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

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How to create dissolved buffers in QGIS with PostgreSQL/PostGIS?

Creating a dynamic buffer in QGIS I use the following query: CREATE VIEW buffer40units AS SELECT gid, st_buffer(geom,40)::geometry(polygon, 31492) AS geom FROM point; Now I want to dissolve ...
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1answer
26 views

Calculate area intersected areas, problem

(I'm working in QuantamGIS) I intersected two layers creating a new layer. Within the attibute table of this new intersect layer i would like to calculate the new areas. However, it just doesn't ...
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1answer
22 views

assigning random points to unique values

I have generated random points in qgis and would like to assign the value of their geometry to a unique column in another table. I would like to do this in qgis or postgres or spatialite. Table A ...
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12 views

QGIS: Action on group of features from layer

I need to implement a rename action on a selected group of features in a certain order. The idea is that I would rename one feature and then select the features that are 'next in line' and execute a ...
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16 views

How Does Ogr2Ogr Simplify Work?

Can someone explain how the ogr2ogr simplify works? I am trying to use raster data which has a spectral resolution of 30m. The vector file that I am trying to import into Google Fusion is large in ...
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10 views

Transform GeoTiff to WMT

I'm not a gis specialist at all so this question may seem dummy to you. I have a GeoTiff base of images (hundreds) I'd like to transform to a WMTS repository to put behind a web server. Web pages are ...
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2answers
3k views

How to delete overlapping polygon features from one of two layers?

I really need your help! I have two overlapping layers of polygons, and i need to somehow erase the areas the overlaps. -This way i should end up with two layers of non overlapping polygons. Sounds ...
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1answer
1k views

How to open File Geodatabase in QGIS (Ubuntu)?

So far I have found instructions on stack exchange but they are for windows. And so far the information I have found is for windows. I currently have Ubuntu 13.04 Raring tail. I am using qgis 1.8. I ...
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23 views

Strange circles have appeared on QGIS map?

Why are circles appearing on my map? It started after using QGIS dev build 2.9 and now appears even on 2.8.1. Also I've noticed that the usual list of CRS does not appear while using the dev build. ...
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16 views

Is there a way to export entire projects or groups to KMZ?

There is a lot of questions about exporting single files, Im trying to see if there is a way to export an entire group in QGIS to a .kmz file that can be opened in google earth. I know there is a way ...
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16 views

How to reset query format in QGIS?

I have a raster layer (wms) that I can query for some info (1). The query window offers different formats for this (2). However when I select "Object", the query result vanishes (3). I looked ...
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12 views

Display tabs don't appear when files and folders are selected in QGIS?

My setup: QGIS 2.8.1 Wien on OS X 10.10.2 I'm a complete beginner at GIS and I'm having trouble on getting the Param/Metadata/Preview/Attributes tabs to appear in the Display Window. When I select a ...
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1answer
131 views

How to recover deleted data from an edited point layer?

As a newbie in GIS, I didn't fail to make a newbie mistake. While editing a point layer I accidentaly deleted all the introduced data. I duplicated a layer, as it was more convenient (same style and ...
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12 views

ST_Buffer with segment AND endcap parameters

Making a QGis plugin that buffers a line and I want to declare a high number of segments and a flat endcap. ST_Buffer(geom, 40, 25, 'endcap=flat') This doesn't work with both parameters entered, ...
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10 views

QGIS topology overlap check

I have checked topology rule must not overlap with and i get error The problem is that i have check this many times, and made hole vertex after vertex so it is not possible that these objects ...
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1answer
41 views

Problem rasterizing

I am trying to rasterize a shapefile using the "rasterize" tool in qgis. The problem is that the resulting raster doesn't seem to rasterize correctly... The teal and purple lines show water flow, ...
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11 views

Clip layer with selected object from another layer in QGIS

In ArcMap i can clip layer with selected object from antoher layer using editor toolbar. I want to do the same operation in QGIS. I want to create holes in landuse layer by selecting object from ...
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1answer
16 views

Change name of category heading in legend

In QGIS 2.8.1, I have a SHP layer. In the display it is categorized by one of the fields, "Sannsynlig". In the table of layers and in the legend, it is also identified as "Sannsynlig", as the name ...
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16 views

Black map after attempt to style by column in QGIS

I'm very new to QGIS and I'd really appreciate some guidance. I have a shapefile of NYC census tracts and 2 csv info files with tract info joined with it. I'm trying to style the individual tracts to ...
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16 views

How to control QGIS from within Anaconda's Spyder (Continuum Analytics Python distribution) in Windows

I would like to control QGIS from within Anaconda's Spyder, in particular use the QGIS core modules. My config: Windows 7 Anaconda 64x for Python 2.7 Spyder 2.3 Postgresql 9.4 PostGIS 2.1 QGIS 2.8 ...
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1answer
70 views

What causes wrong placement of JPGs in QGIS 2.8.1?

I have the same issue explained in this post: How to keep georeferencing from ArcGIS when importing raster into QGIS? But my problem is with .jpg files. I have georeferenced with ArcGIS 10.2.2 many ...
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1answer
21 views

Is there a solution to glitches when deleting features from Shapefiles on network drives?

We are a small GIS department of 4 folks working with a shape file composed of points. We have local installs (C:) of QGIS 2.8.1 on our workstations, which run Windows 7 x64. The shape file in ...
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1answer
133 views

Python Error while installing Cartogram

I am quite new to GIS and qGIS especially. I would like to install cfarmers cartogram plugin. From what I understand, this has to be done manually - so I 've followed the instructions from ...
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1answer
11 views

Where can I find Open feature form under options menu?

Going through the tutorials in the documentation for QGIS and I am stuck looking for a check box in the Options menu. The check box is labeled "Open feature form" and seems to have been moved in QGIS ...
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1answer
26 views

How to sum up values within grid polygon in QGIS?

I have a grid full of hexagons that I am trying to bin points. However, instead of using the Vector > Analysis Tools > Points in Polygon which counts the number of point inside each hexagon, I'm ...
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1answer
145 views

How to map flood areas from a set of points containing surface and height of water?

I am working on the damages made by the typhoon Haiyan. I use QGIS 2.0 with extensions and toolbox, and MapInfo. I have vectors, rasters of the place. I want to map the flood area along the ...
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10 views

How do you snap polygons as you draw in QGIS? [duplicate]

I need to draw a long row of patient rooms for a hospital. I have the following plugins installed in QGIS 2.6: Rectangle Ovals Digitizing CAD Digitize I want to drag a set of polygons that aligns ...
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0answers
7 views

ECW support on ubuntu 14.04 - QGIS 2.8.1

I've followed instructions for lubuntu 14.04 - QGIS 2.2 ( Answer in Unable to install ECW support on lubuntu 14.04 ), adapting to QGIS 2.8.1. No problem to install packets, but result of gdalinfo ...
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6 views

Easy to Install QGIS Server Web Client for Windows

I am looking for an easy to install (.exe file for example) web client for QGIS Server. I found a hard to install software: QGIS Web Client in Windows does not load map But maybe in the last months ...
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2answers
24 views

QGIS modeler - how to extract polygons by multiple arguments?

I'm using QGIS modeler to extract lines by not one, but multiple attributes. For example, I have a road network, and I want to extract only road with character values in field TYPE: value_one and ...
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1answer
40 views

Why is the display of QgsMessageBar delayed?

When a function is called - a file is tested for existence. This checksum pushes a messageBar() object for both circumstances (True/False), yet the actual bar does not display in MapCanvas until ...
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16 views

QGIS 2.8.1 - SVG markers rendered bigger or smaller than described size in XML tags

I have a bunch of SVG road sign images to be mapped in QGIS 2.8.1. I resized them to an appropriate size using librsvg2-bin's rsvg-convert in Linux. All road signs are displayed in Map Units. ...
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1answer
35 views

Resolution problem in QGIS raster

I have a raster file I need to clip. I created a virtual raster which I used to "copy" the extent from in QGIS raster calculator. As a result, I get the raster with the extent I need, but pixel size ...
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1answer
31 views

How to read landsat images from Amazon S3 using python?

I would like to read and process landsat images from Amazon using pyton thanks,
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1answer
59 views

Why are all tiles white when using the OpenLayers plugin?

I installed the OpenLayers-Plugin and set the CRS to EPSG:3857. When I go to Web / OpenLayers plugin I get the menu with the various maps, but whatever map I choose, all the tiles are white. The ...
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2answers
33 views

Why QGIS Raster clipper does not work on reprojected layers?

I try to clip a hillshade raster and I get this error. The hillshade was the result of a reprojected DEM from WGS84 to WGS84UTM. When I to clip the hillshade or even the reprojected DEM, I get the ...
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0answers
30 views

How to call QGIS modules (qgis.core) from python idle as I can call arcpy

I was trying to set up path to be able to call qgis modules as it defined in their website Introduction and set PYTHONPATH=c:\qgispath\python . I also try to follow suggestion in link below How to ...
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1answer
282 views

Export to Open Layers plugin doesn't work with Raster and WMS

i am trying to export a Qgis_2.4 project to openlayers using the "Export to OpenLayers" plugin. I cannot export raster layer. I am not getting any error message, but the raster layer doesn't appear ...
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1answer
16 views

Using pyQGIS transform a layer of polygons into a layer of holes inside a bbox

I'm using python in QGIS. I have a layer of polygons (its a result of some earlier dissolving and has no overlapping polygons but some holes and islands in holes etc). I want to build a new layer ...
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1answer
19 views

Cleaning shape file with multiple boundaries defined more than once

I have a shape file which contains a lot of polygons which define airspace. These polygons overlap and this is fine (e.g. different airspace configurations for the same airport). My problem is that ...
2
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1answer
137 views

Loading features attributes into numpy array

I am currently working on an add-on that relies on the user choosing fields of tables (that can be from shapefiles, csv or dbf) that are open in QGIS and then making computations with such data. ...
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2answers
39 views

Convert a tiff Float32 image to 8bit tif (or jpeg) image using GDAL and Python

I need to convert a Float32 tiff image to 8bit format in order to display the image in a web page. In order to do that I need a jpg image but this conversion is not correctly done with GDAL because ...
11
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1answer
837 views

How to define Winkel Tripel in proj 4.8.0?

I have QGIS with proj 4.8.0 installed. I'd like to add Winkel Tripel projection which seems to be defined as +proj=wintri But that definition string does not work. Is this a bug in my proj version, ...
2
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1answer
43 views

How to change no data value from -32768 to -3.40282e+38 in raster in QGIS?

I am trying to change the null values of a raster from -32768 to -3.40282e+38 in QGIS. I tried using warp tool setting the no data values to my desired number but it did not change it. Then I used ...
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1answer
6k views

How to select features within a polygon from another layer?

I'm using QGIS 1.8 with a PostGIS database and I have three postgis-layer in qgis a lines layer, a points layer and a polygon layer. What I'm trying to do is to select a polygon in the polygon layer ...
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2answers
56 views

Is there any library can perform polygons buffering/ inflating/ merge/ overlap at server side?

I have a set of polygon data express in lat long. I would like to perform some tasks (polygon buffering, inflating etc etc ..) in server side and output the result to client side (client is a web ...
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1answer
64 views

How can I avoid displacements in exportet JPGS from QGIS 2.2? [duplicate]

I observed a small but annoying problem for a long time now. I have to design maps/plans of survey areas for work including maps where a satellite image is printed under a vector-layer showing the ...
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1answer
144 views

Trying to set NAD 1983 EPSG 102631 in QGIS

I was able to find the right coordinate system online NAD 1983 Alaska But now I don't know what to do. I can't find the coordinate system on QGIS. When I choose the one I think is correct it warps ...
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1answer
20 views

QGIS bar chart with labels

I am trying to get a simple bar chart on my QGIS 2.6 map. I have done that with diagrams. It seems to me it is not possible to add simple values to each bar (say there are three bars at a point). I ...
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19 views

QGIS Map Export in PDF / PNG format - overlapping layers - not printing

I am using map composer in QGIS 2.8 (Wien) where the legend layer overlaps the Map layer without any transparency. While I export the map to PDF or a PNG, the legend layer is not printed. What ...