# Copying set of points perpendicular along polyline

I have a polyline which represents the middle of a river. Perpendicular to this polyline there is a layer with a set of points. These points all have an `"X"` and `"Y"` coordinates as well as a height relative to sea level and represent the profile of the river.

However, these points are only present at one point. I want to copy this set of points to multiple locations along my polyline so that I can interpolate these points and get a DEM to load into a simulation programme that needs river cross-sections as input.

How to copy the point layer perpendicular along the polyline given a set interval (e.g. a meter between each set of points is sufficient)?

The points are lying on the same line, but I think the visualisation of QGIS makes it look like they are not.

• What distance should be considered between neighbours (sets of points)? Are points lying on the same line? Apparently, from the image above it seems like not. Which line should be examined as a centre line (produced probably out of points) that has to be ⊥ to the river? What are those predicates/rules, e.g. a direction, abearing etc. or simply a middle point between the most left and the right etc.? Commented Dec 18, 2019 at 9:12
• Sorry if everything is not as clear as possible, it is my first time using stack exchange and I'm relatively new to Qgis. The distance between the set of points is not of great significance, but i think a meter between each set of points is sufficient in this case. The points are lying on the same line, but i think the visualisation of Qgis makes it look like they are not. For the last question the middle between the most left and the right is sufficient.
– Taj
Commented Dec 18, 2019 at 9:27
• No worries, I was also 'virgin' at some point with GIS SE). Okay, I got your remarks. BTW when points are lying on the same line, then my question `"Which line should be examined as a centre line (produced probably out of points) that has to be ⊥ to the river?"` is neglectable. Commented Dec 18, 2019 at 9:29
• @Taj Did you solve your problem? I tried to solve using python. But it needs more effort. If you solve the problem. please share solution with us. Commented Dec 22, 2019 at 15:09
• @KadirŞahbaz As I am not as familiar with Python and the use of the Python console in Qgis, I did it by hand. I did it by creating parallels of the polyline at the distance the point lies from the central polyline and inserting the Z-coördinate in the attribute tabel for every parallel. After that I merged the parallels and used line to points to generate points and natural neighbour to convert it to a raster.
– Taj
Commented Dec 23, 2019 at 8:30

So i started with a line which represents a river and a set of points with a certain `"X"`,`"Y"` and `"Z"` coördinate, which represents the profile of the river. Every points also contains information on the distance between the first point (most northern point in this case) and the point itself.
1. Then I manually added a `"Z"` coördinate to each line, used densify by interval to create more vertices and lines to points to create a raster of points.