User's Manual

27 | Page
Proprietary and Confidential Revised 10-11-11
? The SXL1 encodes 180 degrees of LATITUDE as a 24-bit (3-byte) signed integer.
? The SXL1 encodes 360 degrees of LONGITUDE as a 24-bit (3-byte) signed integer.
? The encoded LATITUDE data is the first three bytes of the location data payload
? The encoded LONGITUDE data is the next three bytes of the location data payload.
Lat2 Lat1 Lat0 Long2 Long1 Long0
? Lat2 – Latitude MSB
? Lat1 – Latitude
? Lat0 – Latitude LSB
? Long2 – Longitude MSB
? Long1 – Longitude
? Long0 – Longitude LSB
CALCULATING LATITUDE FROM ENCODED SXL1 MESSAGES
Latitude may be calculated by converting the 3 encoded latitude bytes represented in hexadecimal to
a decimal number and multiplying this decimal integer by the DEGREES_PER_COUNT_LAT
conversion factor 90.0 / 2
23
.
Since the latitude is signed and can range from –90 to 90 degrees, if the above result is greater than
or equal to 90 degrees, 180 must be subtracted from the result.
Negative Latitude corresponds to Latitude in the SOUTHern Hemisphere.
Positive Latitude corresponds to Latitude in the NORTHern Hemisphere.
CALCULATING LONGITUDE FROM ENCODED SXL1 MESSAGES
The longitude may be calculated by converting the 3 encoded longitude bytes represented in
hexadecimal to a decimal number. This decimal integer is multiplied by the
DEGREES_PER_COUNT_LONG conversion factor 180.0 / 2
23
.
If the above result is greater than or equal to 180 degrees, 360 must be subtracted from the result
since the longitude is signed and can range from –180 to 180 degrees.
Negative Longitude corresponds to Longitude in the WESTern Hemisphere.
Positive Longitude corresponds to Longitude in the EASTern Hemisphere.