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

learn more… | top users | synonyms

7
votes
2answers
700 views

What is the difference between != NULL and IS NOT NULL?

I have a shape layer with an attribute containing NULL values to which I would like to apply a filter for values different from NULL. Using the available gui for such query construction, one would ...
0
votes
0answers
2 views

GRASS dependecies issues in Windows QGIS (i.vi for instance)

I have QGIS (2.14.3) and GRASS (7.0.4) desktop installed on windows 7 and have successfully installed the "GRASS" plugin in QGIS (using plugin manager). However, some of the GRASS dependencies, such ...
2
votes
1answer
212 views

SAGA Cluster Analysis for grids projection issue

I am having an issue with the SAGA cluster analysis for grids tool within QGIS 2.4. I am actually taking this as an online class through Del Mar and we are going over supervised and unsupervised ...
0
votes
0answers
24 views

GDAL Raster plugin doesn't work

I am connected to Oracle, using QGIS and can see the vector data table. I am trying to use the GDAL Raster plugin to view raster data, in QGIS. When I click on the Oracle GeoRaster plugin, get a ...
0
votes
0answers
12 views

QGIS Atlas turning on/off raster layers

I'm attempting to create a series of maps in qgis atlas with the same coverage and background data but different raster outputs (flood mapping outputs for a range of scenarios). I've created a .shp ...
1
vote
2answers
56 views

Calculate distance between two points with QGIS 2.14.0

I don’t use QGIS that much. I have two shapefiles with the following information: List A: ID 1, xA, yA, ID 2, …. List B: ID 1, xB, yB, ID 2, …. x/y = lat/lon I want to calculate the ...
1
vote
0answers
45 views

How does NULL data effect weighted mean calculations?

I am using QGIS. I've been calculating weighted means based off a database. The database was created by combining two different sets of Data together. The Attribute Table then shows Null values for ...
1
vote
2answers
32 views

Can't normalize LiDAR point cloud with lasheight and -replace z (LAStools)

When I try to use lasheight with -replace z to normalize the point cloud, the height of points are changed (destroyed heights; see pictures below). Without using -replace z everything is ok, but the ...
0
votes
0answers
25 views

How to remove the white border of polygons using QGIS

I use the graduated color style for the polygons. But there are white borders between polygons. I tried to set Border: transparant, Border stype: No pen, Border width: 0. It did not work. I found a ...
2
votes
1answer
34 views

Why do I get “Data source is invalid” error when calling method?

QGIS 2.14 on Windows 7. I'm trying to call a method in a python script from the QGIS python console. I've put the directory in which the scripts resides in the PYTHONPATH in both the windows system ...
2
votes
1answer
43 views

How to speed up QGIS vector clip?

I'm trying to clip a large polygon shapefile (nearly 440,000 features, 0.5GB) to a shapefile containing a single polygon. Both shapefiles use the same CRS (EPSG:27700). With QGIS, using Vector > ...
1
vote
0answers
21 views

How to move projects from a server to local hard disk or removable drive?

I have a QGIS project on a desktop that I need to move to a laptop to take into the field. Whilst in the office, both PCs talk to the project on server via a persistent mapped drive (L:) - ie. ...
0
votes
2answers
41 views

Is it possible to import a Shapefile from Manifold into QGIS with the same projection?

is it possible to import a shapefiles from manifold to Qgis with the same projection?
1
vote
2answers
557 views

How to connect an oracle 10g database to QGIS? (TNS:Could not resolve the connect identifier specified)

Trying to connect an oracle 10g database to QGIS. I'm getting the error below: ORA - 12154: TNS:Could not resolve the connect identifier specified Anybody ever seen this error, or could provide some ...
1
vote
0answers
21 views

Is there a way to have custom functions automatically load in QGIS on start up?

I have a custom function for the print composer that prints out copyrights, but every time I start QGIS up and go to the Print Composer for the first time, I have to the Insert Expression > Function ...
13
votes
3answers
10k views

How to create polygons with straight lines and right angles in QGIS?

I am running QGIS 1.7.0 on Mac OS X 10.6.8. When creating a polygon, how do I do it so that the lines are straight (90, 0 degrees, etc.) and when I create corners they can be right angles? For ...
5
votes
1answer
233 views

Permanent Histogram Stretch with QGIS or FWTools

Is there a way to permanently stretch a histogram of a raster within QGIS or gdal? I would like to stretch a satellite image with a Standard Deviation 2.5 stretch. I would prefer to use QGIS or ...
0
votes
0answers
12 views

How to quickly add a DWG with multiple layers?

In QGIS 2.14 "Essen", I need to add a DWG with multiple layers. So I choose "add vector layer" feature in QGIS 2.0 to import the .dwg/.dxf file. However, QGIS adds all layers from the DWG file ...
2
votes
1answer
23 views

QGIS 2.14.4 attribute table fields not visible in Statist plugin

I had one point shapefile to which I joined new numerical attributes by a csv text file. I saved it by right clicking and everything works fine, I use it for calculations etc. But when I use the "...
1
vote
0answers
15 views

Grid Reference autotext expression

I am trying to create some extremely user friendly print composer templates that have an awful lot of autotext data that updates for each composer without having to manually type it in. I ave done ...
1
vote
1answer
50 views

how to join a road network into as few lines as possible?

I am processing a polyline file that contains multiple lines representing city roads. I would like to join the lines together into as few lines as possible. I've tried using the 'join multiple lines' ...
0
votes
0answers
12 views

How to add legend to rasterlayer in Qgis2Web plugin while exporting maps?

Is it possible to add a legend for Rasterlayer directly from the Qgis2Web Plugin or do I need to add the code manually?
4
votes
0answers
39 views
+50

Problem executing vectorgrid (from processing) in a standalone script using QGIS 2.8.6

I have the following piece of code which I execute within QGIS 2.8.6 import processing import ogr restrLayer = QgsVectorLayer("/home/usr/Desktop/trial/EligibleAreas_polygons_filtered.shp", "...
2
votes
1answer
110 views

Finding list of all shapefiles that overlap with single shapefile using QGIS?

I have a list of 34 shapefiles. These shapefiles are range maps for different species. I would like to take 4 of these shapefiles and document a list of those shapefiles (within the 30 shapefiles), ...
1
vote
2answers
53 views

Add attributes to layer

I'm trying to add a new attribute to a vector layer in my plugin. But it does not work.. Why? selectedLayerIndex = self.dlg.comboBox.currentIndex() selectedLayer = layers[selectedLayerIndex] name = "...
3
votes
1answer
29 views

Re-import custom functions without restarting QGIS

I have a python file (in [user]\.qgis2\python) with some functions that I'm working on. It's just a .py file with a bunch of def function_1, def function_2 etc. in it. On startup I import the .py file ...
1
vote
2answers
28 views

Setting up rulebased labelling programmatically in QGIS?

In my plugin I do some labelling a vector layer with QgsPalLayerSettings. This works fine for me with QgsMapRenderer::setLabelingEngine. But now I also want to implement the rulebased labelling. In ...
0
votes
0answers
15 views

Getting HTML webpage into QGIS layers panel

I have created a webpage that capture information from heremaps and write to DB using Heremaps API and PHP. How do i run this webpage into QGIS like other WMS or WFS and do the same mechanism which it ...
0
votes
0answers
18 views

Add attribute column with road's altitude [duplicate]

I have some vector layers with a set of latitude and longitude coordinates.Is it possible to add a new column to the attributes table containing the altitudes of the road? (the data was collected ...
1
vote
0answers
17 views

Three dimensional Routing [on hold]

I have created a route by hand using the Tracing Tool available in QGIS. I wanted to export all the coordinates to another program, so I saved them in a CSV file. The problem is that I can only see ...
2
votes
1answer
57 views

Clipping of a Raster changes Range of Cell Values

I'm facing a strange problem. I created a mosaic of two landsat scenes which contains values from ~ -5 to ~11 (Biomass estimation). As my study area is much smaller then the mosaiced Landsat8 scenes, ...
1
vote
0answers
36 views

Corrupted Shapefiles when saving edits in QGIS

Has anyone experience regular corruption of Shapefiles when saving edits in QGIS? Since testing the new LTR, we have had regular occurrences of the Shapefile being corrupted, and "_packed" SHP and ...
0
votes
0answers
13 views

Install unstable Qgis-master alongside release version [duplicate]

Good day I have the release version of Qgis (2.16) installed into Mint and it can be updated just with apt install qgis whenever a notification comes out that a new version is released. I want to ...
1
vote
2answers
290 views

How to compile QGIS from source with Grass?

I recently decided to reinstall QGIS and build against the latest version of GDAL - something I have been putting off for ages because I suspected it would be a nightmare. Lo and behold it has been, ...
5
votes
4answers
1k views

How do I rename Shapefiles in QGIS?

I have a huge list of layers in a project that are named in a foreign language. I want to translate and add the English title to the name. When I right click on a layer and choose Properties -> ...
2
votes
2answers
19 views

Correct syntax for loading virtualxl spatialite table?

I believe I have successfully loaded a virtual Excel table into a spatialite database using the SQL below - typed into the qspatialite plugin for QGIS. create VIRTUAL TABLE MyVirtualTable1 USING ...
0
votes
1answer
19 views

Direct access to DGPS data in QGIS?

I'm heading out to the Arctic Circle (Spitsbergen) I have a Sokkia DGPS and Magnet on a tablet device (connects to the DGPS and logs the data), they connect via blue tooth etc. Can I bring the data ...
3
votes
1answer
197 views

Is it possible to create tiles with transparent background using Qtiles?

I had created the tiles from shapefile using qtiles plugin in QGIS and that shapefile layer is a label layer created using MMQGIS plugin. But the thing is I want that tiles with transparent background....
1
vote
1answer
35 views

Why is the legend symbol alignment in Print Composer worse than in the main window layer list?

I created a point layer where point-symbols' size depends on a column of the attribute table. When they appear in Layers Panel, symbols look like this (every circle's centroid has the same "X-value" ...
2
votes
1answer
142 views

QGIS crashing/failing when dissolving multiple shapefiles in a Python loop

I am using QGIS 2.10 (but I've also tried 2.8) to loop through all the shapefiles in a folder (those ending in .shp) and perform a dissolve function on each of them. However, when I run the following ...
1
vote
1answer
65 views

Extract height values from vector to CSV

I have generated a CSV file (using the MMQGIS plugin) expecting to obtain all the coordinates of a vector layer that I have created. But the output file only contains the latitude and longitude ...
2
votes
1answer
223 views

Trouble Converting from a shp. to gpx file and up loading to GPS

Currently I have a series of random points within a shapefile that I would like to upload to my GPS. Every time I try to upload the points via "Save file" it come up with an error message (posted ...
0
votes
0answers
23 views

Join attributes by location - QGIS

I am trying to perform an attributes join by location between a shapefile (with points) and a second shapefile (with polygons). The points are hydrometric gauges, whereas the polygons are catchments. ...
3
votes
2answers
1k views

How to connect a PyQGIS plugin with Postgres?

I have some questions for you: I created a python-plugin in QGIS, then I created a Qt gui fom my plugin and at last I created a Postgres DB now I need to make a connection between Qt-gui and ...
2
votes
1answer
27 views

Why does my reprojected globe visualisation not draw?

I have followed all of the instructions in QGIS Map Design, Graser and Peterson, Locate Press 2016, and cannot get the visual of the reprojected shapefiles clipped to Rome coordinates to draw as in ...
3
votes
2answers
286 views

latitude/longitude to linestring or points

I have a gps file that I have converted to csv, I would like to convert a longitude/latitude to linestring if the next row have a diferent longitude/latitude (if the car mooved) and if not convert it ...
1
vote
1answer
19 views

QGIS: SAGA-GIS module “Add raster value to point” Error: unknown option 'INTERPOL'

I encountered an error while using the "Add raster value to point" SAGA-GIS module in QGIS (2.16) to retrieve altitude values from a raster DEM previously interpolated from TIN points (as vector ...
2
votes
0answers
35 views

QGIS GRASS: Error when converting vector to raster

I am trying to convert a vectorial layer (a grid of regular points with values, representing probabilities, associated to each point). I tried to use QGIS, but I got this error: ERROR 1: Attempt to ...
0
votes
1answer
23 views

Furthest point from polygon/point

I want to calculate distance between smaller dots (they represent towns, villages etc.) and these larger red dots (capital cities of admin. region). My goal is to show wich location is the furthest ...
11
votes
1answer
329 views

PyQGIS save raster as rendered image, then use GDAL tools on it

I have tried to use the code from QGis Save Raster as Rendered Image. i is a raster layer: pipelayer = i pipeextent = pipelayer.extent() pipewidth, pipeheight = (pipelayer.width(), ...