[C320-list] Longitude Lattitude Garmin

[Scott Thompson]

The Garmin undoubtably knows where it is.  The problem as you have found 
is with how to describe this to the rest of the world, and whether the 
rest of the world is in the right place.

Display issues:  My older Garmin let's you switch between many display 
modes, including degrees, degrees & minutes, or degrees & minutes & 
seconds.  In each case the last item will be expressed in decimals.  So 
if you are in the first mode you get decimal degrees only, while in the 
last one you get integer degrees and minutes, but the seconds are decimal.

Another issue is the map "datum" setting.  There is more than one system 
for measuring latitude and longitude (and altitude) in use, and if the 
one that your GPS is using to display location is different from the 
chart then they won't agree, even if your location is displayed very 
precisely.  "WGS 84" is the map datum used on most U.S. charts, and is 
the default in most GPS units I believe.  Check the setup pages on your 
unit to make sure it is set to this.

Real world issues:  A number of channel markers on charts are not 
indicated in their actual location.  One of the sailing magazines 
published an article a few years ago that was basically a list of horror 
stories for how you could end up on a reef if you blindly assumed that 
chart locations (whether paper or in a chart plotter) for actual 
obstacles were as accurate as your GPS.  In the early days of plotting 
GPS devices, a  lot of people complained that they weren't accurate 
because they would show, for example, a fixed marker as being somewhere 
else when your boat was right next to it.  Or show you driving parallel 
to, but not on, a country highway.  Such problems were universally 
problems with the underlying chart data, and not with the GPS position 
information.  There's one such marker a few miles from my house that's 
off by about 1/2 mile on the charts, even on recent charts.

On the other hand, with Google Earth you can get pretty accurate 
information from aerial photography.  I can see my mooring ball on 
Google Earth and the Lat/Lon displayed matches what I get on the GPS for 
all but the last displayed decimal point.

Which reminds me of a question:  How many 320s are visible on Google 
Earth?  I'm pretty sure you can see my boat on the hard from last winter 
here:   38° 57.645'N,  76° 28.868'W



Joe Abbagnaro wrote:
> I think I might have Figured it out.
> The Garnin is giving Long and Lattitude in Decimal Format
> The Chrts are formatted in Hour Min Sec ???
> 
> On Tue, May 6, 2008 at 10:16 PM, Jon Vez <jonvez at comcast.net> wrote:
>> Joe,
>>
>>  Garmin's tech support is actually very good. I would suggest hanging on
>>  until you get someone. It could be an issue with the internal software,
>>  which can be fixed with a download or they will send you a flash card. I had
>>  an issue with mine when I first bought it and that's how they handled
>>  it...Good luck...
>>
>>  Regards,
>>
>>  Jon Vez
>>  Solstice #582
>>
>>
>>
>>  -----Original Message-----
>>  From: c320-list-bounces at lists.catalina320.com
>>  [mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of Joe Abbagnaro
>>  Sent: Tuesday, May 06, 2008 10:11 PM
>>  To: C320-List
>>  Subject: [C320-list] Longitude Lattitude Garmin
>>
>>  I installed a new Garmin 4208 it works very nice
>>  When First installed it knew the boat was in the parking lot in the Marina.
>>  It preety much knows where it is according to its internal charts.
>>
>>  This past weekend we took the Boat from New Jersey to Westbrrok CT.
>>  The garmin knew where it was on the Chart plotter except for one big
>>  issue . We were with a captain who had a hand held garmin and are Long
>>  and Latttudes did not match at
>>  all.  The Gramin knows that the boat is the slip in Westbrook CT ,
>>  but if I look at the longitude and latitude it is off by at least 5 miles.
>>
>>  My Readings are
>>  41.27.301
>>  72.46.850
>>
>>  Anyone have any ideas what is going on ?
>>  I tried calling garmin but could not wait in there call Queue.
>>
>>  Thank You
>>  Joe
>>
>>