Questions tagged [qgis]

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

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6
votes
1answer
54 views

Find out what Expression has been used to populate an attribute column in QGIS

I need to find out what expression has been used in the field calculator to populate a number of columns in the the attribute table in QGIS. Does anyone know how to get it to display this info? Like ...
1
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1answer
47 views

Handling NULL values in QGIS

I am using QGIS to make some boundaries adjustments of the Italian provinces over the years. I have a shapefile with the provincial boundaries in 1961 and another one with the boundaries in 2001. No ...
1
vote
1answer
23 views

QGIS dissolve algoritm: how to select multiple field in modelbuilder

I am trying to make a model in the processing modeler of QGIS. I need a step where a layer with polygons is dissolved based on two fields. At the moment I do this manually. When I open the dissolve ...
0
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0answers
35 views

Join attribute by location giving bigger results QGIS

I have created a grid over South Africa, each cell being 10 km x 10 km. In addition, I have a raster layer that has been polygonized, each polygon containing a population count. The total of these ...
0
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0answers
16 views

Raster reprojection error with gdalwarp

I want to reproject a raster from the rather common EPSG:4326 (WGS 84) to EPSG:5677 (DHDN / 3-degree Gauss-Kruger zone 3 (E-N)) : gdalwarp -s_srs EPSG:4326 -t_srs EPSG:5677 -r near -of GTiff C:/.../...
0
votes
3answers
65 views

Speed up rendering background vector data in QGIS

I have a geopackage of ordnance survey background data (field boundaries, rivers, roads, etc). I won't be doing any analysis on this data it will purely be used as a background / basemap. My problem ...
1
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0answers
36 views

Not able to use previous fields for default values expression

I've got the following problem : I have different periods (selected with a drop-down menu, which is like "Paléolithique", "Mésolithique"... etc) and I'd like the fields "Année inf" and "Année sup" to ...
2
votes
1answer
35 views

Export labels from autocad to qgis

Is there a way to export my labels from AutoCAD into QGIS? Right now i have to label everything again in QGIS. importing an dxf-file does not work. Only points, lines or polygons will be inserted.
6
votes
2answers
142 views

QGIS and PostGIS, dimensions problems

I have a point-layer i Postgis v12 which is ST_point, ST_NDims = 3. When creating a new point i QGIS and then tries to save it, I get an error: Column has Z dimension but geometry does not When ...
1
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1answer
30 views

QGIS - Using Rule Based Labels With Related Tables

I have a two csv tables that have been related to eachother (RelatedResults): Table 1 = Locations which is loaded as points Which has the fields[ID] [Type] [X] [Y] Example: Point_1, Frogs, LAT, LONG ...
0
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1answer
43 views

Looping through list of coordinates to create polygons on Google Earth Engine

I have imported a CSV file with just one column. Each row of the column has multiple coordinates required to draw a polygon. (This was collected on the ground) I have used the below code to extract ...
1
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0answers
36 views

OSM in QuickMapServices not displaying baselayer image on QGIS

[I am attempting to load a QuickMapServices OSM baselayer image on QGIS 3.4 LTR and nothing is displayed, even though it says that the layer has been added. Nothing seems wrong with my plug-ins and I ...
4
votes
1answer
55 views

Display photo stored as blob in GPKG

I maintain a layer in my project that indexes geotagged research photos. Right now, the layer (in a gpkg) has an attribute PhotoPath which points to the photos stored separately on disk. I then use a ...
0
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0answers
31 views

Land parcel area inconsistencies in EPSG:4283 and/or ESRI:102171

I have parcel data from Landata, the agency that looks after land parcels in Victoria, Australia. I am finding a huge difference in the area calculated in QGIS for the parcel compared to onground ...
1
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0answers
18 views

How do I install QGIS Server and QWC2 via Gitpod?

Maybe this question is better suited to the Web Apps SE. I want to create a self-hosted instance of QGIS Server and the QGIS Web Client 2, for times when I'm not on a computer with admin access (such ...
1
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0answers
23 views

Using Odoo as a database for QGIS

Is it possible to link an Odoo database (CRM) into GGIS? I have an online Odoo Studio account with lots of data including long/lat data etc. Is it possible to link the Odoo database directly with Qgis ...
0
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1answer
20 views

Trying to recode raster with CSV using the Grass r.recode.attr but getting error “name 'xrange' is not defined”

I'm trying to recode a large GSSURGO soil raster with CSV using the Grass r.recode.attr following these instructions https://pvanb.wordpress.com/2014/12/13/recode-your-raster-file-in-grass-gis-using-a-...
1
vote
1answer
34 views

PyQGIS: drop features belonging to same group conditional on other attribute expression

I have a polygon shapefile on which I need to eliminate features belonging to the same group (identified by a variable/attribute XG) on the base of the values taken by another variable YA. In ...
1
vote
1answer
51 views

QGIS 3x viewshed plugin returns wrong results for visibility map

I am wondering, where I could make the mistake seeing the wrong result, which is coming from the Viewshed plugin in QGIS. There are a few options, I selected the "Viewshed", which looks like this: ...
0
votes
1answer
22 views

QGIS sum up polygon features inside grid

I have a grid with population points inside each of the individual cells. I've used the "join attributes by location" tool to join each population point to their respective cell. Now I'd like to sum ...
0
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0answers
19 views

Importing coordinates from Google Maps as CSV into QGIS, but points are displaying in wrong location [duplicate]

I'm using QGIS and am trying to import coordinates pulled from Google Maps as CSV but they are displaying in the wrong location. They should be showing up in CA, however they are only displaying in ...
0
votes
0answers
70 views

Display parcel by number entered into QLineEdit

I created a custom search form. Once displayed in QGIS, if I enter a record number into QLineEdit and hit OK button, I want to display and zoom corresponding parcel. Here is my code : from PyQt4....
3
votes
1answer
51 views

Exporting shapefiles as SVG polylines

Recently I've been using QGIS to create fracture tracemaps as line shapefiles. I need to export these lines as an SVG that uses the tag polylines rather than paths. I've used the SimpleSVG plugin but ...
0
votes
1answer
54 views

Verify PostGIS connection, username and password

I wrote the code below, but I need that the PostGIS connection to be verified, to be sure that the username and password are right. I tried this: How to access user credentials in database connection? ...
0
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0answers
38 views

Select Channel Network within QGIS

I have created a Channel Network polyline shapefile from the Channel Network tool in QGIS. I now need to select any channel routes which flow through the red polygon as shown below. The attribute ...
1
vote
1answer
26 views

Remove white gaps which appear when the local tile map is zoom in-out in QGIS?

I am using QGIS with local XYZ layer. When I zoom in, zoom out and move the map the layers load slowly. First there is white gaps int the edges, then the map loads and the gaps close. On the other ...
0
votes
0answers
25 views

Polygon bends when exporting out of AutoCAD

I came across a strange issue when exporting a polygon layer from AutoCAD Civil 3D to a shapefile. The original AutoCAD drawing looks like this: When loading it in to QGIS it looks correct: But ...
1
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0answers
50 views

Interpolating xyz-points to raster in QGIS

I want to interpolate xyz-point data to a raster. x,y,z 3435339.20,5412714.28,-0.22 3435340.19,5412714.28,0.06 3435339.20,5412715.28,-0.20 I imported it as csv and saved it as shape. Then I ...
1
vote
1answer
24 views

Put the start and the end name of a point object into the layer of the line object that connects them? [duplicate]

I am new to QGIS. I am given two layers with point objects. In their attribute table each of this objects has a code (name) given previously to it by someone else. Then I import the lines from AutoCAD ...
0
votes
1answer
32 views

Update path of attributes to a new path

I have a layer with photos that are linked/displayed through the path attribute. Now I need to move this path and need to update it. I could of course create a whole new file but I wonder if it could ...
4
votes
1answer
153 views

Where is QGIS master password stored

I have a QGIS project, based on data from a PostgreSQL database. In this database I create an extra user, with limited rights. I want to give this project to other users, but I don't want that they ...
1
vote
2answers
41 views

Removing both sets of duplicate points

I'm trying to create points on the edges of polygons. So far I have converted the polygons to lines, then exploded the lines, then ran the following code which plots a point in the middle of the ...
0
votes
1answer
17 views

GRASS v.transform tool producing no results QGIS

I'm working on a simple polygon feature representing the Western Cape province of South Africa. My goal is to enlarge the polygon so it can stand out from the others. To do so I've used the v....
0
votes
0answers
22 views

Using Projected Coordinates with 3D building data in QGIS

I want to upload my 3D building data i.e in ESRI ArcGIS Pro. My data is working perfectly fine but I want to upload same data in MapBox, too. So when I convert the projected coordinates in the format "...
0
votes
1answer
61 views

Rule-based symbology based on given table

I would like to ask if it's somehow possible to create script with rule-based symbology in QGIS which would be based on expressions given from separate table (for example CSV, or Excel sheet). I used ...
2
votes
1answer
72 views

QGIS Export Satellite Imagery

We cannot seem to find any way to export our projects as PNG/JPEG through the print layout/composer. We draw normal line and point SHP files over the Bing/Google Earth etc layers, but the exported ...
0
votes
1answer
30 views

PyQGIS Script failing to project layer to EPSG:54002

I'm trying to write a Python script to convert a vector layer using 4326 to EPSG:54002 World Equidistant Cylindrical for road distance calculations, but the script fails to do the conversion, I've ...
1
vote
0answers
23 views

AusMap plugin loading/intall error

I receive the following error running 3.8 on mac high sierra - thoughts? Couldn't load plugin 'AusMap' due to an error when calling its initGui() method AttributeError: 'NoneType' object has no ...
0
votes
0answers
39 views

Tracing path of lines in network using QGIS

I am using QGIS 3. I want to trace the path of lines in network. I found that I can use Snapping Toolbar to trace the lines but in manual and I want to do it in automatic, I give start node and it ...
1
vote
1answer
53 views

Legend Items in QGIS Atlas

Using the Qgis atlas functions im having trouble with the atlas filtering out the features that do not show up in the map extent. For example i want the full color ramp to show up, even though there ...
2
votes
0answers
12 views

Using QGIS Webmap with Mapbox

Im trying to produce a contour map using QGIS and exporting using Mapbox. The map is rotated 90 degrees in QGIS and it returns to its normal orientation if I use Leaflet. Unfortunately, using the ...
2
votes
1answer
50 views

Tool in QGIS to Get Area Weighted Average

I am looking for a tool that can give me an area-weighted average. I have a shapefile of parcels and another shapefile with Curve Numbers. I want to get Area Weighted CN for each parcel. If I do it ...
4
votes
1answer
85 views

How to create Polygons of a specific size?

I'm trying to create polygons of specific size in square meters that represent the areas surrounded by roads. The roads are stored in PostGIS as points / lines. If required, I can convert the data to ...
0
votes
0answers
30 views

Extracting Population Data from OpenStreetMap

QGIS 3.0 When using ORS' "Isochrones from Layer" algorithm, a population figure is provided in the output as shown below. Is it possible to tap into these population values and join them into a ...
1
vote
0answers
23 views

Changing GPS tracker symbol

As the title suggests, how can I change the GPS tracker symbol in QGIS desktop? Little explanation: I connected a GPS to my QGIS trough a COM port, the position is showed accurately on the map, but it ...
0
votes
0answers
32 views

QGIS GDAL Build VRT results do not reflect input raster values

I am having trouble successfully creating a VRT. My Build VRT gdal command results in values of ±1.79769e+308. The values should be 1,2,3, or 4. I've verified projection info is the same across the ...
0
votes
0answers
25 views

How to create a clean-graph/network layer to be used in Offline Map-Matching algorithm in QGIS

I want to use the Offline Map-Matching algorithm in QGIS to match GPS trajectories with a road network. This road network layers needs to be "a clean graph following a node-edge-model, i.e. different ...
-1
votes
0answers
28 views

Measure area of a polygon [duplicate]

How can I measure the area of a polygon in QGIS? I clicked on "Measure Area" but I have to trace all the borders by hand. Is there a faster way to do that?
0
votes
1answer
24 views

Extracting number values from atribute with mixed data

Sorry for my bad English. In my attribute table I have column "Name" which contains data about type number and name of streets. For example: “SR 18 DI FIUGGI”. What I need is to create another column ...
0
votes
0answers
17 views

How to apply thresolding filter in qgis?

i am using google earth image for extracting building footprint. For that result, I have done edge extraction (orfeo toolbox) and after that I need to apply thresolding filter as per workflow stated ...