UKC Forums - GPS position formats

GPS position formats

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BattyMilk 11 Jan 2018

I'm going for a walk in the Brecon Beacons this weekend and for a backup I'd like to be able to use my watch (Suunto Ambit 3) to get my GPS position if I need it.

I'm looking at the settings on the watch and am baffled by all the options:

WGS84 Hd.d°
WGS84 Hd°m.m'
WGS84 Hd°m's.s
UTM
MGRS
British (BNG)
Finnish (ETRS-TM35FIN)
Finnish (KKJ)
Irish (IG)
Swedish (RT90)
Swedish (SWEREF 99 TM)
Swiss (CH1903)
UTM - NAD27 Alaska
UTM - NAD27 Conus
UTM - NAD83
New Zealand (NZTM2000)

Which of these should I use for conversion free compatibility with an Explorer or Landranger map?

Cheers

Fiona Reid 11 Jan 2018

In reply to BattyMilk:

From the list you've given it's likely British (BNG) - for British National Grid

99ster 11 Jan 2018

In reply to Fiona Reid:

> From the list you've given it's likely British (BNG) - for British National Grid

Yep - it's British (BNG) you want for using with OS maps.

Post edited at 13:54

OP BattyMilk 11 Jan 2018

Beautiful. Thank you both!

MarkJH 11 Jan 2018

In reply to BattyMilk:

> Which of these should I use for conversion free compatibility with an Explorer or Landranger map?

Also make sure that the datum is set to the correct value for the maps that you will use. From the list of options that you give, it sounds like this it tied to the position format, but some GPS units will let you use any datum with any position format. This may lead to a situation where your GPS positions look ok, but are a few 10s of m out, in a manner that isn't always obvious.

Always a good idea to check against a known feature when you 1st use it.

Post edited at 14:17

Inchewan 11 Jan 2018

In reply to BattyMilk:

As other posters say, the Postion Format is BNG. (British National Grid). Also, the Map Datum is Ord Survey GB, and the Map Spheroid is Airy. These are the three compatible settings.

Typically if you are in the Alps. Position format is UTM UPS, Map Datum is WGS 84, and Map Spheroid is WGS 84.

This helps with the newer GPS friendly maps, in all the Alpine countries. Universal Transverse Mercator (Universal Positioning System) has simplified all the individual French, Swiss, Italian, Austrian etc variations, and there are many. Much easier to work with than Lat/Long. This should keep you on the right track or route or path. Don't forget to set your Activity to direct routing.