Trimble Outdoors SK8 - Manual (Page 204)

Glossary-6 Lassen-SK8 Embedded GPS Module
Glossary
maximum PDOP A measure of the maximum Position Dilution of Precision (PDOP) that is
acceptable in order for the GPS processor to determine a location
solution (see PDOP).
NAVSTAR The name given to the GPS satellites, built by Rockwell International,
which is an acronym formed from NAVigation System with Time And
Ranging.
NMEA National Marine Electronics Association. An association that defines
marine electronic interface standards for the purpose of serving the
public interest.
NMEA 0183 message NMEA 0183 is a standard for interfacing marine electronics navigational
devices. The standard specifies the message format used to communicate
with marine devices/components.
packet An “envelope” for data, which contains addresses and error checking
information as well as the data itself.
parity A scheme for detecting certain errors in data transmission. Parity defines
the condition (i.e., even or odd) of the number of items in a set (e.g., bits
in a byte).
PDOP Position Dilution of Precision. PDOP is a unitless figure of merit that
describes how an uncertainty in pseudo-range affects position solutions.
PDOP constellation switch A value, based on PDOP, that defines when the GPS receiver/processor
should switch between 2-D and 3-D GPS modes. The PDOP
constellation switch is only active when the GPS mode of operation is set
to Auto.
PRN Pseudo-random noise. Each GPS satellite generates its own distinctive
PRN code, which is modulated onto each carrier. The PRN code serves
as identification of the satellite, as a timing signal, and as a subcarrier for
the navigation data.
protocol A formal set of rules that describe a method of communication. The
protocol governs the format and control of inputs and outputs.
pseudo-range A measure of the range from the GPS antenna to a GPS satellite. Pseudo-
range is obtained by multiplying the speed of light by the apparent transit
time of the signal from the GPS satellite. Pseudo-range differs from
actual range because the satellite and user clocks are offset from GPS
time and because of propagation delays and other errors.
RAM Random-Access Memory.
random-access memory Memory in which information can be referred to in an arbitrary or
random order. The contents of RAM are lost when the System Unit is
turned off.
2-D Two Dimensional. A 2-D position is defined as latitude and longitude.
Altitude is assumed to be fixed.