Encoding Position Data in User Location Protocol Beacons

Position data is provided as latitude and longitude, to 4-minute resolution, encoded in the PDF-2 of the second protected field (bits 108 - 132) as indicated below.

Bits

108

109 ---------- 115

116 ---------- 119

120

121 ---------- 128

129 ---------- 132

133 -- 144

Latitude Flag

North = 0

South = 1

Latitude Degrees

(0 to 90) in 1 degree increments

Latitude Minutes

(0 to 56) in 4 minute increments

Longitude Flag

East = 0

West = 1

Longitude Degrees

(1 to 180) in 1 degree increments

Longitude Minutes

(0 to 56) in 4 minute increments

BCH 2

The default values indicated below should be coded into bits 108 - 119 and bits 120 - 132 when position data is not available or if the beacon radiates a long message in the self-test mode mode:

Bits 108 to 119: 011 111 110 000
Bits 120 to 132: 011 111 111 000 0

Note: Latitude and longitude data are rounded off (i.e. not truncated) to the available resolution. See table below for an example:

Real Position Position Encoded in Beacon

43 deg : 31 min : 59 sec North 43 deg : 32 min North

01 deg : 29 min : 15 sec East 01 deg : 28 min East