Novatel Software Version 4.45 OM-20000026 Rev 1 USING RTCM SC-104 LOG TYPES, USING RTCA LOG TYPES

1 Quick Start

to collect updated ephemeris data as well.

A delay of 120 to 130 seconds will typically ensure that the rover stations have collected updated ephemeris. After

the delay period is passed, the reference station will begin using new ephemeris data. To enter an ephemeris delay

value, you must first enter a numeric placeholder in the DGPS delay field (e.g., 2). When operating as a reference

station, DGPS delay will be ignored (see the DGPSTIMEOUT command found in Chapter 2 and Appendix C for

further information on using this command at rover stations.)

Syntax:

Example:

dgpstimeout 2,300

USING RTCM SC-104 LOG TYPES

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

synchronous transmission and reception along with other data types.

REMEMBER: 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.

USING RTCA LOG TYPES

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

Differential Global Navigation Satellite System (DGNSS) Special Category 1 (SCAT-I) precision approaches. 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 regular word sizes used. RTCA is transmitted in 8-bit words, which are easier

DGPSTIMEOUT dgps delay ephem delay

Command Option Description Default

DGPSTIMEOUT Command

dgps delay min. 2

max. 1000 Maximum age in seconds 60

ephem delay min. 0

max. 600 Minimum time delay in seconds 120