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

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6
votes
3answers
2k views

How to extract slope from topographic raster map?

I am working on a project for a machine learning class wherein I extract features from a topographic raster map and then classify the traversability of the terrain. One of the features I need to ...
7
votes
1answer
1k views

Sort layers in QGIS table of contents?

When I load a bunch of layers into QGIS from PostGIS, they seem to load in reverse alphabetical order. Is there any tools or plugins that allow you to quickly sort the QGIS TOC in a different order? ...
10
votes
3answers
8k views

How to import coordinate data from excel into QGIS?

I have an excel file containing data collected over many years as latitude and longitude coordinates for archaeological sites - how can I import it into QGIS as a new layer?
2
votes
1answer
566 views

How to debug 'Layer is not valid error' from Python plugin?

I'm trying to understand what goes wrong with a QGIS python plugin. Basically I'm trying to render a series of POINT. The query works fine, at least giving it by hand from inside PostGIS DB: "SELECT ...
3
votes
3answers
1k views

Summing attributes intersected by under a radius

Apologies - new user. I am working with QGIS on Mac OS X and with shapefiles downloaded from the US Census Bureau that show population data by state and by county. How do I: select certain points ...
2
votes
1answer
114 views

How to close and fill Gulfs and inlets in QGIS or Grass?

I have a raster layer from which I extracted only zones with a certain color, then polygonized it with QGis. I just generalized the new vector layer in GRASS to smooth things a bit. There are many ...
3
votes
3answers
2k views

How to extract POINT from a [LINE|MULTILINE]STRING

I'd like to create a vectorLayer in QGIS to display all the points that form a LINESTRING or a MULTILINESTRING stored in a PostGIS DB. I think that I need to transform all points of LINESTRING (or ...
1
vote
0answers
61 views

calibrating vector line in qgis

I have loaded GPS points into a QGIS vector layer. I also imported a vector line from a dxf file which doesn't have georeferencing. I would like to fit in line geometry between the GPS points - how ...
4
votes
1answer
133 views

Measurement not correct in QGIS 1.8

I have a SHP file of sub-areas of U.S. counties (roughly about the size of a Census tract) that I've reprojected into a 'true distance' projection (World Equidistant Cylindrical) in QGIS 1.8. However, ...
1
vote
1answer
1k views

QGIS, how do you break segments of a polygon, ie break 1 polygon into 2 or more?

I have a polygon but would like it to be in broken up to put into different layers. I can't work out how to do this.
7
votes
1answer
252 views

How to debug a QGis python plugin

I'm trying to write a python plugin for QGis. I'd like to debug some DB queries and I need a way to display the result. I thought about using a popup to display it, but I don't know how to show a ...
10
votes
2answers
439 views

How to build a minimum convex hull crossing the 180 degrees line?

I've been building convex hulls for species that inhabit the Indo-Pacific (~ from 20 to -65 degrees of longitude). The problem I've encountered is that for the species that can be found on both sides ...
4
votes
1answer
524 views

Vector tools missing in QGIS 1.8 (Ubuntu)

I installed QGIS 1.8 on an Ubuntu 12.04 Precise Pangolin virtual machine. everything seems to work fine, but I don't get any of the vector or raster tools that (I assume) are part of the standard ...
2
votes
2answers
594 views

Why is Spatialite delivering “Invalid SRID” error message

Qspatialite in QGIS 1.8 (and also Spatialite-gui) delivers an "Invalid SRID" error message when I try to load shapefiles with a SRID value of 3814 (Mississippi Transverse Mercatur). The SRID is ...
5
votes
0answers
132 views

How to add shapefile name as attribute during merge? [duplicate]

Possible Duplicate: How to add field with filename when merging shapefiles with ogr2ogr? I have more 200 shapefiles with a unique name. I would like to merge all of these together and save ...
3
votes
2answers
674 views

set geotiff 0 values to nodata

Is there a way to set all the 0 value pixels on a raster to nodata using gdal or qgis?I world like to use fillnodata to fill some holes, but holes are set to 0,so I need to delete them first
7
votes
1answer
5k views

Is there are QGIS plugin to allow the 3d visualisation of geological borehole data similar to the functionality of Target for ArcGIS?

I'm very new to QGIS, I have started using it as my new company is not willing to pay for ArcGIS and Target at this stage so I'm hoping QGIS can substitute not just in the interim but for good. What ...
3
votes
1answer
262 views

How to create a line with start and end points which are in another layer in QGIS?

In my map, there are lots of points in layer A. I want to make a line layer B and I want to make start & end points of lines snapping to points in layer A manually. Can I use points of layer A as ...
4
votes
3answers
94 views

Left click then right click is treated as double click in Mac QGIS Layers

I am having an issue with QGIS 1.8.0 on my Mac where I left click then right click which gets treated as a double click if the timing is too close together and brings up the Layer Properties box. ...
4
votes
2answers
607 views

How do I set mmqgis create grid options?

I am having a puzzle about using mmqgis create vector layer option. I want to use UTM CSR this are my options. I want a grid of 20,000 meters in the east and north axis. Nevertheless i have an error ...
5
votes
1answer
400 views

Stats on individual grid points nearest neighbours

First, thank you for this extremely useful and easy-to-access forum! I have shp of points where each point is the centroid of the individual cells of a 1*1km grid (~ 500 000 points). For each of ...
1
vote
0answers
217 views

QGIS WMS using tile size restrictions

When I add a WMS layer with a tile size restriction (2048 2048) the resulting WMS datasource in the QGIS project file is ...
2
votes
2answers
2k views

Editing polylines in QGIS (extend, trim, fillet etc)

I was wondering, if its possible to edit lines and polylines in qgis, in similiar way as autocad commands "extend", "trim" and "fillet"? About how the commands for in Autocad, very shortly: The ...
2
votes
1answer
251 views

Raster Analysis - Identifying features from Raster

I have an IDW, tension spline and hill-shade rasters that show an archaeological landscape and from these rasters I want to identify new features which are seen in the landscape as depressions. And ...
11
votes
1answer
423 views

How to create text labels with background boxes?

I'm trying to create some custom labels for point features in a QGIS point vector layer, and I want to write a python plugin to do it. We need our labels to be presented with color tinted rectangles ...
2
votes
1answer
418 views

QGIS ->ArcGIS Server configuration possible?

Is it possible to connect a QGIS Desktop 1.8.0 to an ArcGIS Server 10.0 ? and of course publish services on it?. The configuration would be like this Quantum GIS-> ArcGIS Server 10.0 on Amazon EC2+ ...
5
votes
1answer
141 views

How to convert PostGis Table (Grid data) to Continuous field using Qgis?

I'd like to transform my Gridded Layer (generated form a PostGIS table of points) to a continuous and colored layer. How could I do this with Qgis or any other program? Many thanks and best regards, ...
4
votes
2answers
398 views

Edit Toolbar Became Disabled While Editing in QGIS

My edit toolbar became disabled while I was editing a layer in QGIS. I have closed the window and opened it again to edit, but it is still disabled.
2
votes
1answer
193 views

Sextante “temp” folder?

I have a german Windows and the problem is when I'm using sextante tools the log tells me that I have issues with the folder dokumente und einstellungen (C:\Programme\Quantum GIS Lisboa>saga_cmd ...
1
vote
1answer
72 views

Can't find the New label tools in QGIS

I can't find the New label tools in QGIS developed by sourcepole. I'm using QGIS 1.7.4. Is it a QGIS tool or a pluggin? Thanks!
2
votes
0answers
147 views

Sextante - SAGA- Shape to grid question?

I have a vektor shape (Index 1-5). After using the saga tool (shapes to grid) I'm getting a raster (values 1-5). The problem is that the NO DATA area is defined as 129. Is it possible to set 129 as no ...
1
vote
2answers
473 views

error message when clipping raster with vector layer

When I try to crop a raster using QGIS Clipper tool, I get the following error message: ERROR 1: Attempt to create 0x0 dataset is illegal,sizes must be larger than zero.. Why? The code QGIS generated ...
4
votes
1answer
682 views

Unit of $length in QGis Field Calculator

I'm calculating field of various features in my shapefile using QGis. I'm getting some sample length as 0.134914579766986. I want to know in what unit (eg: meters, km etc) is the above value ?
11
votes
3answers
3k views

Are there open-source alternatives to ArcGIS online that can be hosted on my own server?

I know this might be too broad topic. But I am looking for web-GIS portal similar to ArcGIS online that is self-installable (configurable) to be hosted in my private server. The main features should ...
7
votes
1answer
510 views

Why do vectors disappears when zooming in?

I have imported a .gpx file into qgis and separated the track waypoints using Vector > GPS > GPS tools. When viewing at full extent I can see the original track and component waypoints. However when ...
4
votes
1answer
758 views

how to add a custom SRID to Spatialite

I'd like to create a spatialite database and load it with shapefiles using the Mississippi Transverse Mercator (MSTM) projection, but it doesn't have an EPSG definition in the spatialite library of ...
5
votes
2answers
621 views

How to add a sequence to the attribute table?

Is there a way to use the field calculator in QGIS to create a range of values in a count sequence with a specified input range? For example, if I wanted to have the values 1 to 5 repeated within my ...
1
vote
1answer
3k views

Build Polygons from Polylines

I have to build the polygons from some polylines it is an area like a main land(with some boundaries) and some islands around it,islands are building polygons and main land is missing,when i have ...
2
votes
1answer
211 views

How to label a selection of an OSM layer depending on certain tags?

I just imported original OSM data to export a pdf-map by assigning graphic attributes to the features I need. The label tool in QGIS 1.8 allows to select certain features, like I can do with the ...
6
votes
1answer
550 views

How can I fix QGIS 1.8.0 Spit Plugin “connection failed”?

I want to import shp to to postgreSQL with the spit plugin. Testing the database connection to my PostGIS database ist successfully (I already imported layers with this connection via the "add postGIS ...
4
votes
1answer
81 views

Show derived rasters in titles selection QGIS

I would like to create a map in QGIS 1.8 with indexed titles which are connected with topo-map titles files (geoTIFFs). My endeavor is to make (if it is possible) layer which can react on user mouse ...
2
votes
2answers
212 views

Cannot add Plugins from Python: “Plugin is Broken”

I'm using the latest version of QGIS on a Windows 7 (32 bits), and when I try to add a plugin from the option "Fetch Python Plugins", it simply cancels the installation and I can see the following ...
1
vote
1answer
101 views

Transform csv-coordinates into area

I'm working with an inventory of a species in Southern Sweden. I have recorded my findings (together with coordinates, name of the species and year of finding) and created a CSV-file with i have ...
2
votes
1answer
542 views

Contour Lines Raster Extraction

I've been playing with Mapbox's blog post about converting heat maps to contour lines, and I'm stuck at the extraction part of this process. I used the CSV plugin to create a vector layer of points, ...
3
votes
1answer
151 views

How to find features with NULL values?

I have a layer to analyze and I want to create a thematic map with rule based feature. There is a strange behaviour. I want to find all objects with no data (NULL). All empty objects. The zero value ...
11
votes
2answers
272 views

How to sort by multiple fields at the same time?

Is it possible to sort multiple fields at the same time in QGIS? For example, I'd like to sort a table by state name, and then within each state, sort by county name. This would be the same as the ...
1
vote
1answer
70 views

Is there a free tool for configuring WMS configuration xml?

Instead of writing WMS xml file from scratch with notepad , is there a tool that is easy to create/configure such a file (or convert a GIS workspace - MapInfo / QGIS into WMS file) ?
10
votes
6answers
1k views

How do I make a heat or Choropleth map that uses polygons in QGis?

I've been playing around with the heatmap plugin for QGIS and I am wondering if it is possible to make heatmap with using a similar plugin/tool that uses polygons as well as points? I would like to ...
4
votes
1answer
132 views

How to aggregate point measurements in areas?

I have a shapefile with the geographical boundaries of towns in a specific region; then i have a csv file (with xy coords) with a lot of measurements about pollution in this region. I'd like to have ...
1
vote
2answers
379 views

How can I fix Print Composer errors due to huge file size?

I have put together a map using the British OS Strategi data set which is pretty densely detailed. It is surveyed at 1:250,000 and so contains roads down to track level, rivers, villages, railway ...