Calculate the similarity of two polylines

[mjaschen]

An algorithm for calculating the similarity between two given polylines should be implemented.

Idea:

• create a corridor area around the first polyline (with configurable corridor width); a polygon instance can be used for this (check: what happens if the polyline crosses itself?)
• check how much of the second polyline is located within the corridor
• the result is a floating point number between 0 and 1; 0 means that no parts of the second polyline are located within the corridor and 1 means that the second line ist located entirely within the corridor
• additionally provide a check if the directions of both polylines are the same

Sounds reasonable?

[TheCelavi]

What is the real-world appliance? Like, if vehicle/someone follows some path when traveling?

If you decide to add support for GEOS (like https://geophp.net/geos.html), there is "within" function, so when you construct a corridor, you can easily check if polyline is within polygon.

However, you can have issue there if you are trying to determine if object follows a "one way" path.

Let say that there is a path A-B-C-D, so you want to check if object follows that path. With function "within" object can go A-B-C-B-C-B-D and you will get result that evaluates to "true".

There are additional issues related to "path following problem" which has to be considered, but I can not explain them without drawing...