MIL-STD-1477 Symbols for Army System Displays MetricThis standard prescribes the physical characteristics of ground and air track symbols, unit/installation symbols, control measures symbols, equipment symbols, and associated alphanumeric information for U.S. Army Combined Arms system displays which are generated by electronic, optic, or infrared technology and presents information in real time or near-real time.

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MIL-STD-1477C(MI)

so that the operator can realize that multiple tracks exist.  A capability should be provided to allow an operator to zoom-in or change scale in order to gain more separation of track symbols.

5.2  Size

5.2.1  Symbol size.  The following equation shall be used to calculate the size of symbols and alphanumerics specified below:  Symbol height = Tangent (viewing angle subtended) x (viewing distance).  For example, at the minimum recommended viewing distance of 50 cm, a single friendly track should have a diameter of 3.7 mm (see figure 2).

5.2.1.1  Local tracks.  The major or vertical dimension of a single local track symbol shall subtend a visual angle of not less than 7.3 mrad of arc nor more than 10.2 mrad of arc when measured from the operator's eye in its normal viewing location.

The horizontal bar (line) denoting a rotary wing aircraft track shall have the same length and the width of a single track symbol.  The values, stated for local and remote tracks and also for unit, installations, control points, and equipment (5.2.1.3 through

5.2.1.6) are for symbol luminances which are above 0.35 cd/m2  and symbol-to-

background luminance contrast of not less than 0.88 (L1 - L2 / L1) as defined by MIL- HDBK 1908).

5.2.1.2  Remote tracks and alphanumeric data.  The major or vertical dimension of the basic track symbol for a single remote track and the height of alphanumeric characters shall subtend a visual angle of not less than 4.7 mrad of arc nor more than

6.6 mrad of arc when measured from the operator's eye in its normal viewing location. When a system is receiving only remote track information, an optical capability should be provided to automatically increase the size of the remote track symbols to the size

of the local track symbols.  Also, when remote tracks correlate with local racks, only the local track symbols shall be displayed.

5.2.1.3  Ground units.  The vertical dimension of a ground unit symbol shall subtend a visual angle of not less than 10.6 mrad or arc nor more than 12.0 mrad of arc when measured from the operator's eye in its normal viewing location.

5.2.1.4  Ground installations.  The major or vertical dimension of a ground installation symbol shall subtend a visual angle of not less than 2.0 mrad of arc nor more than 14.0 mrad of arc when measured from the operator's eye in its normal viewing location.

5.2.1.5  Control points.  The major dimensions of all control points shall subtend a visual angle of not less than 14.0 mrad  of arc nor more than 16.0 mrad of arc when measured from the operator's eye in its normal viewing location.

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