Tagged Questions

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

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10
votes
5answers
574 views

Database versus Files for Solo Developer

I'm just getting started in GIS and am interested in using it to create maps of mountain biking trails in my area and nearby. I've been learning QGIS and have made enough progress to generate a decent ...
1
vote
2answers
662 views

Is there any known reason for QGIS recurrently crashing in windows7?

I use (and been a big fan of) QGIS daily for 7 months now, and only recently - past couple weeks - been experiencing problems with QGIS recurrently crashing. This is even more serius cause it happens ...
2
votes
1answer
1k views

QGIS [500]INTERNAL SERVER ERROR

My Name is Daniel and I'm from Indonesia. Short story recently I was learning how to set up qgis server. So here's the trouble I've encountered so far: I was using OSGEO Live 5 Distribution ISO' ...
1
vote
3answers
2k 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
569 views

How to refresh QgsMapcanvas?

I am using Qgis 1.7 and I want to refresh the mapcanvas so I am using refresh() function of QgsMapcanvas class and Nothing is happening to the Map Canvas. I am using Python for customizing
4
votes
1answer
2k views

Loading a raster using QGIS into a PostGIS2.0 enabled database

Following on from my attempt to install a postgresql 9.1 db with postgis 2.0 on windows 7, I am trying to figure out how to load a raster. I have successfully loaded a shapefile, and am trying to do ...
14
votes
5answers
9k views

Is it possible to make a DEM from contours in QGIS?

Is it possible to make a DEM from contours in QGIS? I have a shp file (contours) and their heights, can I use QGIS for produce a DEM without using GRASS? I find this creating a dem from contours but ...
4
votes
3answers
2k views

How do you open/display and extract NetCDF files info?

I am working with NetCDF files using R & Matlab and I would like to know if the GIS community is using them. I know that ArcGIS can open & display, however most of the times the results are ...
5
votes
1answer
423 views

Is there any plugin for QGIS to calibrate contrast and brightness of a raster layer?

I frequently need to deal with the contrast and brightness of raster layers in QGIS and I miss the tools in ArcGIS for this task. Should there be a plugin already developed for QGIS? If there is, ...
0
votes
1answer
2k views

How to set up QGIS + georeferencer for easiest georeferencing

The goal is to make converting scanned paper maps to map tiles as easy as possible. I've done a few, but the slow part is manually entering coordinates of points. What I'd like to do is for each ...
3
votes
1answer
4k views

Changing the coordinate system of a qgis layer to the projection of Google Earth

I want to know how to change coordinate value of a vector layer (13293061,-572595) to 119.413,-5.13677 (vector data & Google Earth do not match). If I output my data using Google Earth as ...
1
vote
2answers
782 views

Can you reorder a classified vector layer in QGis?

I have a GML file that I'm displaying in QGis - it contains a set of contours and they are written out in such a way that the lowest contour (largest polygon) is drawn last thus covering up all the ...
11
votes
5answers
7k views

How to perform Raster Reclassification in QGIS?

Is there a way to do reclassify a raster image to Qgis? In Arcgis you can do that in Spatial analyst Tools→Reclass→Reclassify Any ideas?
6
votes
2answers
7k views

Manipulate .asc files in qgis

I have an .asc file and I want to import in QGIS. The standard way to open it is from "add Raster layer" ("import Raster Layer"), there is another way? I know is strange that ask but I need it. And I ...
3
votes
1answer
2k views

Why does the QGIS Server WMS layer not load in QGIS Desktop?

I have created a .QGS file with one PostGIS layer which is the alaska.shp file that comes from the samples. It was loaded via the shp2pgsql utility. When looking at my qgs project referencing the ...
1
vote
2answers
1k views

How to load NASA JPL WMS Global Mosaic into QGIS

I was playing around with uDIG and realized that its WMS capabilities are awesome! The Global Mosaic perfectly fits a map I created! However, I was planning to use the WMS layer as an orientation for ...
5
votes
2answers
436 views

Is it possible to use the Goode Homolosine projection in QGIS?

Is it possible to use the Goode Homolosine projection in QGIS? Both QGIS and GRASS seem to have trouble with the interruptions, squashing the higher latitudes together. I tried +proj=goode ...
3
votes
2answers
2k views

How to import a non-spatial Table into QGIS?

Can I import tabular data in Qgis, without any information about X and Y only the table? I need to join them after importing them.
2
votes
1answer
607 views

Does QGIS support parsing of date strings in tables?

It is straightforward to load GPX files (GPS downloaded tracks / points) into QGIS, then save and manipulate them as shapefiles. However, the recording date (in the comment (cmt) field) of waypoints ...
11
votes
1answer
720 views

Method to shade or overlay a raster map to reflect time of day and ambient light

I have a daytime raster of my study area. I have 20+ counters in the study area that count "stuff" with a timestamp. Using PyEphem I determined the type of ambient light for each collected data ...
1
vote
0answers
160 views

Can I overlay layers in Dealul Piscului 1970 and WGS84 in QGIS?

I have a 10 Gb ECW file (mosaic of a whole county) that is in Oblique Stereographic projection with Datum: Dealul Piscului 1970. The problem was that no matter the Default CRS for new project was, ...
7
votes
2answers
882 views

Is it possible to run an R script on a layer in QGIS?

I'd like to run an R script on a layer loaded in QGIS (to rotate a set of points created there using the Vector:Research Tools:Regular Points tool). I thought ManageR might work but cannot get it ...
4
votes
2answers
480 views

How to fix a raster with wrong Eastings?

I get an error when trying to warp a tif file in QGIS: ERROR 1: Too many points (35721 out of 35721) failed to transform, unable to compute output bounds. I am using QGIS 1.7.0 Wroclaw with gdal ...
17
votes
1answer
1k views

What's the status of Postgis 2.0 topology support in QGIS?

Having followed the Postgis developments over the past 6 months I have noticed a bunch of features which seem to be incredibly cool especially in the area of topologies and associating calculations on ...
10
votes
1answer
3k views

How to display geoJSON from an URL in a layer?

I am looking for some type of plugin or code which would allow me to add a geojson URL, define the areas to input the lat/long variables from the visible Qgis canvas map and call/render the results ...
2
votes
2answers
2k views

How to union polygons with common ID in QGIS?

I have a shapefile with lots of polygons and I need to union all polygons which have the same identifier-id into a new (multi-)polygon, ideally with the same identifier-id on another (new) layer. As ...
9
votes
5answers
2k views

Developing GIS Application on Android

Is there any Open Source GIS Software for Android in which we can perform Various Geoprocessing Operations (like Buffering,union and intersection) and that should be customizable eg: what we do in ...
2
votes
1answer
388 views

How do I select all points that lie within a layer's bounding box?

I'm using QGIS to do this. I have a mesh created from the v.trimesh tool. I want to find all the points that lie in the bounds of a layer. How should I go about doing this?
5
votes
2answers
371 views

Which is the best way to create a polygon with the extents of a raster file in QGIS?

I have a tiff image file and want to get a polygon with the extent of the tiff. Is there a direct way of doing this? Right now i have to convert the image to vector (with gdal_polygonize) and then ...
9
votes
1answer
3k views

Dot Density Maps in QGIS?

Is there a 'friendly' way to create dot-density maps, where a polygon attribute data defines the number of dots (e.g. 1 dot = 100 ) using QGIS 1.7+? I say friendly because after a couple of hours ...
5
votes
1answer
1k views

How to calculate the size of a particular area below a buffer in QGIS

I have a point shapefile of villages where data was collected in Northern Kenya. I created a buffer around those villages. The second vector layer contains polygons defining areas according to ...
5
votes
3answers
1k views

How to find line length in QGIS while editing?

I am using QGIS (before, I used ArcView). I would like to know if there is any way during the editing phase of a vector (line or polygon) to know the length of the line (total and partial) that is ...
3
votes
1answer
366 views

How do I get the x- and y-coordinate values of points in UTM using QGIS?

To get to know the size of the study area and how far objects are separated, I need to know x- and y-coordinate values. Although the $x and $y of Field Calculator returned latitudes and longitudes, ...
1
vote
1answer
473 views

How to use buffers to estimate the attribute data for a given polygon?

I have two layers: point and a polygon. The point layer has lat/long and I have created buffers of a 1/4 mile. The polygon layer has data such as age and income. Is there a plug-in that can ...
4
votes
1answer
227 views

Migrating Feature Datasets from ArcSDE to postgis

I am currently planning the migration of a database from ArcSDE/ Arcmap to postgis / Qgis. The data is stored in raster catalogues and feature datasets. Is there an equivalent to feature datasets ...
2
votes
1answer
624 views

QGIS 1.7.1 and PyQT4 conflict: what am I doing wrong?

I've just started playing with QGIS with a view to eventually developing a few simple plugins in Python. I downloaded QGIS 1.7.1 for Windows and started working through these workshop notes. If I've ...
1
vote
1answer
593 views

How to change the the style of a vector layer programmatically?

I want to change the style of the polygon contained in the vector layer. Is there any API available? (I can click the properties of the shapefile, then select the style and change the symbol ...
6
votes
1answer
910 views

Is there a way to automatically snap loose points of lines to close by vertices with Quantum GIS?

I have a vector layer of lines that were drawn with the snapping option off. I need to have them snapped but, there are hundreds of lines. Is there any solution to do this automatically or ...
3
votes
2answers
486 views

How can I do this geometric-operation in QGIS?

My problem: I have 3 polygons (a, b, c) on layer 1 and two other polygons (1 and 2) on layer 2. Now I want to "crop and melt" (forgive me I don't know the terminus technicus) my three polygons ...
4
votes
3answers
2k 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), ...
1
vote
1answer
2k views

“Add Delimited Text Layer” plugin is enabled, but does not show up in the plugin menu

I'm using QGIS 1.7.1 on Windows 7. I want to import a delimited text layer, but that option does not appear in the "plugins" menu. This problem persists, despite the following steps I've taken to ...
5
votes
2answers
298 views

How can I create a “setback” buffer in QGIS?

I've been going a bit crazy in trying to create a "setback" buffer on QGIS for coastal lines in a map projecting this buffer outwards towards the sea. I've managed to create a normal Bidirectional ...
3
votes
2answers
254 views

strange behaviour of piechart function of QGIS

I am using QGIS to visual health status of elderly in an elderly home, whether they have medical devices or not is one attribute that I am trying to visualize. I have create the map using mapwindows, ...
6
votes
3answers
828 views

How to place multiple symbols on one polygon centroid?

I am using QGIS for visualizing the health conditions of elderly living in an old age home, some of the elderly have multiple medical device with them and I want to show them on the map. Suppose I ...
12
votes
2answers
2k views

How to select features with NULL attributes in QGIS?

I need to identify which features have null attributes in the attribute table of a shapefile. When i try [field]= 'NULL' it selects the features with value=0 (see picture) Suggestions?
6
votes
2answers
729 views

Can I change the GDAL/OGR library that QGIS uses?

I have been adding a new format to OGR, all seems well and OGRInfo works. Now I would like to test my code out using QGIS. Is there an easy way to switch which GDAL lib QGIS uses on a windows box? ...
21
votes
3answers
3k views

What do I need to know, to develop a plugin for QGIS?

I wish to develop a simple plugin for QGIS, which will open some data, and some specific processing. I have quite a it of development experience with ESRI's Arcojects, but haven't developed with QGIS ...
7
votes
3answers
1k views

Does anyone know how to install the Orfeo Toolbox in QGIS?

I already tried this http://hg.orfeo-toolbox.org/OTB-Qgis-plugins/ repository and couldn't get it... This guy seems to have it: http://www.elance.com/samples/orfeo-toolbox-qgis/24111664/ Help, ...
3
votes
2answers
2k views

Workflow for creating line features between two coordinate pairs in QGIS

I have a table of stream reaches with xy coordinates for their respective tops and bottoms. I'd like to convert the table to a feature, using the xy coordinates as the endpoints of the line. Any ...
11
votes
1answer
571 views

Nearest Neighbor Grouped Selection in QGIS

OK - so I have an interesting problem I am trying to solve. I have a list containing over 100,000 points in lat/long format which I have imported into qgis. Now, what I am trying to do here is group ...