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

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537 views

How to read the attribute values using pyQgis?

What is the way to get the information contained in the attribute table, say in column 2, row 2 using pyQgis?
4
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1answer
323 views

What functionality exists to calculate Cut and Fill for excavation?

Does qgis have the ability to compare and quantify existing versus proposed elevations?
3
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3answers
112 views

How to match air photo to existing vector layers on Mac OS?

I'm trying to add an air photo to a project and match it to existing data. CanVec data is mostly based on the old CIA dataset of the 60's and is hopelessly out of date, but the roads are up to date - ...
4
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1answer
185 views

Can county level info be brought into a map?

I have a csv file of Clovis projectile points that were recorded only with the county in which they were found, no coordinates at all, no shapefiles. Is there a way to bring these into a state map ...
4
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2answers
478 views

QGIS, Postgis: Is it possible to create a new postgis layer?

Situation: I have a postgis vector lay that has lots of line segments (the features). I want to create a set of new layers each of which contains a subset of the features of the original layer and ...
2
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1answer
62 views

QGIS: Making changes to vector layers stored in PostGIS

I have a vector layer stored in PostGIS. I split several lines in the layer and simplified others by removing vertices. When I tried to save the changes to the layer I got postgres more postgres ...
11
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2answers
1k views

How to create contiguous area cartograms in QGIS or R?

Here is what I want to achieve (on the right): I am looking for a tool or a method to transform a shapefile (with QGIS or R) into this form. And please be aware: It's not just clipping a hexagonal ...
0
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0answers
256 views

How to use raw_input() in QGIS python console?

I'm hoping to use raw_input() inside a loop to prompt the user when s/he wants to continue running the script. However, I'm getting an error: Traceback (most recent call last): File ...
2
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2answers
318 views

Create polygon of buildings from Quickbird images in QGIS

I have Quickbird/Ikonos/GeoEye image and want to extract all the buildings from the image as an independent layer in QGIS. How can i achieve that?
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2answers
234 views

Having problems creating VRT in QGIS from png files

This is similar to a question asked by someone else, re OS tiles, however, there is a difference! I am a bit of a amateur in GIS and python, but if I take it slow I can usually just about work it out! ...
4
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2answers
482 views

Field Calculator decimal places - how can I limit them?

I've added a new column to an attribute table and performed an operation with the field calculator to populate the new column. The result is a column with a percentage. My problem isn't major but I ...
1
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2answers
387 views

styles for QGIS

Could someone point me to a source of line and point styles for QGIS (*.qml) - railways and transmission lines are the first two I've run up against, but I know there will be more.
1
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1answer
282 views

Rpy2 Unable to Load in Fresh QGIS Install

after installing qgis the a message given below is shown Unable to load the plugin: Unable to load required package rpy2. Please ensure that both R, and the corresponding version of Rpy2 are ...
2
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0answers
163 views

QGIS not rendering WMS layers

I'm a bit of newb' at GIS so be gentle with me. In Qgis I've set up a wms for the British Geological Survey: http://maps.bgs.ac.uk/ArcGIS/services/BGS_Detailed_Geology/MapServer/WMSServer? Now ...
4
votes
1answer
273 views

Personal shell launcher for PyQGIS

I have changed a shell launcher found at http://inasafe.linfiniti.com/html/id/developer-docs/platform_windows.html as to fit my wish: setting the system environment variables to be able to use PyQGIS ...
2
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0answers
216 views

WMS and Quantum GIS/ArcGIS

I periodically use a nice basemap served by the Utah state government in QGIS. Recently they upgraded their server from ArcGIS Server 9.3 to ArcGIS Server 10.1. Ever since then, I can't seem to get ...
1
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1answer
132 views

Can not import qgis.core in python

I installed OSGeo4W. I have no other Python version on my computer. I can import osgeo. But when I try to import qgis.core I am getting the error: >>> import qgis.core Traceback (most ...
6
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1answer
418 views

ISIS to GDAL to QGIS: Georeferencing Mars Images

I'm trying to use QGIS to view some images from the Mars Reconnaissance Orbiter Context Camera. I use ISIS3 to download the images and convert them to mapped .cub files, following the instructions ...
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0answers
58 views

How to delete a point with known coordinates in python?

I was wondering if there is a piece of code that does the opposite that setGeometry does and removes a point if there is one at x and y coordinates?
4
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3answers
671 views

Can OpenLayers layers in QGIS have transparency?

I often would like to set the basemap back by lowering the transparency. I would love to have this option in QGIS for OpenLayers layers, such as the stamen layers, google, etc. Is this possible? I ...
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0answers
139 views

How do I stop polygons from a .kml layer disappearing as I zoom in on the layer?

I am relatively new to GIS stuff and have a query about .kml files in QGIS. I have downloaded the .kml filefrom ...
1
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1answer
130 views

Modify 'Codepoint with Polygons' to add new fields

Sorry if this is a simple question - I'm just beginning in QGIS. I'm using OS Codepoint With Polygons data set which provides shape files of each Postcode area within the UK. Within each postcode ...
4
votes
1answer
324 views

How to measure the distance of multiple points to a line

I have two shapfile in QGIS to which I am trying to find the distances between. I have a shoreline which is a vector line and then I have hundreds of data points in the ocean. What I am trying to find ...
2
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0answers
306 views

Transform RGB-Map to CMYK (qgis, opensource tools)

I want to print a map I made with qgis. For the print I need CMYK-colors but the print-composers pdf-output is RGB. How can I convert the RGB-map/-pdf to CMYK?
1
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1answer
139 views

How to run “create mask” from the console?

There's a plugin called "create mask" for qGIS and trying out some simple scripting from the Python console. I would like to call it after I select the vector features I want, then do more related ...
6
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1answer
77 views

Is there a way to select only a certain polygon for editing?

I have a spatialite data base with 4300 polygons contained within. I wish to be able to edit the polygons but once i have highlighted the Polygon from the attributes table i find it hard to edit the ...
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0answers
58 views

Avoid rounding of coordinates in pyQgis

If I get the coordinates of a polygon in qgis by x = geom.asPolygon() It rounds off the coordinate from i.e. -27,200,334.86 to -2.72003e+07 How can I avoid that?
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2answers
147 views

loading CanVec directory full of .shp files

I'm totally new to QGIS, and trying to view a Canadian Topo map as published on an iMac - I don't want to change it. ...
1
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1answer
81 views

How do you Select an existing vector Layer and Edit it, using python?

I'm developing a small plugin that needs to be able to select a vector layer programatically based on what layer the user has selected. However I'm not sure how to do so. I believe I found the two ...
3
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3answers
144 views

QGIS Python Intro Text

After reading replies regarding starting a mapping business, I think I'd better read a Python book. Any intro-level Python books to recommend? Mila
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2answers
1k views

Total of attribute field of point layer per polygon layer

I have a polygon shapefile of many lakes, I also have a point shapefile of locations on those lakes where fish were caught. The point shapefile contains the attributes: Fisherman_iD, Fish_Caught, ...
2
votes
1answer
152 views

Setting coordinate systems in QGIS: “transform error caught”

I'm learning how to use QGIS (v 1.8.0 "Lisboa") on Mac OS 10.6.8. My goal is to create a simple county map of Illinois using the base data shapefiles available from the Illinois Natural Resources ...
1
vote
1answer
93 views

Why can I only see a default list of KML attributes in attribute table?

I converted a shapefile to kml using ogr2ogr. Glancing at the output, it looks correct -- it has a <Schema ...> and each <ExtendedData> references the schema (I uploaded a snippet here). ...
6
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3answers
447 views

How to Display Overlapping Lines?

I have multiple line layers that represent bus routes and many of the routes overlap (i.e. near terminals, transfer locations, etc.) Is there a function in Qgis which will display both features ...
0
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1answer
168 views

QGIS not Printing to PDF [closed]

Simple QGIS 1.8.0 not printing to PDF. Suddenly stopped. Is this an error or something. the resultant PDFs are blank pages. When i file print and use a pdf printer it creates blank docs. when i ...
3
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1answer
98 views

How to select features by matching attributes of two SHPs?

I have one line shape file with lot of road sections and a point shapefile, some of these points are outside my area of interest. The files have one attribute in common and I would like to do ...
2
votes
1answer
739 views

QGIS Zoom from python console

What are the commands to apply all types of zoom (full, on selected layer, etc.) in python console? I'm searching both on pyqgis cookbook and API documentantion, but I'm not finding anything ...
1
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1answer
269 views

Rasterize vector with gdal

"I would like to calculate the Euclidian distance from a residence to a public service of interest e.g. the distance from a residence to a green space (as the crow flies) in QGIS. After browsing the ...
2
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2answers
1k views

Extract coordinates from vector layer in PyQgis

In Qgis, I have made a polygon, and from that polygon I have made a vector grid via research tools-> vector grid. The grid covers the entire polygon. Now I want to extract these grid points in the ...
8
votes
1answer
505 views

How to create a Human Trafficking Heatmap in QGIS?

I'm trying to create a heatmap with about 325 points distributed around the city of Houston. (FYI Houston is a major human trafficking in the US: a title shared with LA and Atlanta depending upon ...
2
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0answers
171 views

How to use Memory layers in QGIS plugin to store results of Geoprocessing tools

I'm building a plugin to perform Multi Criteria Analysis (yes another one...). As part of my workflow intersecting vectorlayers is needed. I use QgsOverlayAnalyzer.intersection (a pity union is not ...
1
vote
1answer
146 views

Is the QGIS plugin repository broken?

I'm connected to the QGIS plugins repository, using QGIS 1.8.0 on Windows 8.... and although I can see a total of 119 available plugins, I can't see Sextante anywhere in the browser. I tried ...
5
votes
1answer
765 views

Does anyone know the proj4 Coordinte Reference System command line for Rectangular Polyconic Gores?

I am a GIS beginner using QGIS 1.8.0 I am trying to transform a world map from the standard WGS84 Coordinate Projection System to a set of rectangular polyconic gores, with a gore count of 12. ...
1
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1answer
232 views

how to find share segments between two shapes (line) using QGIS?

I have two line shapefiles. I want to find between them, where are located all share segments and extract the new selection shapefile. Can anybody help me? I am using Quantum Gis. I know that in ...
2
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0answers
400 views

z-Coordinate and interpolation plugin in QGis

I've a csv file that includes weather stations locations (x,y,z) and precipitation values. I loaded the file by using add delimited text and then converted it into a point shapefile WS84. By using the ...
4
votes
1answer
770 views

How to customize label color in QGIS: Data defined label settings? Expressions? Both? What are the steps? [duplicate]

Updated to show more current screenshot and clarified the question (Which tools? What are the steps?) I'm learning QGIS (1.8 "Lisboa" for Mac). On the QGIS Layer labeling Settings window there is a ...
3
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3answers
2k views

How to create lines between pairs of two coordinates?

I have a table with pairs of points. Out of that I want to create a line layer (that keeps all attributes of the table). One line for each raw from point to point. I want to calculate the length of ...
2
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1answer
275 views

Why are JPG files invisible in Georeferencer?

I want to georeference a jpg file (map) with QGIS 1.8.0 on a Windows 7 (64 bit) machine. The georeference window opens, but the map is not visible. When converting the jpg file into a tif file (e.g. ...
6
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2answers
843 views

Tilemill Dynamic Tile Generation

I have recently used Tilemill and I wish to implement it for dynamic tile rendering.As I've seen an CartoDB doing in cloud system,they can query & generate dynamic tile for request with UTFGrid. ...
2
votes
1answer
93 views

Where can I get a comprehensive list of Rules expression operators?

I'm selecting and styling my points layer on a contour map of Philadelphia using Rules Based Styling. (see: Can I use rules based rendering in QGIS to select features?). The filtering process using ...