Novatel OM-20000041 用户手册

3

Data Logs

42

 MiLLennium GPSCard Software Version 4.50 Command Descriptions Manual Rev 1

The Wide Area Augmentation System (WAAS) is a safety-critical system that provides a quality of positioning
information previously unavailable. The WAAS improves the accuracy, integrity, and availability of the basic GPS
signals. 

The log WALA/B (see its descriptions on Page 222), provide WAAS satellite-specific data. For more information
on MiLLennium GPSCards with the WAAS option, see Page 29.

The pass-through logging feature enables the GPSCard to redirect any ASCII or binary data that is input at a
specified port (

COM1

 or 

COM2

) to any specified GPSCard port (

COM1

 or 

COM2

). This capability, in conjunction with

the 

SEND

 command, can allow the GPSCard to perform bi-directional communications with other devices such as

a modem, terminal, or another GPSCard.

There are two pass-through logs 

 and 

, available on MiLLennium GPSCards.

Pass-through is initiated the same as any other log, i.e., 

LOG

 [to-port] [data-type-A/B] [trigger]. However, pass-

through can be more clearly specified as: 

LOG

 [to-port] [from-port-A/B] [onchanged]. Now, the [from-port-A/B]

field designates the port which accepts data (i.e., 

COM1

or 

COM2

) as well as the format in which the data will be

logged by the [to-port] — (A for ASCII or B for Binary).

When the [from-port-A/B] field is designated with an [A], all data received by that port will be redirected to the
[to-port] in ASCII format and will log according to standard NovAtel ASCII format. Therefore, all incoming
ASCII data will be redirected and output as ASCII data. However, any binary data received will be converted to a
form of ASCII hexadecimal before it is logged.

When the [from-port-A/B] field is designated with a [B], all data received by that port will be redirected to the [to-
port] exactly as it is received. The log header and time-tag adhere to standard NovAtel Binary Format followed by
the pass-through data as it was received (ASCII or binary).

Pass-through logs are best utilized by setting the [trigger] field as onchanged or onnew. Either of these two
triggers will cause the incoming data to log when any one of the following conditions is met:

•

Upon receipt of a <CR> character

•

Upon receipt of a <LF> character

•

Upon receipt of 80 characters

•

1/2 second timeout following receipt of last character

Each pass-through record transmitted by the GPSCard is time tagged by the GPSCard clock in 

GPS

 weeks and

seconds.

For illustration purposes, you could connect two GPSCards together via their 

COM1

 ports such as in a reference

station, labelled as reference station in Figure 5-1, to remote station scenario. If the reference station were logging

PVAA

 data to the remote station, it would be possible to use the pass-through logs to pass through the received 

PVAA

differential correction data to a disk file (let's call it 

DISKFILE

.log) at the remote station host PC hard disk.