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

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3
votes
2answers
92 views

Method for automatic aggregation of polys with sparse data

I am part of a project on presenting health related data on maps. In order to maximize the analytical usefulness of the data, we wish to divide them into as small areas as possible. However, to ...
1
vote
3answers
958 views

Calculating slope in percentage

I'm working with qgis, v. 2.0.1. I have several soil types. They are (amongst others) described with slope indications. I already calculated the slope from the dtm in degrees, but as de description of ...
2
votes
1answer
120 views

How to add an interpolation raster from the python console in QGIS?

I'm trying to add an interpolation layer based on an existing vector layer by using the Python Console (initially in the menu Raster/Interpolation), but can't find anything related in the ...
0
votes
1answer
147 views

How to open QGIS using VBA?

Using VBA, I want to open QGIS (the actual GUI) and execute a simple script through the Python console or the editor.
0
votes
2answers
345 views

How to add polygon height in QGIS or PostGIS?

Is there an easy way to set the height of polygons in QGIS or PostGIS? I am trying to visualize polygons by turning them into volumes (same shape at the base and roof, but with walls). I would then ...
1
vote
2answers
161 views

How to split a (road) buffer using the centerline?

I have a road centreline dataset which I have buffered using the road width. I used the standard QGIS buffer tool. I realise for my analysis I actually need to split the road buffer in half and ...
2
votes
1answer
240 views

How to undo misclicks while drawing a polygon?

I'm trying to draw some polygons in QGIS 2.2 and I lose it, because everytime I misclick, I don't find a way to undo that point and start drawing again. I'm sure there's a way. Does anyone know it?
1
vote
3answers
40 views

Adding combined footage to points from the beginning of a line

I'm trying to add the footage of each point from the beginning of the line to the end. There are around 4k vertexes between the two ends that I need to put the footage from the beginning of the line ...
1
vote
1answer
239 views

Reprojecting a raster DEM from meters to feet using QGIS?

Is there a tool in QGIS that does the same as reprojecting a raster DEM from meters to feet as in ArcGIS's 3D Analyst > Raster Math > Times ?
0
votes
2answers
203 views

How to make a routable graph from a Point and a Line shapefile, using Networkx?

I have one shapefile which consists of all the streets in the study area, and another shapefile which has points representing origins and destinations. I would like to know if it's possible to find ...
1
vote
0answers
14 views

QGIS DBmanager import file append not working [duplicate]

I am using QGIS and connecting to Postgresql database. I want to import shapefile data into database table via DBmanager tool. But Append data to table selection is inactive like following image. I ...
2
votes
1answer
58 views

Is there a way to clip a polygon layer according to DEM elevation?

I have a polygon layer on top of a DEM. Is there a way to clip the polygon layer according to elevation, ie the clipped result being only those areas of the polygon layer between x and y altitude? ...
0
votes
1answer
36 views

QGIS GRASS plugin: r.composite quality loss

When using the r.composite tool within the GRASS plugin in QGIS, the result raster has a cell size of 150x150 while the input rasters have a cellsize of 30x30. Can this be overcome somehow or is this ...
0
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0answers
43 views

QGIS Fill Ring tool problem

Using the new (in 2.2) 'Fill Ring' tool and it doesn't seem to work correctly in all cases. It seems that if I try and digitise the new ring close to the polygon boundary, TWO (or more) geometries ...
-1
votes
0answers
31 views

what is the math behind rasterization? Doubt [duplicate]

In Figure 4 you can see how the overlap is not complete (marked with circles). What I would like to know which algorithm that QGIS uses the rasterization? What is your standard? Is there a percentage ...
0
votes
0answers
27 views

Point Sampling Tool does not preserve set layer order in a qgs project

My qgs project contains multiple raster layers in a certain order. It also has a point vector layer at the top position. I used the Plugins -> Analyses -> Point Sampling Tool to extract the raster ...
0
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0answers
54 views

change raster values in a specific region on a single band

I am currently using ERDAS IMAGINE 2013. I have a 28 Band MODIS image. In one of the bands, I need to change the values of a certain region. I tried the following: Load the .img file into IMAGINE. ...
2
votes
1answer
285 views

How to make a Python script that does a task in QGIS?

When I run this code in QGIS Python console it works fine, but I want want to run it from an external Python script. What I want the script to do is: 1- Open QGIS 2- Run this code 3- Close QGIS from ...
0
votes
1answer
87 views

qgis's georeferencer renders my white map with a translucent blue tint, can I prevent this?

I'm running QGIS 2.0.1-Dufour on MacOSX and when loading a PNG or TIFF into qgis as a raster its always getting rendered with a blue tint. Here's what it looks like before being loaded into QGis's ...
2
votes
0answers
129 views

PyQGIS: Programmatically Adding Point Features via QgsMapToolEmitPoint

I've created a map tool for QGIS 2.0 Python plugin that emits a point with the click of the mouse. I'm trying to create an edit tool, adding a point feature at the emitted point while selecting ...
3
votes
2answers
432 views

How to automatically draw lines with a given angle from one single point in qgis 1.8?

I'm new to qgis so please be patient. I need to draw a bundle of lines all originating from the same point and with a 10° angle between each line (e.g. lines bearing at 0,10,20 ..90..110..220..350). I ...
1
vote
2answers
41 views

error using the QGIS “terrain profile” plug in

I have searched the home page for the "terrain profile" tool but have not found why I am getting error when trying to utilize it. Any ideas? I have a polyline and 4 dems ready to run the tool. Would ...
1
vote
3answers
183 views

What is the math behind rasterization?

I'm taking the first steps in QGIS (version 2.2 Valmiera) and I am having some difficulties in knowing what mathematical criterion that QGIS uses when converting polygons (shapefile) to raster. I'm ...
0
votes
0answers
18 views

recover toolbar in visualizer qgis 1.8.0 lisboa

I accidentally removed the toolbar in the printer visualizer. Anyone knows how to recover it? I would expect a button of show toolbar or something, but I can not find it anywhere... Thanks!
2
votes
1answer
193 views

Label all features of shapefile with PyQGIS

I have a problem when trying to label all features of a shapefile with a Python routine. If I open my shapefile in QGIS "by hand", and select a .qml with pre-defined label selection, the labels are ...
0
votes
0answers
84 views

Digitizing with OpenLayers Plugin seems incorrect

I am attempting to digitize some buildings based on floor plans using QGIS. To do this, I have taken the blueprints, georeferenced them against openlayers bing aerial plugin. I then digitized the ...
1
vote
1answer
371 views

Is there a SWAT model integration for QGIS?

I am trying to use SWAT (Soil and Water Assessment Tool) for watershed management activities. It is a set of commandline tools and needs a complex set of input data some of which can be generated from ...
0
votes
1answer
47 views

QGIS Python - Executing functions for multiple directories

I would like the user to select 2 directories, each directory having their own defined algorithms. For example: First_Directory will add a column to all shapefiles in the chosen directory; ...
5
votes
2answers
349 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 ...
1
vote
1answer
130 views

What does “PostgreSQL layer has no primary key.” when loading layer from database manager mean?

I have a complex join that I have working in the database manager but when I try and load it nothing appears and I found this in the logs: PostgreSQL layer has no primary key. What is actually ...
2
votes
1answer
173 views

Route to cover entire network

I have a road network where I have to cover every road for visual inspection. I need to design a route map for this task. What tools are available to a QGIS user? How would you describe the workflow ...
0
votes
0answers
126 views

I am getting NULL values when I use “point sampling tool”?

I am trying to extract values from a raster using a point shapefile, but I am getting NULL values. I think that NULL values are obtained because the Coordinate Reference System (CRS) are not the same ...
0
votes
0answers
78 views

qgis web client installation

I recently joined github and I found this very interesting application. I was trying to test it and install the qgis/qgis-web-client application. I got the following error by following the ...
1
vote
1answer
162 views

Get Coordinates of Voronoi Polygon Vertices [duplicate]

Is there any chance to get the exact coordinatas of the voronoi polygons? I am using Qgis software and I have the "center" (redpoint) of the polygons and I would like to export the polygons corners ...
0
votes
0answers
34 views

QGIS Distance Matrix on large tables

I have a table with around 1 million addresses.I am trying to run a 'Nearest Address' on all of them and I understand QGIS has this capability. Yet I am wondering about the most efficient way to run ...
0
votes
0answers
86 views

QGISCloud in mobile QGIS

I’m new with QGIS mobile, I can’t open shapefile on QGISCloud using samsung note 8. Does anyone know how to do that? I haven’t found qgis plugin for mobile yet. Thank you
1
vote
1answer
204 views

Problem with CadTools plugin in QGIS 2.2

I've just downloaded the CadTools plugin from QGIS Plugins page (can't do this through QGIS itself as I'm behind a proxy) and after installation I keep getting an error saying that it "Couldn't load ...
0
votes
1answer
34 views

How to adjust spacing and alignment between legend symbol and text in Qgis

I'm getting some weird and seemingly random spaces between the symbol and text labels in the legend for the Qgis print composer. How can I set the symbols and text to align left/right or divide the ...
0
votes
0answers
88 views

Translate data from MapServer to Qgis server

Might you help me in this question: I've got operational Mapserver with shape- and map-files on it (*.shp *.map). How can I show them on Qgis server using Qgis web-client or Lizmap? This is my ...
2
votes
1answer
204 views

qgis-2.2.0 database tab missing

I have recently installed QGIS-2.2.0 but the Database tab in the top-menu bar is missing. It looks the main reason is missing libgdal1h library. But when I am installing it, it's removing ...
2
votes
1answer
193 views

Why does the file size increase after I clipped the polygons to be smaller?

I have a polygon layer that shows properties along a road. I want to create a kml-file of the polygons, and to downsize the file, I tried clipping the properties with a buffer. But, the filesize of ...
3
votes
1answer
47 views

Why are Google Mercator and UTM rotated towards each other?

Being a self-taught GIS user, I struggled a while before getting the grips on map projections. But now this: because I like to use OpenStreetMap as a background layer for orientation, I have saved my ...
0
votes
2answers
115 views

How do I mask a raster in TileMill?

I've tried just about every single TileMill compositing operation on the vector and raster layers in question, and I have to admit that I can't figure it out: How the heck can I mask a raster with a ...
0
votes
1answer
78 views

How to integrate pascal code into a QGIS model or plugin?

I have a console program that is written in pascal (lazarus) that reads in some raster files and parameter values as input. The code use dynamic 2D arrays to represent the rasters. I would like to ...
1
vote
2answers
183 views

TatukGIS SQLite Spatial vs. Spatialite

I must apologize in advance, I'm just getting into GIS and trying to figure things out. I have an SQLite spatial database that I'm pretty sure was created in TatukGIS. I've tried to open it in QGIS ...
1
vote
1answer
151 views

Is there a way to access the GeoProcessing tools in QGIS, in code

Is there a way to access the GeoProcessing tools in QGIS, in code? I want to find the Difference between two layers and make a new shapefile with the result.It can be manually done by selecting ...
0
votes
2answers
111 views

How to join data in postgis tables to form layer with subset of attributes

In QGIS I am trying to join data from two postgis tables. I can not figure out how to do this at sql because add layer tools seem to allow one to select just one table to filter on. Instead I ...
1
vote
1answer
121 views

label vector line with multiple attributes in QGIS

I have a line with two 2 attributes. I would like to display both information along with the line in frequent interval, one info above the line and the other is below the line. I am working in QGIS ...
0
votes
0answers
30 views

Semi-Automated Classification Plugin ROI Creation Failure

I can't get the Region-growing to work when running the ROI creation module. What am I missing? Please see the "AttributeError" line halfway down: # An error has occured while executing Python ...
2
votes
3answers
381 views

convert a shapefile into graph with nodes and edges

Is there a way to convert a shapefile into graph with nodes and edges(except networkx). I'm using qgis and I want to convert a road vector layer into a graph, so that I can use it to apply shortest ...