zephyr-data-specs/GMNS

Too much restriction on free_speed when using metric system.

joren-tml opened this issue · 3 comments

joren-tml commented

The free_speed field in the link specification has the following schema:

"name": "free_speed",
            "type": "integer",
            "description": "Optional. Free flow speed mph",

If GMNS is to be used more generally, this specification is too restrictive. Networks located in countries using the metric system cannot follows this specification (integer speeds in km/h become decimal numbers in mph).

As a solution, I would propose to leave the option to express speeds in km/h. Of course, the length field should then also be expressed in km instead of miles.

ssmith55 commented

Thank you for raising the issue. A GMNS network will work with metric units, provided that what you are using is consistent with what your GIS and analysis software expects. It should be possible to use

  • km rather than miles
  • km/h rather than mph
  • meters rather than feet (for lane widths and the like)
ianberg-volpe commented

I made some edits which remove specific units from the field descriptions. @ssmith55, we should think about the best way to formalize the config file we've discussed before (not just metric vs. Imperial, also coordinate systems for geometries, etc.)

joren-tml commented

Thank you for updating the specification. I was indeed just using the metric unit equivalent for now.

As @ianberg-volpe proposes, I think it would be appropriate to have a config file that specifies unit systems etc.

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