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

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42 views

How to get the upstream average of a raster data layer that falls into a river network?

I have a raster layer of a network of rivers and a raster layer of data I want to extract. For each pixel of the rivers, I need to know the upstream average of the data layer that falls into the ...
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3answers
54 views

Why does Georef'd image show as a large black area

Using QGIS2.4.0 I just added 2 maps to an existing project. Both are scanned images of pre-1800 plans. One is a jpg file, I georef'd and added to QGIS no problem and plan displays in the project. I ...
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68 views

Snapping feature nodes doesn't work after feature creation (filter involved)

I've experienced a strange behaviour during editing mode: I have set a filter to 2 features (polygons), part of on of my PostGIS layers: "name"='A' OR "name"='B' After that I have created a new ...
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40 views

Batch processing ( offset of font marker) in QGIS

I have a group of layers with type linestring. Every line consists of simple line and marker line (font marker). I have a batch file(csv) with offsets of font markers. Do you know if there is any ...
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1answer
212 views

Spatial Query: The query from “LayerName” using “FID” in field not possible

In QGIS Wien, I am performing a spatial query with two layers (points and buffer areas) and receive the following error when creating a new layer with intersecting features: The query from "LayerName" ...
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1answer
102 views

QGIS for geophysical surveying?

I need to make 30x30 and 20x20 grid layouts with co-ordinate points in the corners. These points then need to be relayed to a GPS to be able to set the grids out in person and then survey them. The ...
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1answer
73 views

Visualising Multiple Routes from pgrouting in QGIS

I am able to Visualise the Single Route from Source A to Target B by the following code in QGIS SQL "id" in ( SELECT id2 as id FROM pgr_dijkstra( 'SELECT id, source, target, cost FROM ways', ...
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1answer
263 views

Layers with the same CRS in QGIS do not line up

I am busy with a project where I have to layer a .dxf and a .kml file but the layers are not lining up. The .dxf file's coordinates are completely wrong and the scale also does not appear to math up ...
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2answers
260 views

How to select features containing specific text string using an expression in QGIS

I need to style a survey parcel polygon shapefile, based on whether the polygon is a mineral claim or not. Unfortunately, the only information on whether a polygon is a mineral claim or not is ...
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1answer
127 views

Calculating area using dissolve and merge but getting shapefiles with empty attribute tables in QGIS?

I have a shapefile of a country with the 29 provinces. I also have shapefiles with the areas which are protected from construction (there are 4 categories for protection, within 4 shapefiles. Some of ...
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0answers
66 views

From track+waypoints to elevation profile with waypoints

I have a track and waypoints (1) imported in QGIS. I want to calculate the closest point from every waypoint to the track (2). Then, I want a table with data that allows me to draw an elevation ...
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0answers
63 views

Creating random points using QGIS?

Has anyone else had any issues using the random points tool in QGIS? When I try using it I'm selecting the option to use a value input field. The tool starts but then freezes once it gets to the 10% ...
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1answer
133 views

QGIS2WEB white screen on export/preview?

When I export my QGIS2WEB project it goes through, but when it loads up in my browser after the export is done all I see is a white background with the zoom/minus feature in the top left hand of the ...
2
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1answer
62 views

How can I save a QGIS project with hyperlinks?

I have already created an hyperlink project using actions, it works, when I click on one point of my shapefile it opens a photo, but when I re-open the project, the action is gone and I have to create ...
2
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1answer
103 views

QGIS Plugins & Tools that replicate Select ArcPy Tools

I developed a complex python application for road generation from GPS Devices that uses a few Arcpy Tools. I want to try and replicate this Applications functionality using a freeware like PyQGIS ...
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2answers
207 views

QGIS2WEB Error when exporting to Leaflet/OL3

I am having all kinds of problems with the QGIS plugins fr exporting my map to Leaflet or OL3. Whenever I try to preview my project I just get a white screen with nothing. Then when I try to Export to ...
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0answers
52 views

How to create displacement vectors in QGIS using GPS points with different dates?

Is there a way to calculate and visualize displacement vectors in QGIS ? I have DGPS points taken at the same place (ground control points), but their position moved over time as they are located on a ...
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2answers
241 views

PostGIS - How to calculate linestring length from WGS84 after transforming from OSGB 36

I am having problems getting lengths from multilinestrings after transforming data from EPSG:27700 - OSGB 1936 / British National Grid to EPSG:4326/ WGS 84. I'm doing this conversion to import a ...
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0answers
26 views

line from min to max of a digital elevation model

I have some geometries as multipolygons and a dem (digital elevation model). I need a line from the max value to the lowest value of the dem for every multipolygon. Is qgis a tool i could use or do i ...
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1answer
59 views

Update points coordinates directly on the map using QGIS?

I have many locations or points overlapped each other, so is there a way using QGIS that I can update locations directly on the map using QGIS features, please let me know as I'm new to GIS.
2
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1answer
68 views

Update GPS coordinates to overlapped locations? is there a quick way to do so? I'm using QGIS?

If I have two many locations overlapped each other, and I want to update their coordinates to make the view clear and be able to spot the locations? How can I do this easily? I have more than 512 ...
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2answers
110 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 ...
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1answer
126 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 ...
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1answer
37 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 ...
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2answers
230 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): ...
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0answers
81 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 ...
2
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1answer
293 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 ...
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0answers
75 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" ...
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0answers
134 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
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1answer
272 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 ...
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0answers
79 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 ...
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1answer
127 views

How to create multipe labels on polygons?

Is there any tool or function to create muliple labels on polygons? Edit: Meanwhile I've created a point layer for label placement using the refFunctions plugin. geomwithin('polygon', 'label') ...
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0answers
157 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 ...
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1answer
111 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 ...
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1answer
55 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
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1answer
345 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= ...
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0answers
188 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 ...
2
votes
1answer
184 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 ...
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2answers
374 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
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1answer
100 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
2answers
114 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 ...
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0answers
31 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 ...
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1answer
60 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 ...
3
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0answers
310 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 ...
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2answers
218 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 ...
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0answers
35 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 ...
2
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1answer
83 views

Why value relation doesn't work when I delete and connect reference layer?

I'm trying to connect reference table (domain) with data(text) to my vector layer (id's) using value relation. I have database in Oracle connected. It works fine, but when I delete the reference layer ...
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1answer
83 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' ...
3
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1answer
332 views

Performing viewshed analysis with Dutch AHN files in QGIS?

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. ...
2
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1answer
118 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 ...