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Questions tagged [qgis]

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

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1answer
15 views

Avoiding intersecting lines in transect generation

I'm trying to generate transects using the QGIS transect tool under vector geometry as a step in generating an interpolation layer. Unfortunately, the transects are intersecting, which will lead to ...
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2answers
33 views

DEM and vector data won't match using QGIS

I have just started using QGIS for my research at university. I have a DEM comprising Italian regions of Lazio, Tuscany and Umbria. I then have a set of vector data from surveys carried out in these ...
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1answer
13 views

Show the whole track in QGIS animation

I mostly followed this excellent guide for animating a route on QGIS. The main thing I did differently is that I started with a csv with timestamped lat/lon data, converted it to a GPX file using GPS ...
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0answers
13 views

Maxar Premium Imagery in QGIS

Openstreetmap has access to satelite imagary from maxar premium imagery. how can i get this as a layer into Qgis? i mean just like you can add Openstreetmap layer that we can zoom into,how can i add ...
1
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1answer
58 views

Corruption of export using Merge feature in QGIS 3

Using QGIS 3.2.0 - Bonn I'm getting a nasty corruption when trying to use the Merge feature to pull together a selection of .map (OziExplorer) files and merge into a single .bmp file. They load in ...
1
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1answer
32 views

QField crashing when new point data added with error “Feature 0 could not be fetched after commit”

I have an issue with QField and am not sure how to troubleshoot it. Sometimes when creating a new point (after entering its attributes and pressing the check mark to save it), QField freezes with an ...
9
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3answers
228 views
+200

Sort attribute table by hidden column in Print Composer

In a QGIS 2.18.20 attribute table I have some values with random numbers, but at the print composer I want to show them with order (clockwise). So I made a new integer column, and added numbers with ...
0
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1answer
26 views

Connecting dots with lines, thickness depended on attribute value

I am having a point data of in total of 10 destinations within a region. The goal is to present how many people which were in destionation "A" also visited the other 9 destinations. I have this data ...
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0answers
8 views

Running PyQGIS standalone script on Ubuntu terminal (docker)

I am running a PyQGIS standalone script on Ubuntu terminal in a QGIS docker: from qgis.core import * QgsApplication.setPrefixPath("/path/to/qgis/installation", True) qgs = QgsApplication([], False) ...
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0answers
12 views

Error: QGIS VectorFieldCalc plug-in “Raster_Parameters_Errors: More than one raster band in raster”

I have used VectorFieldCalc plug-in in QGIS several times before, to make maps of marine currents from .nc satellite data. Recently, I have tried to redo some of the maps and when I try to calculate ...
1
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0answers
142 views

Error on simple standalone script

I want to develop a PyQGIS standalone script only using Ubuntu terminal, so to start I use: from qgis.core import * QgsApplication.setPrefixPath("/path/to/qgis/installation", True) qgs = ...
0
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1answer
29 views

Clipping by canvas extent using QGIS

I am trying to clip my .tif image using qgis(Zanzibar) as before but having trouble to get it in .jpg or .jpeg as it appears black (as picture below) after the function is performed. I choose the ...
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0answers
44 views

Shapefile appears correct on QGIS, but wrong on Google Earth

I've created a shapefile on QGIS, drawing over a raster that I've just georeferenced. The raster is a map with UTM lines drawn every 50 meters, so it was easy to georeference. Moving the mouse over it ...
1
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1answer
32 views

QGIS- What is the meaning of the Query Builder operators?

I am learning to filter my data, and I understand how to use the basic operators (e.g. =, OR, AND, !=, less than, more than etc) however there are some operators that are less obvious. What do the ...
1
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0answers
22 views

QGIS raster tool closing on parameter input

I'm trying to run the Merge tool on some rasters using Qgis 3.8 and when I add the layers as inputs, the tool just automatically closes... everytime, no matter which parameters I'm checking or ...
2
votes
1answer
23 views

QGIS - Extract by location, what does Cross do?

I don't understand what Cross does when extracting by location, and how it differs from Overlap- the definition on the user guide is very confusing - it says: Cross: Returns 1 (true) if the ...
1
vote
1answer
33 views

Check if points that share attribute intersect polygons

How to check whether points started in red and ended in a blue polygon (and vice versa) while sharing the same attribute? To check if the first location of the unique ID is in one polygon and last in ...
2
votes
1answer
100 views

Can't delete polygon

I drew a polygon, and then went to delete the layer I drew it in, but it didn't delete the polygon. I know have a random red shape that isn't attached to any of my layers in the middle of my project. ...
5
votes
1answer
122 views

Filtering layers in QGIS atlas

In processing several spatial data sets (tbl_data_01, tbl_data_02, tbl_data_03, etc) using FME I establish a spatial table called "tbl_metadata" with information about each of the data set. This table ...
2
votes
1answer
344 views

Raster pattern recognition

I'm wondering if it is possible to do pattern recognition with QGIS. I have 5 NDVI Landsat images and I try to find areas automatically (constant pattern). Is there a tool in QGIS? The pic below ...
1
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1answer
172 views

Exporting images attached to a geodatabase using QGIS

I have an ESRI file geodatabase that was exported from their survey123 app, and the geodatabase has images attached to it. I do not use ArcGIS, and was wondering how to export them from QGIS with ...
13
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4answers
9k views

Implementing Spatial Autocorrelation using QGIS or PostgreSQL or any other free application? [on hold]

I new to GIS. I have two layers in a PostgreSQL database. The first layer contains points where events happened in Europe. The second contains a shapefile of Europe. I have been able to map the ...
2
votes
1answer
55 views

QGIS saves Eastings and Northings as 0, despite displaying correct coordinates

A point layer in a geopackage contains easting format_number($x,0) and northing format_number($y,0) fields to record co-ordinates. The CRS for the project and the layer are set to BNG. When creating ...
1
vote
1answer
811 views

Add and edit Oracle Spatial Layer in QGIS

When I connect oracle layer are not enabled me all editing options. I can create and delete but not update. It is an issue of users? permissions or privileges? metadata? All works OK in AutoCADMap3D ...
0
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0answers
191 views

Oracle spatial cannot load data [on hold]

Have just installed QGIS 1.9 with Oracle spatial abilities. We maintain geodata in an Oracle 9.2. spatial database. I get connected to the database but I can not load the data. The table shows up ...
0
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0answers
32 views

Calculating cross section area in QGIS or R [on hold]

I have a DEM with altitude and a point shapefile with depth. How can I calculate the cross section area in QGIS?
1
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2answers
53 views

Losing raster values when exporting in QGIS

I have raster from Landsat 4 that I have created a symbology for. I want to save the new raster and to keep the NDVI values, but whenever I save the raster I lose the NDVI values. On the left side ...
2
votes
0answers
32 views

Passing parameters from QGIS to a SQL Server stored procedure and link this as new layer?

I'm new to QGIS and may not have understood the principle properly yet. I'm coming from database development. Question: I have a stored procedure in SQL Server that uses a date range as a parameter. ...
1
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0answers
14 views

v.extrude extusion failed - The following layers were not correctly generated

I am using QGIS Grass v.extrude tool for extrusion but it giving me this error (the bold text is error). scale Scale factor sampled raster values default: 1.0 null_value Height for sampled raster ...
2
votes
1answer
71 views

Labeling features in given order in QGIS?

I want to sort the address numbers where would show only the bigger number and smaller value should be suppressed away. I have used earlier ORDER BY-method when using PostGIS but now it isn't ...
5
votes
2answers
111 views

QGIS: Cannot add negative numbers in a field

I am using QGIS 3.4 and when I finish drawing a feature (line), I try to add a negative value (-1) in the attribute dialog and it is automatically changed to NULL. The field is integer. Even if I ...
1
vote
1answer
411 views

Does QGIS support topological editing of lines?

Does QGIS support topological editing of shared vertices between two or more lines? When in editing mode, if I select a vertex at an intersection, it seems that sometimes it will move all lines ...
2
votes
1answer
45 views

Points along lines at set elevation intervals [on hold]

I am looking for a way to create points along lines (roads) at set elevation differences (0.5m height differences) using QGIS.
1
vote
2answers
49 views

QGIS 3.4 feature filter maximum() does not work

I would like to filter a layer with the maximum value of field_a, grouped by field_b. I tried this expression: "field_a"= maximum ( "field_a","field_b") But it doesn't work (there are no more features ...
3
votes
2answers
622 views

Fitting wrap column in print composer of QGIS

i have an attribute table in the map composer, and the field i want to see is quite long so i wrap it, but the field width is not fitting this new length. Is QGIS 2.4 able to do that?
2
votes
2answers
68 views

Extracting a single value to a new raster from a singleband pseudocolor raster image

I have a large raster image depicting land use. It's a singleband pseudocolor image whose values are contained in a text file. There are 5 classes. Following the example of this question I thought I ...
1
vote
1answer
110 views

QGIS 3 PyQGIS Script - Merge Layers and Export to csv with KML geom field

I previously had a script in 2.18 that exported csv files with kml geometry's file by file. I'm now wanting to move to QGIS 3 and do the same process except Merge the point layers then add the ...
0
votes
1answer
71 views

Using r.reclass.area.lesser in QGIS?

I want to reclass small areas in QGIS 2.18, but it seems to fail calling the algorithm in GRASS GIS. The interesting lines from the Log of the tool: ... C:\PROGRA~1\QGIS2~1.18\bin>g.region n=...
2
votes
0answers
34 views

Custom formatting coordinate grid using QGIS

I am custom formatting my coordinate grid. Is there a way to change the following formula so that the output comes with a decimal and suffix? substr(@grid_number, length(@grid_number) -6,5) The ...
1
vote
1answer
22 views

Assigning attribute based on selection points on a graph?

I have a bunch of points on a map on a river that branches. I want an easy way to select one branch from the other and was hoping I could just somehow "grab" those points on the map and add a column ...
2
votes
2answers
2k views

Reading Esri TIN file directly using QGIS

Can QGIS open directly a TIN file generated with ArcGIS Desktop?
1
vote
0answers
525 views

QGIS Print Composer grid - curved latitude lines

QGIS 2.8.1 I am preparing a map of the North Atlantic and Arctic Regions in EPSG:3996 IBCAO North Polar Stereographic to display the geometries closer to their shape and size. In Print Composer, I ...
0
votes
1answer
28 views

Redistribute raster pixel value in underlying polygons

Given a raster layer (e.g 10km resolution) and a vector layer with many features (with finer resolution), is it possible to redistribute the value of each raster pixel in an attribute among the ...
2
votes
1answer
73 views

In which format am I working and how can I plot it correctly on GIS?

I've been working recently replicating this paper: "Constructing Street Networks from GPS trajectories". They got a repository with the implemented code. Anyway, the issue is that their data is in the ...
2
votes
1answer
1k views

Creating dynamic maps based on updated attributes in SHP file [on hold]

I am new to GIS. I can create maps and do basic transformation of the SHP file using QGIS. I also succesfully applied formatting based on attributes. I am able to add new attributes to SHP file in ...
2
votes
2answers
49 views

Clicking on point to have additional points and geographical information show up in QGIS

I am mapping nonprofits in Costa Rica, using the headquarters as the main points on the map. I want end users to be able to click on the points and see additional information about each individual ...
0
votes
1answer
55 views

QGIS transparency as 4th input layer

I have a file that contains four rows. The first row indicates the longitude, the second row indicates the latitude, the third row indicates the colour of a specific longitude and latitude and the ...
1
vote
0answers
34 views

Operation between raster using QGIS

I create two raster using QGIS Interpolation tools starting from two vector (Point): one with an accessibility index( between 1 and 5) for each point and one with population (number of people) for ...
0
votes
2answers
47 views

Sum of attributes of a subset of the features

This is my attribute table of a line layer: How can I get the length of all segments where Rohr_1 equals SNRVe 7x12x2 ?
0
votes
1answer
62 views

Raster display problem [on hold]

When I zoom too much on a raster the layer does not appear anymore. How to make it appear anyway?