Commandant
2100 Second Street, S.W.
United States Coast Guard
Washington, DC 20593-0001
(202) 267-0980
COMDTINST 16500.20
JAN 22 1993
COMMANDANT INSTRUCTION 16500.20
Subj: Aids to Navigation Positioning Datums
Ref: (a) Aids to Navigation Manual - Positioning, COMDTINST M16500.1B
(b)Aids to Navigation Manual - Administration, COMDTINST M16500.7
(c) COMDTNOTE 16500 of 14 May 92
1. PURPOSE. This instruction is directed towards all aids to navigation servicing units. The
intent of this instruction is to reiterate the importance of knowing what horizontal geodetic
reference datum is being used when either positioning or reporting the positions of aids to
navigation.
2. DIRECTIVES AFFECTED. These changes will be reflected in an upcoming revision to
references (a) and (b).
3. DISCUSSION.
a
The current positioning software used in the Coast Guard is CAP II version 6. Many of the
positions in the aid and object files used by CAP II are not referenced to the North
American Datum of 1983 (NAD 83). When positioning an aid to navigation, units must
ensure that the assigned position of the aid (stored in the .aid file) and the positions of the
objects used to locate that aid (stored in the .obj file) are referenced to the same datum.
b In anticipation of the release of the Laptop Automated Aid Positioning System (LAAPS),
NAD 83 LAAPS aid/object files were distributed to the districts in the Spring
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