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

learn more… | top users | synonyms (1)

0
votes
1answer
10 views

How to get ST_MakeLine ready for QGIS?

CREATE VIEW new_line AS SELECT point1.gid, ST_MakeLine(point1.geom, point2.geom) FROM point1, point2 WHERE point1.gid = point2.gid; It's possible to load the layer but QGIS says 'There is no entry ...
0
votes
1answer
24 views

find the population density of some points in qgis/postgis

I have the tiger census data of population density in each block group. I also have a different kind of data: traffic accident data, where an accident has a lat/lon pair. My goal is to find the ...
0
votes
1answer
17 views

How do I enable lineweights for my symbology?

I imported an OSM shapefile of roads data. In the layer properties, I classified the roads based on type (motorway, trunk, residential, etc.). I can assign colors but cannot assign lineweights. I can ...
0
votes
1answer
15 views

QgisInterface.addVectorLayer Error

I am Esri-trained, trying to move into QGIS using Python. Simply trying to add a vector layer in Qgis returns the below error: TypeError: QgisInterface.addVectorLayer(QString, QString, QString): ...
0
votes
0answers
9 views

QQIG/SAGA “merge shapes layers” algorithm removes underscores/pluses from layer names

I have a bunch of layers that are named layername_number+number that I want to merge. I need their names as source attribute so I used the "merge shapes layers" algorithm found under SAGA in the ...
0
votes
1answer
29 views

How to export the map in very high resolution

I made a map in QGIS. Now I want to export the resulting image (layers upon layers) for further processing in GDAL. The print composer only lets me export an image up to a fixed size. If I try to ...
0
votes
0answers
13 views

qgis atlas : problem with scale bar

Good afternoon, I'm working with qgis 2.8 (windows). I 'm abble to generate maps thanks to qgis atlas. But i have everytime a problem about the scale bar. When i generate atlas with "fix scale" ...
2
votes
0answers
12 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 ...
2
votes
1answer
36 views

different way to build qgis python standalone application

There seems to be 2 different ways to start a Python QGIS standalone script. The official tutorial is using : from qgis.core import * # supply path to where is your qgis installed ...
1
vote
0answers
27 views

Drawing “proportional” buffer using QGIS?

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 ...
2
votes
1answer
59 views

How to create multipe labels on polygons?

Is there any tool or function to create muliple labels on polygons? I've already created point geometries which refer to the polygon geometries but QGIS gets slower and slower with every new ...
2
votes
0answers
20 views

QGIS, faulty Zonal Statistics calculations in case of empty polygons

I run QGIS 2.10 on a 64-bit Debian system and am currently trying to do some basic raster vector statistics. However, I found that when applying the Zonal Statistics plugin, I end up with completely ...
0
votes
1answer
37 views

How can we export shapfile to svg format using Pyqgis

I am doing a project where i have to export file from shapefile to svg format using Pyqgis. i have read some articles regarding simplesvg plugin but i don't know how can we achieve the same task using ...
1
vote
1answer
27 views

How to restrict panning in QGIS to a given extent

I'm going to build a QGIS standalone application. According to the requirements full extent equals to the extent of a predefined rectangle (say bounding box of a parcel). The application should start ...
4
votes
1answer
53 views

QGIS Export Shapefile

i am trying to export selected feature using pyqgis. till now i have tried these codes. after using this i can select feature but dont know how to export selected feature to new shapefile. canvas= ...
1
vote
0answers
25 views

Error: GRASS 7.0 and QGIS 2.8.1 in Linux Mint from the ubuntugis-unstable

I have installed GRASS 7 and QGIS 2.8.1 from the https://launchpad.net/~ubuntugis/+archive/ubuntu/ubuntugis-unstable (Trusty 14.04) in Linux Mint 17.1 64bit(sudo apt-get install postgis libgdal1h ...
1
vote
0answers
22 views

Maps with numbers and postcodes using QGIS?

I have a list of UK postcodes and a number of participants in a survey. I would like to map the first three letters of the UK postcode and I would like a shape....a circular shape for example which ...
0
votes
2answers
29 views

QGIS2Leaf Plugin installation error “cannot import name AlgorithmDecorator”

I have been using the qgis2leaf plugin and succeeded in creating interactive maps, adding legend, photos, etc. But suddenly I noticed that the OSM base layer has disappeared and the polygons are not ...
2
votes
1answer
56 views

How to create a sequence for a table which was created by selecting data from another table?

I have created a new table by selecting data from an existing table: CREATE TABLE polygon2 AS SELECT gid, geom FROM polygon1; CREATE SEQUENCE polygon2_gid_seq; SELECT SETVAL('polygon2_gid_seq', ...
2
votes
1answer
28 views

Qgis2leaf doesn't show layers with scale-dependent visibility

When I add layers to the QGIS2LEAF dialog box it accepts it and opens up the preview in my web browser, but when I starting looking for the layers, in this case points for campgrounds, I dont see any ...
0
votes
0answers
21 views

QGIS 'Clip raster by mask layer': Problem loading output [on hold]

I'm using QGIS 2.8, currently developing a python plugin and at some point I have to execute consecutive processing algorithms. When it comes to loading the layer created by GDAL algorithm 'Clip ...
1
vote
0answers
19 views

QGIS Wien 2.8. Openlayers plugin doesn't work [duplicate]

I have installed the latest version of QGIS wien 2.8. Windows 8.1 downloaded the stand alone version from official QGIS website. I had to uninstall the latest one I had because Openlayers plugin was ...
1
vote
1answer
16 views

Getting NULL-values when point sampling USGS (SRTM 1 Arc-Second Global) grid (QGIS 2.8.2)

I use the Point Sampling Tool in QGIS to transfer gridvalues (of DEMs) to point features. This goes well with grids from f.i. MapMart (SRTMHARRIS_DEM), but I get only NULL-values when using grids from ...
2
votes
0answers
24 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 ...
-1
votes
0answers
27 views

ArcGIS and / or QGIS and UAV tech [on hold]

I see it has been almost a year since the last "UAV and GIS" question was asked here. Finding some incredible youtube videos recently showing remarkable results doing UAV and GIS together here and ...
4
votes
2answers
99 views

Meaning of GCP in QGIS

Im a geomatics student, During a geo referencing with QGIS, a .Points file is saved. I open it with Notepad++ It is written under this form : mapX,mapY,pixelX,pixelY,enable ...
1
vote
0answers
14 views

Error in merging two raster files (precipitation) in QGIS

The newly computed geotiff shows the extent of both raster layers, but only the data of one. If I use identify features tool it gives me only the values of the visible part not of the other part. I ...
1
vote
1answer
29 views

trigger postgis and dump qgis 2.8.2

I created a trigger that checks if geometry is valid on insert and update. create or replace function check_geom() returns trigger as $$ begin --insert a polygon IF st_isvalid(new.geom) = 'f' ...
2
votes
1answer
43 views

How to perform viewshed analysis with Dutch AHN files?

i downloaded the new (dutch hight data) AHN files, and was trying to perform a viewshed analysis at some point near UTRECHT. The plugin (grass plugin) works ok, i tried it before with a dem map. ...
0
votes
0answers
20 views

QGIS Spatialite Views problems

I am trying to wrap my head around spatialite views in QGIS. However there are severe limitations that make it very cumbersome: Spatialite views in QGIS do no update, if the corresponding tables in ...
1
vote
1answer
25 views

How can I create polygons for a 3D map from a DEM in grass/qgis

I have a SRTM 30m DEM of my area. I want to create a physical 3D terrain map from it (from felt, 3D printer, you name it). I have two questions about this process: With grass r.contour I created ...
1
vote
0answers
14 views

How to export from WINSTAR to ArcGIS [on hold]

I have data in a very old "winstar" type of format. However, currently I only use ArcGIS for Desktop and QGIS. Does anyone have an idea on how I can import this old-fashioned winstar stuff to ArcGIS ...
2
votes
1answer
32 views

How can I copy non-blank values to a new column from different columns in the same layer in QGIS?

My data: n1 n2 n3 NEW_COLUMN 11 null null null 33 null null null 55 My desired result: n1 n2 n3 NEW_COLUMN 11 null null 11 null 33 null 33 null null 55 ...
2
votes
0answers
9 views

Remote sensing Classification and texture analysis compared with QGIS zonal statistics

Some back round: Using Geomatica to analyse suburban spectral signature in Las Vegas. Ran a texture analysis on all band images. Combined texture bands with original image bands to run an unsupervised ...
1
vote
0answers
14 views

Toggle layers on print composition

I want to use QGIS to make several views of bold colors for one same map. I've been using the layers in order to keep one on top of another. How could i make a composition on the print composition ...
1
vote
0answers
14 views

Change detection between two Landsat scenes? [duplicate]

I want to do time series analysis and find change in NDVI. I have rasters where each pixel is represented by some value at a time. Also I have same thing but represented by points. And I would like ...
2
votes
1answer
36 views

How do I make a hexgrid in QGIS with cell identification numbers

I'm getting started with QGIS as part of my interest in military science and wargaming. I'm running into a problem adding identifiers (column and row) to the hexcells that I've created with mmqgis. ...
1
vote
1answer
35 views

Using proj to convert EPSG:2263 to WGS84

I have input data in EPSG:2263 with X and Y coordinates such as: X,Y 987043,206407 982441,212359 990907,209020 (these locations are within NYC). I need to convert these to WGS84. Using QGIS if I ...
0
votes
1answer
42 views

Merge shapefiles heatmap

I have to merge few shapefiles into one and create a heat map out of it in qgis. I'm a first user of the QGIS, I tried to do it there: vector-management tools-merge files into one, but it kept to make ...
2
votes
0answers
15 views

Add individual fields to delete-log-trigger when deleting PostGis-Objects via QGis

I am using a PostGres Database with PostGis extension (on Windows). QGis serves as a client to access (visualize and edit) certain database-tables. I need to create a delete-log-table that saves all ...
1
vote
2answers
23 views

Load USGS DRG into QGIS

I'm trying to load some DRG data from the USGS into QGIS. The source data uses UTM coordinate and I can't seem to get it to overlay with WGS 84 vector data. I (think) I've followed the recommended ...
2
votes
1answer
38 views

Adding QGIS feature, that shows coordinates and scale, into a custom application

I'm writing a standalone application using PyQGIS and I'd like to add the QGIS feature that shows coordinates and scale as the cursor hovers over the map. I need to know this mainly in case of ...
3
votes
0answers
34 views

How to develop QGIS Plugin to fully run Spatial Queries With PostGIS?

I'm developing a QGIS plugin that fully run spatial queries with PostGIS. Actually I developed all spatial queries wish need some adjustment. I'm looking for some ressources or documents to know how ...
1
vote
3answers
46 views

Rotating labels in QGIS 2.8.2

I have a question concerning label placement in QGIS. I'd like to rotate every label by 180°. Therefore, I set the rotation value to 180 (I've tried different ones as well as different variable types) ...
0
votes
0answers
16 views

GML geometries are not rendered

I tried to view a GML file and I have a problem with viewing of polygons from a feature type ps:ProtectedSite with QGIS. This feature contains a MultiSurface with a surfaceMember with a ...
3
votes
2answers
40 views

How to fix the error between two coordinate systems?

How do you think the shift of line is due to morphological change of river? Or it is due to deviation between two coordinate systems? Please point out !!
2
votes
1answer
37 views

Layer Order panel seems to be broken in QGIS 2.10, it duplicates layers

I'd like to just confirm that a problem I am having in QGIS 2.10 is not unique to me. I am using the Layer Order panel to control the rendering order of layers in my projects, it's very useful when ...
2
votes
1answer
20 views

Merge and export two layers that utilize blending modes

I have a new question that I'm trying to solve. Spent more time than I can to admit trying to come up with a solution that doesn't require bringing the layers into Photoshop or the GIMP (which would ...
2
votes
1answer
35 views

Can I use TIFF files for zonal statistics in QGIS or ARCGIS?

I am completing a remote sensing paper and am doing most of the work in PCI Geomatica, where I have 2 separate files. One from running a texture analysis algorithm containing 6 band layers from a ...
3
votes
2answers
58 views

How to place coordinates points on a vector layer?

I have got GPS coordinates collected from a number of farms in my country (Malawi). But when I plot these GPS coordinates on a vector layer (my country map) using QGIS, the points are falling outside ...