Questions tagged [qgis]
QGIS is a cross-platform GIS application licensed under the GNU General Public License.
32,253
questions
5
votes
1answer
112 views
QGIS: Create polygon shapefile of ellipses from points using Geometry by expression tool
In QGIS 3.16.6 I need to create a polygon shapefile of ellipses from points. I am doing the following:
Processing Toolbox -> Vector Geometry -> Geometry by expression
Input layer - points_in....
2
votes
2answers
178 views
Passing variable to URI filepath
I want to load CSV file to QGIS. It works if I use the strings below:
uri ="file:///C:/Users/User/Desktop/Alex working/Tracks//Track.csv?delimiter={}&crs=epsg:25831&xField={}&yField={}...
1
vote
0answers
17 views
WMS: How can I connect to deegree (localhost)?
I have deegree version 3.4.16 running on 127.0.0.1:8080 (localhost). I want to connect QGIS version 3.10.5-A Coruña to deegree (localhost).
I have set the following parameters in "Create a New ...
0
votes
0answers
53 views
Calculating the greatest length of a polygon using QGIS [duplicate]
I'm new to QGIS and I need to know the easiest way to calculate the greatest length of a polygon. I already know the "rule" tool but I want to do it automatically because I have a huge ...
3
votes
1answer
150 views
Creating the minimum convex hull that contains certain percentage of points in QGIS
I'm working with QGIS 3.16 Hannover. I've got a point layer (shapefile) with 3,000 features and I want to create the smallest convex hull that contains 90% of those points. Well, ideally, I would like ...
1
vote
1answer
52 views
Creating a polygon around a “real estate” depending on my point “control” using QGIS
I am new to GIS and trying to learn as much as I can. Currently, I am not able to understand how one specific project works.
What I have:
Layer "Controls"
layer "Base Map of the city&...
3
votes
1answer
46 views
Generate point layer (grid values) with Z coordinate of (TIN) interpolated raster in QGIS 3.16
1. Question With Additional Information:
I would like to generate a sparsely packed layer containing points labelled with the Z-column of an existing interpolated TIN raster
A sample photograph what ...
0
votes
0answers
23 views
QGIS - error connection of database in RiverGIS
Currently, I am facing a problem to connect Postgres database to RiverGIS. It shows this error.
Couldn't connect to river database: rivergis@localhost
Please, check you database connection settings!
...
0
votes
0answers
25 views
How can I define a threshold or outlier for the elevation difference between two different time period taken in rock, that should be zero?
I am doing the geodetic mass balance of a glacier and I have the elevation difference that was produced in the glacier, but now I have to correct this data but making the mean of the elevation ...
0
votes
0answers
24 views
Grid from SAGA natural neighbor results in black grid
I'm new in QGIS and I'm following tutorials mainly on YouTube so I created a path in Google Earth then exported to kml which is converted to txt via GPS visualizer.
When added delimited layer it shows ...
1
vote
1answer
42 views
Perpendicular line creation is not working in QGIS
I run the transect tool with 90 degree required parameter to draw perpendicular lines from a line. I got the output but when I measured the angle it is not showing as 95 degree.
What will be the error?...
1
vote
1answer
35 views
Use attribute of all filtered features of one layer as label in the Print composer
Is it possible to filter some features in one layer and use those filtered features as labels in the Print composer of another layer?
I am trying to make an atlas. I have two layers, one which has the ...
1
vote
1answer
45 views
Finding the gaps/holes in DEM [closed]
I have a SRTM DEM and need to find whether it has voids or gaps in the data.
4
votes
1answer
55 views
Selecting the transect lines which touches the divide of a polygon from the river line
I have a polygon and transect lines which passes inside the polygon.
Here I want to select the lines which touch the drainage and divide. The transect lines split at the river intersection.
Since ...
0
votes
0answers
21 views
v.net.steiner tool in QGIS not producing output
I have a shapefile of a network of points mostly on roads (a county shapefile from TIGER downloads). I want to find a minimal length tree along the road network that hits all points within 100m of the ...
0
votes
0answers
22 views
Users can't save styles on the db PostGIS
I have a PostgreSQL database, and only with the PostgreSQL user (who's the owner of that table), I'm able to save styles to the database. I checked the user's permissions for the other group roles and ...
0
votes
1answer
40 views
Download all coffe-shop locations in Italy from OSM. Stuck with Qgis, R and geofabrik
I wanted to download all café locations from OSM in Italy.
I tried various ways and one of them was in qgis. I used the awesome quickosm-plugin and did the following:
But it always fails with a ...
1
vote
1answer
41 views
Iteration over features in PyQGIS processing modules
I have an issue with processing.run commands where I would like to do an iteration over features in a layer with polygons.
zsj = QgsVectorLayer("/data/grassmaster/testVlado/zsj_ba_test.gpkg",...
9
votes
3answers
229 views
Calculating semi-major and semi-minor axis length of an ellipse in QGIS
I have a layer that contains ellipse-shaped geometries. The layer has projected CRS and there are also rotated ellipses in the layer. I couldn't find a tool or plugin related to semi-major and semi-...
1
vote
0answers
21 views
QGIS Raster Merge Outputs Mysterious Bands
I am using the Raster>Miscellaneous>Merge tool in QGIS to merge two different GeoTiff(s) into one layer. They are two different agricultural fields. When I merge them, it seems that the rgba ...
3
votes
1answer
61 views
How to create border around multiple polygons
Spent hours on a search. No luck. I need to create a border around selected adjacent polygons. Concave Hull and Convex Hull don't give the desired results. It seems to be a simple request. The problem ...
3
votes
1answer
35 views
How do I automatically remove the lines across the midrib which a river doesn't overlap?
I have a river line, mid-rib and transect line
I am trying to get a transect line by keeping mid-rib as the reference and I need to include only the transect lines that overlap the river.
Just like ...
0
votes
0answers
12 views
Loading GeoTIFF altimetry file created from GDAL or QGIS into a GeoServer failed
GeoServer version : 2.18.2
GDAL version : 3.1.4
QGIS version : 3.16.3
I have a GeoTIFF altimetry file with some missing data which is loaded perfectly in my GeoServer. I just extracted a new GeoTIFF ...
1
vote
0answers
40 views
Extracting ridges and peaks in QGIS
Is there a way to extract mountain ridges in QGIS? I have been trying to use the Valley and Ridge Detection SAGA tool, but it freezes for hours and I am wondering if there is a faster or alternative ...
0
votes
1answer
20 views
Merging several ASCII (.asc) files together and then converting it to a GeoTIFF (.tif)
In QGIS I'm trying to merge several ASCII (.asc) ESRI files in REGCAN95 (EPSG:4083) projection together to make one big file, and then convert it to GeoTIFF (.tif) in WGS84 (EPSG:4326) projection for ...
1
vote
0answers
16 views
QGIS clipping OpenStreetMap but still being able to run functions such as ORS Tools on the layer [duplicate]
I have struggled to find a solution to be able to clip an OpenStreetMap (OSM) raster layer but still run functions using plugins such as ORS Tools. I would like to clip OSM with an overlaying vector ...
3
votes
1answer
61 views
How to optimize PostGIS Intersection Query
I've 2 sets of polygons in 2 tables and the sets overlap each other. For each polygon in set A, I get the ID of the polygon in set B that it overlaps the most.
This is the query:
SELECT DISTINCT ON (a....
1
vote
1answer
32 views
Extract administrative boundaries with physical borders at the coast line from OSM data
I successfully downloaded the OSM data from https://www.geofabrik.de/ and converted the .osm.pbf file to a .gpkg using og2ogr. Now I want to extract administrative boundaries using DB-Manager and SQL:
...
1
vote
1answer
23 views
How to create a NetCDF mesh with x y vector data for QGIS mesh display
I have created a NetCDF mesh with u and v variables for velocity. I can load it onto QGIS 3.14 as a mesh layer. The variables are not recognized as vector though (isVector : No is displayer in group ...
1
vote
1answer
32 views
Extract the mean elevation from a raster by a mask with several spatial objects
I am working with a glacier and I want to get the Hypsometric curve of the elevation difference between two time periods. I divided the mask of the glacier by the contour lines (each 50 m) and now I ...
1
vote
1answer
30 views
Expression to extract part of an address [closed]
I have a column of addresses and want to separate into several parts.
Ex. house number, street name, city, zip. For example lets say I have a cell with this string: '111 Example St, City, State 89786 ...
0
votes
0answers
35 views
Mass downloading raster tiles using QGIS
I want to mass download georectified sat image tiles (XYZ tiles) and save them locally.
I could setup QGIS so I can see google sat images.
So for example, I want all tiles of Los Angeles in a geo ...
1
vote
1answer
48 views
Flooded roads and deprived communities: QGIS route analysis function to avoid flooded roads?
In QGIS I am analysing the flooding of road networks. I have created a vector line layer of all the stretches of roads in my study area where high risk flood extent areas intersect them. I now want to ...
1
vote
0answers
27 views
Non-alignment of vector and raster layers in QGIS
I have a vector map layer, raster climate data and added a delimited text points layer. My problem is that the raster extent does not quite match the edge of the vector map, and as a result, some of ...
5
votes
1answer
71 views
Remove all but one lines in cluster of parallel lines
I just want one line that represents the centroid of a bunch of parallel lines, which one in each bunch doesn't matter.
I've already tried doing a dissolve operation to make one thick line that ...
0
votes
0answers
37 views
Draw a centroid line through a line-like polygon feature?
I have all these line segments travelling between points:
I want all the one close to each other to be merged into a single feature. So I dissolved them like so:
Now I just want one line travelling ...
7
votes
2answers
127 views
Automatic fill-in of columns in QGIS
I collect data on birds in my city. In my column, I have the Names of the Birds, their scientific name and their abbreviation.
Now I am searching for a simple solution to simplify the work. I would ...
3
votes
1answer
45 views
How can I create a 10 day composite image of the snow cover extent using QGIS?
I have 10 singleband rasters of the snow cover extent (1 raster/day from 1st of December to 10th of December). I have to create a composite image that merges all of them. I tried the r.composite tool ...
-1
votes
0answers
20 views
reclassify raster based on pixel color
I rasterized a vector layer with the intent of having a binary raster layer. Somehow I ended up with a raster that looks right but both the black and white pixels have the value 1 - i want the white/...
2
votes
1answer
34 views
Exporting same attribute values to separate layers and merging them in QGIS
I am trying to split watersheds of the same attribute table into separate layers.
The Two two repeated values, for eg. SW1 and SW1 both are splits from a same watershed called 'SW1'. I am trying to ...
6
votes
2answers
145 views
Merging multiple temporal inputs in QGIS Graphical Modeler
I want to do a simple merge of some algorithm outputs in QGIS graphical modeler (not for an iterative process, like my previous question "Collect results of iterative processes in QGIS graphical ...
5
votes
1answer
43 views
Collect results of iterative processes in QGIS graphical modeler
I'm using QGIS graphical modeler to build an iterative process that is supposed to:
extract features from vector layer 1 (VL1) overlapping with features from vector layer 2 (VL2) (iterative per ...
4
votes
1answer
76 views
Getting all of combinations of features found on two layers using QGIS
This is a problem that seems like it should be simple, but it's a little difficult to explain. I have two polygon layers, each with a few hundred features (specifically the districts of England and ...
1
vote
0answers
53 views
QGIS crashes when I try to check for double or check for crossing lines
I have a LineString layer that I want to check for double geometries and/or intersecting lines. I've tried two different tools (Check Geometry (Geometryprüfung) and Check Topology (Topologyprüfung)) ...
4
votes
1answer
64 views
QField - create a form for multiple, 1:n photos
I have read the QField support on how to add a series of pictures to a feature. I've also read other threads and GIS Stack Exchange questions and answers on this: e.g., Setting QField for 1:n photos. ...
3
votes
1answer
57 views
Adding legend for specific ranges not for discrete values in QGIS
I want to add legend for a QGIS proportional symbol map rangewise. That is my data ranges from 57000-630000. So I want the legend as:
57000-60000,
60500-70000,
74000-79000,
81000-87000,
90000-94000,
...
0
votes
0answers
15 views
QGIS Expression Dialogue for Reclassify values problem
I'm trying to reclassify values (simple) for a raster grid within a Model Designer (process modeller). I want to incorporate a 'number input' within the range for reclassifying e.g.:
[0, @MaxDepth, -...
3
votes
2answers
161 views
Creating border at a particular distance from country border
I am new to GIS platform. I am using QGIS. I want to create lines inside map similar to border of country at a particular distance (say 100 KM). My data is in geographic coordinate system.
2
votes
1answer
47 views
Adapt attribute table QGIS legend from bottom
I have an attribute table controlled by Atlas on map composer from QGIS. I need to adapt the table for each map and its features but from bottom. In other words, I need to make grow the table from ...
0
votes
0answers
24 views
DEM water body visualisation (QGIS): extract areas with a min amount of pixels with the same value (= water surface)
I want to create a background map of a DEM (1m spatial resolution) to show the study area.
The study area (Northern Germany) contains many water bodies. I have problems with the visualisation of these ...
