[GIS] Drawing curved segment in QGIS

cadcurvedlineqgis

I have to create segments like the one in the picture:

I need to draw a segment where there is a straight line and other parts of segments with arcs of different angles.

The part of the segment that curves must be only created by 3 points, a starting a center, and an ending point.

Creating different arcs can be a solution but the contact between two arcs create a step that I don't want. Probably a cube spline can be the solution but I cannot find a working plugin for QGIS 3.4.

I installed the QAD tool, which is the CAD plugin but even there I cannot find the solution.

I just tested in ArcGIS the tool 'Bezier Curve Segment' and it does what I am searching for. Does this functionality exist in QGIS?

Best Answer

In QGIS 3.10, I can suggest paying attention to two cases.

A Native QGIS's toolbar 'Shape Digitizing Toolbar' where you can 'Add Circular String', see image below.

A QGIS’s Plugin 'Bezier Editing'.

'Bezier Editing' toolbar looks as following

The result of applying the 'Bezier Editing' Plugin might be this

References:

Related Solutions

[GIS] How to reproduce Smoothing from Generalizer Plugin in v.generalizer in Processing Toolbar using QGIS

There is a difference in wording but I think the options from the Generalizer plugin exists in the v.generalizer interface. Using Google Translate (yes, not the best thing to use) for the Generalizer Homepage, we can find a description on each algorithms used and their corresponding parameters.

In terms of Hermite Spline Interpolation, the homepage tells us:

Threshold - Determines the distance between the created points.

Thightness - Factor determining the degree of bending of the resulting line.

Now looking at the Help section in v.generalizer, we can try and find those parameters mentioned above. For Threshold:

threshold=float
Maximal tolerance value <------ This is in the options.
Options: 0-1000000000

For Thightness:

Minimum angle between two consecutive segments in Hermite method <--- This is in the options.

Hermite

In terms of Chaiken's Algorithm, the homepage tells us:

Level - Determines the number of iterations of the algorithm.

Weight - Determines the shear rate, the bigger the fillets are closer to the line of nodes.

Now we look at the Help section in v.generalizer again. For Level:

Number of iterations <----- This is in the options.

For Weight:

betweeness_thresh - It denotes to what extent a line is in between the other lines in the network (unsure if this is the correct parameter!)

Chaiken

I could be wrong with this, in which case hopefully others can advise and/or re-edit this post.

QGIS – Calculating Max and Min Height of Route Segments Using DEM

Preparations:

Make sure each segment is a feature on its own with a unique id field (use Explode line if that is not the case and create a new field with field calculator and the expression $id).
Raster and line layers should be in the same, projected CRS. Otherwise, reproject.

Workflow:

Run Menu Processing / Toolbox / Points along geometry with a distance of 10 m. The resulting points will contain the unique id from your line layer.
Create a new attribute called elevation with field calculator on the resulting point layer with this expression: raster_value( 'raster_dem', 1,$geometry) and replace raster_dem with the name of your raster (DEM) layer.
Create two new attributes min_elev and max_elev for min and max values, grouped by the unique id, representing the segments the points belong to: minimum( elevation, id) and maximum( elevation, id).
Go to the layer with the line segments and create a new attribute max for the maximum elevation for each segment, using this expression (and repeat it replacing max_elev with min_elev on line 3 to create an attribute for minimum elevation):
```
attribute (
   get_feature('Interpolated', 'id', "id"), 
   'max_elev'
)
```
Remark: end of line 3, the first 'id' is the name of the unique field in the layer Interpolated (the layer containing the points created in step 1), the second "id" is the name of the (corresponding) attribute in the initial line layer. They should normally be the same (as set in the initial line layer).

Best Answer

Related Solutions

[GIS] How to reproduce Smoothing from Generalizer Plugin in v.generalizer in Processing Toolbar using QGIS

QGIS – Calculating Max and Min Height of Route Segments Using DEM

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