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

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2
votes
1answer
859 views

Calculate EVI From Landsat 8 in QGIS [closed]

I have calculated atmospherically corrected reflectance values for Landsat 8. From that, I am getting correct values of NDVI in QGIS, but for EVI I am not getting the correct values. For some images ...
2
votes
0answers
67 views

Align & Sum Grids in Python

I have two grids. One, call it A, is 4320x2160 cells and spans the whole globe. The other, call it B is 8640x3432 and spans the circumference of the globe, but is clipped toward mid-latitudes. Both ...
1
vote
2answers
462 views

QGIS Convert Polygon M to polygon

I have been using Argis 10.1 and been able to convert polygon m to polygon shapefiles. I would like to do this with QGIS but I am having difficulty in finding the correct tool to do so. Please Help
2
votes
0answers
828 views

I cannot install QGIS 2.4 on my Windows 7, 64 bit machine [closed]

I am running Windows 7, 64 bit and cannot install QGIS 2.4 after several days of trying. I have also tried downloading 2.2 with no avail. I keep getting this error: The text of the error is: ...
1
vote
0answers
80 views

QGIS crashes when trying to display features form MySQL

I import shapefiles into MySQL using the following command: ogr2ogr -f MySQL MySQL:GIS,host=localhost,user=root,password=root /home/user/Public/myshape.shp -nln Shape_table -update -overwrite -lco ...
3
votes
3answers
273 views

How to display a table with more than one geometry column in QGIS?

In PostGIS, it is possible to use addgeometrycolumn more than once on the same table. Example: I have one table "scenes" with many attributes, and 2 geometry columns: the_geom1 and the_geom2. select ...
1
vote
0answers
228 views

QGIS Relation Manager

I have a PostgreSQL database with a one-to-many relationship. Here is a reduced example: CREATE TABLE buildings.building ( objectid serial NOT NULL, building_no character varying(40) NOT NULL, ...
1
vote
2answers
928 views

QGis 2.4 - Python 2.7 PyQT4.Qtcore.QStringList Import failed

I receive an import error when trying to import QStringList from the Qgis Python console (or when loading a custom plugin). from PyQt4.QtCore import QStringList Traceback (most recent call last): ...
2
votes
1answer
125 views

How to set QGIS options in standalone pyqgis application

I have a standalone application which uses the QGS api to view and query map layers. One layer is a WMS-C layer which automatically caches tiles which is great. I want to also activate a setting which ...
3
votes
0answers
99 views

access point layer representation in qgis with pyqgis

I am exporting the style of a categorized point layer with qgis: unfortunately my code only extract the size of the symbol in the definition of the properties of the layer but not the ...
7
votes
3answers
6k views

How to export polygon coordinates to CSV (not WKT)?

I am new to QGIS, and I am now trying to export polygon coordinates from a shape file to a csv file, but so far all my attempts have failed. I have found numerous questions and answers about this, but ...
3
votes
0answers
526 views

How to export data from sql server into shapefile in the decimal format in QGIS 2.4?

The last couple of days, I have been working on exporting data from SQL to a shapefile in QGIS 2.4. While converting into a shapefile, the data type changes automatically from Float to Integer in the ...
3
votes
1answer
713 views

How can units be defined in QGIS for the Rasterize tool?

I am using QGIS 2.4 (Chugiak) via the kyngchaos build for OS-X. My question is--when using the Rasterize tool to convert a point vector layer to a raster and using the "Raster resolution in map units ...
3
votes
1answer
246 views

How to add dashed line in QGIS print composer

I want to display two maps in the print composer: a main one, and another showing a zoomed in section of the main map. I've drawn a rectangle over the original region and want to add two dashed lines ...
3
votes
1answer
179 views

How to find and replace a singe word in a string?

How do i find and replace a single word of a string? e.g. Calle Iparraguirre to Iparraguirre I've tried: replace( 'Calle\\s', 'Calle\\s', '') replace( "name",'calle','') and all combinations ...
1
vote
1answer
194 views

Coordinate System changes after reprojection

I have changed the projections of some Natural Earth Shapefile to "WGS 84/Pseduo Mercator", that works fine (after cutting out the artic), but now the co ordinates of the shapefile are all out of wack....
1
vote
0answers
85 views

How to set a defined distance between nodes to digitize in qgis?

Using QGIS (by now I have the 2.4 version) I would like to set some parameter (I don't know if such exists) that would impose a definite or maximal distance between nodes when digitizing a polyline or ...
1
vote
1answer
319 views

PyQgis Message Bar Woes [closed]

Having a bit of trouble with the basics of getting the (awesomely discreet) new user prompt/warning to properly display. Here is the (troubled) code I am using: self.iface ... iface.messageBar()....
2
votes
1answer
856 views

“Data source not valid” problems with QGIS processing

I'm having a lot of problems with QGIS processor. Most of the algorithms show me this QGIS log error: La fuente de datos no es válida. (Data source not valid) This happens with SAGA and GRASS ...
1
vote
1answer
649 views

PyQGis - Working with Spatialite

I wrote a Vector layer to a spatialite file/db using the dedicated API tool, using valid driver names supported formats by OGR. When connecting to that db, I can't retrieve properly the geometry ...
2
votes
0answers
40 views

Is it possible to drag&drop line precisely 6 meters to right or left?

I use Quantum GIS 2.2.0 Valmiera I have a polyline layer. I can drag&drop polyline nodes by using "Node Tool". Is it possible to drag&drop line precisely 6 meters to right or left?
2
votes
1answer
113 views

A way to transform by special epsg-code

In my country, we have a special epsg-code for transformation (#4649). In the definition (http://www.epsg-registry.org/report.htm?type=selection&entity=urn:ogc:def:coordinateOperation:EPSG::4649&...
1
vote
1answer
154 views

Shapefile not projecting correctly [duplicate]

I am still new to this, so I apologise if I don't make a lot of sense! I am using QGIS 2.4.0 Chugiak. I am working on a project set to the GDA94/MGA Zone 50 coordinate system with 'on the fly ...
3
votes
1answer
392 views

Where can I find information about the development history of QGIS?

I know very little about early versions of QGIS (far far away from now..) and i'm feeling curious :-) I am looking for various information about the past of QGIS, including: Do you know in what ...
1
vote
0answers
316 views

Way to split and create buffer space between polygons in QGIS or ArcMap

After performing a feature extraction of rooftops, some of my buildings have been joined together as one polygon. I want to split these large polygons so that each new division is only covering one ...
2
votes
0answers
46 views

Looking for a QGIS solution to make aerial imagery ArcSDE compatiable [closed]

Would like to avoid having to use 3d Analyst and use free raster tools in QGIS or elsewhere to make aerial rasters ArcSDE compatible. This 18 page work flow is what I am trying to use. Any suggestions ...
1
vote
0answers
56 views

Vector Layer Symbol (ism) properties?

I would like to streamline the render of a polygon grid vector layer as a simple line (no fill) via Python coding. I am I bit confused by the implementation referenced by the API. Is it possible to ...
1
vote
1answer
93 views

How to test for multiple map items in Composer using python?

I am building a QGIS plugin and I need to check for multiple maps items in Composer that works on all platforms. Currently I am getting the first map in the composition using the code below, but ...
3
votes
1answer
576 views

Benchmarking QGIS and ArcGIS for Desktop speed for “significant buffer on very large shapefiles”?

I am a newcomer to the world of GIS. I realized that QGIS was relatively similar to ArcGIS for Desktop. I would like to know if the two programs are comparable in terms of computational speed. For ...
5
votes
1answer
226 views

QGIS 2.2 - possible to do a JOINS from the Action list?

I have a set of layers that need to be joined (Layer Properties > Joins) to one specific layer. The reason for this is that I will be updating and adding new layers into my project and would like a ...
4
votes
2answers
245 views

Is it possible to decrease detail level (decrease file size) in Spatialite OSM export?

I currently use Spatialite exports from OSM data (together with Google maps like styles by Underdark) which are very useful for me as the files are easily portable with the project and I do not need ...
3
votes
2answers
2k views

How to set the Identify Feature tool in QGIS 2.4?

The Identify Results window does not appear when using the identify feature tool in QGIS 2.4. I guess there's a check box somewhere I need to check/uncheck, but the settings of the tool changed ...
1
vote
0answers
283 views

How to export data from sql database in the decimal format in QGIS?

Currently I am working with QGIS and fetching data from SQL server and export it in the format of shapefile in QGIS. While importing the data from sql server attribute table showing data with ...
1
vote
0answers
87 views

Compiling QGIS for Slackware (Slak 14)?

I use a Slak 14 box and tried to install QGIS on it. the compile process goes on for 30 minutes or so (dual Xeon 3.2 ghz) and then I get the errors below. Says the compiler doesn't work. Have had no ...
2
votes
1answer
419 views

How to make crs transformation of a QgsVectorLayer?

I need to transform QgsVectorLayers in python from one crs into another crs. By googling I found the following solution (https://qgis.readthedocs.org/en/latest/docs/pyqgis_developer_cookbook/05_crs....
5
votes
3answers
267 views

How to count polygons in multipart features?

I'm trying to count the number of polygons in a multipart feature. My aim is to have a 'count' attribute to quantify fragmentation of multipart land parcels. I've looked at the field calculator and ...
1
vote
1answer
99 views

How to automatically connect point [closed]

I have to draw all the rows connecting the 2 edges with a line. It's not so hard to it manually, but it takes a lot of time. Is there a way to connect the two edges of the rows automatically? For ...
3
votes
1answer
77 views

Why is the SelectionChanged signal triggered every time i click on the layer?

i'm making some experiments with the SelectionChanged signal of a QgsVectorLayer. i try this piece of code : curLayer.selectionChanged.connect(self.test) and "test" print a warning message. The ...
1
vote
0answers
106 views

How to programmatically interrupt QGIS initialization and startup

I'm wondering how to interrupt the initialization of QGIS 2.0 on Windows XP before start up. I've put a dialog in one of my plugins that shows up on start up. However, I'd like to make a quit button ...
2
votes
0answers
224 views

Saving/Loading QGIS style .qml and avoid specified symbology

Is it possible to save QGIS styles without the symbology style? This may seem like a strange question, but I am trying to automatically set the ValueMap widget under layer properties via a plugin for ...
1
vote
2answers
82 views

How to calculate regrowth area?

Thanks to Best Landsat-5 TM band combination for detecting fire scars I am able to calculate burnt area in an absolute way (Normalized Burn Ratio). Does a ratio or delta operation exist to calculate ...
2
votes
0answers
193 views

How to compute the ls factor equation for USLE model in qgis grass r.mapcalc

To compute the LS factor for the USLE model, the following equation easily works in ArcGIS. How can I perform the same in QGIS under GRASS r.mapcalc? LSfator = Power (("flowaccNW") * resolution/22.1,...
2
votes
1answer
295 views

Add XY Column in QGIS [duplicate]

Following on from a previous question of mine, where I was given coords in degree-mins, I have successfully converted them to decimal degrees, thanks for the help. I have created a CSV file from ...
1
vote
1answer
293 views

Does the experimental QGIS2leaf plugin not work on mac OS?

I am trying to get the experimental QGIS2leaf (Leaflet web maps) plugin to work on my macbook air (2012, Mavericks OS), but when I open the outputted index.html file, no interactive image shows up in ...
3
votes
2answers
1k views

How to delete column/field in PyQGIS?

How to remove or delete column fields in a shape file using python?
4
votes
1answer
220 views

Pulling CSV file directly from website into QGIS?

I want to be able to automatically update my csv files in a QGIS project. My organization has an online database that can easily export csv files. These csv files are constantly updated with new ...
0
votes
1answer
303 views

How to perform an attribute-weighted sum of multiple polyline features from a single vector layer?

I have a shapefile of ~8000 polyline vector features representing traffic journeys on road routes. Each has an attribute representing volume of traffic for that journey. The routes are all generated ...
2
votes
1answer
188 views

QGIS Filters and Queries

In QGIS is there a way to filter a layer using the Query Builder to show all values which include a particular phrase. For example I have a list of organisations and I want to filter all those which ...
2
votes
0answers
74 views

Lat Long to Useable values in QGIS

I am using both QGIS 1.8 and 2.0. So either is helpful. A client has given me locations of trial pits but i cannot load them into QGIS no matter how hard i try. For example, 50°24.711 North 7°25....
1
vote
1answer
257 views

Apply new style to selected features in QGis

Let's assume that I have selected some features in QGis. Now all the features in that vector layer already has some style applied to it. Now, I want to apply some new style to the selected features. ...