Chapter 2 - Video Status Overlays
TM00358 Rev. A
October 2007
L-3 WESCAM
22
All Rights Reserved
The accuracy of Terrain Elevation value will affect some of the system’s automated functions; like focus clarity,
when operators are utilizing Geo-Focus, or target hold precision in Auto steering mode.
The Terrain Elevation value will be displayed in reverse video when the operator slews the turret to steering
coordinates issued by RCS or a Moving Map source. The reverse video value will report the static command
position, and the value will not update until cleared by a steering mode change. For example, reverting to Manual or
Forward steering.
Figure 2-10 Terrain Elevation After Slewing to Issued Coordinates
Target Bearing.
Reports the target’s angular measure for bearing relative to True North.
Slant Range.
Reports the calculated or measured distance of the target’s slant range. Slant range is the distance
from the turret to the ground intercept point along the line-of-sight. Display units can be configured by the operator.
Figure 2-11 Slant Range Distance
Measurement Mode.
Reports the system’s current measurement mode for calculating target distance. There are
two modes, of which both are passive and managed by the system:
•
LOS mode (passive measurement)
The target’s slant range distance and position data (lat and long) are calculated as the line-of-sight ground
intercept point, on the Earth’s surface, as defined by the navigational coordinate system of an assumed Earth
model (WGS84). For long range distances, the calculation applies correction factors for the earth’s curvature
and atmospheric influences. While accurate, the calculation of target location cannot account for: angular
measurement errors, inaccuracies in GPS position and altitude data, or timing errors introduced by either
extreme turret movement or from latent data updates. For example, viewing a subject at very narrow vertical
angle off the horizon or steering the turret too fast will impact distance calculations.
•
MAP mode (passive measurement)
The target’s slant range distance and position data (lat and long) are calculated as the line-of-sight ground
intercept point, on the Earth’s surface, as defined by the elevation contour supplied as Digital Terrain Elevation
Data (DTED) from a digital map. Accuracy of this measurement mode will depend upon your map system’s
DTED Level. For map data with a DTED Level of 1 or 2, the resolution is between 30 to 100m (98.4 to 328.1 ft).
For map data with DTED Levels 3 through 5, the resolution is much higher (1 to 3m [3.3 to 9.8 ft]), and the
measurement accuracy is comparable to that of a laser range finder. The calculation of target location cannot
account for angular measurement errors and timing errors introduced by either extreme turret movement or
from latent data updates. For example, viewing a subject at very narrow vertical angle off the horizon or steering
the turret too fast will impact distance calculations.
22NV2006
09:45:12
UTC+0.0
MAN
EOW
90
2X
COL
DFLT
AUTO
50
2000
2%
ACFT
27:46:12N
82:57:16W
352°
11050FT
679FT
153°
35.3NM
TGT LOS
27:46:05N
82:57:22W
01
00
-01
N
34 35 00 01 02
34 35 00 01 02
679FT
TEM
SPA
Slant R
ange
Sea Level
Terrain
