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

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8
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4answers
2k views

How to find dead-ends in road network using ArcGIS for Desktop or GRASS?

I'm trying to remove all the dead-end roads in a road dataset (lines) that are less than 100m long. How do I identify roads that are dead-ends (no exit)? The 100m part is easy. I know how to use ...
8
votes
7answers
4k views

Extract boundary from detailed layer in ArcGIS Desktop or QGIS?

Is it possible to return the boundary (outside) permiter of a polygon layer? Let's say you have the map of the USA, for simplicity, broken down to the county level, is it possible to return the ...
7
votes
5answers
1k views

Are there open source solutions for travel demand modelling?

I'm looking for open source tools for travel demand modelling (eg The four-step UTMS). Preferably in a GIS environment. That works well with Qgis, Grass and Postgis. My question is not related to ...
7
votes
3answers
3k views

How to extract slope from topographic raster map?

I am working on a project for a machine learning class wherein I extract features from a topographic raster map and then classify the traversability of the terrain. One of the features I need to ...
7
votes
4answers
14k views

How to export highlighted features from attribute table to an excel file?

When i selected some portion of the map in QGIS, in the attribute table the selected features gets highlighted... How to export the highlighted features from attribute table to an excel file ...
7
votes
2answers
3k views

How to use Heatmap plugin and its output?

I have a layer of points which I would like to depicted as a heatmap concentration of points for visualization. In QGIS 1.8 I tried the built-in heat map plugin, leaving the default values as is, and ...
7
votes
3answers
2k views

Does anyone know how to install the Orfeo Toolbox in QGIS?

I already tried this http://hg.orfeo-toolbox.org/OTB-Qgis-plugins/ repository and couldn't get it... This guy seems to have it: http://www.elance.com/samples/orfeo-toolbox-qgis/24111664/ Help, ...
7
votes
2answers
3k views

How can I export a linestring to a GPX file in QGIS?

I have a linestring in a vector layer in QGIS. How can I expot/save this linestring as a GPX file? I tried to select the linestring, then right click on the vector layer and choose "Save selection ...
6
votes
1answer
3k views

Syntax of conditional statements in QGIS Field Calculator(s)

I have a shapefile which I need to modify. There is one column "CLASS" with the attributes: "A", "B" and "C". I need to change "A" into "1!, "B" into "2" and "C" into "3". I tried it with case when ...
6
votes
1answer
2k views

How to transform a selected multipart feature into singlepart features while editing in QGIS?

There are several questions and respective answers for how to make a multipart features Layer into a singlepart features one using QGIS: How to break a single polygon into multiple polys? How to ...
6
votes
1answer
676 views

How to create a drop down list?

I want to show a drop down list in the feature attributes dialog. Example: I have 3 different building zones. The hot Wohnzon A, B residential zone and residential zone C. Now I have an attribute ...
6
votes
2answers
1k views

How to display an arrow pointing to a specific bearing in QGIS

I have a number of point features which contain an attribute I call "bearing" and another one called "slope". Each point has a bearing between 0 to 359 degrees. And the slope is either "+15" or "-15", ...
6
votes
2answers
601 views

Is it possible to use the Goode Homolosine projection in QGIS?

Is it possible to use the Goode Homolosine projection in QGIS? Both QGIS and GRASS seem to have trouble with the interruptions, squashing the higher latitudes together. I tried +proj=goode ...
5
votes
2answers
552 views

Calculating the average / MEAN of an attribute field in a QGIS model

I need to know how to calculate the average / mean of an attribute field in my point shape file. Is this possible to do with the field calculator? I just found the options min or max but not mean. The ...
5
votes
1answer
1k views

What is the procedure to load LAS files in QGIS 2.0.1?

What is the present procedure to load LAS files in QGIS 2.0.1? After some searching I found a paper outlining the procedure; however, it was for 1.8.something, and related posts here are all rather ...
5
votes
1answer
836 views

How to programmatically associate a layer with a custom UI?

I know it is possible to associate a layer with a custom UI for editing feature attributes using the QGIS interface. But is this possible with Python? This link shows how to achieve the result ...
5
votes
2answers
879 views

How to draw lines from two points in a CSV?

I have a CSV file where one line looks like this: Duration, user, lat-start, long-start, lat-end, long-end 298, Casual,38.9101,-77.0444,38.91554,-77.03818 Each row in the CSV has two points and I ...
5
votes
1answer
498 views

How to add attributes in proportion to intersecting area from another layer

I am new to using QGIS. I have two polygon layers: Voronoi of Access Points Census block maps with population I want to get number of people covered by each Access Point (Assuming uniform ...
5
votes
1answer
961 views

How to create a custom data viewer on top of QGIS?

I was exploring the possibility of creating a simple Data Viewer based on QGIS. I would like to create an simple application that will open QGIS up with a limited set of tools & menus. QGIS would ...
5
votes
4answers
5k views

Advanced colour palette for raster data

I'm working with satellite date namely chlorophyll and sst. Each geophysical parameter generally has standard colours to represent them. I'm importing geotiffs into Qgis and I'm having difficulty ...
5
votes
2answers
1k views

Looking for an explanation of QGIS Edit Widgets

I have noticed "Edit Widgets" under the Quantum GIS and would like to know in detail the use case and usage of this widget. For any opened vector file, under the Properties -> Fields Tab, for every ...
5
votes
1answer
1k views

QGIS - export a project with dependencies

I was wandering if there was a way to save a specific project with all layers as dependent files to make it easy to share with collaborators. for example, create a zipped or non-zipped folder ...
5
votes
1answer
3k views

How to fill my column with consecutive numbers

I m very new to Qgis, so forgive this simple question. Searching in older topics didn t help either.So: I make a new column in my attribute table and it has a default value(for example 0). I want to ...
5
votes
2answers
7k views

snapping polygons and lines

I recently downloaded QGIS on a Mac OSX 10.7.4 (lion) and purchased a master map shape file, of a particular area. I am trying to divide it into polygons following features on the master map vector ...
5
votes
2answers
3k views

Statistics or simple pie chart in Quantum Gis

Does anyone know how to perform pie charts based on table values within QuantumGis and include them in the print outs? thanks a lot
5
votes
1answer
275 views

Seeing QGIS Python Commands

When learning MapBasic I found the most useful way to learn how to do certain tasks was to do them using the GUI and then watch the MapBasic window in MapInfo to see how they were achieved in code. It ...
4
votes
1answer
215 views

How to display multiple fields as labels if one field is null?

I am having some issues trying to show multiple fields for a single label in QGIS. In QGIS2.6, attempting to display labels for a feature consisting of multiple fields results in an empty label if one ...
4
votes
1answer
420 views

QGIS 2.4.0 Chugiak How to remove topographic effects like shadows from landsat image

I am using QGIS 2.4.0 Chugiak on my windows 8.1, for classification of landsat 5-7 image that contains hilly mountains with dense forest and 60% area are plains. I am classifying through ...
4
votes
1answer
655 views

How to create a catchment from a point using a DTM raster in QGIS?

I need to find a better way to delineate a catchment from a given point on a watercourse using a DTM - currently I am either using FEH, or if the catchment is too small using contours to draw ...
4
votes
4answers
1k views

Matching GPS tracks

I'm looking for a proper way to process multiple GPS tracks (so time ordered list of lat/lon points) and match/classify that segments, that are covered by multiple tracks: So it's not about ...
4
votes
1answer
262 views

How to find a single point furthest from any road?

I have a road layer of a country. What method or plugin would you suggest, to find a single point furthest from any road (but as you can see, there is a coastline, so points in the sea can't count) ...
4
votes
1answer
955 views

How to transfer styles from QGIS to ArcGIS?

We have a QGIS project that has symbols for a lot of different lines. Data comes from a geodatabase that is accessible to both QGIS and ArcGIS. We now want to use the symbology of the QGIS project to ...
4
votes
0answers
343 views

Weather conditions forecasting / interpolation

I'm trying to carry out weather conditions interpolations. I have information of 92 weather stations for 800,000 km2. As you can imagine the extension of land is huge and I need some kind or weather ...
4
votes
1answer
859 views

How to create an extent indicator in QGIS 1.8 print composer?

I'm looking to put an inset map for my main map frame onto my map layout in QGIS print composer. I would like it to indicate the extent and location of the main map on a larger regional map. This ...
4
votes
1answer
106 views

Why are raster z-values changed when reprojecting?

I have raster data with height values (z). When I try to reproject/warp the raster to Gauss Kruger 3, the z-values are changing (several meters). (The data is already GK3, but I have to reproject ...
4
votes
2answers
510 views

How to convert numeric fields into strings with leading zeros?

I'm trying to define an action in Quantum GIS using on of my fields but I have some problems with its format. I have a numeric string like '5' and I need to have a format like '005'. I've tried ...
4
votes
2answers
2k views

QGIS Server limitations?

QGIS Server seems to be fairly simple to setup and create services, however I'm wondering if there are any limitations with using it opposed to MapServer or GeoServer. My current server ...
4
votes
1answer
474 views

QGIS - Add a combobox to a toolbar

Is there a way to add a combobox to a toolbar for QGIS? So far I can only find examples that add buttons. I found this tutorial which seems to explain how to do this with general PyQT but haven't had ...
4
votes
1answer
3k views

Installing QGIS on Mac OS 10.7. “The GDAL framework is required.”, and yet I have it

what did I miss? I'm trying to install QGIS on my MacBook (Mac OS 10.7). I'm following these instructions: https://sites.google.com/site/eospansite/qgis-installation/installing-qgis-1-6-on-macosx It ...
4
votes
2answers
2k views

Can QGIS automatically load an SLD with a Shapefile?

I have SLD's/lyr files with my shp/gdb files. They all have the same name except for the extension. Is it possible for me to force qgis to load the sld with the shp so that I don't need to manually go ...
4
votes
3answers
2k views

Using CityGML data with ArcGIS Desktop or QGIS?

I'm looking for advice on how best to use the CityGML data-structure and GIS (preferably ArcGIS/QGIS). I've read through their website and wiki and saw a list of software here that can be used to view ...
3
votes
2answers
178 views

How to define layer's CRS and avoid the CRS dialog in PyQGIS?

There is an existing Shapefile, which I want to add. At the moment my code looks like: self.iface.addVectorLayer(self.shpFilePath, "Track", "ogr") It works fine, but i want to define the crs ...
3
votes
1answer
201 views

How to clip a single layer of overlapping polygons in QGIS

I have a single layer of polygons. Some of the polygons overlap. I wish to make a new layer of just the parts of the polygons that overlap. What is the best way to do this in QGIS seeing it's ...
3
votes
1answer
1k views

How to install LAS tools in Processing for QGIS 2.4?

Does anyone know were the processing menu moved in QGIS 2.4? Specifically I am trying to install the Lastools box for QGIS following these instructions. ...
3
votes
3answers
225 views

How to apply a specific Rendering to a Raster and export to JPEG?

We have a specific process which generate an interpolated single band 32-bit Float Raster in Erdas Imagine (.IMG) format. This process generates an image every hour. We wish to apply a specific ...
3
votes
2answers
974 views

Is it possible to give 2d contours a Z-height from their attribute table in QGIS? (Or ArcGIS?)

I have a contour data file downloaded from UK Ordnance Survey, which gives 2d contours of an area in gml format (also supplied in .shp format) with the heights of each contour attached to the ...
3
votes
1answer
268 views

QGIS: Colour GPS track by speed

sorry íf I might ask this question the 101 time, but I didn't found anything with google or SE. I have a CSV file with WGS84 trackpoints and visualizing them with QGIS textplugin works fine. The log ...
3
votes
0answers
270 views

PyQGIS joining a dbf to a shapefile [duplicate]

I am trying to join a shp and dbf file using the PyQGIS API. The code I'll use is below: from PyQt4.QtCore import * vector1 = QgsVectorLayer("path to dbf file", "test1", "ogr") id1 = vector1.id() ...
3
votes
2answers
3k views

How to draw bar diagrams on the map?

I need to draw simple histograms in QGIS version 1.8 linked to data from an imported DB. I need a double bar diagrams (eg: male/female - in/out) but I only find the possibility to set pie charts. Is ...
3
votes
2answers
481 views

How can I turn islands into individual features in QGIS?

I have what seems like a pretty straightforward task in QGIS: I have a shapefile that, in some cases, groups multiple separate landmasses into a single feature. For example, the Hawaiian islands are ...