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canboat / canboat

CAN Boat provides NMEA 2000 and NMEA 0183 utilities. It contains a NMEA 2000 PGN decoder and can read and write N2K messages. It is not meant as an end-user tool but as a discovery mechanism for delving into NMEA 2000 networks.

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analyzer unit conversions?

freol35241 opened this issue · comments

commented

Hi and thanks for all the work put into this set of tools!

I think there are som inconsistencies with regards to unit conversion in the analyzer command-line tool, this was noticed when used to parse PGN 129026 (SOG and COG rapid update).

When running analyzer --json (which would implicitly set the --no-si flag I believe?) we see that:

  • COG gets converted from radians to degrees
  • SOG is not converted and remains in m/s (I would have expected this to be converted to knots)

https://github.com/canboat/canboat/blob/master/analyzer/fieldtype.c#L138-L183

commented

Sorry, this will not be merged. Changing the output in non-SI mode would need a major version change, as this impacts the compatibility of the analyzer program with other projects.

For historical reasons the 'non SI' units need to remain the same to remain compatible with historical downstream packages. The recommended way to use analyzer with other downstream packages is to always use the -si flag.

commented

@keesverruijt fair enough, thanks for getting back on this.

If not already, I would suggest to document the recommended way of using analyzer (i.e. with the --si flag) to avoid future confusion. And also perhaps clarify what one can expect in terms of output when using the --no-si flag.