1

I need to create points along a polyline in QGIS 3 at every 1000m of ellipsoidal distance and have tried several tools, as suggested in other answers:

  • Points along geometry
  • QChainage plugin
  • Convert lines to points (SAGA)

All of these can create points along a straight, two-node line, but do so at planimetric distances, so when I measure with my measuring tool (in planimetric mode) I get 1000.000 m:

point distances planimetric

However, if I switch on the WGS84 ellipsoid distance measurement, I get a deviation:point distances ellipsoidal

I'm working in WGS84/UTM32N. I already know the ellipsoidal length of my line and the last measurement point at the end of the line should have the same ellipsoidal value.

Is there any way to do this in QGIS 3? Am I missing some basic coordinate system logic? I am working in a UTM CRS, which is planimetric, I guess?

  • 1
    Maybe the Geodesic Densifier or the Shape Tools Plugins could be useful – FSimardGIS Dec 8 '18 at 3:56
  • UTM projection involves stretch at around the edge of its zone (coefficient varied by 0.9996/cos(theta) ). If you are working in the area close to the margin of UTM zone, the distance measured in UTM will be longer than that of ellipsoidal calculation. – Kazuhito Dec 9 '18 at 13:27
0

I would believe that you need to project the line to a azimuthal equidistant system, centered on the line origin.

Proj4: +proj=aeqd +lat_0=LINE_ORIGIN_LAT_HERE +lon_0=LINE_ORIGIN_LON_HERE +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs  

Densify there and then verify measuring the ellipsoid distance. It should work..

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.