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

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67 views

How to identify to which polygon a point belongs to?

I have 3-4 polygons containing lots of lon/lat points. I want to identify to which polygon a specific point belongs. Any help in this matter is appreciated.
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0answers
155 views

How to fix “Error processing specified tolerance!” in Polygon Centroids tool?

I am using QGIS 1.8.0 to find the centroids of 92 features (i.e. smaller polygons) in a polygon layer. However, while using (Vector -> Geometry Tools -> Polygon centroids), I encountered the ...
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3answers
332 views

clipping polygons (vector) map with a polygon (vector) layer

A frustrated newbie with QGIS Lisboa version in Windows 7. I want to clip a soil map (multiple polygon vectors) with a single polygon (rectangular polygon vector). The project projection is set at ...
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0answers
375 views

GRASS Plugin to QGIS error

I am installing QGIS and GRASS as part of an FOSS GIS class I'll be teaching this summer. I used the OsGeo4W installer. This installer has always worked flawlessly for me except on the machines at the ...
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1answer
361 views

Problem to clip a raster with a shapefile

I need to clip a rasterlayer with a vector layer. When I try this, the following error appears: **ERROR 1: Attempt to create 0x0 dataset is illegal,sizes must be larger than zero.** What am I ...
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2answers
222 views

Data points Imported into QGIS are in the middle of ocean

I'm new to QGIS and tried importing some GTFS data in the CSV format (stops.txt). The project CRS, base map CRS and GTFS CRS have all been set to Google Mercator, but the points that are supposed to ...
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1answer
746 views

How to create a 3D shapefile from a raster?

I´m trying to make a 3D shapefile from a raster feature but not working. Tried already to run the command in OSGeo4W but nothing happen. I'm using the Qgis 1.8.0 Lisboa. The purpose is to get a final ...
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2answers
164 views

How to handle adding a PostGIS layer in pyQgis without saving password?

I'm writing python plugin and trying to find the right way to add PostGIS layer on the map without storing user password. After adding layer on the map, I strip out the password from uri like this: ...
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1answer
416 views

How to address the new “Task-Completed” QgsMessageBar in Python?

I am really amazed what huge steps the QGIS development has taken in the last months. The new iconset, the improved Print composer and many more changes to be seen in QGIS 2.0 are really awesome! ...
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1answer
640 views

QGIS - Save as GPX [duplicate]

I would like to convert .shp into .gpx. I tried to "save as" gpx but it gives an OGR error: creation of field ObjectId failed (OGR error: Field of name 'Name' is not supported in GPX schema. Use ...
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1answer
193 views

How to enable label orientation?

Mac OSX 10.6.8 QGIS 1.8.0 : I'm mapping an area that's a rectangle slanted at 26 degrees, and neighbourhood maps are always printed so the rectangle is horizontal. I'm trying to make the labels ...
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1answer
96 views

Vector Layers are not lining up and are scaled differently

Hey I am a first time user of GIS and I am working for a transportation map of North Carolina for a project at my work. So what I have been doing is first placing the Tiger County Boundary by using ...
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1answer
97 views

With multi-line labels, how to show the 2nd line only for labels that need it?

Mac OSX 10.6.8 QGIS 1.8.0 : I've two columns in the attribute table, name, and name2 for those labels that need to be 2 lines; multiline labelling is checked. But when I use "name"||'\n'||"name2" I ...
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2answers
369 views

QGIS Field Calculator Results Removed When Saving Edits

Mac OSX 10.6.8 QGIS 1.8.0 : Using the field calculator from the attribute table, the $area of each feature is shown nicely in the table until I try to save it, then all the values are replaced by NULL ...
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1answer
77 views

Why can't I see any joined string fields for categorization?

After the join I can see all my data in the attributes of the card but when I want to select statistics in the tab style to categorize, I don't see them. I see that the real type variables and not ...
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0answers
39 views

Do I need to deal with warnings about row count and spatial index to use pgRouting?

After read this nice post from underdark A Beginner’s Guide to pgRouting, although I still have some little problems, I think I can begin the "Creating a routable road network" stage right now. I got ...
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1answer
345 views

How to add one or more points to an existing polyline or polygon?

Using the following code, I make a polyline with two points. vl = QgsVectorLayer("LineString", layerName, "memory") pr = vl.dataProvider() vl.startEditing() fet = QgsFeature() ...
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0answers
198 views

Compilation of QGIS master branch under CentOS 6.3

I tried to compile QGIS master branch 1.9 (qgis-Quantum-GIS-b99ff61) under CentOS for many hours now as explained here and here / here Compilation: [ 7%] Generating ui_qgsmapserverexportbase.py ...
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1answer
107 views

How to check if two qgsPoints are equal in PyQgis

I have two points: a=QgsGeometry.fromPoint(QgsPoint(227739,908343)) b=QgsGeometry.fromPoint(QgsPoint(227739,908343)) but when I run: a==b it returns False. What am I doing wrong? Update: it ...
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1answer
643 views

QGIS python location problem

It seems that MacPorts installs Python27 in /opt/local, but that MacPorts QGIS updates and uses the Apple Python27 in /Library. The result is that MacPorts additions to Python27 such as OpenCV don't ...
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1answer
129 views

How to save after using fet.setFeatureId in pyQGIS?

By using the following code, I want to change the id of the line when saving the line. But the setFeatureId command, gives a false when doing the commitChanges(). Any idea how to change the id? vl = ...
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2answers
224 views

How to write an equivalent to MapBasic's CreateLine in pyQGIS?

I know this kind of question has been asked, in part, before - specifically: Seeing QGIS Python Commands and: How is object created as line using createline stored in .tab file? but this is a specific ...
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1answer
350 views

How to store selected attributes of vector layer using PyQGIS

I'm following this PyQgis workshop: http://www.qgisworkshop.org/html/workshop/python_in_qgis_tutorial2.html#accessing-data-attributes I have a point layer shapefile. I want to be able to retrieve and ...
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3answers
647 views

export 3D data dxf file

I'm trying to export a DXF file from Qgis1.8.0 Lisboa and can not have a 3Dfile in Autocad! Or micristation. It results always in 2D file. How can I export height data from a shape file in Qgis? ...
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1answer
420 views

Varying Line Widths According to Attribute Values

I'm trying to draw a vector map of Europe on QGIS 1.7.3 with lines symbolizing the transmission of energy (power transmission lines) between the different countries on the map. I am trying to ...
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0answers
90 views

'D8 Slope Grid' in Sextante-QGIS is not working

I can't make 'D8 Slope Grid' work in QGIS-Sextante. 'Pit Filled' and 'D8 Flow Direction Grid' output work okay. I used the function: Geoalgorithms > Uncategorized > Basic Grid Analysis tools > D8 ...
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2answers
2k views

How to convert Shapefiles to 3D DXF?

I'm using QGIS version 1.8.0-Lisboa and I'm trying to convert a vector line file and it's not working. I right click on the layer>Save as>Autocad file>DXF. After that I try to open the output file in ...
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1answer
117 views

problems about setting pgrouting with QGIS under windows

I followed this website:A Beginner’s Guide to pgRouting and now facing some problems. I finished steps before "Creating a routable road network", and open QGIS 1.8, click the PostGIS Manager plugin, ...
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0answers
51 views

Problem with compilation

I have tried to compile Quantum GIS by it's source code on Windows 7 (32 bit).i have follow it's installation guide.i have download and install all it's dependencies . i have run it on C-Make but it ...
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2answers
180 views

How to create a line from more than two points?

I have a loop which calculates two points for each iteration (x3,y3) and (x4,y4). As seen in the code these two points are added for each iteration, which gives i-1 lines. Each line has a individual ...
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2answers
441 views

Flow modeling and FOSS GIS; lahars and HEC-RAS

What are the options for FOSS flow modeling of dilute debris flows in QGIS or GRASS? Have you, or can you refer me to studies where the authors, tested these models/plugins/functions/etc. for use in ...
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0answers
408 views

How to calculate weighted mean coordinates within polygons?

I'm using QGIS 1.8 on OSX 10.8.3. I have a polygon shapefile of all of the US state legislative districts. I also have a layer of points that are centroids of US Census Tracts, with a field for the ...
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1answer
742 views

Multiple reclassification using RasterCalc in QGIS [duplicate]

Is there any way to perform multiple reclassification using RasterCalc? For example reclassifying value 1 to 100 in map Map can be written as: eq([Map]@1, 1, 100) But if there are multiple values ...
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1answer
556 views

How to clip raster by multiple polygons in multi rasters?

Using QGIS, I want to clip a raster by multiple polygons contained in a single shapefile. I read that gdalwarp can clip my raster by multiple polygons BUT the output is a single merged clipped raster. ...
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2answers
203 views

Is there a way to call the clip function in pyQGIS from the python console?

Is there a way to call the clip function in QQGIS from the python console? It is found under geoprocessing tools in the vector menu.
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2answers
952 views

How to add a column in QGIS via python

I have a point shapefile and a polygon shapefile in QGIS now I want to use the point shapefile's value add to polygon shapfile(be a column in the end) there are colors with each value and make the ...
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2answers
123 views

Manually add a new point to PostGIS table [duplicate]

I did accidently delete a table row - or well, in fact a whole subway station. My attempt to solve the problem was this PostGIS function: ST_GeomFromText('POINT(coordinates)') But then PostgreSQL ...
3
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1answer
118 views

Differences in raster extents in gdalinfo, SAGA & Quantum after resampling

I recently resampled a raster file using SAGA's Resampling module. The aim was to widen the extent of the new raster to two decimal places, where the original raster has three decimal places. The ...
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2answers
335 views

What's the correct transformation for Lambert Conformal Conic for Wyoming?

I am a newb in QGIS. I have loaded QGIS 1.8 (Lisboa) and practicing with a number of maps for portions of the state of Wyoming. My maps are mostly in UTM 12N NAD 27 & NAD 83 some are in decimal ...
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1answer
299 views

matching a border of one polygon to another [duplicate]

I have a polygon (A) that I drew the eastern border of in QGIS. I have another polygon(B) whose western border I want to nest against the eastern border of polygon a so they are touching but not ...
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2answers
185 views

Problem with reprojecting raster from MGI 6 to WGS

When I reproject a raster from Mgi 6 to WGS 84 using Warp in Quantum gis it makes mistake ( about 380m). Is there any way to avoid this?
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2answers
236 views

Autocorrelated DEM with QGIS or Grass

I was wondering if there is a way to make an Autocorrelated DEM within QGIS or Grass. I am looking to do this with stereo aerial photography. I am able to do this with a number of COTS tools, but I ...
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2answers
1k views

QGIS Server limitations?

QGIS Server seems to be fairly simple to setup and create services, however I'm wondering if there are any limitations with using it opposed to MapServer or GeoServer. My current server ...
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2answers
871 views

Reducing the resolution of a huge raster

I'm not much of a GIS user, but I've got a big ascii file that I'm trying to convert into a lat long data x1 y1 d1 x1 y2 d2 x1 y3 d3 x2 y1 d4 ... etc format, so that I ...
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5answers
1k views

Where to start learning how to make maps with QGIS?

I have no skills in GIS, "map-making," or any other map program. Been a county planner for 25 yrs, where there was always a "drafting" staff. I'm in another agency now and need to be able to produce ...
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1answer
352 views

How to calculate all paired shortest path using PyQGIS?

The code for shortest path analysis with PyQGIS specifies start and end nodes explicitly: pStart = QgsPoint( -1.37144, 0.543836 ) pStop = QgsPoint( -1.1027, 0.699986 ) ...
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0answers
131 views

Event Layer plugin - setting/verifying z coordinate (Measure attribute)

I've loaded a shp file (ROUTES.shp) layer containing geometry for highway segments with a ROUTE attribute for each. I understand that the plugin uses the "z" coordinate of the shp file segments to ...
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1answer
402 views

How to label each polygon in a layer?

QGIS 1.8.0 Mac OS 10.6.8: I want to label each polygon in a layer in a similar way to this image (done in WP Presentations) and am totally confused by the manual. Obviously I have to find a list of ...
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1answer
145 views

Modify CRS to match boundaries of shapefile

I have boundary data in WGS'84 lat/long and data in a custom generated CRS. The data in the generated CRS appears to be offset by a particular vector compared to WGS'84. I want to attempt to match the ...
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1answer
313 views

How to join nodes to network lines ( and not the other points)

I'm trying to do a shortest path analysis on my network. In order to prepare the network and attach polygon centroids to the roads, I used GRASS' V.NET operation=connect. the problem with this ...