is overlapped with the same layer on QGIS 1.8.0

My issue: I received data which was created without "Avoid intersection of new polygon". There a few overlapped feature with the same layer. I could fine overlapped feature by the spatial query. But ...
1
vote
1answer
1k views

How to find the watershed area for each point in the river network using DEM?

Update#1: Thanks, Micha, I have followed your instruction and successfully use the modules in GRASS. I use r.watershed to get the basin raster and the drainage line: and I use r.water.outlet to get ...
1
vote
1answer
946 views

How to get correct format of coordinates for export to geojson from QGIS?

I've created a custom map in QGIS with a few shapefiles. I'm using leaflet.js to render the map and the shapefile points and everything lines up correctly. The CRS is set to 4326. When I export the ...
4
votes
0answers
1k views

Loading raster from PostGIS DB into QGIS: succeeded yesterday, fails now [closed]

I have a PostgreSQL(v.9.2)/Postgis(v.2.0.3) database which includes raster layers (added through raster2pgsql). To open them in QGIS (v.1.8.0-Lisboa), the "Add Postgis layer" menu will not work; ...
1
vote
2answers
219 views

How to select two points on a map using QGIS?

I need to select two points on a map in QGIS. I selected the element selection tool in menu view and I want to select two points. How can I accomplish this? Are there other tools or methods to ...
0
votes
1answer
173 views

QGIS Python - Convert geometry from Postgres to QgsPoint()

I have made a query in Postgres to get some points to use with python. This points are in geometry data. How can I convert that geometry in decimals to use QgsPoint() in python? Thank you
0
votes
0answers
102 views

Adding a WMS - connection timed out?

I am trying to add a WMS service to qgis but am having some problems. After adding the url and name of the service and clicking on connect, I am receiving the following error message:- "Could not ...
0
votes
1answer
396 views

Nearest neighbor analysis not showing results

I'm trying to do a nearest neighbour analysis on fish shoals distribution. I go to Vector > Analysis Tools > Nearest neighbour analysis. I choose the appropriate layer and when I hit ok the black ...
0
votes
1answer
56 views

How to find the overlap of three polygons?

I have three polygon areas showing different land types and I want to create a new layer based on where the three layers overlap each other. I thought this was a subtraction query but havent been able ...
2
votes
0answers
142 views

travel survey multi stop routing problem

I have a travel diary survey dataset that I am attempting to transform into more useful information. Currently, the data comes in the format of: Survey# , PlaceVisited#, TravelMode, TripPurpose, ...
1
vote
0answers
247 views

Handling “bad layers” in QGIS version 1.9

I'm having a problem every time I try and open any project in qgis 1.9. It will load part of a few layers and then a yellow bar comes up across the top of the map area that says "Handle Bad layers: 23 ...
2
votes
1answer
181 views

Why are layers imported into a DB with Spatialite-Gui locked from editing?

I have a Spatialite DB which I have imported some shp files too using Spatialite-Gui. I have full read-write access to these layers via the Spatialite-Gui, however when I open these layers from QGIS I ...
1
vote
1answer
418 views

How to create a Winkel-Tripel map of countries with different colors?

I need a good quality rasterized world map, Winkel-Tripel projection, in which all countries have different (random?) colors. No borders, text, grid or anything else on the map. Is GIS the right way ...
0
votes
1answer
62 views

How to write an Advanced Query which gets the same results as the simple query option

Working with my data set on Late Woodland Village reanalysis in QGIS, the previous question was somewhat answered by defining the issue as a many to one. As a work-around, I summarized the info into ...
1
vote
1answer
187 views

Can I open a form in layer action?

I want to open a form (made in QTDesign) in the layer action. It is possible?
2
votes
3answers
593 views

How to preserve text when converting from .dxf to .shp?

I have tried using dxf2shp converter in QGIS but the text in dxf file is being lost during the conversion process, despite selecting export text labels. I would be grateful if someone can help me ...
2
votes
1answer
152 views

Having trouble with Webserver configuration on Windows

im currently working on a WMS with QGIS 1.8.0 Desktop with apache from xampp. What I want to do is to have my .qgs file displayed on my webpage as a OpenLayer. So I followed this tutorial: ...
0
votes
0answers
18 views

QGis non blocking notifications with pyqgis [duplicate]

I'm searching for the way to use the new QGis non blocking notification system with the QGis python wrapper. I found informations on this fonctionnality but nothing on how to use this especially with ...
0
votes
0answers
53 views

plugins available via WMS?

I have QGIS server up and running and all is well, and I want to create a plugin in PyQGIS. But I need the plugin to be available to the users of the web maps in which my server serves. So is it ...
7
votes
2answers
1k views

Can the new Mapbox Vector Tiles be used as a QGIS basemap?

With the implementation of the mapbox vector tiles begs the question of how these could be used as a basemap in a QGIS printed map (assuming anyone cares about printed maps anymore!). To use OSM data ...
6
votes
1answer
634 views

Splitting polylines according to coincident (or touching) points with other polylines?

The question is unfortunately not answered yet. I'm looking for a method or python script to split polylines according to coincident points with other polylines, but avoid splitting the ones which ...
2
votes
1answer
98 views

How to convert QGIS Field Calculation to ArcGIS?

I have a field calculator expression I use in QGIS to generate unique IDs that are sequential, but start with a text string. I now need to perform the same thing in ArcGIS, but I am unsure of how to ...
1
vote
0answers
363 views

QGis Grid statistics for polygons error - Module caused access violation!

I'm trying to calculate statistics for a raster layer using an overlaying polygon layer, I'm using SAGA "Grid Statistics for polygons" function, but it returns an error, sadly.. So in the sextante log ...
0
votes
0answers
200 views

Spatialite, to speed performance, when should I create Views, Indexes or additional spatial tables?

I’ve got a large Spatialite database with a table of lines (roads, rail and water). I created a spatial index of the geometry to speed things up. This works amazingly well when I’m zoomed in ...
4
votes
1answer
252 views

Raster to vector with gaps in Landsat ETM

I need to find size of water area from a raster (jpg) using QGIS 1.8.0-Lisboa. The raster is a Landsat image with gaps of data in it. I used Polygonize, but the output file shows wrong polygon size ...
3
votes
1answer
162 views

Is there an address gazetteer for QGIS?

I have a SQL database that has our local address database on it - it has no geometry within it, just a list of addresses and X and Y co-ordinates. I want to use this data to enable people to search ...
1
vote
0answers
208 views

Convex Hull issue in QGIS 1.8

When creating convex hulls based on input field in qgis 1.8, there seems to be always one less convex hull created for the unique values in the input field. For example; I have a point vector file, ...
3
votes
1answer
99 views

How to delete points from CSV point layer?

I have a point layer produced from importing a Delimited Text Layer and I would like to delete some points. It seems that it is not possible to toggle editing in a point layer. How can I delete the ...
1
vote
1answer
230 views

Extraction of contour lines starting from 0 elevation

I need your help regarding extraction of contour lines in QGIS. I am new to QGIS (in GIS actually). I followed the tutorials on extracting contour lines from DEM (which I downloaded from cgiar.srtm) ...
1
vote
0answers
106 views

Heatmap plugin with relatively small area

I'm trying to make a heatmap using points in a relatively small area (about 50km by 50km) and I just get a single red block every time (even after switching the color map to 'pseudocolor'). I've read ...
1
vote
1answer
659 views

QGIS - “Bad Allocation” Exception - on identify

I have QGIS (v1.8) set up to identify in Top down mode. When I use the identify tool on the map, I frequently get a Bad Allocation exception message and I was wondering what gives rise to this error. ...
3
votes
3answers
828 views

Is it possible to batch clip rasters in Quantum GIS?

I have been able to batch clip rasters in one directory using python in ArcGIS. However, I am not sure how to do the same in Quantum using the python console. Is this possible? If there are different ...
1
vote
1answer
358 views

spatialite.dll with Python and QGIS - the specified module could not be found

I'm having a bit of a nightmare getting to the bottom of this DLL loading problem. The stand alone script works absolutely fine but the exact same code does not work within QGIS. import sys from ...
2
votes
1answer
335 views

importing coordinates via a csv file does not work

I tried to manually add point data via a CSV file to an empty project in QGIS 1.8.0. The points do show up all right with the correct coordinates, but already the scale is not correct (using the ...