COMDTINST 16500.20
JAN 22 1993
of 1992. These files were converted from CAP II aid and object files previously sent by the
districts to the Research and Development Center. To position an aid to navigation with
LAAPS using the differential Global Positioning System (DGPS), it is necessary that the aid
position be referenced to NAD 83.
c
During this transition stage from the older datums to NAD 83, it is imperative that the
districts and units ensure that the datums not be confused when positioning aids to
navigation.
d With the exception of the Ninth and Fourteenth Districts, many of the aid positions stored in
the district's Aids to Navigation Information System (ATONIS) have been transformed
from an older datum to the North American Datum of 1983 (NAD 83). Aid positions
referenced to a datum that could not accurately be converted to the NAD 83 datum were
documented in letters back to the districts. Plans to convert the remaining aid positions are
now being discussed.
e
The majority (approximately 89%) of the nautical charts published by the National Oceanic
and Atmospheric Administration (NOAA)/National Ocean Survey (NOS) are referenced to
NAD 83. Please note that reference (b) provides direction that the Local Notice to Mariners
list geographic positions in the same datum as the current edition of the nautical chart on
which that particular correction appears.
f
North American Datum Conversion (NADCON) Software was distributed to the districts at
the Spring 1992 LAAPS Conference. Districts may have already received another copy of
the software through the procedures outlined in reference (c). The NADCON software will
help the district perform position datum transformations between NAD 27 and NAD 83.
The current version of NADCON is 2.0.
g Reference (b) also contains additional information on the use and implementation of NAD
83.
4. PROCEDURES.
a
Districts should notify Commandant (G-NSR) if CAP II positions referenced to datums
other than NAD 27 were forwarded to the Research and Development Center for conversion
to NAD 83. These files probably would have been sent in January or February of 1992.
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