[BC] dBm, dBc, dBd

[RSTYPE@aol.com]

In a message dated 11/15/2005 12:18:31 AM Eastern Standard Time, 
khcs at juno.com writes:
Danny pondered:

>On that same subject, why does the FAA use NAD83, while the FCC still 
uses NAD27 coordinates in some licensed services?

----------

Probably because it would be too much trouble to convert every station 
license over to the new coordinates.  


Glen Kippel
KHCS
Palm Desert, CA


It's much more complicated than that.  Converting the coordinates for all AM, 
FM, and TV facilities would also require revising the notifications for all 
of these stations to Canada, Mexico, and IFRB and could also possibly raise 
issues regarding Canadian and Mexican consent for the revised coordinates.  It's 
hard enough at times to obtain timely consent (especially from Mexico) for 
actual changes in facilities.  Trying to do this simply to slightly revise the 
coordinates for all stations notified to these countries would be an absolute 
nightmare.  Making such a conversion would probably also require that all of the 
procedures and equations specified in these international agreements to 
calculate distances and azimuths be modified to be accurate for the revised datum, 
which would also be an administrative and negotiation nightmare.  (We recently 
had the FCC refuse to correct the tower numbering scheme for an AM 
dir4ctional in the CDBS to correspond to the numbering scheme which the station has 
employed since 1948 because doing so would have required Canadian concurrence.  It 
turned out to be easier for the station to modify the numbering designation 
for the towers to match the CDBS.  Isn't bureaucracy great!)

This is also an issue for USGS.  Only a small percentage of the 7.5' topo 
maps have been updated to NAD83, while the rest are still based on NAD27.  This 
really gets to be fun when setting up measurement radials that cross from a  
map in one datum to a map based on the other datum and is complicated by the 
fact that the NAD83 maps are scaled at 1:25,000, while most of the NAD27 maps are 
still scaled at 1:24,000.

Roy Stype
Carl E. Smith Consulting Engineers