Trimble Outdoors SK8 - Manual (Page 60)

4-8 Lassen-SK8 Embedded GPS Module
Operation and Performance
4.7 Coordinate Systems
Once the Lassen-SK8 achieves its first fix, it is ready to commence output of position,
velocity, and time information.
This information is output over serial communication channel in either the TSIP, TAIP, or
NMEA protocol, as determined by the settings of the receiver. These protocols are defined
in the following Appendices:
• TSIP - Appendix A
• TAIP - Appendix C
• NMEA - Appendix E
To change from one protocol to another, please see “Configuring your Receiver” in
Appendix A.
4.7.1 TSIP Coordinate Systems
TSIP has the widest choice of coordinate systems. The output format is chosen by TSIP
command 0x35. The output formats include the following:
• LLA position — Latitude, longitude, altitude (LLA) according to the WGS
ellipsoid or one of over a hundred other datums. See Appendix A, Table A-86 for
a list of available datums. Altitude can be chosen to be height above ellipsoid
(HAE) or height above mean sea level (MSL).
• ENU velocity — ENU velocity is the velocity in East, North, and Up coordinates.
These coordinates are easily converted to speed and heading.
• ECEF position and velocity — ECFF position and velocity is Earth-Centered,
Earth-Fixed frame is a Cartesian coordinate frame with its center at the earth's
center, the z-axis through the North Pole, and the x-axis through longitude 0
degrees, latitude 0 degrees. Velocity is reported relative to the same axes.
• UTM — Universal Transverse Mercator (UTM) is a mapping coordinate system
used by many government agencies.
There are also two time coordinate systems:
• GPS time — GPS time is determined by an ensemble of atomic clocks operated
by the Department of Defense (DOD).
• UTC time — UTC time is the world standard maintained by an ensemble of
atomic clocks operated by government organizations around the world.
GPS time is steered relative to Universal Coordinated Time (UTC). GPS does not
recognize leap seconds resulting in a situation where GPS time is currently 12 seconds
ahead of UTC time. Time tags for most output messages can be in either UTC time or GPS
time, as chosen by TSIP command 0x35.