Garmin FIT Coordinate System

Question

I am trying to decode a .FIT file from a Garmin Instinct GPS Watch. Sourced from the file Lctns.fit.

However, I am unsure how to interpret the entries values as coordinates.

Given this entry:

# Output from parsing the FIT file.

* unknown_1: 571162134
* unknown_2: 92300401
* unknown_254: 12
* unknown_3: 63
* unknown_4: 4930

# The same entry as Lat / Long

N 47.52.4554
E 007.44.1918
Elevation: 486m

How can I determine what coordinate system is being used inside the FIT file as to convert to Latitude and Longitude?

I have tried converting from UTM with no success: http://www.rcn.montana.edu/Resources/Converter.aspx

Answer 1

For the latitudes and longitudes, you can divide the numbers by 11930465 (2^32 / 360) to get values in decimal degrees. The values seem to be stored in a signed 32-bit integer range, to represent the full range of geographic coordinate values possible.

Here is a link to a related question: Convert Garmin or iPhone weird GPS Coordinates

Answer 2

I am unsure how to decode the elevation data from the .FIT file. But once you have the lat/long coordinates in WGS84, you can lookup the elevation for those coordinates with a different service, such as https://www.gpsvisualizer.com/elevation.