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

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2
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5answers
3k views

Is there any way to extract coordinates of a road segment using QGIS?

I add my own road vector data on top of Google map using open layers plugin with QGIS. The vector layer is generated using PostgreSQL DB. Is there any way to extract coordinates of a road segment ?
4
votes
1answer
357 views

Looking for a SVG library for construction

Would anyone be able to suggest a good library for svg symbols for construction please? To be used in QGIS. Ideally water and pipeline network symbols. ciao
6
votes
1answer
564 views

PostGIS query vs QGIS filter

I have a PostGIS dataset with around 3 million shapes. I only need to view about 1,500 of these shapes at any given time, but the shapes I need to see depends on which feature is selected in a ...
2
votes
1answer
835 views

What happened to Live GPS Tracking in 1.8.0-Lisboa?

Dang, I was just getting used to Live GPS Tracking in 1.7.4-Wroclaw. I downloaded the new version 1.8.0-Lisboa on another computer. The Live GPS Tracking thing was in the View pull-down menu in ...
1
vote
2answers
1k views

Problem loading vector layer (pyQGIS)

I've installed the qgis on ubuntu 12.04 following the instructions on http://hub.qgis.org/projects/quantum-gis/wiki/Download. I am trying to test the Python API and try to do the follwoing from ...
3
votes
0answers
322 views

Freehand plugin query

I've installed the QGIS 'Freehand' plugin and I have a query regarding it. When drawing a polygon qgis automatically closes the polygon when the pen leaves the graphic tablet. Is there any way to ...
1
vote
2answers
957 views

How to access vector coordinates in GRASS GIS from python?

Is there a way to iterate over lines and their vertices using python? I'm new to GRASS GIS, and it looks like there are ways to read raster (for numpy), but I don't see a direct way to access ...
2
votes
1answer
1k views

Basic User Questions: Tracing a Border in QGIS

The project: I'm plotting a dilapidated cemetery, I'm using GPS waypoint data to plot the headstones in QGIS. The map I'm making is to show the orientation of the graves, and who is in them. I ...
3
votes
3answers
5k views

Calculating the minimum distance between points and polygons in QGIS

I have two vector layers: one point and one polygon and I want to calculate the minimum distance of each point from the polygons (ie the distance from the closest point of the closest polygon). Is ...
1
vote
1answer
962 views

Concatenate Fields into One Field in QGIS

I have seen some posts on this, but only for ArcMap. I am looking to take a range of values from two fields and concatenate them into one field to make a unique value. For example: XMAX YMAX ...
4
votes
1answer
934 views

How to reclassify in Rastercalc?

I now need to reclassify, I'm using rastercalc... but I can't get the syntax right!! I need that values >0 become 1 I found this example... eq( [relief]@1, [mask]@4, 150 ) so I tried: ( [raster A ...
5
votes
1answer
2k views

How to perform Ordinary Kriging in SAGA via QGIS SEXTANTE Plug-in?

I'm trying to learn how to apply the kriging analysis in QGIS using the SEXTANTE plug-in and SAGA tools. It appears that I have my SEXTANTE and SAGA folders configured properly according to the user ...
0
votes
1answer
248 views

How to find embedded Coordinate Reference system in a Layer

I want to find CRS in an added shape file. Ex. In Arc GIS if we go to Layer Properties and Source we can find embedded CRS to a layer. How to find in QGIS, embedded CRS ia a layer/ Shape file??? I ...
6
votes
1answer
2k views

Features to 3D from 2D in QGIS

Is there a way to convert 2D features to "3D" features in QGIS? I know there is a way to do this in ArcMap by using an attribute value in the attribute table, but I am looking to do this with ...
2
votes
1answer
226 views

How can i include program form (created in Designer ) to my QGIS plugin?

How can I include a form created in Designer in my QGIS plugin? And how to get controls values (textbox,label,etc)?
3
votes
1answer
1k views

How can I add button to the QGIS toolbox or create my own toolbox?

I want to create a button and add it to the QGIS toolbox or alternatively create my own toolbox and add the button here. A plugin should be started when the user clicks the button.
1
vote
0answers
2k views

download and installation of sample data [closed]

I have downloaded the sampe dataset under "my documents". When I extract the contents of the zip file, the only folders that are actually installed, are "gml", "gps" and "shapefiles". Thus, ...
1
vote
1answer
1k views

How to install sda4pp plugin with missing repository in QGIS

I see that the repository for the sda4pp plugin went down in 2011. Does anyone know if there is another way to download the plug-in with the repository missing? If this plug-in is no longer ...
2
votes
1answer
216 views

Can't load PYQGIS

I get this error; any comments Couldn't load PyQGIS. Python support will be disabled. Traceback (most recent call last): File "", line 1, in ImportError: ...
4
votes
1answer
163 views

Where are the Spatialite settings stored?

after moving a spatialite-database to another directory, qspatialite says "Can't connect to Database" / Error unable to open database file. Even no project is open or I try to create a new project. In ...
5
votes
5answers
10k views

How to break a single polygon into multiple polys?

I created voronoi polygons after which I dissolved them on the basis of one attribute. Now there are cases where in for one single attribute "abc" I have3 polygons at different places with same object ...
10
votes
5answers
2k views

How to identify duplicate attributes in a field?

I have a point shapefile with thousand of points. It has an ID code field that supposed to be unique. Every now and then the data entry clerk wrongly type the id creating duplicates.Right now I'm ...
1
vote
2answers
604 views

How to fix Error 14 — Unable to open ~/.qgis//qgis.db?

I get this error: Error 14 -- Unable to open ~/.qgis//qgis.db -- QGIS version 1.8.0-Lisboa -- Ubuntu 12.04 It was discovered when I tried to define a custom CRS and save it under: settings/custom CRS ...
9
votes
2answers
311 views

How do you protect your PostGIS credentials when using QGIS 1.7?

I'm fairly certain this should be a community wiki, but I don't know how to make it one. So if an admin sees this please change if appropriate. So.....How do you protect your PostGIS database data ...
3
votes
1answer
537 views

Correct ASTER with SRTM or Topographic Map

I have a problem with my DEM again. I decided to use ASTER GDEM2 (for different reasons). ASTER GDEM2 have its problems, I know, and I dont want to discuss that again. I have to use it, because SRTM ...
6
votes
4answers
1k views

How to sum up pixel values in QGIS?

I need to know the value of the sum of all pixels in a raster. However, in the Statistics section of the Metadata tab in Properties, under Sum of All Cells it always indicates 0.00. I have tried with ...
1
vote
1answer
175 views

Looking for CRS for NAD 83 UTM Zone 30N

I'm curious as to why the UTM zones are incomplete for NAD 83 in QGIS? I have a WGS84 shapefile that I would like to project to NAD83 UTM Zone 30N but can't find it in the QGIS CRS list. I see how ...
3
votes
2answers
1k views

How can I specify the CRS of a raster layer in pyqgis?

I manipulating netcdf raster data from the QGIS python console. The metadata of my netcdf file does not provide the Reference system. However I know it is 'EPSG:4326' I am writing a python script to ...
5
votes
1answer
1k views

How to fill my column with consecutive numbers

I m very new to Qgis, so forgive this simple question. Searching in older topics didn t help either.So: I make a new column in my attribute table and it has a default value(for example 0). I want to ...
1
vote
1answer
1k views

How can I create a custom form to display the attributes of the selected object?

I have already appealed to the selected objects, and found a way how to put them in a MsgBox. But I need to output was in the form
4
votes
2answers
534 views

How to represent an imaginary flat world in QGIS without using a round-world CRS

Like one or two other users, I'm interested in using QGIS to map an imaginary flat world. A previous answer suggested simply refraining from defining a CRS for such a world, but I cannot seem to make ...
1
vote
2answers
464 views

How to batch process (100s) of interpolations in QGIS or other open source software programs?

Is there an efficient way to run 100s of interpolations in QGIS or other open source software programs? I have groundwater contamination data collected from monitoring wells at about 800 different ...
3
votes
1answer
211 views

How to calculate maximum distance to an interpolated value along a contour in QGIS?

I'm planning to enter concentrations of groundwater contaminants collected from well locations into QGIS and then use interpolation functions to create contours of the groundwater plume. Can QGIS ...
6
votes
1answer
125 views

Finding Ring Smaller than a certain tolerance

In Simplifying a shapefile for world timezones http://efele.net/maps/tz/world/ all generalize/simplify algorithms fail on 5 countries/states, shown in this shape file ...
3
votes
1answer
148 views

How to display a particular area?

Hy, I'm developing a plugin in python for Qgis. I would like the user to select a particular area in a list (let say a country list) and zoom in the map on the corresponding area. Actually I'm ...
0
votes
1answer
190 views

Qgis : QGraphicsTextItem's position not updated?

I'm using QgisInterface->mapCanvas()->scene()->addItem(QGraphicsTextItem) to add a QGraphicsTextItem to the map canvas. The problem is that when I use the pan tool to move the display the added ...
0
votes
0answers
62 views

How can I create form with controls using QGIS(python)? [duplicate]

Possible Duplicate: How do I build a custom form for entering attributes in QGIS Help me, please create a form with controls using QGIS plugin. Thanks!
5
votes
2answers
5k views

snapping polygons and lines

I recently downloaded QGIS on a Mac OSX 10.7.4 (lion) and purchased a master map shape file, of a particular area. I am trying to divide it into polygons following features on the master map vector ...
6
votes
1answer
2k views

Why does QGIS Simplify Geometries delete entire polygons?

I am reducing the size of a world timezone shapefile, http://efele.net/maps/tz/world/tz_world_mp.zip But at a 0.01 tolerance, entire countries disappear Anybody know a way round this? QGIS shows ...
5
votes
1answer
922 views

Auto node drawing tool in QGIS

I'm new to QGIS and am more familiar with MapInfo. I've been playing around with QGIS to do some habitat mapping based on aerial photography and was wondering if there is a feature in QGIS which ...
4
votes
2answers
3k views

How can I extract data from OSM which includes the street names?

I am exporting OSM data (in .osm) files to use in qGIS. I am interested in having the street names displayed. I know they are in the OSM data set because they are displayed when I browse the data ...
3
votes
3answers
272 views

How to visualize the vertices of a graph in QGIS?

I tried to visualize the graph generated by osm2po and rendered that graph in qgis. Now what I am trying to do is plot the vertices in the graph. So that I can visually see where the nodes/vertices ...
3
votes
1answer
192 views

Can Openlayers plugin be faster?

Can the Openlayer QGIS plugin be modified to have better map loading performance? I use only google satellite/maps. Thanks.
2
votes
1answer
1k views

Problems with Google layers plugins

I currently use Quantum GIS 1.7.4 at work and I have trouble to open Google layers extension. In fact, when I start QGIS 1.7.4 the following message appears and I cannot use Google layers extension. ...
9
votes
3answers
1k views

How to prevent text labels from overlapping other markers?

Is their a way within QGIS to prevent text labels from overlapping icons used to label a point layer? In the example map shown below, there are two layers: Roads layer which is labeled using the ...
2
votes
2answers
2k views

How to access attribute data type in QGIS?

I've been developing a plugin on QGIS platform using PyQGIS. So far plugin does the following: You can select any feature of the already loaded vector layer in QGIS. After selection, plugin displays ...
2
votes
1answer
742 views

Filtering a raster by pixel value ? (Qgis)

I have downloaded Globcover data in GeoTIFF format. I want to create a new grid which only has values where the Globcover data (the only band in the TIF file) has one certain value (==190). Can I do ...
5
votes
1answer
474 views

How to handle spatial join 10 chars field name limit?

When I try to perform a spatial join between a point and polygon file, I get a notice saying spatial join will not be performed because following field names exceed 10 Characters. Kindly help to ...
2
votes
1answer
847 views

How to draw lines, dashed lines, routes and add images to the QGIS mapcanvas?

I need to draw a rectangle in a map canvas and inside it draw routed dashed lines and add small images to it. These actions are to be performed using the QGIS API. Is there any place with examples ...
1
vote
1answer
337 views

Adding table from Postgis

While trying to import a table containing raster data in QGIS , Raster column is not being imported ... I am getting following messages: Database connection was successful , but the accessible ...