Tagged Questions

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

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0
votes
1answer
357 views

Check if layer is a QGSVectorLayer from Python Plugin within QGIS

I am trying to extend some concepts in the QGIS Workshop tutorial. Basically, I would like to check if the layer is of type "QGSVectorLayer". In the QGIS Python console, I am able to type canvas = ...
2
votes
2answers
366 views

How do I set the working directory in QGIS?

I'm learning QGIS and lovin' it. But one thing that annooys me a little is is that each time I want to save data, the default directory is the QGIS folder under Program Files. How can I set this, ...
4
votes
2answers
352 views

Does QGIS support internationalization?

Does QGIS support multiple languages? I have some shapefile with Arabic names in its attributes, and they appear as: ???? If I want to see the names in Arabic, do I need to purchase multi-language ...
0
votes
1answer
1k views

Producing NDVI maps in qGIS

I'm trying to produce a simple NDVI map in qGIS using a Macbook pro (2011) from landsat raster images. I've tried using the 'Measuring Vegetation' plugin, but for some reason that goes absolutely ...
4
votes
2answers
3k views

How to generate a DEM from a contour Shapefile?

I want to create a DEM from depth contours (shapefile) in QGIS. I've been trying to work out how to do this based on this previous question, notably from this link from that page, however I'm stuck, ...
1
vote
0answers
120 views

GRASS v.overlay.or Error when trying to split a polygon with a line

I am using the Grass plugin in QGIS for Windows (1.8.0). I am trying to split a polygon with a line feature. I am using the v.overlay.or function within the QGIS Grass plugin. I have the line layer ...
1
vote
0answers
50 views

Generating “weighted convex hull”

sadly I don't have any keyword that reflects what I'm looking for: I have a vector layer consisting of points, which have an integer attribute ("signal quality" here), that I want to plot as a convex ...
2
votes
0answers
55 views

“Map 1” vs “Map 0”

When I compose a map to print, and get everything all set; then close it for some reason; then reopen it--the scale bar appears messed up. I then go to the Scale Bar settings, and find that under ...
0
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0answers
167 views

catchment delineation

I am trying to use qgis to delineate between three sub-sub-catchments. I have contour shape file of 20 meter height. Sub-catchment is about 12 square kilometers area but consist of three ...
0
votes
1answer
291 views

Running a script with QgsFeature from within the console

I am trying to run a script from the QGis Python console (similar to: http://spatialgalaxy.net/2012/01/27/qgis-running-scripts-in-the-python-console/) The line feat=QgsFeature() operates fine from ...
0
votes
2answers
191 views

How to rotate (svg) symbols in QGIS map composer to match map rotation?

Because of my thesis layout requirements, I have to rotate 270° some of my maps in composer. There are (many) svg smbols (icons), and they are rotated as well. I would like to (non-)rotate them in ...
1
vote
0answers
129 views

Is it possible to integrate the mapping capabilities of QGIS with Stata?

I was wondering of the possibility of integrating the mapping capabilities of Q-GIS with Stata, by using the programming aspect of Stata as opposed to using R or python. Is this possible?
0
votes
2answers
2k views

Multi-Band (RGBA) into single band raster

I have the raster which contains 4 bands (RGBA), which ilustrates the pupulation (traffic) density. I want to convert it to the simple gridded ascii, however I'm getting in the trouble when I try the ...
0
votes
1answer
258 views

CSV and GDAL 1.10 in QGIS

It seems the GDAL upgrade from 1.9 to 1.10 changed the way CSV files are handled so that I now have a non-functioning QGIS. App hangs trying to import csv data file when previously had no problems ...
2
votes
2answers
1k views

saga & grass configuration in sextante (ubuntu)

I have some trouble in running saga and grass algorithms in sextante. When I double click it appears a pop-up saying: Missing dependency.This algorithm cannot be run :-( This algorithm requires SAGA ...
1
vote
2answers
1k views

Find and list all polygons that overlap with another polygon

I am working with two polygon layers which overlap but are unrelated (one is congressional district boundaries, the other is MPO area boundaries). I would like to generate a list of all the ...
3
votes
1answer
485 views

How calculate areas between certain contour lines in qgis?

Sorry for asking a question which I found in similar ways already here, but I am trying this for days and just got no result: How do I calculate the area between certain contour lines (e.g. 0-800, ...
1
vote
1answer
104 views

how do i assign values to shapes to be displayed in my map

I apologize for the simplistic nature of this question, I'm VERY new to QGIS. I'm trying to use QGIS to display political information. I have a map of my state, with each town as it's own shape. I ...
-1
votes
1answer
331 views

QGIS and Python - create line with multiple points in postgis [closed]

How can I create a line, with Python functions, with many points that are records in Postgis? Thank you
1
vote
0answers
137 views

Looking for best practice to connect multiple road vector line layers for routing (pgRouting) purposes

The Data I have: Bridges (line layer) Municipal_roads (line layer and does not include information in Bridges) State_roads (line layer that doesn't include Municipal_roads or Bridges) Question: ...
15
votes
2answers
6k views

What's the relation between QGIS and GRASS?

I have been working with GIS and remote sensing in an university and professional environment some ten years ago (ArcInfo etc), so I have some experience even though somewhat outdated Right now I am ...
1
vote
1answer
3k views

'Couldn't load PyQGIS' after upgrade to Raring Ringtail?

I upgraded my Ubuntu to Raring Ringtail. After that, when starting QGIS I receive a message: Couldn't load PyQGIS. Python support will be disabled. Traceback (most recent call last): File "", ...
0
votes
2answers
238 views

Emergency Services: How to optimize routing by measured travel time?

I would like to optimize the service areas / catchment areas for an emergency service. Therefore, I have several measurement points on the streetmap, where people have stopped the travel time from ...
-2
votes
1answer
666 views

How to digitize a map in QGIS?

I am relatively new to QGIS and using it on windows vista. Problem: I have to digitalise an aerial map and then extract the coordinates. I have absolutely no idea how to start Thanking you in ...
2
votes
1answer
2k views

Watershed Analysis using DEM [duplicate]

I stumbled upon your question regarding the mosaic feature in qgis, the thing is I'm also using Quantum and this is my first encounter with GIS this semester, so if you can please help me with a ...
0
votes
0answers
146 views

QGIS GDAL polygonize - how to set scale

I've got some old contour plots, paper copy only, that I'd like to be able to put into QGIS. I get as far as a successful polygonize into shp and it looks fine, but the scale is wrong. How might I ...
1
vote
2answers
225 views

Hypothetical Cost Saving Question: Proprietary v Open Source

I am writing a paper for my GIS MSc and trying to justify a move for the EPA from proprietary GIS software to open source (QGIS). Can anyone hazard an educated guess as to how much ArcGIS would cost ...
0
votes
1answer
333 views

AttributeError: HelloWorld instance has no attribute 'connect'

Here's the code: import sys,os import win32api from PyQt4.QtCore import * from PyQt4.QtGui import * from qgis.core import * import ctypes from PyQt4 import uic class HelloWorld: def ...
2
votes
0answers
207 views

ArcGIS Raster Calculator VS QGIS Raster Calculator [closed]

Are there any major differences between ArcGIS Raster Calculator and QGIS Raster Calculator?
1
vote
2answers
164 views

How can i mark movement route to the map with QGIS?

I am beginner with QGIS and i am having problem with marking movement route to the map. So i would like to ask how can i mark movement route to the map with QGIS. I have a list of cities and i have to ...
0
votes
1answer
74 views

Give Properties to a shapefile to be used by another person [duplicate]

I have bedrock geoology data. I want to classify the data so it appears with the same propeerties as it does on the suppliers website. Is there a way i can attribute a property to a layer (in this ...
0
votes
2answers
256 views

How to select polygons in polygon and export to CSV?

I have two polygon layrers, each layer a table in PostgreSQL: One layer with polygons areas in a city. Another layer with buildings (polygons) that are within areas. How can I to do to know what ...
2
votes
2answers
263 views

Identify points near roadside in QGIS

How do I create an attribute list from points that run along roads in a shape file containing road data? The points don't intersect the road centre lines and are not consistent in their distance from ...
2
votes
1answer
259 views

Merge attribute data using spatial query in QGIS

I have 2 vector layers that I wish to correlate attributes - a shape file containing boundary polygons and a shape file containing point locations. I'm using the vector>spatial query tool to generate ...
3
votes
1answer
146 views

Filter contour lines in QGIS

I have a shapefile of contour lines, with an ALTITUDE attribute with the height ASL in metres. The source data is in 0.5m intervals, but I'd like to filter it down so I get contour lines at (for eg.) ...
0
votes
1answer
691 views

Cant Instal psycopg2 on mac 10.8.2

I know there Have been a lot of similar questions asked but none address this issue as I far as I can tell. When I am trying to install the sextante plugin, or run PostGIS Manager in QGIS I receive ...
2
votes
0answers
117 views

Installing knn on PostgreSQL for windows

I am trying to install the extension KNN for clustering as an extension on my PostgreSQL database. I have downloaded the file http://www.pgxn.org/tag/analysis I found instructions on how to ...
0
votes
1answer
662 views

How to set Marker Line symbol for QgsVectorLayer by using Python?

QgsVectorLayer Right click->Properties->Style->Single symbol->click on simple line in tree node ->symbol layer type -> Marker line Kindly help me to set marker line symbol programmatically by using ...
0
votes
0answers
92 views

Is there free desktop WFS client with BBOX support?

To troubleshoot WFS server (geoserver) with big dataset (global OSM btw) I have tried number of free GIS desktops which work on Mac: QGIS (1.8, 1.9dev), uDig, gvSIG - none of them seems to support WFS ...
0
votes
1answer
228 views

“Request contains a format not offered by the server.” Error when using CRS transformation with WMS in QGIS

When I try to load a WMS layer which has a WSG84 as a default projection and use a CRS transformation on it, it gives this error message: Request contains a format not offered by the server. The WMS ...
5
votes
2answers
2k views

How to implement Spatial Autocorrelation using QGIS or PostgreSQL (or any free application)?

I am a total newbie on the GIS scene so I hope this is not a stupid question. I have two layers in a PostgreSQL database. The first layer contains points where events happened in Europe. The second ...
0
votes
0answers
20 views

De facto QGIS projection for EPSG4326 / 'unprojected' reference systems? [duplicate]

This is my understanding of projections/datums: To get a map of the earth on a plane you need to project the 3 dimensional earth by 'wrapping' a plane around it in the way that suits you (according ...
2
votes
0answers
243 views

How to create stacked bar/column charts in QGIS?

I know that conventional bar charts (with the bars adjacent to each other) based on feature attributes can be plotted in QGIS. But can you please tell me if there's any way to plot the bars in the ...
1
vote
0answers
26 views

Displaying PDF files associated to feature objects location. [duplicate]

Are there any other methods allowing user to display PDF files associated to points feature object other than using Actions function available to QGIS Layer Properties? I have more than one thousand ...
2
votes
1answer
651 views

How to create a date field in QGIS shapefile

When I create a new shapefile in QGIS, I'm presented with the "New Vector Layer" window, where I specify the Shapefile type (Point/Line/Polygon) and am then able to create attribute fields. I'm only ...
1
vote
0answers
114 views

Why doesn't dissolve finish? It just stops without error message

I have a shapfile of the whole UK that contained Postcode area, district, and full postcode. I was going to try and dissolve the regions into seperate business areas by joining a lookup table that ...
0
votes
2answers
224 views

How to make line with arrow head in QgsVectorLayer using python?

I need to draw line with arrow head or after drawn the line i need to make it as arrow head line by using python. or can we set any arrow head symbol for line features by using python? Kindly help me ...
3
votes
3answers
496 views

How to clean layers from non topological databases?

I'm doing my internship in a consulting office which is switching from MapInfo to QGIS/GRASS 1.8.0. I posted here a few days ago about the way to clean a polyline from a Lidar data with v.clean. ...
0
votes
0answers
56 views

Problem with Georeferencer not scaling TIFcorrectly

I am trying to use QGIS and the Georeferencer to digitize paper maps but I am unable to get the raster to rotate afte I pick my control points. Below is a brief outline of the steps I used to ...
1
vote
1answer
96 views

I don't seem to be able to save Layer Styles in QGIS

I have created and saved layer styles, not recently I admit but have done in the past. For some reason or other I just don't seem to be able to save any new ones in QGIS. No file is created. It does ...