Novatel Software Version 4.45 OM-20000026 Rev 1 用户手册

Comparison Of RT-2 And RT-20

MiLLennium Command Descriptions Manual

213

If the loss of differential corrections lasts longer than 30 seconds, the

filter is reset and all ambiguity

and monitor model information is lost. The timeout threshold for

differential corrections is 30

seconds, but for Type 1 pseudorange corrections, the timeout is 60 seconds. Therefore, when the

can no longer function because of this timeout, the pseudorange filter can produce differential positions
for an additional 30 seconds (provided

RTCM

Type 1 messages were transmitted along with the Type 59

messages) before the system reverts to single point positioning. Furthermore, once the link is re-
established, the pseudorange filter produces an immediate differential position while the

filter takes

an additional 14 seconds to generate its positions. The monitor models require 7 monitor observations
before they are declared useable, and this will take 14 seconds, based on a 1/2 Hz differential correction
rate. The monitor model must be healthy before solutions are logged to the

POSA

and

logs, so

there is a delay in the use of real time carrier positioning to the user once the link has been re-established.
The

log uses matched observations only (no extrapolated observations), and these will be

available after three monitor observations are received, but will have about 1.5 seconds latency associated
with them.

Figure E-8

RT-20 Re-initialization Process

The

system is based on a time-matched double difference observation filter. This means that observations

at the remote site have to be buffered while the monitor observation is encoded, transmitted, and decoded. Only
two seconds of remote observations are saved, so the monitor observation transmission process has to take less than
2 seconds if any time matches are to be made. In addition, only remote observations on even second boundaries
are retained, so monitor observations must also be sent on even seconds if time matches are to be made.

REFERENCE

REMOTE

Reference

Doppler

Start generating

RTKA/B logs

Models

Ready

Generate
RTKA/B

logs

RTCM59 messages

required following

RESETRT20

reference phase

models and

and

PRTKA/B