[expression] Add line_interpolate_point_by_m and line_locate_m expressions (Request in QGIS)

[qgis-bot]

Request for documentation

From pull request qgis/QGIS#58483
Author: @nirvn
QGIS version: 3.40

[expression] Add line_interpolate_point_by_m and line_locate_m expressions

PR Description:

Description

This PR adds two new functions to our expression engine to work with M values along line strings:

• line_interpolate_point_by_m: returns a point geometry of a matching m value interpolated along a line containing an m dimension.
• line_locate_m: returns a distance from the beginning of a line where a matching m value was found.

These two functions coming in extremely handy when working with temporal data, e.g. a linestring representing a GPS track where the M value represents the epoch value.

Using this function alongside of temporal controller makes for beautiful animations that were previously harder to unlock:

vokoscreenNG-2024-08-26_11-56-29.mp4

Commits tagged with [need-docs] or [FEATURE]