Creating perpendicular line transects in PostGIS

Question

I have a river network (Line with arrow as shown in image below) and I need to create perpendicular lines to the river at every 15 meters as you walk along it (see image below).

Is there a function in PostGIS capable of doing this?

Answer 1

No clear existing function to do this, but working back from the great suggestions on this post: Making perpendicular lines through each polygon edge using PostGIS?

Assuming you are good with PostGIS syntax, this might help you:

1. Split the line into 15m segments, like this: https://www.northrivergeographic.com/qgis-split-a-line-at-an-interval
2. Loop every segment in the newly segmented line and for each segment:
3. Create parallel lines with ST_OffsetCurve with a desired distance D (can be as longer than the lake/sea as shown above, we will clip them later), on both sides of the line
4. For every 15m segment, make a new line from the centroid of that segment to the centroid of the corresponding parallel lines with ST_MakeLine
5. You should have perpendicular lines, spaced 15m extending beyond the river basin/lake
6. Clip the lines with the sea region