Questions tagged [qgis]
QGIS is a cross-platform GIS application licensed under the GNU General Public License.
38,525
questions
13
votes
15
answers
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Redefining nodata value into zero in QGIS
I have an image which I clipped 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 ...
- 5,482
2
votes
0
answers
270
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 ...
- 2,360
12
votes
2
answers
9k
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?
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21
votes
8
answers
41k
views
Deleting fields using 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.
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3
votes
1
answer
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 ...
- 31
13
votes
2
answers
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 ...
- 5,482
0
votes
1
answer
333
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 ...
- 1
3
votes
0
answers
783
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 ...
- 31
4
votes
3
answers
5k
views
Counting pixels of raster in polygons using QGIS
I need to compute some statistics of the pixels of a given raster that are coincident with the polygons of a vector file. Is there a simple and effective way to do this in Quantum GIS or similar?
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19
votes
5
answers
40k
views
Concatenating fields in field calculator of QGIS?
Is there a way to concatenate fields in field calculator of QGIS? (e.g. hectares + ' ha')
- 5,482
7
votes
4
answers
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 ...
- 5,482
5
votes
1
answer
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 ...
- 237
7
votes
1
answer
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 ...
- 1,772
7
votes
1
answer
9k
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 ...
- 1,772
9
votes
4
answers
6k
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 ...
- 5,482
22
votes
2
answers
10k
views
How to have a drop down list for feature editing (attributes) in QGIS?
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 ...
- 5,482
6
votes
2
answers
997
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 ...
- 3,009
18
votes
1
answer
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 ...
user681
1
vote
1
answer
463
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.
- 5,482
1
vote
1
answer
893
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 ...
- 11
2
votes
2
answers
489
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 ...
- 125
8
votes
3
answers
5k
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 ...
- 4,214
2
votes
4
answers
5k
views
Export to new projection in QGIS 1.7
Suppose I have layers A and B. I don't know their projections but by the looks of the map I know they are not the same.
In QGIS 1.6 I would use one of my favorite features:
Vector> Data ...
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4
votes
2
answers
562
views
Total newbie. Creating map from aerial photo of golf course in QGIS
I have a aerial photo in tif with a tfw file of the golf course that I work at. I would like to create vector data of different features on the course such as greens fairways tees, etc. to calculate ...
40
votes
5
answers
28k
views
Joining attributes from nearest point in QGIS?
I have two layers with points, call them A and B, each with different attributes.
For each point in A I want to join all the attributes from the nearest point in B.
Ideally this would also include a ...
- 682
36
votes
5
answers
19k
views
Identifying clusters in vector point data using QGIS?
I have a vector dataset of rural broadband data-points (how fast, etc.) and I'd like to explore if there are clusters of points with similar characteristics, and to plot polygons encompassing them.
...
- 1,133
1
vote
2
answers
3k
views
QGis import partial PostGIS layer using query builder
I'm sorry, but I'm terribly new to the GIS scene (and PostGIS & QGis). I have loaded a whole bunch of OpenStreetMap data into a PostGIS database and successfully drawn a map using Mapnik. Now I ...
- 175
16
votes
5
answers
27k
views
How to Zoom in QGIS Print Composer Without a Scroll Wheel
I am attempting to print a simple map from QGIS in portrait orientation. When I use the "Add New Map" tool it brings the map in at an extent which matches my original data frame if I were to use ...
- 2,292
1
vote
1
answer
455
views
Python console not loading with QGIS1.7-Ubuntu 10.04.2 LTS lucid,
Any tips on how to get the Python console working on Q-GIS (Quantum GIS)? (Its not working from the software's menu.)
System:
Python 2.6.5
QGIS1.7 OS
Linux: Ubuntu 10.04.2 LTS lucid
Error message ...
- 826
3
votes
2
answers
1k
views
Overlaying GPX data on rasters in QGIS
I have a series of raster map images that I would like to use in QGIS and overlay some simple GPX routes over the top to produce a custom map image.
This is all quite new to me. I am struggling to get ...
- 115
1
vote
2
answers
2k
views
Problem reprojecting data from personal geodatabase using QGIS
I have a dataset in the form of a personal geodatabase (mdb) and am interested in using certain feature classes for further processing.
My problem is - I am using USGS data orthoimagery which comes ...
- 135
32
votes
7
answers
41k
views
Joining multiple records to single feature using QGIS
I'm trying to create a join/relate in QGIS where I have a shapefile of buildings and to that I would like to join a non-spatial table (.csv-file) containing people who work in each building. So I have ...
- 321
6
votes
1
answer
2k
views
How to force QGIS Centroid Fill inside the Polygon?
I would like to use a centroid fill to enable me to place a letter inside a polygon. The advantage of using a centroid fill is that it also shows up in a legend, whereas labelling the layer would mean ...
- 4,214
6
votes
1
answer
916
views
Vector Legend item names in QGIS Map Composer
Is it possible to get the text for a legend item to go over multiple lines? I have some long item names and I have a set legend width that I have to use.
Without being able to make the text go over ...
- 4,214
5
votes
2
answers
309
views
How to deal with multitype data sources in QGIS?
Today I was trying to import a DXF to Qgis, the result is that qgis displays everything LINES and POINTS but it only displays options for the POINT objects.
When I try to export to a shapefile, it ...
- 9,759
2
votes
3
answers
486
views
Has QGIS 1.7 been released as a stable version yet? [closed]
Has QGIS 1.7 been released as a stable version yet?
I see on the QGIS site the windows download on the is still referring to 1.6 and the OSGEO4W install has 1.6.0-7 as the stable release.
I had seen ...
- 3,009
34
votes
2
answers
20k
views
Styling road maps with QGIS?
I am trying to design a beautiful map using QGIS.
There is a similar question here Seeking QGIS tutorials and web resources? but I would like to focus on "designing a map using QGIS".
I was looking ...
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6
votes
1
answer
3k
views
Calculating Standard Deviation in QGIS?
Does anyone know of a way to find the standard deviation of an attribute lying within any given polygon?
The plugin dialog "Join Attributes by Location" gives only the options Mean, Min, Max, and ...
- 63
4
votes
2
answers
303
views
How can I make my data efficient and "light" to do 3D Visualizations in Google Earth?
As a test run, I'd like to visualize population on census blocks for a few states (New England for example). I assume that the kml to do this will be huge, when you factor in the census boundaries and ...
- 8,533
4
votes
1
answer
3k
views
How to import qgis.core in a Osgeo4W installation?
when I try to import qgis core module from python:
from qgis.core import *
I get this error:
ImportError: DLL load failed: The operating system cannot run %1.
Searching the web I found that I need ...
- 9,759
5
votes
1
answer
1k
views
How to insert 3d line into postgis database?
I have 3D line which I exported from GRASS in .shp format. When I try to insert this line to Postgis database with QuantumGIS, it gives an error:
ERROR: Invalid type name - valid ones are:
...
- 4,968
6
votes
1
answer
1k
views
Can I specify a point and get all features within a certain radius of this point?
I have recently shifted to QGIS from ArcGIS and am looking for some help/pointers with the following:
Does QGIS have a method by which I can specify a lat-lon coordinate (or a utm x,y coordinates, ...
- 135
68
votes
5
answers
122k
views
Clipping raster with vector boundaries using QGIS
In QGIS I would like to clip a raster precipitation layer using an admin boundary layer that is vector data. However the Geoprocessing tools seem to be usable only for vector data.
How can I clip this ...
- 681
13
votes
2
answers
24k
views
How to enable projection transformation in QGIS
My QGIS project has two layers, one layer is retrieved by Google layer plugin which fetches the static Google map image whose CRS is +proj=merc +lon_0=0 +lat_ts=0 +x_0=0 +y_0=0 +a=6378137 +b=6378137 +...
- 297
16
votes
2
answers
2k
views
How to overcome field truncation when converting OSM to shapefile with QGIS?
I am trying to convert an OpenStreetMap file into a shapefile, but I am having problems with the "tags" field being cut-off after 80 characters. With QGIS 1.4, I use the OpenStreetMap plugin to 'Load ...
- 375
26
votes
6
answers
7k
views
Creating a small web-mapping/map-tiling service
I am looking for a small-scale and easy way to present one or more polygon shapefiles online (on a municipal website without any existing map-server infrastructure, to be precise). Right now, I'm ...
- 1,401
7
votes
6
answers
2k
views
Southern hemisphere projections for Landsat upsets GRASS
Does anyone have the last word on why Landsat scenes don't project in the southern hemisphere. This causes no end of trouble in GRASS, less so in QGIS.
What I mean is, take an original scene from ...
- 1,772
8
votes
1
answer
2k
views
How to create point labels from midpoints of road polylines in QGIS?
I have a road polyline layer (singlepart ie has several features per road, grouped by an id field), and i want to (after merging the parts) find the mid point of the resulting lines. This is for roads ...
- 467
26
votes
5
answers
12k
views
Obtaining print quality PDF or PNG output from QGIS?
I work with people who use ArcGIS Desktop and they have found the best resolution output images are made by creating PDFs. They tell me that *.png and the rest out of ArcGIS Desktop are not ...
- 1,772
16
votes
5
answers
27k
views
Reading ODBC connection using QGIS? [closed]
I have a co-worker who manages a large MS Access database that contains X & Y fields for various locations he tracks. We have previously exported the data to CSV and used the QGIS Delimited Text ...
- 22.8k