Motorola M12 Oncore User's Guide download pdf (Page 42)

Chapter 3 – Receiver Description

Motorola GPS Products - Oncore User’s Guide

DATA LATENCY

The Oncore receiver can output position, velocity, and time data on the TTL port once

each second. The start of the output data is timed to closely correspond with the

receiver measurement epoch. The measurement epoch is the point in time at which

the receiver makes satellite range measurements for the purpose of computing

position. The first byte of TTL data in the position message is output between 0 and 50

ms after the most recent Oncore receiver measurement epoch.

Refer to Figure 3.11 for the discussions that follow.

Let T

be the most recent measurement epoch. The Oncore Receiver takes about one

second to compute data from the satellite range measurements. Consequently, the

data output 0 to 50 ms after T

represents the best

estimate of the position, velocity, and time based on the measurements taken one

second in the past, at time T

_1. Position data (latitude, longitude, and height) is

computed from the most recent measurement epoch data, and is output immediately

after the next measurement epoch, which is 1.0 to 1.05 seconds after the original

measurements were taken.

Revision 5.0 08/30/02

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Motorola M12 Oncore User's Guide Page 42