Instruction manual

Glossary Page Gloss-1
Glossary
Glossary
Almanac
A comprehensive database of all pertinent
information for all satellites- orbit, position,
health, etc.
Ambiguity fixing
A process to determine carrier phase cycle
ambiguities to integers.
Altitude hold
A means of reducing the number of satellites to
3 for a position computation. If altitude is not
held (fixed), 4 satellites are required. Altitude
hold is seldom required now that a full
constellation of satellites is available.
Autonomous
A GPS position determined by a single sensor
without reference to a precise known location.
The autonomous solution contains errors
arising from ionosphere, SA, troposphere, and
multipath. Accuracy is in the range of tens of
meters.
Carrier Phase Cycle Ambiguities
The constant offset contained in the carrier
phase measurements. This constant offset is of
integer nature.
CB EN
Ashtech proprietary message format containing
position, velocity, solution status, position
RMS and covariance, number of satellites,
PDOP. ASCII or binary. Binary format is
packed and is not compatible with IEEE format.
Clock offset
The difference in time between GPS time and a
satellite clock or a sensor clock (less accurate).
Code Phase
See Pseudo-range
CPD
Ashtech’s proprietary carrier phase differential
method for GPS positioning. Pseudo-range and
carrier phase measurements in DBEN message
format are transmitted from base to rover via a
data link (usually a radio), allowing the rover to
compute an extremely accurate differentially
corrected position, in centimeter ot subcentimeter
level.
DBEN
An Ashtech proprietary binary message format
which contains a message header, receiver time,
receiver site ID, pseudo-range and carrier phase
measurements, checksum, and message tail. This
message is for CPD operation.
D-file
GPS time-stamped descriptor text file.
Double Difference
The code phase (pseudo-range) measurement or
carrier phase measurements can be differenced
between two sites and differenced between two
satellites. This is called double difference. Double
difference removes/reduces most of the common
errors between the measurements. It is a way of
differential processing. Difference between two
sites removes/reduces Ionospheric delay
Tropospheric delay Satellite clock error,
including S/A effects
Difference between two satellites received from
the same receiver removes/reduces the receiver
clock error
Ephemeris
A subset of the almanac containing inform ation