BendixKing SKYMAP IIIC - Manual (Page 137)

DIFFERENTIAL FUNCTIONS (Skymap IIIC only)
Uses Of DGPS
Standard GPS provides good accuracy for most navigational tasks, but the additional
precision available through DGPS opens up other possibilities in aviation and in many
other spheres of activity. Once the aviation authorities are prepared to approve DGPS-
based low-visibility approach and landing systems, these could provide low-cost precision
facilities worldwide. The benefits of this could be especially useful at small airports where
the expense of an ILS or MLS system could never be justified and in developing countries
where few if any navigation aids exist today.
DGPS has also already become an essential tool of the offshore oil industry, enabling drill
bits to be placed with more precision than any other system. Marine navigation, survey work
and cartography, emergency services, agriculture and forestry and road transport fleet
management are just some of the non-military applications already relying more and more
upon the accuracy of DGPS.
Data Connection
To operate correctly in differential mode, Skymap IIIC requires a 9600 baud RTCM SVC-
104 Version 2.0 format sentence.
To connect the Skymap IIIC to a differential receiver unit, connect the 0v or ground lines
(pin 5 of the Skymap IIIC connector) and the data output line from the differential receiver
to pin 1 of the Skymap IIIC connector.
Once connected to an operating differential receiver, switch your Skymap IIIC on and
select Screen 3, GPS Status Screen, by pressing Key 1 from the Main Menu Screen.
Once the unit has a fix and differential sentences are being decoded, the word
DIFFERENTIAL will be displayed next to the STATE: heading. If the data is not
recognised or is not present, the word DIFFERENTIAL will not be displayed.
All the time that DIFFERENTIAL is displayed, the Skymap IIIC is in differential mode and
corrections are being applied to the position fix calculations.
APPE
NDICES
Rev 9 Jul 2006 E-2 Skymap/Tracker IIIC Pilot's Guide