Inconsistent ways to represent coordinates

[habrahamsson-skanetrafiken]

Is your feature request related to a problem? Please describe.

Different parts of the OTP code base are using different ways to represent coordinates.

These are the main ways:

• WgsCoordinate - an internal value object class. Takes parameters as lat, lon.
• jts Coordinate class. Takes parameters as x, y.
• Unstructured lat, lon values.
• Unstructured x, y values. Here x = longitude and y = latitude.

Using unstructured x, y and lat, long values are a bit error prone since it is easy to get the order wrong. At the call site it's not obvious which of these is the correct:
new Vertex(lat, lon) or new Vertex(lon, lat) since it depends on if the Vertex class operates on x, y or on lat, lon.

Goal / high level use-case

Treating coordinates in a consistent way within OTP would make code less brittle and easier to maintain.

Describe the solution you'd like

Consistently use our internal data object WgsCoordinate for representing coordinates.

Describe alternatives you've considered

• We could leave the code as it is.
• We could use the jts Coordinate class instead of the WgsCoordinate class.

[t2gran]

The jts Coordinate uses (x, y, z) while the WgsCoordinate only has (lat,long), all doubles. The memory footprint would be 16 + 3 x 8 vs 16 + 2 x 8 bytes. In addition there is 8 bytes for each reference. If memory is an issue, we could also change the WgsCoordinate to use integers for the lat/long - the precision is good enough. Hopefully we will be able to inline WgsCoordinate later.