Tagged Questions

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

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6 views

Contours with negative values using the model example in QGIS?

I have a data set of water level ranging from -6 m below sea level to +30 meters. But when I use the model example for creating contours from points, the minimum contour value is zero (0). What can be ...
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1answer
14 views

What's the QGIS Legend Format Syntax to label percentage values?

I asked a question about formatting legend text a while back and I'm happy to see the issue has been solved in QGIS 2.6: How to remove trailing zeros from QGIS Graduated Style Class labels? But I'm ...
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1answer
18 views

How to calculate the perimeter of the polygon using python programming

Is it possible to calculate the perimeter of each feature of the polygon? For calculating the area we are using: area=feature.geometry().area() is there any function to calculate the ...
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0answers
26 views

Using Google Maps plugin in QGIS?

I was using Google Maps with OpenLayers plugin in QGIS with my vector layer with projection EPSG:4326 with google map projection EPSG:3857 and "on the fly" transformation enabled. It was matching ...
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0answers
7 views

Creating a Raster of Road Distance to Point

I'm trying to create a raster of distance to a certain point on a road; preferably using the Road Graph package or something similar in QGIS (using v2.6). I was wondering if I could create this ...
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0answers
12 views

How to draw coordinates QGIS print composer? [duplicate]

I am trying to add coordinates to a map, I fix all of the settings, but they don't show in the map... Do I need to do any previous work?
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0answers
16 views

Raster legend visualisation problem

With the new 2.6 QGIS version I often have problems with raster colors. Is there a problem I could solve by myself?
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1answer
35 views

QGIS 2.6.0 Minidump crash EVERY TIME I SAVE

Just got QGIS 2.6.0 running on Windows 7 service pack 1 64 bit. Project loads, edits, saves editing changes, adds removes, layers no problem. Only problem is saving the project. Do that and it's ...
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0answers
11 views

Help with Parameters in Qgis Python lidartools:lasclip

I am trying to use the python console to batch quite a few processes from lastools. I'm having trouble with the arguments to lasclip. clipped_las = processing.runalg('lidartools:lasclip', True, ...
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0answers
9 views

How to create a macro-localization in print composer (QGIS)

Is there a way to do a macro-localization in Qgis 2.6. I am currently working in a map of the Baja peninsula so I need a macro-loc of Mexico or North america...
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1answer
33 views

QGIS 2.6 Brighton: Problem with zoom

I seem to have a problem with the zooming levels in QGIS 2.6 Brighton. When I go to zoom in to a vector or raster layer, e.g. for digitizing purposes, the scale seems to be fixed at 1:2,256, I can't ...
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1answer
47 views

How to import multiple shapefiles without any dbf to a postgis database?

I have a polyline shapefile (.shp and .shx) without .dbf. I would like to import the shp into Postgis. In order to do that, I created the corresponding .dbf using the r code provided by mdsumner in ...
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0answers
17 views

Saving a QGIS project using the API loses mapcanvas (and other) XML nodes

I'm using the following python script to open a QGIS project, modify some things, and save it under a different name: from PyQt4.QtCore import QFileInfo from qgis.core import * def main(): ...
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0answers
18 views

Creating a mosaic with gdalwarp - How to deal with no data and overlap

I want to create a mosaic of satellite imagery in .tiff format. I want to create an actual mosaic, not a vrt, because afterwards I will cut the image in to tiles that make sense for my users. Gdal ...
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0answers
18 views

QGIS nearest neighbor parameter description

Could anyone explain me the following parameters, which I get by doing a nearest neighbor statistic on a point shape? I suppose that Observed mean distance is the mean distance between two points ...
2
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1answer
11 views

Intersection between polylines feature to polygon in QGIS

I would like to transform a line shapefile into polygons. However, the tool Vector>Geometry>Line to Polygon doesn'to work to me. What I would like to do is using the intersection between lines and ...
2
votes
1answer
21 views

How to get the length of each line segment in a line shape file in QGIS

Iam new to QGIS. I drew a line depicting a small length of road. But I drew it in segments and then atlast right clicked at the end point and gave id=1. I extratced the nodes, their geometry. But what ...
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1answer
57 views

How to add vertex to an existing polyline programatically?

I have a Polyline and would like to add new vertex to before start point or end point or at any part of the polyline using python in qgis. How can i do that?
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0answers
7 views

Avoiding intersections with QGIS Spline plugin (Version 2.0)

Has anyone gotten the QGIS 'avoid intersections' option to work when adding polygons via the Spline plugin? When checking the option and enable topological editing, I continue getting overlaps in my ...
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0answers
19 views

How i can have the same xMin,yMin for vector files in Qgis 2.4

i have a .shp file(polygon) in EPSG:2100 - GGRS87 / Greek Grid and an other .shp(points) in the same system(EPSG:2100 - GGRS87 ) but different xMin,yMin. The first has xMin,yMin 583309.00,4152885.94 ...
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1answer
67 views

How to convert local Coordinates to lat/long Coordinates

I'm using QGIS to do some data analysis and visualization for my newspaper. I received some x,y coordinates from the City of Minneapolis that I can use to build some static graphical maps shaped like ...
4
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1answer
68 views

Digitizing contour lines from paper maps using QGIS?

Is it possible to give digitized altitude lines (from paper map) heights using QGIS?
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0answers
13 views

Adding Raster Layer in C++ application always result in layer invalid

I am trying to add a raster layer in c++ application with QtCreator and QGIS 2.6.0. My code is as follows: QgsRasterLayer * layer = new ...
2
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1answer
19 views

area elevation distribution with QGIS

I have a raster DEM and a polygon covering a part of it. I need an area-elevation distribution (i.e. how many m2 are in which elevation interval). 20m intervals will be fine. I cant figure it out.
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0answers
14 views

Percentage of a polygon at, or less than, a specific height (supplied by a raster)

I am using QGIS to process some LIDAR data. I need to be able to define the area of a pond with respect to its depth (i.e it is 100m^2 at 32mAOD and 500m^2 at 33mAOD). Is there a way of finding the ...
2
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0answers
19 views

QGIS returns “invalid layer” when adding a WMS layer

I want to add a WMS layer in my map. I select the server and obtain the list of layers that are published there. I select one of them (the problem is the same with all layers), but QGIS does not load ...
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0answers
24 views

How do I make my map use a set of coordinates

Right a little background. I've made a custom google map with the google map api which has a few functions that work well within it - one specifically is limiting the user on what they can view within ...
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0answers
8 views

How to merge DMAs using QGIS — Creating Custom Regions?

What I am trying to do might seem basic, but bear with me as I am just hacking my way through a lot of this space. What i am trying to do: I am trying to create a new .shp file of custom regions. ...
2
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1answer
19 views

QGIS print composer, DMS grid when SRC is not in decimal degrees

I have a QGIS project where the layers are in projected SRC, and when I go to the print composer to draw the grid, the units are in millons of meters, and I want them in decimal degrees. Is it ...
1
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1answer
26 views

J2000 to WGS84 in QGIS?

How to transform Earth-Centered Inertial J2000 CRS to WGS84 CRS in QGIS? I searched J2000 in spatialreference.org, however nothing found. I don't know the proj4 string of J2000. Any advice would be ...
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0answers
33 views

Menu actions in QGIS 2.6 feature attributes

I would like to ask about new menu 'actions' in feature attributes which appears in new QGIS 2.6. This menu shows 'actions', defined for the layer but I am wondering if it is possible to add some ...
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0answers
41 views

Apply an sld to a vector layer in OpenLayers

I'm trying to apply an sld style to a vector layer in Openlayers. I already took a look on google and here and I got a lot of informations, but still I don't manage to achieve the result I'm looking ...
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1answer
17 views

With QGIS Plugins/PluginBuilder, how to prevent 2nd instance of Plugin from starting

I am using QGIS 2.6.0, with PluginBuilder 2.0.3 [checking the version, I just noticed that the 2.1.0 update is available] I am writing a plugin; it installs and runs. While running, I am able to ...
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0answers
34 views

QGIS 2.6 Brighton - Graduated Symbols

I can't get graduated symbols to show in QGIS 2.6. This is what I have done. I have two fields of type integer, saved as a shape file which I have tried to import as a shape file and as a secondary ...
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0answers
19 views

Add button to custom standalone QGIS application

Im able to implement zoom in and zoom out functionality as described in the PyQGIS developer cookbook using a tool bar. I would like to have buttons that display above my map canvas layer and have the ...
2
votes
1answer
42 views

How to prevent users to remove qgis layer?

I need to prevent users from removing layers. In my plugin code I use the following to achieve that: QgsMapLayerRegistry.instance().layersWillBeRemoved.connect(self.dontremovefunc) def ...
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2answers
28 views

Using QgsRasterCalculator

I'm trying to make a sum of n rasters and create a new one using QgsRasterClaculator, the problem is, every time the code reaches processCalculation, it makes QGis close and create a dump file. I ...
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0answers
19 views

Compute nearest points to other points using GRASS

I have a layer of address points and a layer of polling stations. My task is to determine the three closest polling stations to each address on the street network. I think that the answer is in ...
2
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1answer
30 views

PROJ.4 - General Parameters: +no_defs

within a QGIS-course I would like to tell a bit about the proj.4 parameters. However, I´m not sure about the "+no_defs" parameter. The proj.4 website (https://trac.osgeo.org/proj/wiki/GenParms) ...
2
votes
1answer
27 views

Incorrect placement of a MrSid file in QGIS

I have a map saved as MrSid file which when loaded in QGIS displays as a southern hemisphere location despite being in the UK. When looking at the .sdw file the northing is positive but in QGIS it ...
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0answers
14 views

Automatically creating index features for a strip map in QGIS

Is there a free/open source equivalent ArcGIS's Strip Map Index Features geoprocessing tool? I'd like to use QGIS's "Atlas" mapbook functionality, but creating the index layer manually would be ...
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0answers
25 views

Is there a way to change floating toolbar orientation?

Is there a way, within QGIS 2.*, to stop the interface from trying to snap in floating toolbars (as attached pic)? I want to maximise canvas space, but the interface keeps on wanting to grab my ...
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0answers
29 views

How to create dynamic maps based on updated attributes in SHP file

I am novice GIS'er. I can create maps and do basic transformation of the SHP file using QGIS. I also succesfully applied formatting based on attributes. I am able to add new attributes to SHP file in ...
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2answers
39 views

Is there an algorithm for transforming from CGCS2000 to WGS84?

Is there an algorithm that supports transforming from CGCS2000 coordinate to WGS84 coordinate? CGCS2000 is China Geodetic Coordinate System 2000. Any advice would be thankful!
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2answers
33 views

Reduce squarish effect on group of polygon

I am trying to represent the average speed of some ship in the north of Mediterranean sea. I am interested in aggregate the speed information by zone. The raw data I am working with are .shp with ...
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0answers
18 views

QGIS installation failed - requires matplotlib which has been installed by Anaconda

Is there any way to specify python environment variable to solve this? When I tried to install QGIS on my machine - mac OS 10.9 and Anaconda has installed numpy, scipy, and matplotlib, I got the error ...
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0answers
70 views

Extract Aerial Imagery using QGIS

I need to create city-wide (Warsaw in this case) aerial based map, pretty detailed (clearly visible buildings and possibly 1-pixel-sized cars. So far the only way I found is: Using this method: ...
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0answers
35 views

How to create a map in Pulkovo 1942 with grid?

I have a problem with coordinates when I change projection. With WGS 84 it's fine, I have normal, geographic coordinates. But when I'm changing to Pulkovo 1942 (I need a map of Poland), coordinates ...
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2answers
13 views

Error with layer.pendingAllAttributesList

While coding to obtain individual layers' attributes (field) list, I am stymied by the code. I can identify a specific layer: MyLayer = QgsMapLayerRegistry.instance().mapLayersByName("TestPoint") ...
1
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1answer
15 views

How do I ensure polygons are properly displayed when using 'on the fly' CRS transformations in QGIS 2.6?

QuantumGIS 2.6.0 (Windows 7 64-bit) I have created a PostgreSQL POLYGON as WGS84 (CRS 4326). The polygon is a series of points around (but not actually on) the edge of the map. This is a rectangle ...