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

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QGIS 2: How to create a regular vector grid at fine scale and for large area? [closed]

In QGIS, we wish to create a regular vector grid with 25*25m resolution and over an area of around 12000 km2. We tried to use: -vector>research tools> vector grid - and v.mkgrid function from GRASS ...
4
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1answer
3k views

Convert 32 bit image to 8 bit image in QGIS

I want to convert my images from 32 bits to 8 bits. I'm using otb to calculate texture and the raster output is on 8 bits, I'm going to use this information as a layer stack for my multispectral image ...
4
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2answers
896 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
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1answer
4k 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 ...
4
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2answers
347 views

How to write an equivalent to MapBasic's CreateLine in pyQGIS?

I know this kind of question has been asked, in part, before - specifically: Seeing QGIS Python Commands and: How is object created as line using createline stored in .tab file? but this is a specific ...
4
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1answer
633 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
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1answer
4k 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
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2answers
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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
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1answer
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QGIS: How to load feature (.qml) styles from python? [duplicate]

Possible Duplicate: How to style a layer from console? I'm trying to set the styles for a vector layer by loading the .qml file in the python console. The qml-style file contains all ...
4
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2answers
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How to perform volume calculation in QGIS

EDIT 07/12/12 Ok, meanwhile I came to another problem I want to discuss. I just tried around with the volume calculation with some layers and came to a point where I receive the following error. ...
4
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2answers
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Problem loading vector layer (pyQGIS)

I've installed the qgis on ubuntu 12.04 following the instructions on http://hub.qgis.org/projects/quantum-gis/wiki/Download. I am trying to test the Python API and try to do the follwoing from ...
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4answers
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How can I import georeferenced photos (jpg, kml, kmz) using QGIS or ArcGIS for Desktop?

I've got several georeferenced digital photos as jpg, kml, and kmz. How can I import them into my GIS projects (QGIS or ArcGIS for Desktop) so I can open them as a popup?
4
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3answers
3k 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
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2answers
280 views

Least cost path between various points QGIS

Is there an easy way to find the least cost path (LCP) between various points in an open source GIS? This question has actually already been asked here: How to find a least cost path through several ...
3
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2answers
205 views

Limiting list values based on previous field in QGIS Forms?

Looking for assistance to set up appropriate configuration to enable drop-down lists values to be filtered based on a previous value. Basically, I have a 3-tiered categorisation structure to one of ...
3
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1answer
352 views

How to reproject all the vector files in a folder to a particular projection using ogr2ogr?

We have a folder with all sorts of vector files like tab,shp,dxf. Many of the files are in different projection. I would like to convert all the files to EPSG: 4326 and eventually the non-shapefiles ...
3
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2answers
2k views

Exporting GIS Images with Transparency

I'm trying to export some images of Gulf of Mexico infrastructure that will later be used for non-GIS purposes as overlays onto sea current/weather maps (likely in photoshop). I have no clue how to ...
3
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1answer
624 views

Programmatically Select a CRS in QGIS 2.4 using Python

When you run the following Python code in the Python Console of QGIS 2.4, uri = "file:///C:/data.csv?type=csv&xField=lng&yField=lat&spatialIndex=no&subsetIndex=no&watchFile=no" ...
3
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6answers
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How to clean/edit GPX (tracks) files recorded from GPS device?

During a long trip, I have recorded tracks of my journey with the GPS of my smartphone. I have ended up with about 30 GPX datafiles. Now that I am back, I am trying to draw a map of this trip. I ...
3
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2answers
3k views

Conditional Statements in QGIS raster calculator?

What is the equivalent statement of the following expression in the QGIS raster calculator? Con(((Abs("DEM" - "FSMin") > 120) | (Abs("DEM" - "FSMax") > 120)), 1, 0) I have no problem ...
3
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3answers
322 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
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3answers
2k views

How to extract X Y coordinates and RGB from pixels using python in QGIS?

I'm trying to white a Python plugin in QGIS (2.2) to get, for each pixel of a raster image, its X Y coordinates, as well as, its RGB (3 bands) values. At first I opened the raster file using: rlayer ...
3
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3answers
1k views

Convert 800 .hdf4 files to Tiff using GRASS/QGIS/SAGA/GDAL/R

I've have MODIS ndvi data (MODIS_Grid_16 days NDVI) from the iberian peninsula, from February of 2000 to August of 2012 (really big data). How do I batch convert about 800 .hdf MODIS files to .tif ? ...
3
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1answer
728 views

Got Null values when updating attributes with PyQgis

I'm trying to create and update a field and ,for now, just change it's value to 2. Here is my code: layer = qgis.utils.iface.activeLayer() index = layer.fieldNameIndex("P") # if index == -1: # ...
3
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3answers
878 views

Draw line between points from multiple datasets

I have 2 point datasets and want a tool or script to draw a line between all points in one dataset to all the points in the 2nd dataset. Is it possible? I have tried ESRI "Point Distance" and ...
3
votes
1answer
427 views

How do I access QGIS program settings programmatically?

I am trying to temporarily enable the option in QGIS using PyQt4 to suppress the attribute dialog popup after a feature is added. I found an example in the cookbook but it doesn't indicate how to get ...
3
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2answers
4k views

How to use the replace string function in Field Calculator?

Within an attribute table I'm trying to replace one string with another using the 'replace' function . As an example, there are a number of features whose field 'NAME' contain the string '(B)' and ...
3
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0answers
255 views

Accessing existing instance of qgis from stand-alone python script

For my own data analysis pipeline, I am running a split screen setup with iPython notebooks on one side, generating variables from source data, pushing them to a csv file which qgis then reads/joins ...
3
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2answers
2k 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
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1answer
363 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
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0answers
275 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
5k 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
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2answers
732 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 ...
3
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3answers
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How to convert x y coordinates to longitude latitude using QuantumGIS?

I'm working with this downloadable shapefile that has X Y coordinates. They are akin to '3672187.92698000, 534175.72095400'. I would like to convert them to longitude latitude so they are more like ...
3
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5answers
2k views

Batch processing DEM rasters in QGIS/GDAL

I am attempting to add relief shading to map using .asc raster files, following this tutorial. It works well, but I have only tried it on single tile of raster data which is 20x20km. I want to ...
3
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2answers
562 views

Which labelling tool/engine in QGIS will be supported in the long term?

Why does QGIS appear to have two labelling tools? (Note this is not new and old symbology, but that...) there are two different GUIs, one in the toolbar (which gives the Data Defined Settings option) ...
2
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2answers
281 views

Project file read error: Unexpected end of file at line 9957 column 1

On reading the answers from a similar question earlier i still cannot retrieve my project. I last used this project in June and obviously something went wrong when saving or creating the new layer ...
2
votes
1answer
360 views

Grass 7 no longer works via the Processing Toolbox on Ubuntu

When I try to execute a Grass 7 algorithm via the Processing Toolbox in QGIS 2.10, 2.8.2 or 2.8.1, I get the following error: Missing dependency. This algorithm cannot be run :-( QGIS ...
2
votes
1answer
99 views

How to define map extents based on a feature's geometry?

There is a polygon geometry in my QGIS project which represents the extents of my map. Does anybody know how to use the data defined override to get the X/Y min and X/Y max coordinates of the polygon ...
2
votes
1answer
326 views

How to define an event for features selected in mapcanvas in qgis using python

I have created a push button, when it is clicked it calls the function 'selectfeatures'. This function will call the Select feature by free hand tool of QGIS and allows the user to select features in ...
2
votes
2answers
576 views

Do I need to remove older versions of QGIS?

I have installed up to 2.6.1 of QGIS on my computer. Is it recommended that i remove all older versions? Will it cause conflict if they remain?
2
votes
1answer
503 views

How to apply a filter to multiple vector layers in QGIS?

I am trying to apply an attribute filter to multiple layers in QGIS at once. The filter is to be applied to .osm data brought in through PostGIS to QGIS. I have tried selecting multiple layers -> ...
2
votes
1answer
954 views

Finding the common borders between polygons in the same shapefile

The question is essentially the same as here, except that I want to do it in qgis. Thus, is there a qgis function equivalent to the ArcMap intersect function that will take a polygon layer and output ...
2
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2answers
1k views

Does QGIS attribute edit form support “relationship” data?

Consider I have a geometry table having one-to-many relationship with a no-geometry table. When I create a feature (geometry), I would like to be able to add the relative no-geometry table data in the ...
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4answers
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How to create random point in according polygon for each dataset entry in a list (with R)

I have an area divided into polygons, and a dataset of observations which has a common field with the polygon layer. I now would like to generate a random point for each dataset entry within the ...
2
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1answer
326 views

Split polygon into lines

I have a polygon layer which looks like this . I used the QGIS multiparts to singleparts tool and also polygon to lines. In both cases i got this type of result . I want to extract polygon into ...
2
votes
1answer
2k views

Label callouts in QGIS

Has anyone been using callout labelling with QGIS, either trunk or stable? Used for clustered points. That means the point stays where it is, the label maybe moved if required and a leader (plain or ...
2
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1answer
2k views

How can I create a line with three points with Python in QGIS?

I'm new to Python and I'm having some dificulties. I want to create a simple layer with a line in the console of QGIS with Python. How can I do that?
2
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1answer
1k views

encoding problem with QGIS 1.8 and CSV import

I have following problem with QGIS 1.8. Lisboa (standalone installer, Win 7 Pro 64bit) - I import CSV - text in CP1250 separated with ";" and using "," as decimal separator. I correctly set the ...
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2answers
251 views

Open mail client when clicking feature in Attribute Table

One of the attributes/features of my layer contains an email address. I'd like to be able to open the default mail client by clicking on the mail address from the Attribute Table. After some initial ...