Tagged Questions

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

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5
votes
2answers
318 views

How to filter the MouseWheel event in a QGIS C++ plugin?

I’m developing a C++ plugin for Qgis and I want to filter/override the mouse-wheel event. I created a “maptool” to select a polygon feature on a vector layer, the feature has two attributes : an id ...
5
votes
2answers
1k views

How to move labels in QGIS?

I'm trying to manually move labels but having some trouble. I'm trying to move the labels while in edit mode. I've added fields for x coordinate (all null), y coordinate (all null), rotation (all =0), ...
5
votes
1answer
901 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...
5
votes
3answers
2k views

Quantum GIS and ECW images?

How might I enable Quantum GIS to read ECW imagery? At the moment I'm mostly concerned about this on Ubuntu 10.4 amd64, but I also use WinXP & Win7.
4
votes
3answers
65 views

GIS QUERY on point and buffer

I have a point table and the buffer geometry is created around the point. I have defined the if the point is within the buffer_distance then its value is =1 and if it is outside the buffer its value ...
4
votes
1answer
445 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 ...
4
votes
4answers
1k views

How to split a shapefile into separate files for each feature?

I have a polyline shape files with about 20 kinds of roads. I would like to know how can I create automatically a vector file for each one. I can use Arcgis, Qgis (or Gdal separately). thanks!
4
votes
2answers
201 views

How to Intersect a layer with custom CRS with NED data?

I am trying to create a map with a layer of county tax assessor property parcels plus NED elevation data. The projection of the tax assessor layer is a weirdo -- looks like user-created by the ...
4
votes
3answers
985 views

Conflicting measurement units with buffer ftools

I am new to qgis and I would like to create a buffer around point features. My goal is to create a quarter mile buffer (402.336m) around each point feature, using Geoprocessing Tools -> Buffer(s), ...
3
votes
1answer
56 views

What is displayed when I am using a geographic CRS for my project

I understand that each geographical dataset has a CRS, and that in order to overlay them, you need to either make sure that all datasets use the same CRS, or re-project some of them (or use on-the-fly ...
3
votes
2answers
104 views

Setting rendering order of line layers in QGIS

I have a dataset where different road types are in separate layers, i.e. motorways, primary roads and secondary roads. In turn, each layer is subdivided by embedded codes into different sub-types - 4 ...
3
votes
3answers
110 views

How can I draw squares in PostGIS layers at different angles?

I am trying to draw two squares on a 45-degree angle and then merge them using PostGIS to edit. QGIS can draw squares but only on a perpendicular plane (eg, 0, 90, 180), and I need to be able to draw ...
3
votes
2answers
639 views

How to reproject a vector layer in QGIS?

I have some shape file which is in UTM. I wanted them to convert to Decimal Degreesin QGIS. Hope I can get some better response.. Thanks.
3
votes
2answers
1k views

How do I change the data type in attribute table in QGIS

I have county data in which the FIPs (actually State FIPS and County FIPS combined). I have data imported as CSV with the sames FIPS data titled STCounty. However, the shapefile FIPS is listed as a ...
3
votes
1answer
343 views

Can I access a raster attribute table in QGIS?

I have some Python code that makes Raster Attribute Tables for GeoTiffs using GDAL. In ArcGIS I can see these attribute tables fine and they behave how I like (as classifications). But in QGIS the ...
3
votes
2answers
865 views

How to display both scalebar in kilometers and grid in lat/long degrees in Quantum GIS 1.8 Composer?

Also, how to display both scalebar in kilometers and both lat/long degrees and northings/eastings in QGIS 1.8 Composer? Layer is projected to UTM. Thank you.
3
votes
3answers
2k views

How to install Python libs for XYtools to read Excel files

I need to use the XYtools plugin to read an Excel file. After choosing the XYtools incon and indicating an Excel file to read in, a message appears "there is a problem with loading a python module ...
3
votes
1answer
1k views

QGIS calculate distance of point along a line

I have a polyline (movement path) and points recorded along the line. I would like to calculate for each point the distance along the line in Quantum GIS. I hope for a result which will add a new ...
3
votes
4answers
1k views

How to georeference a dxf?

I have got myself a dxf which is built with units in the wrong scale. How do I upscale that in QGIS? Note it does open in QGIS, just in the wrong map units and location.
3
votes
2answers
683 views

How to reproject from Michigan Georef to WGS84 in QGIS?

I am trying to reproject a michigan state land shapefile which is the NAD83/ Michigan Oblique Mercator EPSG:3078 to the WPG84 EPSG:4326 projection. However when i try to do this my map gets squished ...
3
votes
2answers
533 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 so please bare with ...
2
votes
2answers
140 views

How to calculate the area of rasters in QGIS?

I have been working with some rasters and would like to know how to calculate the area occupied by one element of a raster in Qgis.
2
votes
1answer
122 views

find polygon corner coordinates

I am trying to get the coordinates of each node of the polygon I create. I would like the attribute table to display the name of the polygon (ex. address) and then the coordinates of the nodes (ex. ...
2
votes
1answer
86 views

Is there a difference between ESRI's NAD83 Indiana SPW and QGIS's?

It seems ESRI and QGIS don't have the same definition for my most commonly used projection, NAD83 StatePlane Indiana West (US ft). When I create data in an ESRI product the projection shows up in ...
2
votes
1answer
163 views

update tables data dynamically

Can u help me in creating a trigger and function so that every time i change the flag in table A the buffer distance should get changed and also its geometry field also , ie the polygon area? I have ...
2
votes
1answer
170 views

how to modify shape extents in qgis

I want to change the shape extent of some shape files, I would like to know how to do it in Qgis, since I rasterized some shapes and when I used the calculator to add them, the resulting raster had ...
2
votes
2answers
536 views

Is it possible to extract Coordinates of Polygon Centroid in QGIS?

I have created polygon centroids using one of the "Geometry Tools" but I would like to extract the actual coordinates into Excel for further work. Is this possible?
2
votes
2answers
960 views

How to install OpenLayers plugin in QGIS1.8

I am using QGIS 1.8.0 on Windows 7 (32-bit) but am unable to install the OpenLayers plugin. The Python plugins menu does not include OpenLayers on the plugin list. Can it be somehow added manually? ...
2
votes
1answer
267 views

Plot the nodes of the shortest path found by dijkstra algorithm

I am using qgis and pgrouting plugin to find the shortest path between two nodes and display the route. Currently, the plot shows the shortest path. However, I also want to know which nodes the path ...
2
votes
1answer
397 views

qgis.core import error

I would want to use the Qgis api for custom desktop application. When I imported the qgis.core module, I get the following error >>> import qgis.core Traceback (most recent call last): ...
2
votes
1answer
749 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. ...
2
votes
0answers
414 views

OSGB36 to WGS84 reprojection 'error'

First off, I am a recent convert to QGIS and am greatly impressed with its ease of use and speed compared with the ESRI products with which I am more familiar - my congratulations and thanks to its ...
2
votes
1answer
519 views

Why does my PostGIS query fail with “current transaction is aborted”

I'm trying to create a vector layer in a QGIS project using a PostGIS query. QGIS is returning the following error: Query failed 1 cursor states lost. SQL: CLOSE qgisf1 Result: 7 (ERROR: ...
2
votes
1answer
3k views

Adding Layerfiles (.lyr) to Qgis

at college we're using ArcGis at the moment, but sadly ArcGis 10 doesn't function on my Mac! So as I already have QGis on my computer, I just want to do my exercises with ist, but we do use .lyr files ...
1
vote
1answer
68 views

Problem in libtiff.dll when starting QGIS

When I try to start QGIS 1.8.0 I get the error message "Can't find procedure start address TIFFMergerFieldInfo in libtiff.dll" and the program won't start. I have downloaded and reinstalled QGIS ...
1
vote
1answer
125 views

Polygonize function doesn't overlay the shape file over the raster file

To convert the raster into a shapefile I use raster->conversion->polygonize but QGIS doesn't open the new layer overlayed the first (the raster) but reflected above it. I read this question ...
1
vote
1answer
110 views

Looking for complicated representations of an urban areas

I would like to display some features of an urban area using a map, showing something like telecomunications, roads, or parks, etc. Also, is it possible to get an understanding of how to show more ...
1
vote
4answers
260 views

How to Digitize Free Satellite Imagery in QGIS?

I am trying to digitize OpenLayers data (such as Google satellite imagery) with no success. Whenever I try to move or zoom the canvas the vector layer I digitized loses the position relative to the ...
1
vote
1answer
143 views

How to control what kind of tags / flags are imported with osm2po?

With the help of osm2po, I have successfully inserted the contents of the italian files (italy.osm.pbf) in a pgrouting-enabled database (postgresql 8.4) It displays fine in Qgis, using rule based ...
1
vote
1answer
136 views

Tools to flatten the jp2 to a single band (average the bands)?

I have created thousands of png tiles using arcgis and have merged groups of them into large jp2 files for serving via geoserver. I need to flatten these to a single band so that I can apply a colour ...
1
vote
1answer
169 views

Problem with Orfeo Toolbox integration in QGIS

I'm getting this error: OTB execution console output '"C:\OSGeo4W\bin\otbcli_MeanShiftSegmentation"' is not recognized as an internal or external command, operable program or batch file.
1
vote
1answer
160 views

How to get back closed panes in QGIS 1.8 in Mac OS X?

I was using the map composer in QGIS 1.8 in Mac OS X 10.6.8 today and closed a couple of the object attribute panes on the right side of the map composer. However, I can't find a way to get those ...
1
vote
1answer
270 views

Couldn't load SIP Module

After reinstalling QGIS, the desktop program runs but generates the python error "Couldn't load SIP Module Pythin support will be disabled" Because of this error, no plug-ins will load. I found a ...
1
vote
1answer
130 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)?
1
vote
1answer
209 views

Looking for QGIS Presentation info

I'm preparing a presentation of QGIS to release of the brazilian QGIS user guide. Thus, I would like insert some information about QGIS in global scale. Something like Tim's qgis-for-humanity ...
1
vote
1answer
279 views

Why does Select Feature give nonsensical results?

I am a beginner with Quantum GIS and with no previous experience or expertise in Geography or GIS. I have an ESRI shapefile of New Zealand census area units (CAUs). My goal is to obtain distances ...
1
vote
1answer
374 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 ...
1
vote
3answers
775 views

Using QGIS with a pre-existing installation of Python 3.2 and matching GDAL

I need to have GDAL/OGR working with Python 3.2 because of another dependency. However, I also want to have QGIS for convenience. However, QGIS - FWTools in particular is built against Python 2.5, ...
1
vote
1answer
2k views

Import MySQL Spatial vector layer in QGIS

I have a spatial table called 'places' in MySQL, with a spatial column 'pt' (point). I tried to import it in QGIS and no points appear. I created a view 'places_as_text' which reproduces the table but ...
0
votes
1answer
61 views

Why does Print Composer take ages “Creating icon for file …”?

Every time I open a Print Composer, a box comes up, and text flashes by saying, "Creating icon for file [various random image files that I have on my computer]". It then pauses, and does it again, and ...

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