[postgis-users] Merging points in right order

[George Washington]

Hi, I have some considerable difficulty with the following problem:

I have a LINESTRING table with walking tracks
I have a MULTILINESTRING table with contours (with elevation attribute).

I can successfully get the points of intersection between tracks and contours to obtain the elevation and coordinates at the point of intersection.
What I need to do next, and I don't know how, is to merge the points of intersection for a given track with the track linestring, i.e. add the intersection points to the track linestring (or create a new track which includes the intersection points). However the intersection points have to be inserted in the right position in the track linestring, not just at the front, as ST_LINEMERGE() seems to do. The reason is I need then to traverse the track, point by point, to obtain the distance between points.
Any suggestions will be most welcome, thank you.
George

 		 	   		  
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