Questions tagged [qgis]

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

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2
votes
2answers
328 views

File paths in a PostGIS Table in QGIS

I have a PostGIS table which I have stored the location of some viewpoint photographs. I would like to store the location of the photo file in a field, but when I add a file path in the attribute ...
11
votes
3answers
10k views

Shapefiles and OpenStreetMap data do not overlap in QGIS?

So I'm pretty new to GIS, and I'm working on a mapping project using data for Vancouver, Canada. I want to combine OpenStreetMap data along with data provided by the City of Vancouver. But the City ...
4
votes
2answers
1k views

How to merge street layers in QGIS for exporting to PostGIS?

Is there any way of merging lots of street data in QGIS and getting one layer for exporting it to Postgresql? I know one method using mmqgis "Merge Layer" tool. It works in Ubuntu but not in Windows....
1
vote
1answer
2k views

How to solve an installation problem involving QGIS, Python, and a plug-in?

In an attempt to get the plugin "Profile Tool" working, I installed geoslib and python Shapely 1.2.10 module as requested using following: sudo port install geos Then install Shapely once downloaded:...
5
votes
2answers
868 views

Invalid Geometry Error after ST_ConvexHull

I've a Postgis table of around 80,000 points and want to be able to populate a second table summarizing the data with convex hulls based on points with a common attribute. For example, the data ...
3
votes
1answer
229 views

QGIS 1.7 + MacOS 10.6 : georeferencing from map canvas bugs

I am experiencing issues with the gdal plugin to georeference a raster. It works fine when I enter the coordinates manually but it does not work when I try to link the plugin with the map canvas. ...
2
votes
1answer
481 views

How to move labels in QGIS using the old labelling method

I would like to use the new labelling method in QGIS, however it does not display labels for all of my polygons. If I use the old labelling method (in the properties dialog) the labels display fine. ...
48
votes
8answers
26k views

Comparing QGIS and gvSIG? [closed]

Many debutant GIS users are asking me which one is better QGIS or gvSIG. Since I use Qgis and I don't have any experience in gvSIG, I aways say that both are very nice softwares and the chose is a ...
10
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3answers
6k views

Generalizing Polygons to MultiPolygons in GeoDjango?

I set up a model with models.PolygonField in geodjango, using postgres as database. I try to import shp into postgres. The problem is, shp (compiled with QGIS) mixes polygon and multipolygon, hence it ...
22
votes
6answers
28k views

Moving vectors to specified coordinates in QGIS?

I have a layer of vectors located around, say, (100, 100), and I want to move them to new coordinate like (1000, 1000). How should I do it using QGIS?
70
votes
4answers
43k views

Visualising WKT geometry string in QGIS

A very simple question: Is there a simple tool in QGIS to graphically visualise geometry formatted as text? Example geometry: "POLYGON((571178 6337246,571178 6402217,598061 6402217,598061 ...
20
votes
2answers
3k views

Polygon gradient fills / tint bands in QGIS

Is it possible to use a gradient fill on a polygon in QGIS? I would like to have my polygons with a colour at the edges, fading to clear/white as it moves away from the edge. The majority of the ...
10
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2answers
3k views

How to label raster cells in QGIS?

I try to show a small resolution raster file in the QGIS Print Manager tool. I would like to show a small label with each cell value (position - circa middle of each cell). How I can do it? Is there ...
11
votes
7answers
23k views

Copying attributes from one polygon layer to another?

I have a problem that I can't seem to get my head around. I have two polygon layers: Polygon A - is a subset of polygon B with the same fields and has identical polygons to Polygon B Polygon B - has ...
7
votes
2answers
653 views

PostGIS uuid type not visible in QGIS or GeoServer

This is probably a simple question, but nothing comes to my mind right now. I have created a view in PostGIS containing multiple columns, including one column of data type uuid. When I try to ...
6
votes
2answers
1k views

How to Match Point Data in QGIS?

How do I match the same points (WGS84) in two different point layers? I want to get the points that lie exactly upon each other in the two datasets.
13
votes
2answers
60k views

Changing unit of measure from degrees to meters in QGIS?

I am running QGIS 1.7.0 on windows, and I donwloaded a shapefile of census block group boundaries from TIGER. This file appears to be in the WGS 84 coordinate system, and when I open it in QGIS the ...
7
votes
2answers
3k views

How to calculate perimeter of polygons in Quantum GIS?

Is there a way to calculate perimeter of polygons with the field calculator of qgis, like there is for area calculation?
16
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2answers
806 views

How to clean such a bad shapefile for routing?

I am trying to clean a shapefile to make it usable for routing with pgrouting, postgis, postgresql. Here an intersection, it seems to be connected but when we zoom …. It is not: Same here : Here ...
3
votes
1answer
3k views

Georeferencing with Quantum GIS and reprojecting to EPSG:900913

I'm trying to reproject a map to EPSG:900913 The image I'm reprojecting is the following http://i.imgur.com/HmfLW.png I'm using the cities as reference points obtaining the coordinates from Google ...
46
votes
5answers
20k views

Smoothing DEM using GRASS?

I have a SRTM DEM and I want to create a shaded relief from it. I created the shaded relief in GRASS and the result is very nice, but a little rough because the area is near flat and the DEM is 90m in ...
33
votes
3answers
55k views

How to Add OSM Layer to QGIS 2.X

How can i add OSM layer in QGIS? The help says there is an OSM plugin i can use. But i don't see it the list of plugins. Or maybe there is a WMS URL for OSM i can use? QGIS version 1.7.0-Wroclaw ...
7
votes
4answers
11k views

Is there a layout view in Quantum GIS?

Is there a layout view in Quantum GIS (something similar to ArcGis layout view) ? Anyway I am looking for tutorial or some good practices how i can prepare a nice map to print in Quantum GIS.
11
votes
1answer
1k views

Snap line layer to network in QGIS or PostGIS

I have GPS data I've taken of bus routes, and now I'd like to snap it to my road network. Both layers are line layers in a PostGIS DB. I'd like to use either QGIS or PostGIS, but if I have to go with ...
4
votes
5answers
7k views

When labelling polygons, not all labels are displayed - QGIS 1.7.0

I am trying to create a simple map of Mexico showing the state polygons and their label. The state shapefile is from here, and the specific file is the first one from the top (Áreas Geoestadísticas ...
7
votes
1answer
15k views

How to change projection and show latitude / longitude in QGIS?

I am new to QGIS and pretty ignorant with the subject, but I want to be able to see the latitude / longitude of a point (with a mouse click) in Quantum GIS. I imported a shapefile (roads of finland ...
11
votes
4answers
1k views

Best way to manage large number of GeoTIFF rasters?

I have around 2-3000 1-bit GeoTIFFs of size 11000x9400. Color 0 should be transparent, and QGIS gets it wrong in the first place, so I used a .vrt file to set all the parameters in one single place. ...
7
votes
1answer
2k views

How to create a polygon from other polygon boundaries?

I want to write an algorithm that creates a polygon inside a hole made by a set of other polygons. It's something like a flood fill and it's like the "boundary" tool in Autocad. The image shows an ...
11
votes
12answers
34k views

Redefining nodata value into zero in QGIS?

I have an image which i cliped with an AOI polygon. The contour area was set to pixel value = 0 and I have a nodata value of -32768. I want to redefine the nodata value into zero. I used to do this ...
2
votes
0answers
269 views

RT Sql Layer plugin giving an error [closed]

I am trying to use the aforementioned plugin with QGIS 1.7 and Postgres 9.0/PostGIS 1.5. Added a PostGIS spatial layer w/out a problem and then clicked on the RT Sql layer button which displayed the ...
12
votes
2answers
7k views

Is there any 'Auto-complete polygon' tool in QGIS?

Is there any 'Auto-complete polygon' tool in QGIS, similar to the one existing in ArcGIS?
16
votes
6answers
26k views

How to delete fields in QGIS?

When is the option to delete field in an attribute table enabled in QGIS? I'm in editing mode and still am not able to delete a field...
3
votes
1answer
2k views

How to update only a single vector layer in QGIS map canvas?

I want to update a single vector layer as I am working on 8 vector layers and they are getting fast data from serial port so for updating I use mapCanvas().refresh() which refresh all the layer and I ...
13
votes
2answers
17k views

How to join external tables with a shapefile's attribute table in QGIS?

I need to join a .csv table into an attribute table of a shapefile. I wanted to do this with QGIS and i don't seem to find anyway of doing it. I know that the mmqgis plugin does it, but my shapefile ...
0
votes
1answer
329 views

QGIS 1.6.0 problem during printing & export to PDF

When trying to print or export my map to pdf something happens to my document. When trying to print, the outcome always results in the printer producing a solid grey rectangle, and when I try to ...
3
votes
0answers
749 views

How to read a .GPB file in C#?

I have a .GPB file, I need to extract the common GPS data from it but I don't find a clear structure that specify the contents of that file. as a sample record from file 00000260 02 11 A9 61 E7 96 ...
2
votes
3answers
5k views

How to count pixels of a raster in polygons using QGIS?

I need to compute some statistics of the pixels of a given raster that are coincident to the polygons of a vector file. Is there a simple and effective way to do this in Quantum GIS or similar?
18
votes
5answers
26k views

Concatenating fields in field calculator of QGIS?

Is there a way to concatenate fields in field calculator of QGIS? (e.g. hectares + ' ha')
7
votes
4answers
6k views

How to identify and eliminate overlaying polygons in Quantum GIS?

I have a shapefile with polygons and now, not sure why, most of the polygons became duplicated and overlaid, i.e. when i click to selected one, i get two selected... How do i identify those polygons ...
5
votes
1answer
2k views

How to draw or edit curved lines in free GIS?

I'm searching informations about drawing simple curved arrow lines into free GIS like QGIS, in this problem data geometry is CIRCULARSTRING ( a type which exists in latest postgis version) It seems ...
7
votes
1answer
6k views

qgis to local postgis connection - fails

It seems pretty clear I cannot connect to a local postgresql installation out of QGIS. This is my first experience with PostGIS. I am using PostgreSQL 9.0 on a win7 machine. I can see the successful ...
7
votes
1answer
8k views

How to create a point along a line given distance

I have been given a non-spatial database which contains the names of lines which I have a shapefile for. The database also has names of points and the distance of each point from the origin along the ...
7
votes
3answers
5k views

Making selection color transparent when in editing mode in QGIS

in QGIS, how do I make the selection color transparent? I need to split a polygon and i want to see the layer underneath it. But I have to select the polygon in order to cut it, and when i do that it ...
22
votes
1answer
9k views

How to have a drop down list for feature editing (attributes) in Quantum GIS?

I'm editing a lot of polygons of a shapefile in QGIS and i need to classify them, so i have to write the classes a repetedly a lot of times. In ArcMap there is an option to have domains set for the ...
6
votes
2answers
988 views

Calculating lat/lons from PostGIS table which has projected coordinate system?

I have a PostGIS table in a projected coordinate system (EPSG: 28355 or MGA94 Zone 55). In QGIS (with the PostGIS manager plugin) I calculate a coordinate by performing the following SQL: UPDATE ...
18
votes
1answer
4k views

Voronoi polygons that run out to infinity?

I have been working on implementing the voronoi.py script (Bill Simon's translation of Steve Fortune's code). According to the QGIS link it is basically the same code that I am working with, but the ...
1
vote
1answer
449 views

What is the shell command for the tool 'simplify geometry' in QGIS?

I was wanting to batch the tool 'simplify geometry' for a set of shapefiles, in the osgeo shell.
1
vote
1answer
883 views

Last edited information missing when used QGIS - Dxf to Shp

I am doing as constructed drawings which require the information to be in a GIS system and more specifically drainage as constructed drawings. I must have a separate file for Pipes and Pits. First I ...
2
votes
2answers
449 views

Shapefile CRS changed after exporting from QGIS. Are they equivalent?

I added a shapefile as a vector layer in qGIS 1.7 so that I could join in additional attribute data (not geodata) from another DBF file. The Shapefile that I added has this CRS (as far as I can tell ...
8
votes
3answers
4k views

QGIS and Raster Mapping in 'Seamless' layer

I would like to use Ordnance Survey base mapping in QGIS. I would like to set up something like a seamless table in MapInfo. I think that the equivalent in QGIS is a Virtual Raster Table. The files ...