Questions tagged [qgis]

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

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11
votes
3answers
2k 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 +ellps=...
6
votes
3answers
6k 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
1k 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 ...
14
votes
1answer
2k 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 point. ...
1
vote
0answers
199 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
1k 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
1k views

Fixing raster with wrong Eastings using QGIS and GDAL?

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 ...
22
votes
1answer
2k 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 ...
18
votes
1answer
10k 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 ...
3
votes
2answers
3k 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 ...
11
votes
5answers
4k 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
678 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?
17
votes
3answers
12k views

Creating polygon with extents of 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 ...
11
votes
1answer
9k views

Creating 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 ...
7
votes
1answer
4k views

Calculating size of particular area below 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 ...
7
votes
3answers
9k views

Finding line length while editing in QGIS?

I am using QGIS. 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 being created?
3
votes
1answer
1k 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, x-...
1
vote
1answer
668 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 ...
2
votes
1answer
708 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 ...
4
votes
1answer
5k views

How to change the the style of a vector layer programmatically? [duplicate]

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 ...
9
votes
1answer
2k 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 semi-...
3
votes
2answers
545 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 (a,b,c)...
4
votes
3answers
6k views

Conflicting measurement units with buffer ftools [duplicate]

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 ...
6
votes
3answers
812 views

How can I create a “setback” buffer for coastal lines 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
295 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, ...
7
votes
3answers
2k 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 ...
36
votes
4answers
22k views

Selecting features with NULL attributes in QGIS?

How do I 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)
7
votes
2answers
1k 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? I'...
11
votes
6answers
11k 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, ...
4
votes
2answers
7k 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 ...
14
votes
1answer
827 views

Nearest Neighbor Grouped Selection in QGIS

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 all of these points into box groups and by that I ...
4
votes
2answers
9k views

Why does QGIS scalebar show a wrong scale?

I'm using QGIS 1.7.1 and have added a scalebar. The scalebar usually displays in degrees, unless I switch the map's projection to meters, in which case the units are display in cm. This is not correct....
11
votes
2answers
4k views

How can I export a linestring to a GPX file in QGIS?

I have a linestring in a vector layer in QGIS. How can I expot/save this linestring as a GPX file? I tried to select the linestring, then right click on the vector layer and choose "Save selection as....
6
votes
2answers
13k views

Performing statistics or simple pie chart in QGIS?

Does anyone know how to perform pie charts based on table values within QGIS and include them in the print outs?
13
votes
1answer
20k views

Transforming polygon to linestring in QGIS?

I have a polygon, imported from a shapefile in QGIS. I would like transform it to a linestring instead so I can save it as a GPX file later. How can I transform a polygon to a linestring in QGIS?
2
votes
0answers
301 views

GIS “hack”: ways arbitarily assigning coordinate in order to match the raster and vector layer in QGIS [closed]

Before I raise my question, I have to admit that I am a total newer on GIS, I don't have much background on GIS. But suddenly I need to take over the GIS job from a GIS specialist who just left the ...
0
votes
1answer
3k views

Import Error while Importing osgeo package [duplicate]

Possible Duplicate: How to install GDAL with Python on windows? I have downloaded Fwtools for python2.5 from http://fwtools.maptools.org(windows installer) after installing it, it was giving ...
13
votes
4answers
10k views

Join attributes of point and line layer by location (closest distance) in QGIS

My problem is the following: i have a line shp (target layer) and a point shp (join layer). the second one (point layer) holds an attribute which i want to join with a line layer based on closest ...
11
votes
3answers
8k views

Create Shapefile with auto increment primary key in QGIS

Is there a way to create an auto increment primary key column when creating a new Shapefile in QGIS?
2
votes
2answers
4k views

How to set cell size for vector to raster conversion in QGIS GRASS plugin?

I'm converting a vector (loaded in GRASS plugin in QGIS (1.7.0.-wroclaw) and would like to convert this to a raster with a defined cell size. At the same time I need a value from the attribute tabel ...
6
votes
3answers
869 views

Is there a way to syncronize the current view extent in QGIS with Google Earth?

I already have the openlayers plugin but it's not working has I need it and I wanted to have the same view on both QGIS and Google Earth. Any ideas? Update: I'm using the openlayers plugin which ...
5
votes
3answers
1k views

How can I import only a subset of the polygons in a Shapefile using QGIS?

I have a shapefile that is covering a huge area, with lots of polygons. The area I'm insteresting in is small and limited. Is there any way to only import (using "add vector layer") the polygons from ...
2
votes
0answers
917 views

QGIS Layer Properties Field Tab

When I setup my layer properties I selected some of the attributes to be hidden on the Fields tab. I would like to change the EDIT WIDGET from hidden to a different function however some of them are ...
4
votes
3answers
1k views

Relationship between sp package in R; MapWindow; ArcGIS/QGIS?

I am using ArcGIS at office for some visualization work, but I feel it kinda dump to performing the same tasks several times for visualizing some data on different maps. I am think of automating it ...
8
votes
2answers
1k views

Is there an open source tool to planarize graphs?

I read about the planarize function in ArcGIS, which seem to do exactly what I want. Is there a similar feature in QGIS or another free tool? I have a shapefile with various shapes intersecting each ...
5
votes
6answers
2k views

Is there a Log or Ln function in QGIS Field Calculator?

I can't seem to find any way to take the logarithm (natural or base 10) of a field in QGIS. I have gotten to the field calculator but there is not a button for log and I can't seem find any formula ...
3
votes
3answers
4k views

Georeferencing to x y coordinates with one lat long origin?

We are running parallel transect lines for a survey, which will roughly cover a rectangular area. When making the transects, we will periodically capture spatial locations of features and events we ...
4
votes
1answer
10k views

How to select and copy a group of polygons in QGIS?

I'm new to QGIS. I opened a few shapefiles that cover Europe. Now I want to select a smaller area and if possible copy the polygons in this area so I can work with a smaller set. How should I do this ...
5
votes
3answers
7k views

How to create a map of only one state in QGIS?

This is a very simple question but a Google search did not provide an answer. Basically suppose you have a map of the U.S. with states and county layers, as well as other layers like roads, etc. ...

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