Novatel OM-20000053 Rev 2 Initialization

1 Quick Start

22 MiLLennium GPSCard SW Version 4.503/4.52 Command Descriptions Manual Rev 2

RTCM SC-104 is a standard for transmitting differential corrections between equipment from different

manufacturers. The NovAtel GPSCard is capable of transmitting or receiving RTCM data.

To facilitate transmitting the RTCM data over shared data links, the GPSCard is also capable of sending the RTCM

transmission and reception along with other data types.

NOTE: When sending or receiving RTCM log types, it is important to ensure that all connected equipment are

using the same RTCMRULE for compatibility.

The easiest method to send RTCM standard logs is from the COM1 or COM2 ports of the reference GPSCard. The

easiest method to receive the RTCM data is through the COM1 or COM2 port of the rover GPSCard. The rover

GPSCard must issue the “ACCEPT port RTCM” command to dedicate a port before it will accept the RTCM data

into that port.

The RTCMA log can be intermixed with other NovAtel ASCII data over a common communication port. It will

be directly interpreted by a rover GPSCard as a special data input command ($RTCM). “ACCEPT port

COMMANDS” must be used with this input command. A non-NovAtel rover station will need to strip off the

header ($RTCM) and terminator (*xx), then convert the hexadecimal data to binary before the RTCM standard data

can be retrieved.

The RTCMB log can be intermixed with other NovAtel binary data over a common communication port.

REMEMBER: Use the CDSA/B logs to monitor the COM port activity, success, and decoding errors.

The RTCA (Radio Technical Commission for Aviation Services) Standard is being designed to support

Differential Global Navigation Satellite System (DGNSS) aviation applications. The perceived advantage to using

RTCA type messages for transmitting and receiving differential corrections versus using RTCM type messages is

that RTCM transmits 30-bit words, and the data is difficult to decode and process because of the parity algorithm

and irregular word sizes used. RTCA is transmitted in 8-bit words, which are easier to generate, process and

decode. The RTCA messages are therefore smaller, they have a 24 bit CRC that is much more robust than RTCM

messages, and they permit the use of a four-alpha-character station ID.

RTCA standard logs can be received through the COM1 or COM2 port of the rover GPSCard. The remote

GPSCard must issue the “ACCEPT port RTCA” command to dedicate a port before it will accept the RTCA data

input to that port. The RTCA logs cannot be intermixed with other logs.

The RTCAA log can be intermixed with other NovAtel ASCII data over a common communications port. It will

be directly interpreted by a rover GPSCard as a special data input command ($RTCA). “ACCEPT port commands”

must be used with this input command. A non-NovAtel rover station will need to strip off the header ($RTCA) and

terminator (*xx), then convert the hexadecimal data to binary before the RTCA standard can be retrieved.

The RTCAB log can be intermixed with other NovAtel binary data. The remote GPSCard identifies the RTCAB

log by the message block identifier contained in the message, and will interpret only the RTCA data portion of the

log.

NOTE: The CDSA/B logs may be used to monitor the COM port activity and differential data decode success.

Initialization - Rover Station

It is necessary to initialize the rover receiver to accept observation data from the reference station. If the receiver

is not correctly initialized, it will proceed to compute solutions in single point positioning mode.