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

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1answer
81 views

Where can I find topology-related algorithms used in QGIS?

I have shapefile with polygons and I test topology - overlaps, duplicates and gaps. I tested it in QGIS and now I have to describe algorithms, which uses QGIS for this rules. I must write research ...
14
votes
1answer
408 views

How to query OSM for all beaches facing west? - QGIS preferred

I want to identify all beaches on this planet (or a given subset of it) that are facing westwards (+/- 20-30 degrees). My idea is to use OSM as the data source. Extracting all polygons that have the ...
0
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1answer
165 views

cut square from geotiff

i want to make a 3d modell out of the mount everest and some other mountains. what i need therefore is a 14km² square around the peak from the mountain. so basically i use qgis to extract the area ...
1
vote
3answers
378 views

How to add columns with x/y data to Spatialite Layer? [closed]

I´m new here and I am also quite new at working with QGIS. My Spatialite Database looks like this (arch_locations.sqlite) Fields: pkuid short_ID name geometry I´d also like to have two additional ...
1
vote
1answer
104 views

How to batch interpolate many shp´s to DEM

Here´s the problem: I have about 40 shapefiles of contourlines (type line) and I need to interpolate them to create DEM's (tiff, or better some grid format). To do so, some batch scripting would be ...
3
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2answers
419 views

How to convert a point layer to a raster grid that shows the frequency of points per cell in QGIS

I have a point layer that shows the distribution of a species. Is it possible in QGIS to convert this point layer to a raster grid in which the value of each cell corresponds with the amount of points ...
2
votes
1answer
96 views

How to edit a QGIS plugin GUI?

I have inherited a QGIS system from a former employee and my predecessor built a custom plugin for it. I now need to remove a single checkbox option completely from the UI for this plugin. Is there a ...
1
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0answers
497 views

Error when kriging in SAGA: grid file could not be opened

I have a point and a polygon vector shape (shapes) which I want to interpolate by using the saga tool "Ordinary Kriging". I always get the following error message: Oooops! The following output ...
3
votes
3answers
701 views

Black/white hatching pattern fills in QGis

I am looking to replicate black & white maps in QGis, using hatching patterns and greyscales to indicate different categories of a continuous variable (example below). It is ...
3
votes
1answer
234 views

More than one WMS layer in QGIS

I have a problem when using WMS layers. I'm usin QGIS. I'm loading a WMS layer containing some aerial images. And then on top of it another WMS layer that contains information of the city, boundaries ...
0
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1answer
84 views

How to list..only the Field names for a group of files in a folder?

I am having...for eg, 27 files in a folder (may be a shp or tab). Is it possible to list the Field_Names (ID, Type, Date, Allotment, etc..) alone of all those 27 files in a csv format or xls format?
3
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0answers
65 views

How to include external libraries with my QGIS plugin?

I'm developing a plugin which makes use of "networkx" library extensively. However, networkx is not part of Python libraries pre-installed in QGIS. Is there a way to include this library with my ...
0
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2answers
100 views

QGIS Connection PostGIS and shapefile

I'm working on QGIS with a database created in PostGIS and a shapefile. Inside the database, I have geometry type data about location of some points, instead on the shapefile there some selected ...
0
votes
1answer
321 views

JPEG base map doesn't match shapefile locations

Relative Newbie Question: I have Civil War earthworks tied to the State Plane Coordinate system with a jpeg of the terrain as a 100k scale USGS Quad of the area that is not georeferenced. When I work ...
1
vote
1answer
98 views

Overlap or intersect two choropleth [closed]

I have two choropleth of the same area but with different concentration data and I need to overlap them. My aim is to highlight the areas of intersection between the points with the highest ...
1
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2answers
513 views

How to calculate distance in meter between QgsPoint objects in PyQgis?

I tried to calculate distance between QgsPoint objects in qgis, i used QgsPoint StartPoint.sqrDist(EndPoint). but i don't find an expected result, i also tried import math ...
1
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1answer
155 views

How to remove thin lines and small points from qgis raster

I want to digitize the roads of a raster map to vector format using QGIS and GDAL preferably. By using the Raster Calculator I have been able to extract the roads and contour-lines from the raster to ...
1
vote
1answer
812 views

How do I use 'model builder' in QGIS 2.2?

I am trying to learn how to use the 'model builder' in QGIS 2.2. I have used model builder in ArcGIS, but I don't understand how to do it in QGIS 2.2? What I want to do is to make buffers, clip ...
1
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1answer
171 views

How can I create an animation with raster data in qgis?

I have 4 raster images showing different coniditions of air flow distribution at different times. I'd like to create an animation to show the change from image 1 to image 4. How can I do this? I tried ...
2
votes
2answers
202 views

Converted GPX file has null values in open attributes

I'm an absolute newbie but I think I'm doing this right. I've got a bunch of .fit files from my garmin. I can use GPSBabel to manually convert these to GPX XML and the map looks fine after the ...
1
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1answer
329 views

How to populate a combobox with layers in TOC?

I am developing a plugin, and I want user to select one of the loaded layers from a combobox. I've already coded this much: self.dlg.show() layerlist = [] self.dlg.ui.layerCombo.clear() # ...
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1answer
96 views

How can I use pyqgis to automate a series of field calculations?

I've got a shapefile with about 30 fields that I'll need to update from time to time by importing a CSV with new data, joining it to the shapefile, and using the field calculator to carry the new ...
1
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1answer
576 views

How to indicate flow of a watershed feature?

While tracing and digitizing rivers, streams, rivulets, etc., is it possible to indicate the direction/flow in the shapefile on QGIS? I'd like to avoid using map labels. Ideally, when done tracing, I ...
3
votes
1answer
72 views

Why are there no more error messages after importing QGIS modules into python?

I have a problem when writing python code whilst including the qgis modules. As can be seen below, when I usually call a variable that does not exist (for example), I receive the usual error message. ...
0
votes
1answer
123 views

Why can't I open a kml layer?

I thought that I could open kml layer like a normal vector layer but it doesn't work (it says "invalid datasource"). How can I open a kml layer in QGIS? Or how can I open it anyway, I never worked ith ...
1
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1answer
174 views

reproject vector layer with pyqgis with new CRS does not worl

In QGIS I am running a script in th python toolbar to export all visible vector layers to a GEOJSON with this snippet: canvas = qgis.utils.iface.mapCanvas() allLayers = canvas.layers() for i in ...
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1answer
163 views

Why can't I open QGIS projects via windows explorer?

We have upgraded from QGis 1.8 to QGis 2.2. Qgis 2.2 is first installed, then 1.8 removed. Since then it is impossible to open .qgs-projects directly from windows explorer. We have checked explorer, ...
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1answer
55 views

QGIS hides few graduated points after reopening project

I have a strange problem in QGIS 2.2 (problem is also present in QGIS 2.1). When I add a point (shapefile) layer, apply graduated style and change point size, everything looks fine. Then I save ...
0
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1answer
57 views

QgsFeatureList features as QStrings

I am catching the selectionChanged signal and passing the selected layer to the registered method. Once here, I want to know the features that were selected. I do this with a call to ...
9
votes
1answer
351 views

How to do Manhattan Voronoi on QGIS?

I've spending last two weeks trying to discover how to do a Manhattan Voronoi on QGIS. For the difference between Manhattan Voronoi and "normal" Euclidean Voronoi, please check this link Can someone ...
3
votes
3answers
287 views

QGIS Mosaicing with null values in images

I have a set of landuse landcover data which needs to be mosaiced. Whenever i try using QGIS Raster>miscellenous>merge tool. giving no datavalue as '0', it returns either (A) ' Traceback (most ...
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0answers
152 views

Programmatically modify layer datasource on project save event (QGIS)

I have a QGIS plugin which allows users to add WFS/WMS layers to the map. I would like to be able to scramble the user ID part (token) of the uri when the project is saved/closed and then use my own ...
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2answers
373 views

How does one export the list of stored WMS-servers in QGis?

Could anyone point me as to where QGis stores the list of WMS-servers you added? I have built a fairly large list of WMS-server on one computer, but the QGis-project file which gets accessed by my ...
0
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0answers
128 views

QGIS custom form and autocompleted data entering with “validation check”

In Qt-Designer I created a custom form where I can choose serveral species names in two different combo boxes. This combo boxes are linked via "value relation" to the accordant non spatial tables ...
2
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0answers
269 views

length and width of polygon

how can i find polygon's length and width in Qgis(regular polygon and irregular polygon)? i have area and perimeter but possible to have length and width ?.
7
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3answers
531 views

Merge images first, or georeference first?

I'm wanting to georeference and vectorise some features from scans of the OS 1896 Town Plans that I have purchased from the NLS (http://maps.nls.uk/os/london-1890s/info.html). The scans provided are ...
1
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2answers
62 views

Where are QGIS application setting file(s) stored?

I have some application settings (Windows/QGIS v2.0) that I would like to pass to other users (such as those settings defined under Settings menu>Options>Rendering tab). In ArcGIS they are stored in ...
2
votes
0answers
165 views

Is there a decent algorithm in QGIS Process Modeller to create a grid?

I am using Process Modeller to automate merging several vector layers and then creating a grid to cover the extent of the merged layer. There are functions which already exist which are not listed in ...
0
votes
1answer
193 views

QGIS: graphical-modeler to calculate area of polygons

I'm trying to calculate the area of polygons using the field-calculator in QGIS (2.0.1). If I do this manualy it works fine, but if I do this using the graphical-modeler I get NULL as area for every ...
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0answers
43 views

How can I see the overlay of two features (point & polygon)?

I am trying to open two digitized layers, one containing points in a region and second which I have downloaded separately for the region as polygon layer. I would like to overlay two of these layers ...
0
votes
1answer
62 views

How to use QGIS field calculator to delete style code?

I am struggling with following issue: How to delete style code before id codes x.x.xx.. and the }s in the end? Examples below. Any help appreciated! {\fArial|b1|i0|c0|p34;A.B.11} ...
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2answers
447 views

How to make multiple qgis mapbook pages in 1 pdf?

Is it possible to export a mapbook in QGIS 2 with multiple pages all in one PDF? Thanks
4
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2answers
907 views

How to add Georeferenced PDF as layer to QGIS 2.0?

I have some georeferenced pdf's that I would like to open in QGIS. I have read that GDAL version 1.8 and higher will support pdf, and I have GDAL 1.10 installed with QGIS 2.0 on Windows 7, but when I ...
1
vote
1answer
191 views

Spatialite Table Difference in QGIS

I am see differences between tables when I view them in spatialite-gui and in QGIS. I have created a table, added columns, and updated the columns in spatialite-gui. Within spatialite-gui I can view ...
0
votes
0answers
166 views

Error: .asc is not a supported raster data source

I am new using QGIS and struggling with this error "...... .asc is not a supported raster data source" when trying to add a ."asc" file as a raster. I downloaded the files from ...
0
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1answer
129 views

Mac QGIS files to Windows Arc GIS compatibility

If I download QGIS on to Mac will the shapefiles and layers I create be compatible with ESRI ArcGIS 10.1 on windows?
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0answers
59 views

Error 14: Could not open CRS database

I am using Python Console and loading a Vector Layer using python commands. When the layer is added, QGIS first asks for the CRS to use, but I don't have all the CRS listed out to select the Reference ...
1
vote
1answer
207 views

extract shapefile attributes from raster colors

I have two layers: a shapefile with states and counties (shp) a raster file (with colors and some text and borders, but not a perfect map) (tiff) I want to use the colors in the raster file to ...
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0answers
75 views

HTML Annotations

I am trying to insert html annotations into my map. I was hoping they would be interactive and pop up as you move over or click on a feature, but they don't seem to function this way (that I can ...
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2answers
2k views

QGIS Select by Expression

A basic QGIS 2.2.0-Valmiera, Select By Expression - Field Calculator question. Introduction I am a geologist searching through a geological database (see attached figure). I have a shape file and ...