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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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12 views

How to use QT signals and slots in QGIS C++ API

I'm developing a standalone QT 5.11.2 application using QGIS 3.6 C++ API. I have defined a slot that is meant to consume a currentLayerChanged(QgsMapLayer * layer) signal. The slot declaration in ...
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0answers
19 views

Checking for exact value in QGIS raster calculator

I would like to single out values which are equal to a certain floating point value using QGIS raster calculator. I tried to run the following: "Converted@1"==-3.40282347*10^38 But I got the error ...
4
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1answer
95 views

How to specify Python code to be used on a user form for QGIS 3

Previously, on QGIS 2.18, I followed this well known tutorial to create a user form with some basic Python driven buttons. https://nathanw.net/2011/09/05/qgis-tips-custom-feature-forms-with-python-...
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0answers
15 views

Compass direction from single PDa point to multiple

I have found the distance matrix tool to provide the distance from a single point to multiple points. However, it would be useful to find a tool to automatically calculate the compass direction of the ...
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0answers
20 views

Split raster to many irregular polygons [on hold]

I'm splitting a national soils raster file into regional (county) rasters, and organizing the soils classifications into a database keyed by region, eventually plot- or farm-level detail. At the ...
1
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1answer
37 views

Which coordinate system/ projection would you use to measure lines globally distributed?

Which geographic coordinate system /projection would you recommend to measure the length of hundreds of lines which are globally distributed (southern and northern hemisphere)? The lines have a length ...
1
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1answer
32 views

Calculate geographic location of point display offset in QGIS

I have a point layer in which some symbols are displayed offset from the feature's true location by a given number of millimetres. As the map's zoom changes the offset symbol's geographic location ...
2
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1answer
25 views

About the method of resize raster resolution

I opened a raster file as a layer, and click the right mouse button and select "Save as..." to change the resolution. I got the new raster, but I want to know what is the method (average, aggregation.....
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2answers
44 views

Calculate the percentage of a Line passing through Polygons

I have a polygon layer of a region (100% coverage, no overlaps) and a line layer in the same region. I want to calculate for each line to which percentage it crosses certain polygons. I have seen ...
1
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1answer
28 views

Rasterize point layer with weighted distance

I have a point layer representing wells in a region. i am able to rasterize it and write the well density into the raster as integer, so far so good. What I aim for is to create a raster with values ...
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0answers
38 views

File SHP needing to be shifted up?

I am new in GIS. I am trying to use the curves of level (downloaded from this site in SHP format) to use them into Tableau Desktop. The problem is that if I loaded the lines, they are not ...
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0answers
30 views

Finding clusters of non-adjacent parcels greater than 'x' hectares [closed]

Background: I have a number of land parcels with "Parcel_ID" and "Area". They are separated from each other by great distances (km's) or short distances (5m), forming 'clusters' on the landscape. In ...
1
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1answer
27 views

Extracting vector/raster data for CSV data points [on hold]

I am using QGIS and I have a CSV file of lat and long coordinates which represents presence points of a species in the USA. I also have vector (the state extents/names) as well as raster information (...
1
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2answers
46 views

Creating shapefile using QGIS?

I start with Create New Shapefile Layer, I give it a name and then select Polygon. I then create my Polygon shape, its all good to this point. I now show a polygon with an outline and light red fill. ...
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0answers
63 views

What is the future of R in spatial data analysis science? [closed]

I am new to spatial data science and have some basic knowledge in ArcGIS and QGIS. I am considering to continue my PhD in spatial analysis related to agronomy; ex precision agriculture, predicting ...
1
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1answer
38 views

QGIS SAGA functions failing “… following layers not correctly generated. …”

I've been having an issue with the SAGA functions for a while now, I believe since upgrading to one of the early 3.x versions. No matter which function I use they all fail with the same error (...
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0answers
30 views

Visualizing 3D focal mechanism (beach ball) in QGIS

Currently, the qgis2threejs plug-in in QGIS allows users to use a 3d model as symbology for point vector data. I made a 3d focal mechanism template (beach ball) and used it in qgis2threejs: You can ...
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0answers
31 views

Extract point data to polygon features [duplicate]

I am trying to import data from a point that lies on a certain polygon feature (or raster). As an output I would like the polygon feature to have the point data as a new field in the attribute table. ...
0
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1answer
27 views

How do I make a map's background transparent in a layout?

I am trying to add an overview map to my layout. The main map is projected while the overview map is a 'globe' (image below). I want to make the white part of the overview map transparent. I have ...
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0answers
30 views

Clipping ocean water shapefile in QGIS [on hold]

My requirement is to find a reliable source of Ocean water shapefiles, this is because OSM or Geofabrik does not provide this information. I eventually landed on this page: https://www....
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0answers
17 views

QGIS Heat Map output not correct

Fairly new to QGIS here. I'm having trouble creating a heat map in QGIS3 from a set of points. I've followed what others have done online (e.g.: https://www.youtube.com/watch?v=o9Gqrr5cYrY) but in my ...
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0answers
25 views

QGIS Process Modeller Multiple Input (3.4.4)

I am trying to build a process with the process modeler. The process is working with one shapefile via Input vectorlayer. But in the final Version the model should do a Folder or Muliple Input. But ...
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0answers
17 views

QGIS Time Manger is displaying events at the same time on different days together

I've got a dataset that has time like below... I have set the plugin to use %d/%m/%Y %H:%M:%S But it is showing events at the same time on different dates together. How can I get it to step through ...
1
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1answer
39 views

Make lines from points in Geometry Generator

I have a data set with a large number of start and end positions. I am trying to generate lines between start and end positions using the Geometry Generator but it does not work. I get no errors ...
1
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1answer
51 views

Creating Bivariate choropleth map a.k.a. Relationship map in QGIS [duplicate]

There is one polygon layer with the number of "immigrants" and "emigrants" respectively. I want to visualize those two values together. Diagram with both normalized values is not an option because the ...
2
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2answers
60 views

Measuring length of edge of polygon

I have a layer of polygons, cadastrals, that i'd like to have the length of the edge of: I thought about doing this: Dissolve the polygons Create one large dissolved polygon Making a; From polygon ...
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0answers
15 views

Load imagery layer on the top of a morton tile through geometry?

tile_col = self.current_tile[0].split("-")[0] tile_row = self.current_tile[0].split("-")[1] tile_matrix = self.current_tile[0].split("-")[2] try: space = "%20" url = "http://...
3
votes
1answer
93 views

Setting correct UTM zone

I am using QGIS for mapping a series of buildings, I got the UTM coordinates from Google Maps and imported them as a delimited text layer. However when I search for the UTM Zone that I need it doesn'...
0
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0answers
24 views

Interpolate 3D raster with Anisotropy

I am building a 3D geological model for soil deposits. I have two approaches to build a 3D raster. My dataset is about 300k points of bh information with texture and permeability at every meter ...
0
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2answers
41 views

Pixel depth and raster output won't align with the original

The problem Need to convert a raster .tif tile (DOWNLOAD) from WGS84 to GDA94 Albers; Need to convert its stored pixel info from Float32 to 8 bit UNSIGNED; Need Compression set to "NONE"; Need to ...
0
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1answer
24 views

ECW not reocgnized as supported file format in GDAL operation

I've installed QGIS 3.6 for MAC, with GDAL 2.4, ECW GDAL Plugin for GDAL 2.4, and manually installed the libraries from ERDAS ECWJP2SDK 5.4. This allows me to insert ECW files as raster layers in ...
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0answers
28 views

Clipping raster to vector polygon

I have a raster file containing landcover classes of the UK. When I clip it to my Derbyshire Dales vector file it comes out as just a black screen with values of 0 and I can no longer see all the ...
1
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1answer
51 views

QGIS 3 Processing Script refer to input layer

I'm new to Python and trying to figure out how to write my first Processing Script using QGIS 3.6 on Windows 10. I'm using the default template provided in QGIS 3 (Toolbox > New script from template)....
1
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1answer
56 views

Generating map tiles with QGIS 3.6?

Similar to this rather dated question, is there a way to generate map tiles on QGIS 3.6? The plugins linked from that question only support QGIS 2.x. I wonder if things have changed in QGIS 3.x ...
1
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1answer
58 views

Can ArcMap open shapefiles made by QGIS?

I have created many EPSG shapefiles in QGIS and would like to import them into ArcMap for analyzing. Can ArcMap open shapefiles made using QGIS?
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2answers
35 views

Get shapefile from ArcGIS online for QGIS

How do I download shapefile information from ArcGIS online and access it in QGIS. An example shapefile that I would like to obtain is linked below: https://morgancountyco.maps.arcgis.com/apps/...
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0answers
23 views

How can I summarize the values of a raster to make a clear legend? [on hold]

I produced a relief map out of a ASTER Satellite Picture by using a colour ramp (Symbology -> band rendering). I want to make a map out of that in the Print Composer but the Legend is very confusing ...
0
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1answer
19 views

Can I import raster files from GRASS GIS in QGIS versions later than 1.8.0

I have a process that I have used for years where I create .ascii files with a Python process, import them to GRASS GIS 6.4.3 and do some raster calculations (r.mapcalc). This works great but then ...
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0answers
31 views

QGIS returning incorrect area as derived property [on hold]

I'm getting huge errors on the derived property of Area. I've checked that all my layers are using the same projection, WGS84. Using the area measurement tool gives accurate results, using the ...
0
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0answers
11 views

Creating points along a line in space and then extracting data from those points in one tool [closed]

I am attempting to combine the functionality of multiple QGIS tools into one and wondering if someone may be able to help. The tools I am interested in combining are the Points Along Geometry, Add ...
1
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2answers
31 views

Creating an arc with set angle and range using QGIS?

I'm currently using QGIS 3.6. For a while now to map the arcs of fire for historical fixed weapon emplacements. Creating an arc to a set range to a set angle is extremely important for my analysis ...
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0answers
19 views

OD-matrix (QNEAT3) doesnt return values for all input parameters in QGIS?

I'm running into problems trying to calculate shortest distance from point (smaller black dots below in image) to a port (tagged MANAUS below). Im using hte QNEAT3 OD-matrix tool (from layers as lines)...
1
vote
1answer
25 views

Prioritising values in accordance to various Columns

I previously asked for help in Prioritizing the Attribute table of a self made polygon layer Prioritising polygons in QGIS Now I want to change this prioritisation in accordance to multiple values ...
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0answers
19 views

QGIS classified raster - compare surrounding pixel classes

I have a classified raster where one class represents tree and around tree can be busches as another class and there is the third classes grass. I don't know how to analyse: I have to compare the ...
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2answers
30 views

How to display an attribute value from a related layer in Atlas?

I work on Qgis 3.4.4 Madeira. I have two related layers in my project :"towns" (polygon) and "interest points" (points), the common field is "town name". In the Atlas, my cover layer is "towns". I ...
1
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1answer
32 views

How do I apply a unique colour for each row of data within a layer? (QGIS 2.18)

I was wondering how I would go about giving each row of data within a layer a unique colour, each row does have a unique ID but I can't figure out how to use this to achieve what I'm after without ...
3
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1answer
22 views

PyQGIS - how to override maximum number of features in combobox

Is there a simple way, how to override a maximum number of displayed features in QgsFeatureListComboBox? It seems that there is a hardcoded limit set to 100 features (in QgsFeatureFilterModel). ...
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0answers
28 views

Determine the direction of groundwater flow using borehole water levels

I am working on a project that focusses on groundwater of the Marico Biosphere Reserve in South Africa and I would like to determine the general direction groundwater flows through the study area. ...
0
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0answers
25 views

Overruling Prioritization [closed]

I created a layer of self drawn polygons for renewable sun energy, which I want to prioritize. Therefore I have serval criteria in ranking order: Area size of polygon groundpoints of agricultural ...
5
votes
2answers
300 views

Finding algorithms of QGIS commands?

I'm looking for the algorithms (the math) used by QGIS but I can't find any documentation about it The ones I'm looking for are: Minimum bounding geometry (convex hull) Clip a polygon by a ...