10
Horizon GPS Chart400 User Manual
3.2 Main Screens
At initial power-up the GPS Chart400 displays chart cartridge information and the following navigation
warning:
BckLgt
Confirm
C-MAP electronic charts (ECs) are derived from
geographical data - including official government charts
- which we believe to be accurate. They are neither
verified nor approved by Hydrographic Authorities. C-
MAP ECs are designed only to ease and speed
navigation calculations and so must not be relied upon as
a primary source of navigation information, but rather a
backup to the use of official government charts and
prudent navigation habits.
There is no direct relationship between the color of
water areas and their depth. The navigator shall always
query the area for depth information and use the official
paper charts. The ECs contained in this C-MAP product
have been derived on agreement with the following
Hydrographic Authorities:
At this point backlighting can be adjusted by pressing the BackLt key to switch the backlighting on or
off. Press the Confirm key to proceed to the Satellite Status screen, the first of the four main
screens.
3.21 Satellite Status Screen
The GPS constellation comprises 24 satellites orbiting the earth. From any one point on the earth’s
surface 12 satellites are “visible” to the GPS receiver. The position of these satellites is constantly
changing. The Horizon GPS antenna tracks all visible satellites simultaneously and selects four
satellites that produce the optimum geometry for determining a 3-D position. The superior performance
achieved with the GPS Chart400 12 channel receiver provides increased accuracy and reduced
Time to First Fix (TFF).
SATELLITE
STATUS
SIGNAL
STRENGTH
GPS Fix
GPS Fix
9 Jan 98
9 Jan 98
07:05:34am
01 14 15 20 21 25 29
01 14 15 20 21 25 29
9
8
7
6
5
4
3
2
1
0
9
8
7
6
5
4
3
2
1
0
29
20
25
MapShft
Aux
HDOP: 1.1
HDOP: 1.1
COG
14
21
15
01
The time from initial power-up to the time the GPS Chart400 calculates the latitude and longitude of
the current position is known as the Time to First Fix (TFF). The TFF varies in relation to a number of
factors, but primarily varies due to the amount of time that has passed since the GPS Chart400 last
obtained a fix. If the GPS Chart400 was last used within four hours the TFF will typically acquire a
position within 18 seconds. The TFF will extend out to 2 minutes if the GPS Chart400 has not been
used for periods longer than a few weeks. If the GPS Chart400 has moved a significant distance,
typically greater than 50 miles, since the last time it was used it will automatically go into a cold start
