I have a Garmin Nüvi GPS and it's filled with XML records that look like this:

<trkpt lat="38.900207" lon="-77.008990">

(line breaks added for legibility)

My question — what are the units for gpxtpx:speed ? I've examined all of the trackpoints for my GPS and the gpxtpx:speed never gets much above 30, and I KNOW that I'm going faster than 30MPH.

I've scanned the documentation and I can't find what the units are.

  • 3
    meters per second (m/s) see topografix.com/gpx_manual.asp#trk if you get to 70mph (112.7kph) you will see it going over 30 m/s (31.2928). – Mapperz Oct 13 '13 at 3:50
  • Hm. I guess it is documented in the Garmin schema. – vy32 Dec 18 '15 at 21:56

There are a few speeds that can be immediately tossed out:

30 ft/s = 20 mph < 30 mph
30 km/h = 19 mph < 30 mph
30 yd/s = 61 mph > 30 mph (not exactly a standard measurement)

The only other "common" speed I'd say is m/s, which works well:

30 m/s = 67 mph > 30 mph

If you can confirm that elevation is given in meters (it looks like it is for that particular point), that would be a nod towards m/s.

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  • your assumption is correct. – Mapperz Oct 13 '13 at 3:51
  • Yes, I've gone through all of the data and it all seems to be in m or in m/s. It's odd that it's not documented anywhere, not even on the Garmin schema – vy32 Oct 13 '13 at 4:19

it is documented here: http://www8.garmin.com/xmlschemas/TrackPointExtensionv2.xsd.

<xsd:element name="speed" type="MetersPerSecond_t" minOccurs="0"/>

and type MetersPerSecond_t is defined as

<xsd:simpleType name="MetersPerSecond_t">
      This type contains a speed measured in meters per second.
  <xsd:restriction base="xsd:double"/>
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