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

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2answers
27 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
37 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
19 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
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
21 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 ...
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0answers
23 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 ...
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1answer
25 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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0answers
23 views

Selecting polygons using another polygon? [duplicate]

Hi, How is the best way or fastest(if there is) of selecting polygons of a different shapefile using a polygon of another shapefile. exercise example: i want select all the light brown polygons ...
5
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1answer
111 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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1answer
24 views

How can a QGIS user plugin reflect the events of UI?

I am developing a plugin for QGIS 2.8 which uses the data of the active layer. It has a dockable window. When the user changes the active layer, the contents of the plugin window's widgets must ...
2
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1answer
64 views

Conditional Value Map widget in QGIS

I am looking for a way to implement conditional value mapping in QGIS. This means that the values available in attribute number 2 depend on the value provided in attribute 1. Example: If the user ...
1
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1answer
36 views

Merging small area units [duplicate]

I am working with population data organised in parish units for the whole of Denmark. Many parishes are very small (ie <500 inhabitants compared to a median of around 1500) so I plan to merge these ...
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0answers
16 views

QGIS/GeoJSON: Dissolve featurecollection consisting of polygons and multipolygons into a large multipolygon

I've read this question. I would like to know how to do this in QGIS. I have a Geojson file with a featurecollection, starting with: ...
2
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1answer
44 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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2answers
69 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
23 views

QGIS GPS not editing offline database

I have a set of layers from PostGIS that I have converted to offline. I am attempting to edit them via GPS. If the layer is point data, then I can add in that data without issue. However when I go to ...
1
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1answer
30 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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2answers
19 views

Should I be able to open personal DB converted to MSSQL as a MSSQL Layer?

I'm feeling like this should work, but I'm banging my head against the keyboard, the documentaion and the google as I can't find any examples to follow for MSSQL. I have 3rd party data only in an ...
1
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1answer
52 views

PyQgis, styling vector layers in different canvas

I'm developing a QGIS plugin and I need some help with styling layers in different canvas objects. In my dialog window I've got two QgsMapCanvas objects canvas1 and canvas2. Layers from registry are ...
1
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1answer
31 views

PostGIS: Is it possible to identify overlapping polygons in the same layer using their geomteries?

I have a single table containing the geometries of ~3 million polygons and I am looking to calculate the number of polygons that overlap with another. I know that you are able to do this in QGIS ...
1
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0answers
15 views

Generating regularly spaced sample points in qgis based on ratio of area

this is my first post on Stack Exchange. The question I have involves generating sample locations in irregular shaped polygons in qgis. In my situation, there are often many polygons in one shapefile ...
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1answer
15 views

QGIS Grid Union Issues

I am trying to create a choropleth map of ice concentration over Lake Erie. I have data for all the lakes (I can clip it all at the end), which are in a point shape file. I have laid a grid over the ...
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0answers
36 views

QGIS's “Points in Polygon” counts zero in every census tract

I am mapping the location of incidents of asthma using QGIS. I would like to count how many points are in census tracts to better understand the areas where asthma occurs most frequently. My map ...
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1answer
27 views

QGIS add layer not working

I have QGIS 2.8. I open up the database manager, connect to PostGIS, and then execute a query. The resulting query has an id column, a name column, a geom column, and a membership column. I click on ...
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2answers
34 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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1answer
20 views

vertical and horizontal scales on raster

I have a raster image which is a log. What I like to be able to do is to extract the X any Y points from the raster. That are in two sets of units The ideal outcome would be an output of an x and ...
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2answers
49 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 ...
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0answers
24 views

How to Transform from Pixel Coordinates (LCC Projection) to Lat/Long?

I want to transform pixel coordinates from a vector graphic (as .svg) to long/lat values. My vector graphic represents germany and consists of multiple polygons. I've already successfully written a ...
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2answers
57 views

QGIS Viewer, QGIS read only?

Is it possible to create a read-only project in QGIS? Or is there any viewer software available for QGIS project file? What I am after is a read-only project that shows and keep labels and rendering.
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1answer
47 views

How to manage label spacing/density in QGIS?

How to manage space in between labels (or density)? I would like to have less labels in order to have more space in between. The label order is not important. I would like to precise is just for ...
3
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1answer
49 views

How to summarize a column in QGIS field calculator

I have data with a column containing a number value, and I want to divide the value of each feature by the total sum of all the values in the column (to get a percentage). So I would like to know if ...
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0answers
12 views

WMS problems Qgis server with postgis

I have installed qgis and qgis server on a windows server. My plan is to use qgis server to generate a wms. It works fine when I'm using shape files in my qgis project, but when I'm adding a postgis ...
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0answers
24 views

QGIS 2.8.1 crashes when connecting to Personal Geodatabase?

I have a problem connecting to a ESRI Personal Geodatabase. I used to be able to connect to the database using QGIS 2.6.1, but I did some editing to the database in Arc and after that I was unable to ...
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0answers
30 views

Never get the information about obective interpollation and optical interpollation

I have point data want to interpolate it and convert it into 3d grid format but i am not get any proper information which interpolation i have to used objective / optical. please let me know any ...
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0answers
20 views

Catchment area calculation

I have a conundrum. I am trying to shortlist optimal physical locations in my county for developing recycling centres that serve the population. I have a vector point layer of the centre point of ...
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0answers
21 views

QGIS Print Composer not exporting [on hold]

When I try to export from print composer the mapper goes blank and nothing happens. This happens when I try to export an image Jpeg etc, if I try to export a PDF I get a file but it has 0kbs. Any help ...
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1answer
36 views

How to show percentiles in Qgis?

I have a polygon layer with several fields, like: population, wage, age, etc. I would like to show the percentile value for those fields. How can I do that in an automatic way with QGIS 2.6.1?
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1answer
43 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, ...
0
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1answer
32 views

Grid and Graticule in QGIS Print Composer in QGIS 2.8

I'd like to add a grid in the print composer. The problem is there is no visible option like it was in previous version. I mean I'm looking for an option "Show grid?" like in the picture below. I ...
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1answer
40 views

Is it possible to change extension name TIFW to TFW in QGIS?

In QGIS from the "project-->Save as image" dropdown it is possible to save the current map canvas as Tiff. A world file is also automatically exported. Nice! BUT, I use the TIFF+TIFW in another ...
1
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1answer
42 views

Shapefile doesn't fit in CartoDB basemap

When I import some shapefiles in CartoDB they don't fit properly at street level, as you can see in the screenshot. In this case, the shp was generated in QGis with CRS EPSG:29193 - SAD69. I have ...
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1answer
19 views

How to change rule-based Layer Styles all at once in QGIS?

Let's say I have a layer with buildings which is only shown when the scale is higher than 1:10000. When the scale is higher than 5000, I want them to show its function color (retail, residential, ...) ...
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0answers
18 views

QGIS WMS Server line style

I have the same problem reported here (QGIS WMS Server), i have one project created in Qgis desktop (tried windows and ubuntu flavors), then exported WMS into Qgis server (ubuntu). All line layers are ...
2
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1answer
73 views

Can QGIS place diagrams in map legend?

I have this map and I want to put these red circles in the legend of the map according to this form: Is there a way to do that in QGIS? Thanks
1
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2answers
46 views

QGIS: digitized object disappear when filling in attributes

When digitizing, for example a point, the attribute window opens for you to fill in the pre-defined columns/information. But no point is shown in the map while you do this in QGIS 2.6. It was shown in ...
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1answer
26 views

Spatial Join Error Python in QGIS

I got this error message when I tried to do spatial join. An error has occured while executing Python code : Traceback (most recent call last): File ...
0
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0answers
32 views

Land use Models and Open source software software for land use Simulation

I need to do a land-use future prediction so I have classified my study area into 4 classes: Urban Barren Surface water bodies Vegetation Now I have to find the feature land-use prediction. My ...
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0answers
13 views

QGIS print composer and label with svg background error

I have a problem with labels in QGIS. I'm using a background svg for some labels (street numbers). In QGIS, it's all ok but when I use the composer there is a bug (I suppose), because I see some ...
1
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1answer
29 views

How to make transparent WMS vector background in QGIS?

I have a WMS vector layer added to QGIS desktop. But the background is not transparent - it is white. How to change that? When I add this WMS to ArcGIS - all is just fine. Here is the WMS link: ...
1
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1answer
89 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 ...