In QGIS I want to create perpendicular Lines on another Line (River). The Lines should be created on points on the Line and should have a length of 40 Meters. I want to create the red lines in the picture below (for the complete River).
2Is this a display issue, or do you need the line geometry?– ErikNov 27, 2020 at 9:06
2I need the geometry.– KartenLappenNov 27, 2020 at 10:08
3The points are distributed on the line with a constant distance? Then I suggest you use GRASS GIS plug-in ''v.transects" , grass.osgeo.org/grass78/manuals/addons/v.transects.html– MarcMNov 27, 2020 at 10:47
1Updated my answer to create geometries– BabelNov 27, 2020 at 12:03
2@MarcM: v.transects is not available in QGIS, at least not in my installation QGIS 3.16.0 with GRASS 7.8.4. on Win10. So it can't be done from QGIS– BabelNov 27, 2020 at 12:09
Edited answer: My first solution (see below) was for visualisation purposes only. But as you mentioned afterwards, you need the actual geometry. So this here is how to do it:
Menu Processing / Toolbox / Create points along input lines to create points on the line in a set distance - as I can see in your screenshot, the points should have a distance of 100 meters along the line, so set the distance to 100. This creates a new pointslayer
interpolated points with an attribute
angle that you can use to create perpendicular lines.
As you need it as an actual geometry, use
Menu Processing / Toolbox / Gemoetry by expression and set the layer
interpolated points as input, geometry type as line and introduce the following expression
extend( make_line( $geometry, project ( $geometry, 40, radians("angle"-90)) ), 40, 0 )
This will add an additional lines layer with the perpendicular lines:
This here is the first solution that does not create new geometries, but is good for visualisation purposes:
Add an additional symbol layer to your line and define it as simple marker, selecting the symbol and size as shown in the screenshot:
In this example, I have created a marker on every vertex. If you need a marker in a regular distance along the line, just make the settings accordingly as shown in the second screenshot (the settings in the red box; the arrow shows where to check for the first solution, every vertex):
3I think he needs the geometry, not the visuals– MarcMNov 27, 2020 at 10:43
Thank you so much for this detailed Answer and for your Time! I am sorry that my question was a little bit missleading, I am not pretty good in English. I should have just written to you in German :) Nov 27, 2020 at 12:37
At least my german screenshots were not a probem dor you. Consider accepting this answer if it was useful– BabelNov 27, 2020 at 12:42
Hi where is the algorithm 'Create points along input lines'? Mar 9, 2022 at 8:49
There are many ways to solve your problem and one of them is the next:
Input data: 1) river_line layer 2) interpolated points after 100 m, see figure below
Action 1 - launch the geo tool "Points along geometry" with a point offset of 50 m as shown in the figure below
The result is shown in the figure below
Action 2, 3 - launch the "PointToPath" geo tool see the figure below
then run the geo tool "ExplodeLines" see the figure below
Action 4 run the geo tool "Rotate" see the picture below
Rezult see the picture below
Action 5 start geo tool "Buffer" on "river_line" layer with distance of 40 m see illustration below
Rezult in the figure below
Action 6 Cut perpendicular lines with the buffer
The result is shown in the figure below
See the figure below for the intermediate result.
Further, in order to close the beginning and the end, you need to lengthen the line in both directions, leave only the outermost segments, turn them 90 degrees, cut and add to the result see Figure 11.
Good luck in knowing about geodata processing :-)....
If necessary, ask clarifying questions on the subject of your question, I hope that I can clarify them...
I first used the geotool "Points along geometry" first and then with the points with the geo tool geometry by expresion I selected the new point layer that I created and I used the next expression:
I put 50 as half of the distance of the perpendicular lines, If you need a different distance you have to change that value.
A couple of years later, but the function Vector Geometry --> Transects does just that at the points. In my case, I had the points, but needed the azimuth perpendicular to the line that joined them. So, I did points-to-path and then Tansects.