Dgps - Wavecom W74PC Manual

Pressing Change Order reverses the polarity of the signal and pressing Default ST restores the default val-
ue. For more information see

DGPS

DGPS (Differential Global Positioning System) data is mainly transmitted in the low frequency band e.g.,
285 - 315 kHz. It is a correction signal for GPS receivers, and is used to increase the accuracy of the sat-
ellite-based GPS signal. DGPS is based on the transmission of correction data by a reference station, the
position of which has been determined with high accuracy by traditional position-finding measurements.
With the correction data, an absolute accuracy to within 4 meters can be achieved.
Parameter
Frequency range
Operation modes
Modulation
Symbol rate
Receiver settings
Input format(s)
Additional Info
Transmissions use MSK (Minimum Shift Keying) with speeds of 100 or 200 baud.
DGPS has been implemented according to RTCM SC-104 "Recommended Standards for Differential
Navstar DGPS Service" v.2.0, Jan. 1990.
 These messages are decoded: 1, 3, 7, 9, 13, 16.
 These messages are NOT decoded, but their type is indicated: 2, 4, 5, 6, 8, 10, 11, 12, 14, 15,
17, 60-64.
 Compared to M.823-2 messages 4 and 5 are not decoded by my implementation neither are the
equivalent GLONASS.
DGPS data, which is formatted according to RTCM v.2.0 or 2.1, is continuously transmitted in frames con-
sisting of a varying number of data words. The two first words of each frame contain the reference station
id, the message type, a sequence number, the frame length and the health of data. A data word has a
length of 30 bits: 24 data bits and 6 parity bits. The last two bits of a word are used as an EXOR function
for selected bits of the succeeding data word. The value of the last bit indicates whether the next data
word is sent with inverse or normal polarity.
158  Transmission Modes
"Symbol Definition" on page 43.
Value
HF
Broadcast FEC
Minimum-Shift-FSK
100.0 and 200.0 Bd
DATA, CW, LSB or USB
AF, IF
ITA-5
WAVECOM Decoder W74PC, W-PCI/e, W-CODE, W-CLOUD Manual V9.1.0