Message Type 139, $PLACCEL

Proprietary NMEA message containing lateral acceleration/deceleration information obtained from the CTM-200's accelerometer data. This NMEA message is designed to be sent whenever the lateral acceleration threshold is exceeded (see cmd accelcond?).

Message format is:

$PLACCEL,hhmmss.ss, llll.llll,a,yyyyy.yyyy,b,vvv.v,uuu.u,ddmmyy,ggggggggggg*hh<CR><LF>

Where:

hhmmss.ss is the UTC time in hours, minutes, seconds, and decimal seconds

llll.llll is the position latitude in degrees, minutes and decimal minutes

a is N(orth) or S(outh)

yyyyy.yyyy is the position longitude in degrees, minutes and decimal minutes

b is E(ast) or W(est)

vvv.v is the velocity in km/h

uuu.u is the lateral acceleration in km/h/s

ddmmyy is the day, month and year

ggggggggggg is the modems ID

hh is the message checksum

Example:

$PLACCEL,172244.00,4915.3932,N,12259.8008,W,000.0,105.9,270511,00000000000*4B[0x0D][0x0A]

In the above example the recorded lateral acceleration value is 105.9 km/hr/sec, or 3g.

"The maximum lateral acceleration is limited by rollover stability for most heavy vehicles and by tire adhesion for passenger cars. Typical values to use for dry conditions are 0.35g (12.32 km/hr/sec) for laden heavy vehicles, 0.7g (24.6 Km/hr/sec) for buses and SUV's and 0.8g (28.2 km/hr/sec) for passenger cars. " exerpt from NCHRP (National Cooperative Highway Research Program) Human Factors Guidelines for Road Systems Second Edition ISBN 0077-5614