Tagged Questions

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

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5
votes
4answers
1k views

Spatial Query from PyQGIS?

Is it possible to reach the Spatial Query plugin functionality in QGIS from a Python script (PyQGIS)? If so, how do I accomplish this? Haven't found any documentation for it, even in the C++ API ...
4
votes
1answer
379 views

How to customize QGIS for vehicle tracking?

I'm doing a project on vehicle tracking using GIS - for that I'm using the open source software package QuantumGIS (QGIS). I would like to know how to customise QGIS using the python console to edit ...
5
votes
1answer
3k views

How to capture a rectangle within the Quantum GIS software?

I want to use "capture polygon" function in QGIS software to draw the indoor office cubical which is a rectangle shape. But the "capture polygon" function is not able to draw a perfect rectangle ...
3
votes
2answers
1k views

How to insert geometries from shapefile into existing table?

I'm running into a problem trying to figure out how I should insert a GIS coverage polygon into an existing table. I'm primarily using QGIS and the PostGIS Manager plugin to handle it. After some ...
3
votes
2answers
583 views

How much information does QGIS's OpenStreetmap Plugin download?

I am using the OpenStreetmap Plugin for QGIS to download the information for my university extent. The information as I see is downloaded in vector format divided into Points, polygons and lines... ...
0
votes
1answer
724 views

Integrate QGIS with ASP.NET MVC3

I'm completely new to GIS and i'm trying to work my way into this. My goal is to integrate a simple map created using QGIS with my asp.net web mvc3 application. The main objectives would be to show ...
2
votes
2answers
2k views

Is there any tool/plugin for QGIS to easily select feature and edit attributes

I need to select polygons and change some attributes in a shapefile. I'm using Quantum GIS - I select the polygon, open attribute table and edit the attributes I want. I know there must be an easier ...
4
votes
1answer
1k views

Union, Dissolve, Buffer — multiple layers, all in one step?

I'm a new user of Quantum GIS (1.7.3) and I need to repeat a task multiple times, so I'm wondering if there is a quicker way to do the following (with three or more polygon layers - each layer has a ...
2
votes
1answer
327 views

How to query OSM tags by polygon?

I do not know whether something like this is possible but nonetheless. If I understand OSM correctly all objects essentially have associated tags based on type of object (street, building etc) ... ...
6
votes
2answers
3k views

how to create a new postgis database for usage with QGIS under windows

After installing postgresql with postgis under windows xp I have 3 databases: postgis postgres template_postgis now I try to create a new spatially enabled database in pgAdminIII: I select ...
0
votes
1answer
218 views

Running database operations against a stored GIS geometry

I'm using Quantum GIS and Postgres with the GIS extensions to store shapefiles that I'd like to run point in geometry and point in union geometries against. While it's easy to save and load the vector ...
1
vote
1answer
463 views

How to create a profile with profile points at discrete altitude intervalls, e.g. each 10 m

In both SAGA and QGIS theres a profile-from-line-function that does a nice job of creating profiles. But there's no way to control the altitude spacing. Any ideas for workflows that would allow me ...
4
votes
2answers
1k views

Using QGIS, how can I add a bounding box attribute?

I have a shapefile where I am exporting the features to GeoJSON objects with ogr2ogr based on a simple where clause. One thing that I would like to be included in the GeoJSON object is the 'bbox' ...
2
votes
1answer
584 views

Select vectors overlapping a raster

I have a raster layer with travel times from a specified point in my city's downtown. What I'd like to do is select all of the census blocks that lie at least partially within 45 minutes of downtown ...
1
vote
0answers
388 views

How do you convert a bounding box into the canvas CRS?

I need to convert the pixel coordinates of a bounding box to the same CRS being used by an existing layer. Here's the relevant code so far: # First, get the layer-coords version of the bounding box: ...
6
votes
1answer
2k views

How to copy a geometry from one feature to another without attributes?

With QGIS it's easy to add a new part to an existing feature/geometry but I can't see how to copy/paste this part from another existing feature/geometry. Is it possible? Thanks
2
votes
1answer
830 views

QGIS and satellite images band combination

When I add a satellite images as a raster in QGIS: 1. Why the image is changed, it looks like it has only one band?; 2. where is a tool for band combination? Thanks!
5
votes
3answers
1k views

Using GIS for Interactive Floor Plan

GIS is brand new to me, but I've spent a couple of days researching so that I can at least ask somewhat intelligent questions. I've decided to use QGIS I need to do an interactive floor plan on the ...
6
votes
2answers
932 views

How to create regular soil sampling grids?

I need to be able to set up a soil sampling grid at regular spacings of around 50 - 100 meters. Then export the points to a GPS so I can be guided to the points. I am new to GIS and have tried to do ...
7
votes
2answers
2k views

Cannot add plugins to QGIS on Ubuntu 11.10 Oneric

I have installed Qgis on ubuntu. it works fine but I am not getting option to add new plugins only option to manage plugins is available. Please help
14
votes
2answers
1k views

How to generalize a polygon file and maintain topology in QGIS?

my problem: I have a polygon-file in shape-format, which I need to generalize. How can "split" the polygons into lines, generalize and than "rebuild" the polygons, so that I can ensure, that there are ...
5
votes
1answer
411 views

How to divide a polyline by intersecting isochrones

I have two shapefiles, the first representing a path (a polyline with a single category), the second representing isochrons from the same origin (point 0) which intersect the above mentioned path. I ...
5
votes
1answer
2k views

How to set QGIS Python path so that I can use system packages on Windows?

Several Python packages are best installed with a Windows installer. But those installers install to the system-wide Python directory. How do I set the Python path in QGIS? I tried setting PYTHONPATH ...
6
votes
2answers
6k views

How to add feature class from ESRI personal geodatabase (.mdb) in QGIS

How do you add a feature class in a ESRI personal gdb in qgis. I understand this can be done through the option add vector layer and select geodatabase. But what after that ? It doesn't allow me to ...
10
votes
1answer
389 views

What is the best way to represent bridges using a point vector layer in QGIS?

I'm working on a hiking/biking maps of trails in the woods which sometimes have bridges that need to be shown on the map. I'm trying to figure out the best way to capture and represent them using QGIS ...
5
votes
3answers
409 views

QGIS Gazetteer query without adding data to canvas

I have a PostGIS database with 30 million gazetteer points, each have an X Y coordinate. I want to query this and then zoom map to location. However, I dont want to add the data to the project because ...
18
votes
1answer
4k views

How to define new custom projections in QGIS?

I'm trying to define a projection in QGIS. I want to add North America Albers Equal Area Conic. From the spatialreference site I copied the proj4 line: +proj=aea +lat_1=20 +lat_2=60 +lat_0=40 ...
1
vote
1answer
681 views

1-band raster colour table workaround in QGIS

Does anyone know what the workarounds are for the 1-band raster colour table plugin in QGIS? Currently I find it will run once, then crash on the second iteration. The workaround I use is to delete ...
2
votes
1answer
607 views

How do I subdivide and edit polygons preserving topology?

I'm using QGIS. I have a layer made up of many adjacent polygons - let's call them "countries". I currently use the Atlas plugin to export each "country" polygon to a .png file. I want to further ...
3
votes
3answers
840 views

Design fiberoptic network in QGIS?

I'm a GIS newbie trying to design a fiberoptic network in QGIS. What I'd ideally need is to draw lines on top of a map or orthophoto, assign a name/id to each line and a type. Get a list of all the ...
4
votes
3answers
760 views

How to create network simulation / temporal models for videos?

I know of ArcGIS Tracking analyst and QGIS Time Manager. I have a transportation network with time based schedule for buses. I will create time aware shapefiles from this data. Is it possible to ...
1
vote
1answer
75 views

Are there Bookmarks with selection highlighted in QGIS?

I have a search query on the attribute table which highlights the features and then zooms to that particular layer. I take a bookmark for this particular view with the selection being highlighted. ...
-2
votes
1answer
1k views

I need QGIS routing plug-in [closed]

I am new to pgrouting. How does it work? What benefits can I get from it? I tried the examples, read some articles, but could not find the QGIS routing plugin for Windows. It is not showing up in the ...
2
votes
2answers
294 views

Is code completion available in QGIS Python Console?

I wanted to know if the autofill functionality is available in the python console for QGIS as the one available in ArcGIS Desktop's Python Console or am I supposed to hardcode it.
1
vote
2answers
735 views

Resources for python scripting [duplicate]

Possible Duplicate: QGIS tutorials and resources I would like to know regarding the available resources for starting to learn about python scripting for QGIS.
0
votes
0answers
258 views

Missing QGIS python plugin database connectors

I am working with python plugins for QGIS.I developed my plugin and inorder to incooperate the same into QGIS i copied the folder in C:\Documents and Settings\comp90\.qgis\python\plugins I opened ...
4
votes
2answers
4k views

How to give multiple colors to features within a single shapefile?

I want to give multiple colors to different features within a shapefile based on attribute values , is this possible in QGIS ? If yes what is the procedure ? Is there a way to provide color by means ...
13
votes
6answers
5k views

Why is the performance speed between ArcGIS and QGIS so different?

Ok I am not a programmer but a prolific GIS user. I know that QGIS is written in C++ and ArcGIS in ??? but for most of my tasks lately I always try to use QGIS not only because it is free but due to ...
4
votes
6answers
7k views

How to divide a single polyline feature into multiple features based on points located on it?

I have a shape file that contains the bus route information for a city. I want to do two things.. Merge all the existing rows so that just one feature represents all the routes... I have a Points ...
2
votes
2answers
160 views

After two buffers operations (+/-), why is the result file bigger than the original?

First file ( .shp ) had 1000KB, after 2buffers ( buffers on polygon, 1st buffer +100, 2nd buffer -100 ( small things near polygon should be removed )) in quantum gis file grown to 1500KB, and after ...
21
votes
5answers
4k views

Is there any model builder in QGIS or other open source GIS?

Like the ModelBuilder of ArcGIS for Desktop to run simultaneous geoprocessing tools, is there any model builder available in QGIS or any other open source GIS software?
0
votes
1answer
151 views

Selection not displaying all results in QGIS

I have a point layer. Of which I have just selected 15 points from the attribute table manually and say show selected attributes. Of these 15 one point does not get highlighted the rest do fine. When ...
1
vote
2answers
2k views

How to save project with data source path as relative in QGIS?

Is their an option in QGIS to save the project with the data source being relative path. I Dont see the option here.QGIS Wroclaw1.7.3
2
votes
2answers
3k views

Can two polygon layers be merged in QGIS on a common id?

Can two polygon layers be merged in QGIS on the basis of a common id? Update: Ok , the dissolve tool works fine. But for instance lets say I have 10 polygons. 8 of them are together , so when ...
4
votes
2answers
5k views

How to use Distance Matrix tool in QGIS?

I have a point data set. Now there are cluster of points based on a field. So I take out one such cluster which has points with same field.I want to find distance between all the points in cluster and ...
11
votes
4answers
3k views

Is it possible to export GeoPDF from QGIS?

Is there any plugin for QGIS which would help me in exporting the map document as a GeoPDF ?
7
votes
2answers
1k views

How to animate raster time series using open-source GIS?

I have a bunch of rasters taken about 10 minutes apart, and I have a nice QGIS project that produces pretty enough maps of them. I'm wondering if there's a way to animate this raster series, with a ...
20
votes
3answers
4k views

How can I calculate the average width of a polygon?

I'm interested in examining the average width of a polygon that represents the road surface. I also have the road centerline as a vector (which is sometimes not exactly in the center). In this example ...
1
vote
2answers
925 views

How to get the altitude of the vector shapes from DTM raster layer?

I have a vector layer containing thousands of vector shapes/polygons and a raster layer with DTM. Every shape has its own OBJECTID in attribute table. I would like to get the altitude of every shape, ...
4
votes
1answer
438 views

How to display intersecting roads and create multiple labels for long roads in QGIS?

I am new to GIS and I am using Qgis 1.7.3 on Windows. Can any one please tell me how to display a map from line shapefile with these two characteristics: Roads are displayed with borders at the ...