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

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4
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1answer
5k views

Saving selection as new layer in QGIS 2.4?

I've selected a number of polygons from one layer and want to create a new layer. Because I can't right click using a mac how do I find "Save Selection As". Its not in the list in the "Layer" ...
3
votes
1answer
77 views

How to display bidirectional flows?

I'm working on a map showing oil shipping. Basically, I have a a series of nodes/line segments that make up the shipping network. I've joined the sums of oil that traveled along each node, so can ...
2
votes
0answers
111 views

Editing the QGIS Attribute Table

Is there a way to edit the name, type and length given to each column on the attribute table once the information has been imported from Excel?
2
votes
1answer
535 views

Merge multiple linestring features into a single multilinestring

Using QGis or ogr2ogr how do I convert a vector file containing multiple linestrings features into a single multilinestring feature? At the moment I've been doing this manually by converting the data ...
1
vote
2answers
420 views

Error while importing CSV File using PyQGIS

Currently I am trying to import a CSV file using the python extension in QGIS and I have run into a problem that I can not seem to solve. I am trying to do a basic import of a CSV file from a python ...
5
votes
1answer
306 views

Sourcing GIS data from First World War (WW1)?

Simple question, but does anyone know where I can get some detailed (eg 1:10m scale) vector data from the First World War? I've been through the archives here, but it seems the best sites for it ...
0
votes
1answer
95 views

Georeferencing image using QGIS?

I am very new at this and when I georeference an image in qgis, I get the same image georeference but rotate and elongated. I use 3 control points to georeference the image but whatever I do, I get ...
1
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0answers
52 views

Is there any autocomplete filter widget for QGIS connecting to PostGIS?

In QGIS, there is Value Relation widget for fields, that contain references to data in external tables or views. While it works fine for small number of choices, it can quickly become overwhelming, if ...
5
votes
1answer
400 views

How to compare two sets of points in QGIS?

I have two point layers with XYZ data; one set are points measured in the field and the second set is a Lidar data set. I want to check the accuracy of the Lidar in comparison to the measured data. ...
0
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0answers
50 views

Reading Points as PolyLines

I'm currently developing an Android app where I need to show some information on a map, which is stored as Shapefiles (.shp + .shx + .dbf). I noticed that when the shapefile is opened in QGis, a nice ...
1
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0answers
243 views

Import QGIS Python modules in Python command line or standalone script

I am running a Windows 7 machine with Python version 2.7.8 (32 bit). I installed QGIS 2.4 (Chugiak) from OSGeo4W and simply want to be able to import the QGIS Python modules (e.g. qgis.core) into ...
0
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0answers
145 views

Polygonize only pixel values of 1 from a raster

I have a raster mask that I have created in QGIS (2.2.0) that consist of 0, 1 and nodata values. I would like to end up with a polygon dataset that consist of only the value of one pixels from this ...
0
votes
1answer
171 views

Determining direction of longest segment of polygon?

I have a shapefile with 9000 agriculture fields and what I like to do is to determine for each field (=each polygon) the direction of the longest segment. For instance, the selected polygon in the ...
2
votes
2answers
138 views

How to extract a new linestring vector from a existing multipolygon in QGIS?

What I want to do: create a new line (named linestring in Postgis?) from existing multipolygon layer in Postgis. Purpose: once these lines are created, I'll run some distance calcs from specific ...
3
votes
2answers
354 views

Generating polygons with shared boundaries using QGIS?

Essentially the problem is that if you digitise each polygon separately the boundaries will not match exactly. My instinct is to have a table of line segments and generate the polygons from that using ...
1
vote
1answer
458 views

qgis printcomposer: can I select features whose attributes to show

I am using the atlas to generate a number of maps. Each map is of a particular zone represented by a multiline vector layer. I have another layer with point data and each map has an attribute table ...
0
votes
1answer
53 views

qgis printcomposer: can I wrap text in attr table?

I have some longish text attributes and when I try and put these on the map using the attribute table they get truncated. Is there a way to get these long lines wrapped.
1
vote
1answer
95 views

Have Atlas sorting and filtering controls been removed in 2.4?

In this diagram the atlas generation tab of the print composer has several controls that I don't see in my version (2.4) of QGIS. In particular the feature sorting and feature filtering, both of ...
1
vote
1answer
55 views

ESRI : 54019 or World winkel II in QGIS

Currently I didn't find World winkel II or ESRI : 54019 coordinate system support in qgis. One of our client using this.. Can any one tell me a solution to load shape files,which are using his ...
0
votes
1answer
157 views

How to Manually add a Z variable in Qgis onto a vector layer

I am trying to manually add one constant Z-variable (e.g. 200meters) across an entire Vector Layer in Qgis so that I may eventually use the Interpolation plugin to generate a Tin. I have not been ...
1
vote
1answer
60 views

What causes this error when loading plugin

After installing pyspatialite on my Mac two plugins fail to load with this error:: This plugin is broken invalid literal for int() with base 10: '2-spatialite' I am fairly sure that the offending ...
1
vote
3answers
198 views

How to convert crs projection of Map in qgis

I am totally new to GIS. I have a qgis project. I am adding the screenshot. As you can see the map is sort of rectangle in projection. How can i project it like this (without the grids) Thanks ...
1
vote
1answer
73 views

What's the difference between Processing GRASS and the GRASS toolbar?

Preparing a QGIS-course for my colleagues I stumbled over the following question: What is the difference between the GRASS commands in the processing toolbar and the GRASS Tools, that you access via ...
1
vote
1answer
175 views

Is there a gallery of QGIS maps anywhere?

Specifically, I want to see the gorgeous map of Chugach State Park that you see when starting QGIS 2.4 "Chugiak". Is there a website out there where people share maps? I would like to share and see ...
5
votes
0answers
131 views

Is there a limit to the number of polygon points you can export to CSV in QGIS 2.4?

Using QGIS 2.4 I am currently importing a csv file with ~30,000 polygons (polygons in WKT format). I also have a United States shapefile. I have used the Clip function to get only the polygons that ...
5
votes
3answers
598 views

LiDAR data density, returns per square meter

How can I compute a raster showing the number of return points per square meter using SAGA GIS or other open source software? My goal is to obtain a mask which would show me the places (cells) ...
1
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0answers
52 views

Link to pdf file through mouse clicking

I need help in identifying the feature attributes displaying a pdf file when click in that feature. I see many examples but I don't have success. I try this code: command = "firefox"; imagerelpath = ...
1
vote
2answers
662 views

How to export a high-res world map image?

I'm trying to get some (very) large world map images (think 10k x 10k pixels etc), but can't seem to do it with QGIS, and would appreciate any help. Manually adding smaller images to a larger one ...
2
votes
1answer
65 views

How to subtract lines with thickness from polygon

I have a polygon and some lines crossing it. I want to subtract the lines with a certain "thickness" from the polygon, so it splits up into various polygons which do not touch each other anymore. You ...
3
votes
2answers
242 views

QGIS Line End Caps

When styling a road network where all sections of the network between junctions are separate paths, I style the ends of the lines to rounded to remove any gaps that might appear where the joins are at ...
2
votes
0answers
266 views

Doubts with Ripley's K function Interpretation

I'm a self-taught person, I'm studying the K Ripley's function and I would need some person who give me some advices. First, I have written a little script of R in QGIS processor: ##Point pattern ...
0
votes
2answers
272 views

Issues calculating range with QGIS 2.0 raster calculator

I would like to calculate a simple range using the QGIS 2.0 Raster Calculator, but am getting strange results. I believe I am not using the correct syntax. To get all values between .003-.5, I ...
0
votes
2answers
94 views

How to calculate x/y in a different coordinate system in QGIS 2.4?

I'm trying to calculate Northing Easting in QGIS. I can get it to calculate my lat/long using $y and $x in the field calculator. I changed coordinate systems to what I want it displayed at, but it's ...
4
votes
1answer
163 views

Does QGIS automatically use spatialite spatial indexes?

When you write a query in spatialite you have to manually join your query to the spatial index for that index to be used to speed up the query. When QGIS displays data does it take advantage of any ...
0
votes
0answers
320 views

How to create correct vector grid in meter

I want to create a vector grid, with squares of 100x100m but have some serious trouble in solving this apparently easy task. I already read all the posts, but didnt find a good solution. Here is what ...
2
votes
1answer
233 views

How to split Polygons by line grid?

I want to split a polygon by a intersecting line into different parts, exactly like in this post(Qgis - Is there a way to split a polygon layer with a line layer?). I have a vector grid to cut the ...
2
votes
1answer
225 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 ...
1
vote
0answers
145 views

How to write a custom map canvas item by subclassing QObject and QgsMapCanvasItem?

I'm writing a QGIS python plugin where I place some QgsVertexMarkers on the canvas like this: marker = QgsVertexMarker(self.canvas) marker.setCenter(QgsPoint(point[0],point[1])) Now i would like ...
2
votes
1answer
173 views

CSV handling in QGIS?

I am using QGIS 2.4.0 and sadly it seems that QGIS imported csv files are somewhat bugged. I cannot use imported csv files the same way as shapefiles. It seems that sometimes it is easier to import ...
8
votes
2answers
329 views

Is it possible to use comments in QGIS Query Builder with shapefiles?

I am trying different queries in the Query Builder. Is there a way to comment the query? I tried with /* */ # -- without success : An error occurred when executing the query. The data ...
0
votes
2answers
163 views

Tool for rendering/drawing maps from coordinates

What tools can be used to convert a set of coordinates into polygons? For example: this code represents a room by providing information about it's four corners. <node id='-202' lat='41.015146' ...
1
vote
1answer
199 views

Merging vector layers using QGIS? [duplicate]

I have dozens of vector layers that I want to join together in QGIS. They have identical fields. How do I do this?
0
votes
0answers
171 views

QGIS startup error (symbol lookup error, undefined symbol) after system update

I'm using QGIS 2.4.0 on Linux Mint 16 MATE 64-bit. This afternoon I did a normal system update via apt-get update && apt-get upgrade followed by apt-get autoclean && autoremove. But ...
6
votes
1answer
395 views

How to replicate QGIS vector smoothing effect in ArcGIS for Desktop?

You can see from the screenshots that QGIS has, in my opinion, much more pleasant on-screen rendering of vector features. I assume there is some sort of smoothing algorithm used in QGIS. Is there a ...
0
votes
1answer
60 views

How to install a Reporter plugin for QGIS?

I can not get the plugin Reporter or SimpleReport to run in 2.4 or 2.2. The plugin manager in qgis says there is no metadata.txt. This is obviously not true and is in there. I have changed the ...
1
vote
1answer
64 views

Layers not displaying in the correct order

I have a shapefile that is in my Layer tree above an aerial imagery layer. Yet, the map covers the shapefile with the aerial imagery. Any ideas how to fix this?
3
votes
1answer
468 views

Not able to save edits to vector layer in QGIS

I have a vector layer with about 200 features. So far I have been able to add polygons to this layer just fine, now it is giving me trouble. When I draw the polygon and try to save edits, the polygon ...
1
vote
0answers
92 views

How to set QGIS action to open and search for features on Google Maps?

At the moment, I have an action that takes each term in an address field and conducts a search on EACH term in Google (ie. multiple tabs are opened for each term). The action code I have is the ...
0
votes
1answer
335 views

QGIS: Multiply Raster Value with Pixel size

i'm working on a map with population densities. My raster data contains values as [People/square meter] for each cell. I have per capita values of energy demand etc. which I want to multiply with the ...
3
votes
1answer
227 views

Can QGIS table editor achieve similar results to Pivot tables in Excel?

Is it possible to achieve similar results to Pivot Tables in QGIS table editor so as to use just QGIS instead of several software solutions? Or are there maybe some plugins capable of achieving those ...