[PUP] GPS height ( was AIS pitfalls )

[Truelove39@aol.com]

Hi John -  
You make some good  points; your statement copied below prompted me to think 
about the GPS receiver  in the Furuno 1943 radar. It is DGPS-capable and so we 
use it for AIS and  CE as well as the built-in ARPA.  
My thoughts revolve  around the fact that the ARPA targets' headings often 
vary wildly in a  seaway and especially at longer distances, although they do 
settle down  closer in. I'm thinking that the height (24 feet) may be the cause. 
Although I  haven't studied it, a glance at the menu tells me I can't defeat 
the internal  GPS and source the data input for ARPA externally from a unit 
mounted lower. I'm  curious why you say, "the dome for that is mounted high 
above everything else  at about 38' elevation to make it work well," when 
conventional wisdom is  to mount them as low as possible to avoid "swing." 
Regards, 
John 
"Seahorse" 

> To your other point, for course input, we do have a GPS  compass  
system... the dome for that is mounted high above everything  else at  
about 38' elevation to make it work well. I understand it uses  3  
GPS's all by itself. It broadcasts heading to all devices on our  NMEA  
bus. It worked great coming up the Pacific coast from  Dana Point to  
Victoria, BC,  even in large, steep head seas when we were pitching  
like crazy. The  swing at 38' above the water must have been  dramatic.





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