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

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41 views

Can QGIS handle EMPTY geometries?

I am writing a plugin and have a postgis table which has EMPTY geometries in the geom column. MULTILINESTRING EMPTY I am having crashes which just close QGIS. I have narrowed it down to the EMPTY ...
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0answers
13 views

Problem with VectorLayer created in memory

I am working in c++/QT whithnthe qgis API c++ I had to build a personnalized vectorlayout called "TRACKS" , so i write a function that create in memory the vectorlayer like this : QgsVectorLayer ...
3
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1answer
77 views

What tools do you recommend to draw historical shipping routes?

I´m working on a project where I have to draw historical shipping routes of trade, whaling, etc. ships from the XIX century. I´ve done some research and checked some questions in this forum but I ...
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0answers
30 views

How can i create a table in pgAdmin using python?

i am using below SQl query in python cur.execute('''CREATE TABLE Ambhara_Survey (id SERIAL PRIMARY KEY, geom geometry, chalta_no TEXT, ror_area TEXT, ...
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1answer
33 views

Event programming in QGIS

I have identified a need to change VRTs raster order through its order of appearance in it's respective XML file. Unfortunately this seems to not be possible to do dynamically using QGIS commands or ...
1
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0answers
16 views

Scrolling features in QGIS following field?

I have a lot of features with labels associated. Because some of this features are wrong placed, I have to scroll them all. Usually I work with the attribute table open and select every single feature ...
3
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1answer
112 views

Gradient colour for lines

My road network is broken up into segments. I want to produce a map that shows where the segments start and finish. I don't really want to create a point layer that shows the location of the ends ...
1
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0answers
23 views

QGIS split line into segments on polygon

Is it possible in QGIS to split a line into segments given which polygon it falls within? I am using 2.8. For example, a line that passes through three polygons will become three separate lines. Each ...
1
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0answers
11 views

How to dynamically change the draw-order of geotiff rasters in QGIS?

In ArcGIS it is possible, via raster mosaics, to choose the raster order depending on various methods. One such method is the center method. The raster that is closest to the coordinate of the center ...
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0answers
12 views

How to join points into overlapping polygons layer?

I'm using QGIS and I am relatively new to it. I have a points layer. Each point is the location of a conflict event and the attributes are the type of conflict, year of the event, number of deaths ...
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0answers
31 views

Schematic Map in GIS Tools?

The Question: Is there way to leverage GIS tools to author/edit a schematic map where elements' geometries has canvas-based coordinates rather than real-world coordinates on Earth? Perhaps to ...
1
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1answer
29 views

Atlas with different projections in QGIS

I have created an atlas -- i.e. a map with a layer defining some regions of interest -- in QGIS. I can render maps of each region using the "atlas" feature of the print composer, but I want to show ...
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0answers
32 views

Make “qgis:delaunaytriangulation” and “qgis:dissolve” save their outputs on a specific predefined layer

I'm new to python and QGIS. I'm working on modifying a plugin which runs algorithms "qgis:delaunaytriangulation" and "qgis:dissolve" like so delone_triangles = ...
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0answers
22 views

Can unicode characters be generated from unicode literals in QGIS expressions?

I know that unicode characters can be copied and pasted into expressions in QGIS, but can they be generated from a unicode literal ie u'\u00C9' without using a custom Python function?
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3answers
53 views

Generate line from unordered set of points

What is the best method to take a set of points and generate a line? There are too many to simply guess a "connect-the-dots" situation & These points do not have an attributes in which they can ...
0
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0answers
13 views

List of default attribute of a feature?

I am working with c++/!qt with the c++ api qgis 2.8.2 for a stand alone project application I had to change and add attribute for feature Does anyone know where i can find the default attribute of a ...
2
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1answer
28 views

How to prepare and upload points/lines to GPS using QGIS 2.8

I would like to upload some points (e.g. locations of transmission towers) and lines (e.g. streams, roads) in .shp format to my Garmin Oregon 600, using QGIS 2.8.2. Could anyone provide with ...
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0answers
18 views

QGIS 2.8.3 + QGIS Server Legends line break

I have very long text for some of my legends so I'd like to add some line breaks. I've tried to add '\n', '\n\r', '\r', <br> strings with no success. I know there is an option in the composer ...
1
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1answer
34 views

QGIS script doesn't commit attribute changes

I have a script to generate random points within a polygon, and to give the points the attributes of their host polygon. It generates points, but for some reason it won't commit the changes to the ...
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0answers
299 views

Does QGIS 2.10 work with Windows 10?

Has anyone tried using QGIS with Windows 10 yet? Does it work?
1
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1answer
31 views

ST_MakeValid is not working?

I have a polyline spatialite database, tried to perform repair geometry in QGIS using python with the following code: from pyspatialite import dbapi2 as db conn = db.connect(r'D:\db.sqlite') cur = ...
3
votes
2answers
54 views

Is the PostGIS st_intersection function viable for very large data-sets?

I am running an area intersection query on two large multipolygon tables (a few million rows). SELECT r.geom FROM public.my_table r WHERE EXISTS ( SELECT gid FROM public.my_table_intersection ...
1
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0answers
11 views

clustering categorized data

I don't know so much GIS specific terminology, so I am sorry for using the wrong words. I'll try to make my point clear by first describing what I want to achieve and then what I tried. [goal] I am ...
0
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1answer
19 views

Add event listener on QGraphicsEllipseItem

I'm creating a QGis Plugin in python which has a QGraphicsView in which I draw and ellipse on which I want to detect if the user clicks. I know the ellipse inherits QGraphicsItem which has a ...
0
votes
1answer
36 views

Import shapfile to Postgis using Python and ogr?

Iam not able to import a shapfile to PostGIS using the same library(ogr). I am using below link but it give me error. Import shp to Postgis using Python and ogr Error : Traceback (most recent call ...
2
votes
1answer
57 views

pyQGIS changing Paletted Raster Layers to Grayscale

I've written a plugin which essentially imports a number of colour geoTifs (map tiles) which works correctly but it would be great to display these as Grayscale after loading in. The geoTifs load as ...
3
votes
2answers
70 views

What percentage of polygon x is in raster pixel y, efficiently

I feel this is a competition worthy problem, due to its size. I would like to weight a set of raster pixels to the attributes of a set of polygons. To do this I need to know the proportion of each ...
0
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0answers
15 views

Need help on how to move a symbol over a map

I'm working in c++/qt and the c++ api qgis 2.8.2 In my application i load a map with a s57 file, this part works perfectly, now i need to make some plot representing different object like boat, plane, ...
5
votes
2answers
128 views

QGIS expression builder include relation attributes

I have a set of symbols based on a table in postgis such as this id|type|action_1|action_2|geom In QGIS I have this table symbolised using a rule expression which works effectively. However this ...
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2answers
50 views

How to make QGIS label only the shapes that are showing up?

I have a layer where shapes are defined by rules (country) and secondly by categories (a type). I then select (check box) the country to show the shapes only for that country. This works very well, ...
1
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1answer
12 views

In QGIS, add to existing dem tiles and expand corresponding contour coverage within a project

In my first QGIS project I have dozens of digitized layers that have spread beyond the contour and dem tile area that I started with. Please recommend how to safely expand or replace the dem and ...
0
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0answers
11 views

is the “configuration dialog” = “Processing” > “Options”

Is the the "configuration dialog" referenced to in help "Processing" > "Options" Note: The 'help' I am referring to is the online Documentation QGIS 2.2 » QGIS User Guide » QGIS processing framework ...
1
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1answer
31 views

osgeo4w not installing processing tools in QGIS toobox. [duplicate]

I have uninstalled and reinstalled QGIS several times from the OSGeo4W application. I have done this with no problem on several other times, but now I cannot get the tools to load. Most of the help ...
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0answers
18 views

Defining and exporting a path from discrete points in QGIS

I'm working with elevation data (NED, SRTM, etc.) in QGIS and I'm wondering how I might be able to pick a set of points from my map and export the coordinates to something like CSV. For example, I'd ...
1
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2answers
46 views

How to prompt for layer selection from python console in QGIS?

During script development it's useful to use the QGIS python console to test the same script on different layers. Currently I've been hardcoding layer strings and just swapping out but it isn't ...
1
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1answer
21 views

QGIS Treat null as zero in raster calculator

In QGIS - I have an irregularly shaped raster - I wish to clip an irregular area out of it (call it raster A) with that area set to null. I masked the area (vector polygon) I want to remove and used ...
0
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0answers
5 views

SegFault on create an EmptyDataSource From a typedef

I had to create a specific type of point, in order to do that I create a function that create a layer from shp file and data extract of the Code : typedef bool ( *createEmptyDataSourceProc ) ...
2
votes
2answers
51 views

Install QGIS on ubuntu using the compressed format qgis-2.8.3.tar.bz2

I just cant use apt install becuase slower internet connection and size of QGIS can you show me how to do insall using qgis-2.8.3.tar.bz2 file. I have tried decompressing and use the command ...
1
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0answers
23 views

How to remove temporary layer source files in QGIS

I am new to QGIS and python. Titles says it all. I'm modifying a plugin that creates some temporary files (layers) during it's run and I need to loop it a couple times. The algorithm works fine for ...
2
votes
2answers
39 views

Avoid intersection is missing QGIS 2.10, 2.8.2

I need to digitize a lot of polygons and I want to ease my work with the 'avoid intersection' button so that the new polygons do not overlap. In the manual I found (for version 2.6) that the button is ...
2
votes
1answer
34 views

pass custom command line arguments?

Is there a way to start QGIS with custom command line arguments and to access those arguments at runtime in a plugin? Background: I'm trying to start QGIS using a third party application(click on a ...
0
votes
1answer
47 views

Is it possible to remove small transparent outline effects between polygons?

after using the vectorizing tool I get the following result (picture). Around the cells you can see a small "boundary". This thin line is transparent and annoying. Is it possible to remove these small ...
0
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0answers
41 views

Coordinate transformation fails in QGIS

I am new to qgis, so this maybe a simple problem, but I don't know how to handle it. I have two layers: One layer is based on WGS84, the other on Gauss-Krueger zone 3 (GK). How can I successful ...
1
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1answer
32 views

Explanations for attributes QGIS

I have one column in my attribute table with attributes "1", "2" or "3". 1 = normal route 2 = special route because of the event (every year) 3 = special route because of the event and construction ...
0
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0answers
11 views

Error using gdal IDW in processing script for postgis layer

I am running QGIS 2.10.1 and I am trying to use the processing toolbox to interpolate a point layer. If I use a shape file with all the default settings it works well but if I use a point layer coming ...
2
votes
2answers
43 views

QGIS legend without print composer

I'm trying to export a series of images using the TimeManager plugin. I'd like to have a legend on each, to demonstrate why my datapoints are sized the way that they are (i.e. this circle size ...
0
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0answers
22 views

new shape file addition problem

I am using QGIS 2.8.2 version, me unable to add new shape file layer. After drawing the line when I right click the mouse the line was disappearing (fig2). The new layer being shown in layer window ...
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votes
1answer
77 views

Why there is no EPSG code in ArcMap? [closed]

In Arcmap, when you right click on the layer >> go to properties >> select source tab there you see the properties of projection. I cannot understand why ESRI did not managed to add SRID EPSG in ...
-2
votes
0answers
29 views

How to calculate Areas of NDVI with Qgis? [duplicate]

How to calculate the area occupied by each pixel of a raster NDVI in QGIS? Excuse me, I do not speak English. Ya calcule el NDVI de una imagen Landsat con Qgis, como calcular el área ocupada por ...
1
vote
2answers
36 views

Query ShapeFile to get informations from coordinates

I have a shapefile that represents all the Hydrological Basins in the world. You can download the file from here: ...