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

learn more… | top users | synonyms (1)

4
votes
0answers
202 views

Is it possible to use memory layers in QGIS processing algorithms?

I am building a QGIS plugin that connects to a MySQL database in the local network, and then adds a subset of one of the tables to an in-memory layer; the subset is based on data currency (only taking ...
4
votes
0answers
281 views

Error when using r.watershed in QGIS 2.10.1 with Grass

I am running r.watershed within QGIS processing the I get the error below. I draw your attention to: GRASS_INFO_WARNING(2205,1): Subprocess failed with exit code 256 GRASS_INFO_END(2205,1) ...
4
votes
0answers
106 views

Merge Raster Layer Specific Order in Graphic Modeler

I'm using the Graphic Modeler/Processing Modeler to automate a process. The last step in this process is Merging three different Raster Layers. I'm using the "Merge Raster Layers" from Saga 2.0.8. ...
4
votes
0answers
91 views

Resampling air temperature gridded data to sub-grid resolution

I'd like to obtain a 30-m resolution gridded dataset of air temperature from the ~1km gridded data of WorldClim, of Hijmans et al., 2005) for a mountainous region. The easiest procedure (I thought ...
4
votes
0answers
304 views

Display a color ramp legend (of a vector layer) in the qgis map composer

I would like to have a color ramp instead of 10 categories of color when displaying my vector layer in the map composer of QGIS. Is it possible ?
4
votes
0answers
351 views

How to debug Quantum GIS PlugIn Visual Studio DLL?

I develop a Quantum GIS plugin layer using Microsoft Visual studio and placed it in my plugins folder of my customized quantum gis application. I now intend to debug the DLL using Microsoft Studio. ...
3
votes
0answers
27 views

How to assign polygon attributes to grid cells using centroids in QGIS?

I am relatively new usign QGIS but have realized it is a great tool. Unfortunately I can´t figure out the following yet. I have two polygon shapefiles, one is a grid I have created using QGIS ...
3
votes
0answers
24 views

r.sun from QGIS toolbox doesn't give realistic value about the hours of insolation

I have a problem with the GRASS module r.sun when I run it in QGIS. I would calculate the hours of insolation in a specific site during a specific day. When I ran the algorithm "r.sun" from GRASS, it ...
3
votes
0answers
30 views

How to calculate average value of a raster, that is clipped by multiple polygons?

I am using QGIS 2.12.0. I have a raster of coherence value (SAR interferometry) and a land use shape. I wish to calculate mean coherence value for those areas with a specific land use. I split land ...
3
votes
0answers
56 views

Python script to automate saving satellite images for different combinations of lat longs

PS. : This is my first try at a GIS application. Please forgive if my question is pedantic. I would like to get a series of satellite images all at the same scale centered around different points on ...
3
votes
0answers
29 views

How to fill composer map with canvas data and export composition as png using Python script in QGIS

I'd like to create a Python script in QGIS that will take some data (shp + tif, in my example), use tamplate Map Composer (from a file) and export created composition to a png image. With almost no ...
3
votes
0answers
42 views

Combine multiple adjoining parts of a single feature

In QGIS, one polygon feature resulted from merger of several adjacent polygons. This one new polygon feature has a single line through it that I would like to eliminate. When hovering over individual ...
3
votes
0answers
50 views

Can qgis_core work with external python distribution (such as Anaconda)

I've built a python application that has its own GUI. I am trying to use qgis.core/pyQgis as map display only. Specifically, i have anaconda 2.3 and its python distribution (2.7.11). After research on ...
3
votes
0answers
39 views

Positional accuracy assessment methods in qgis

I'm doing an quality assessment of openstreetmap's street data. As a comparism dataset I have to use an administrative dataset, which is highly accurate and comes in polygons. Here's a sneak peek: ...
3
votes
0answers
46 views

Can you add summary statistics to a legend in QGIS print composer?

I would like to be able to add summary statistics to a legend in print composer e.g. GB Agricultural Land Classification: - Grade 1 (Area: xx hectares, xx% of total) - Grade 2 (Area: xx hectares, xx% ...
3
votes
0answers
30 views

QGIS Georeferencer is stretching image

I'm trying to Georeference an image. I've followed the guide from QGIS, but for some reason, it's stretching, and offsetting the image from the points. For example, my input of the southwest corner ...
3
votes
0answers
62 views

Is it possible to add intermediate contour values automatically in QGIS?

Let me explain the scenario. We have 100's of elevation contour shp files. In each file, only the 10th contour line has values (200, 450, 700, etc..). We have to attribute values for all the ...
3
votes
0answers
41 views

QGIS Map Composer Label Unit Multiplier - Feet and miles?

I have a map in the WGS84 (EPS:4326) coordinate system and I am putting a scale bar on the map with Scalebar units of Feet and label in miles. When I select Feet from the Scalebar units dropdown ...
3
votes
0answers
21 views

Creating Projection/Datum TransvMerc/OrdSurvGrtBrit in QGIS?

I have Memory Map files QCT exported to ECW. The Projection/Datum is Transverse Mercator / Ordnance Survey Great Britain which is not mentioned in the list of Projections/Datums available. How can I ...
3
votes
0answers
53 views

Creating custom CRS based on local project parameters in QGIS?

I'm having trouble creating custom proj4 CRS files to work with existing .shp files on local project coordinates. (Local in that the coordinates are relative only to themselves and not the 'real ...
3
votes
0answers
57 views

Symbology Representations in QGIS

Is there a way to create and apply non-destructive symbology to features in QGIS? In ArcGIS, you can create 'representations' of a feature classes symbology, which allows you to make independent ...
3
votes
0answers
45 views

Downsampling for beginners using QGIS

I apologise from the outset. I need a full run through of working gdalwarp to downsample a raster to match another i.e. How to resample GeoTIFF images to the same resolution?. Using QGIS 2.12. Using ...
3
votes
0answers
40 views

QGIS atlas export produces map in smaller scale then in composer

I've load in QGIS 2.1, OSM map with OpenLayer plugin and I've create two rectangles represents coverage layer for Atlas. Then I've set Atlas in composer, first picture below; This preview should ...
3
votes
0answers
61 views

spatial index intersection with qgsrectangle only computes polygones

I have the problem, that i only get polygon features inside my defined rectangle. If i switch off my polygon layer(s) i get my lines. TOC: Line-Layer on, Polygon-Layer on: i only get Polygons which ...
3
votes
0answers
20 views

Displaying attribute values in IntraMaps Roam?

I am having troubles with displaying attribute values in IntraMaps Roam. Let me give you more details: My QGIS project is based on an SQLite database The attribute table in QGIS is displaying the ...
3
votes
0answers
87 views

“Error” on Advanced Digitizing Window in QGIS

I have the word "Error" that has appeared on my Advanced Digitizing Panel since upgrading to QGIS 2.12.0 Lyon. It doesn't appear to actually affect anything negatively... has anyone else seen this or ...
3
votes
0answers
38 views

SAGA Tool in QGIS Error: Load table: Proj.4-WKT Dictionary… failed

I have some problems with running SAGA tools in QGIS. I've downloaded and installed the software via the OSGeo4W Installer. It downloaded QGIS 2.12 and Saga 2.1.2. I wanted to use the Tool "Shapes To ...
3
votes
0answers
47 views

PyQgis: Print Composer using input from several Spatialite-tables

How can I create PDFs out of QGIS using the Print Composer Templates that include a lot of text (from a text-template) and within the text several information comes out of my spatiallite-database. A ...
3
votes
0answers
57 views

Using linguistic phonetic alphabet in QGIS?

I want to know if there is a way to use the International Phonetic Alphabet in QGIS? I am working with a group of linguistics that want to map dialectic varibility in a language (Nahuatl) and I am ...
3
votes
0answers
55 views

How are costs returned by the pyQGIS implementation of Dijkstra calculated?

How are the costs returned by pyQGIS implementation of Dijkstra (QgsGraphAnalyzer.dijkstra) calculated? As far as I know, these costs correspond to the distance from the starting node to each of the ...
3
votes
0answers
77 views

QGIS Azimuth and Distance Plugin curve

I have just installed the Azimuth and Distance plugin for QGIS and I have been testing it for use with our COGO workload. However when using the Anti-Clockwise ArcDirection method for a curve to the ...
3
votes
0answers
46 views

QGIS Contours plugin

I am a starter but managed to load osm-data with osm2po, pgrouting, postgis and postgresql into qgis! Yay! Then I did a drivingdistance analysis based on cost to finally get the qgis contours plugin ...
3
votes
0answers
30 views

How do you show agreement between polygons based on hand-drawn maps?

I'm somewhat new to GIS, coming from a linguistic background, and now I'm trying to make QGIS do something that I want from that background. I have some hand drawn maps with certain areas of the ...
3
votes
0answers
82 views

How can I properly rename a table in a SpatiaLite DB?

Spatial layers (tables) in SpatiaLite include various supporting objects and metadata, including triggers, indices, and entries in (at minimum) the geometry_columns table. I'm looking for (preferably) ...
3
votes
0answers
43 views

How to randomly select three points in each polygon?

I have two layers: first layer includes polygons of districts, second layer containts points (phytocoenological relevées). The goal is to create a new layer that will contain max 3 randomly selected ...
3
votes
0answers
83 views

Merge line segments by length (in QGIS)

I have a layer containing line segments which are connected by their endpoints (e.g. as within a street network). I'd like to merge (union) polylines within this layer into one feature until following ...
3
votes
0answers
135 views

QGIS 2.8 Python Plugin Unittest Segmentation Fault 11

UPDATE: This issue may be isolated to my MacBook. The seg fault did not occur in testing on Windows. I have put together a sample unit test for a QGIS python plugin. It is causing a Segmentation ...
3
votes
0answers
62 views

Trouble importing an QGIS ascii DEM file

The output I get from QGIS 7.0.1 for an ASCII DEM file doesn't seem to be a correct format. It differs from the format I get when I download a DEM file from webGIS ( ...
3
votes
0answers
61 views

Printing a 1" scale from 2.8.2 Print Composer

I'm working on a small-scale site survey in qGIS, and for engineering purposes I need to print physical copies of the map that can be used with an engineering ruler. Basically, I need a way to print ...
3
votes
0answers
105 views

MMQGis plugin error

I am using QGIS 2.8.2 and I'm trying to geocode some addresses, but when I run it, I get this error: An error has occured while executing Python code: Traceback (most recent call last): File ...
3
votes
0answers
70 views

Drawing “proportional” buffer using QGIS or GRASS?

I'm working on aquatic vegetation and have a shapefile representing floating vegetation in a lake. By some studies, we know that submerged vegetation extends for a certain extension based on floating ...
3
votes
0answers
153 views

QGIS : transformation types in geo-referencing

Im a beginner in geomatics. I try some images georeferencing in QGIS. I would like to understand what is happening behind the different transformation types (linear, polynomial, Helmert...). What I ...
3
votes
0answers
75 views

SAGA hydrological analysis in QGIS 2.8 on Mac

I am running QGIS 2.8 on a Mac machine and I want to calculate the catchment area using SAGA - Catchment Area. It starts running but after a while when QGIS wants to open the generated files there is ...
3
votes
0answers
94 views

Which projection can I use to see alignments on great circles?

I want to put on a QGIS map some historical sites to check if they are aligned. If an alignement exists, the points should stay on a great circle (is this correct?). I want to visually verify this ...
3
votes
0answers
93 views

Visualizing variability in the size and shape of polygons

I am working with a data set of area restrictions imposed by criminal courts. These restrictions ban a person from entering a demarcated area. These restrictions vary in their size, shape, and ...
3
votes
0answers
35 views

Programatically export map clusters in QGIS

I'm trying to export each microcluster of a large map into a composed map that shows the ff on an A4 sheet: 1) Cluster/grid box of the map 2) Larger index map with the pertinent region highlighted ...
3
votes
0answers
157 views

Is it possible to create Isochrones in QGIS GUI?

I'm new to QGIS and have tried to create isochrones around points for quite some time. Is there any option to create isochrones on the GUI in QGIS? I know how to create them using pgAdmin (using eg ...
3
votes
0answers
128 views

How to offset polyline geometries (not symbology) using QGIS?

I have a polyline layer which has a road network digitized, up the center, in both directions however the polyline are sat "one on top of the other". I can display the lines separately by ...
3
votes
0answers
63 views

How to make a virtual field function use the same Ellipsoid settings as the normal field calculator?

I have a new shapefile layer in CRS 3857, in a project that has the same CRS. Under project properties, the measure tool is on ellipsoid WGS 84. When i use the field calculator to create a new field ...
3
votes
0answers
187 views

Performance difference between focal statistics (ArcGIS) and neighbor (GRAS or QGIS)

I tested minimum, maximum, and average neighbor (circle radius = 161 pixel) using ArcGIS, GRASS and QGIS: ArcGIS (10.1): it takes only one minute GRASS (6.4.3): it takes 123 minutes for every output ...