Novatel Software Version 4.45 OM-20000026 Rev 1 Initialization

1 Quick Start

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 COM1 or COM2 port of the remote

GPSCard must be dedicated to receiving RTCA data only, and so the “ACCEPT port RTCA” command must be

issued. 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.

Before initializing, ensure that the data link with the reference station has been properly set up. As well, ensure that

the COM port which is to receive the differential data is set up to match the bit rate an d protocol settings of the

reference station broadcast data.

Establishing differential mode of operation at the rover receiver is primarily a one-step process whereby the accept

command is used to enable reception of observation data from the reference station.

The accept command is primarily used to set the GPSCard’s COM port command interpreter for acceptance of

various data formats. (see the ACCEPT command in Chapter 2 and Appendix C)

Syntax

Example:

accept com2 rtcm

Once intitialized, the rover GPSCard receiver will operate in single point mode until the differential messages are

received. If the data messages are lost, the GPSCard will revert to single point positioning until the pseudorange

correction messages are restored.

NOTES: Ensure that the GPSCard RTCMRULE settings agree with the bit rule being transmitted by the RTCM

reference station. Unless otherwise set, all GPSCards default to 6CR.

The GPSCard remote receiver has many options for information data logging. To monitor position status, th e user

may find the PRTKA/B logs to be the most informative. Other options exist, such as POSA/B and GPGGA. As well,

velocity data can be found in the VLHA/B, SPHA/B and GPVTG logs. It is really up to the user’s specific applications

as to the full range of logs required by the user.

ACCEPT port mode