Questions tagged [qgis-3]

for questions specific to the 3.x series of QGIS.

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2
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1answer
46 views

Visualize polyline n-to-n relations in QGIS using PyQGIS

I have 2 traffic networks (A and B) with links relating to each other. Each link has an id. E.g. link 1 of network A can have a relation to 3 links of network B. Link 2 of network A might also have a ...
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0answers
26 views

gdal2tiles QGIS 3.10 not referenced properly

I processed virtual rasters with gdal2tiles. The output seems reasonable and it is displayed correctly on the generated output maps (Leaflet, Openlayers, Google). I then copied the tiles to a nginx ...
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0answers
32 views

Adding labels to contours created with the rendering option of rasters in QGIS 3.16

Is it possible to add labels to raster contours created using this option in the "Render Type" under "Raster symbology"?
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0answers
54 views

QgsAttributeDialog in PyQGIS Standalone Application

I am trying to implement a desktop application with PyQGIS 3, I have not been able to program a layer info using the attribute dialog that the QGIS API. This is part of the code that I use: def info(...
3
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1answer
88 views

QGIS: Making flow-map, with curved arrows of different colours and varying sizes

I have a shape file for the World Map and the following data in text file (Added as delimited text layer): I would like to use QGIS 3.10 to achieve three things: a) To make a flow map to have CURVED ...
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0answers
28 views

Clipping OpenStreetMap basemap using QGIS

I'm using QGIS, and I am trying to clip my metro region data to only show the OSM basemap in the the metro region, using this thread: Clipping OSM Standard Basemap using QGIS I created an inverted ...
2
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2answers
41 views

How would I separate the time observed from this column and create it as a new attribute?

I'm using QGIS and I am working with a file in which there is a attribute "time_obser" that is written as yyyy/mm/dd time (ex:2019/07/13 19:47:45.000). I would like to create a new field ...
0
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0answers
30 views

Hide Symbol if the label name not display / rendered in exported file [duplicate]

I am using QGIS 3.14. I downloaded world cities name kml, which has markers symbol on every label. I want to display the symbol only on every name which rendered / displayed on exported file. ...
4
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1answer
46 views

Avoid features to be automatically selected in table

In the screenshot below you will notice that in "Feature", a country has gotten automatically selected. I don't understand why. I have not selected any part of the data or the map. I don't ...
2
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0answers
75 views

Changing the raster layer symbology in QGIS with PyQGIS is not reflected in the layer properties. How to fix this?

I have managed to alter the raster layer symbology, even creating my own symbologies, in its different variants 'multibandcolor', 'paletted', 'singlebandpseudocolor' and 'singlebandgray'. Changes are ...
2
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1answer
87 views

Convert scripts for processing toolbox

Does anyone know how I can turn this console script into a script that I can integrate into the processing toolbox? I tried a few options, but I don't do very well in python, and I always get stuck. # ...
-1
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1answer
38 views

QGIS to ArcGIS Feature Class [closed]

I have data in QGIS I have to get it into ArcGIS (ArcMap) (ESRI's) GeoDB as a feature class, I have tried 2 routes but I can't find a route through. Route 1. I've exported from QGIS to GeoJSON, ArcMap ...
1
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0answers
36 views

Output of Processing Algorithm Doesn't Show Up in Layers Panel

I'm writing a PyQGIS Processing plugin that takes a series of inputs and uses them to run other PyQGIS processing plugins that I wrote. The problem I'm having is that the layers my plugin returns don'...
2
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2answers
39 views

to_date arranging dd/MM/yyy

I have a column as a string 10/12/2020 13:14:39 I want to convert it to Date format (I'll do that using the refactor tool later). First I need to rearrange this so the time is discarded and the dd/MM/...
2
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1answer
34 views

Merging multiple shapefiles and finding which shapefile gives the minimum value for each attribute in QGIS?

I have several different shapefiles that I want to combine into one based on the minimum value of each attribute. I found this solution. However, I also want to know which shapefile each minimum value ...
2
votes
2answers
74 views

datetime to date in QGIS field calculator

I have a string column with a datetime in it, I want to drop the time and reformat the column to date format. In field calculator I type: to_date( (EndDate), 'yyyy/MM/dd') This gives the following ...
3
votes
1answer
39 views

Field Calculator case sensitive issue in QGIS graphical modeler

I use QGIS 3.10 with the graphical modeler and I'm facing an issue while creating new field in field calculator: it seems to be case insensitive thus it does not create the field I want. Problem ...
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0answers
16 views

Information [18]: Select at least one signature

While performing run / previewing classified image in SCP, the statement Information [18]: Select at least one signature appears. What is the solution to this?
1
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1answer
42 views

Does symbology work on grid layers?

I'm using QGIS and I created a grid and joined a column with observation points to it. I'm trying to use symbology to shade the cells of the grid based on the values that I joined. But it looks like ...
1
vote
1answer
30 views

Is there a way to merge a grid with a shapefile?

I'm using QGIS and I have a shapefile that's a grid I created and another shapefile that is points. I would like to join them so each grid section is linked with points that fall within in. The grid ...
0
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0answers
33 views

Why is 'Count Points in Polygon' returning zero values for all NUMPOINTS?

I'm using QGIS and I have a file of points (Coyote_Clipped). I'm trying to count the number of points in each grid cell. I ran "Count Points in Polygon" on the grid and it worked without ...
0
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1answer
37 views

How do I lay a grid and count the number of points within each sector?

I'm using QGIS and this represents a metro area that is 3,965 square miles. I want to lay a grid over it and measure the number of points in each sector. I haven't used any of the grid tools before ...
0
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0answers
62 views

Display map tip in QGIS does not show latest image while hovering

In QGIS 3.14 project I have a polygon layer with fixed names (zones) and I generate png figures (with pyqgis script) with the name of the zone to show them while hovering with map tip (Display). ...
3
votes
2answers
159 views

Counting Points in Polygon to analyze data using QGIS

I am using QGIS, and I have a shapefile that has 23 different land classifications. I have another file that lists coyote observations as points. I would like to find out how many coyote observations ...
1
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0answers
28 views

How do I combine heatmaps in QGIS?

I'm trying to create a view of two heatmaps in the same time with QGIS. I tried following the suggestion on this thread: Can I combine two heat-maps in QGIS? But it didn't work. The virtual layer ...
4
votes
1answer
103 views

Emitting signal when project property is changed using PyQGIS

QGIS API provides QgsExpressionContextUtils to set project properties. But in the class, there isn't any signal. I hope to connect to a signal whenever some of the properties were changed. So is there ...
4
votes
5answers
174 views

Is there a way to see all of the different values in each field?

I'm using QGIS. I have an attribute table that lists different land classifications under the "Land Type" column (agricultural, industrial, etc.). I don't know what all the land types are ...
0
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1answer
34 views

Why does making a join layer editable cause so many issues?

I'm using QGIS. When I do a join it creates new column values with a long title because of the prefix it adds from the join. I need to shorten the column names in order to create new shapefiles from ...
0
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2answers
33 views

Converting XY Coordinates to Projected Local Coordinate System using QGIS

I am working in QGIS 3.14, and I have created a shapefile with X and Y coordinates that has COVID testing centers in Maryland and the EPSG is 4386. I want to do a buffer algorithm on these sites to ...
0
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0answers
26 views

GRASS ERROR “raster not found” with i.image.mosaic tool in QGIS 3.10.10

I'm trying to mosaic multiple DEM files using the GRASS 7 'i.image.mosaic' function in QGIS 3.10.10, on a Mac. I keep getting the same error code and have not been able to figure it out. Details of ...
2
votes
1answer
23 views

How to set the number of vertices by shape digitizing tool in QGIS 3?

Can we set the number of vertices of the created circle or ellipse. (e.g. a circle/ellipse with 24 or 36 vertices) I can use "add regular polygon and set the point #" for circle, but i don't ...
0
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1answer
66 views

Unable to rename attribute table columns using QGIS

I'm using QGIS and trying to remove the "ACS block group" prefix from each field in this attribute table. When I try to rename my attribute columns it says "Failed to rename field to .....
3
votes
1answer
51 views

QGIS prints proportional circles when value is 0 but not when NULL

Using QGIS3, I'm making maps with proportional circles based on an attribute value (integer). When this attribute is NULL, no circle is printed, which is what I expect. When this attribute is 0, a ...
1
vote
1answer
65 views

How do I batch edit field values in my attribute table?

I'm using QGIS. I have an attribute table that has some very long attribute names because of a join I did, and it seems to be causing errors when I try and select values using an expression and ...
1
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0answers
62 views

Buffers are oval not circular

I've tried the solution in this post but haven't been able to resolve so hoping that someone here might be able to help. I'm attempting to create a buffer layer of 5km radius around a collection of ...
1
vote
1answer
25 views

Selecting snapped vertices of different two features individually by QGIS 3.X vertex tool

In QGIS 2, I can use node tool, click on feature 2 click on the vertex (of feature 2) to select it. Delete it. I QGIS 3, by using vertex tool, I can't select which feature I want to modify, it ...
3
votes
1answer
49 views

Configuring QGIS for external editor

The editor pane in the python console has a button "Open in External Editor". How do I tell QGIS what program to use as the external editor?
0
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0answers
25 views

How do I join ACS data to this Census shapefile?

I'm using QGIS. I am trying to join the .CSV data from the American Community Survey (ACS): https://gisdata.mn.gov/dataset/us-mn-state-metc-society-census-acs With the shapefile from the 2010 Census: ...
0
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0answers
59 views

Why is heatmap turning red in QGIS

I'm using QGIS 3.16.1. I'm creating a heatmap using the symbology. At first it appears like a normal heatmap, but it is still rendering. When it finishes the whole heatmap turns red. Here's a ...
0
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0answers
20 views

QGIS 3.10: forms_2 parents table/1 child table

I have 2 parents table (shape): one for trees (pk = id_tree); another for parks (pk = id_park). I have 1 child table to list our works (fk = fk_works related to 'id_tree' and 'id_park'). In both cases,...
3
votes
1answer
60 views

QGIS 3 - default marker symbology

Working with QGIS3 (QGIS 3.2.3) Is it possible to change what the default point symbol is when adding a new point layer to a new project? Context: I have to work with massive point layers very often. ...
0
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0answers
17 views

How to read postgres sql Table (No geometry) in PYQGIS? [duplicate]

In my database there is a table without geometry. how to read that from from pyqgis. self.uri = QgsDataSourceUri() self.uri.setConnection(self.Hostname, self.Portid, self.Dbname, self.Username, self....
-2
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1answer
94 views

What causes the “could not create destination layer” error when creating a heatmap?

I'm using QGIS 3.16.1. When I try to make a heatmap I got an error message saying "Could not create destination layer." I then tried using a smaller row and column size, and it runs the ...
1
vote
0answers
28 views

Apply expression to synchronize multiple map extents in QGIS 3 layout using PyQGIS

I am using the following code to make a map with multiple map items. I would like to add the synchronization of the maps extents. How do you apply an expression to the min/max extents of a map item on ...
2
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0answers
35 views

Dividing polygon into tiny polygons of particular size

I would like to divide/cut an irregular polygon into tiny polygons of a particular size(1.6m x 1m) in such a way that most of the irregular polygon area has to be utilized (an OPTIMIZATION MODEL) The ...
2
votes
0answers
31 views

Is there a way in QGIS to display vector files on a shared drive without others being able to edit the file?

So just like lyr-files in ArcGIS. I have read that qlr-files are QGIS answer to lyr. But as far as I can see when I try, the receiver can edit in the main source of the data through the qlr-file. So ...
1
vote
0answers
24 views

Why do I get the error “OGR error setting feature:5” while changing the attribute of the layer?

Getting the error while changing the name of one attribute in the point layer. Errors: ERROR: 1 attribute value change(s) not applied. Provider errors: OGR error setting feature 5:
8
votes
1answer
71 views

QGIS plugin creating the Duplicates tool bars why?

I created a custom tool bar with QGIS plugin but when reload the plugin its creating another duplicate toolbar. My code: class TestToolbar: """QGIS Plugin Implementation.""...
1
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0answers
37 views

QGIS 3.16 - unpractical changes to intersect tool? [closed]

I currently am testing QGIS 3.16. I just ran intersect without any input modifications on a buffer layer with 12 polygons (first input) and a layer with 417 administrative districts (second input). ...
7
votes
2answers
204 views

Deleting any characters after certain character in QGIS label expression

I have a shapefile with attribute values like this: C834 K9 L523;L553 W2,T48 I want to display only the characters before certain characters, for example ; and , : C834 K9 L523 W2 How to achieve ...

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