Catalina - Capri - 25s International Assocaition Logo(2006)  
Assn Members Area · Join
h.jpg Home.
a.jpg Association Forum
s.jpg Ships Store
c.jpg Cruising
r.jpg Racing
t.jpg Technical Tips
g.jpg Photo Gallery - New
o.jpg Boat Search - Updated
m.jpg Manuals & Brochures
3rdrpt.jpg Swap Meet
l.jpg Links
f.jpg Officer Flag Line & Staff
b.jpg Bylaws & Constitution
 
1.jpg Members Area
1.jpg Join the Association
 
Notice:
The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.
 
Association Forum
Association Forum
Home | Profile | Register | Active Topics | Forum Users | Search | FAQ
Username:
 Password:
Save Password
Forgot your Password?

 All Forums
 Catalina/Capri 25/250 Sailor's Forums
 General Sailing Forum
 GPS question		  New Topic  Topic Locked
 Printer Friendly
Author Previous Topic Topic Next Topic  

AADIVER
Admiral

Member Avatar

USA
966 Posts
Initially Posted - 12/12/2007 :  12:10:52  Show Profile  Visit AADIVER's Homepage
Various makes and models of handheld GPS's agree on degrees and minutes but are way off on seconds. This becomes a problem with GPS treasure hunts especially around small areas, i.e. Two Harbors, Catalina Island. Does anyone know how to calibrate several handhelds so they all agree on the seconds? Thanks.
Frank Farmer
Long Beach, CA
aa.diver@verizon.net
http://mysite.verizon.net/aa.diver

PRETTY PENNY
'01 C-250 WK, Hull #558
Edited by - on

delliottg
Former Mainsheet C250 Tech Editor

Members Avatar

USA
4479 Posts
Response Posted - 12/12/2007 :  12:29:45  Show Profile  Visit delliottg's Homepage
Frank,
Take all this with a grain of salt, because I only have Garmin GPS units, and Magellans, Raymarine, etc. might be slightly different. However, the abbreviations I give you should be good across the board, I think.
There are generally [url="http://en.wikipedia.org/wiki/Geographic_coordinate_system"]two to three ways[/url] for most [url="http://en.wikipedia.org/wiki/GPS"]GPS [/url]units to display coordinates:
<ul>
<li> Degrees, Minutes, Seconds, abbreviated <b><i>DMS</i></b> and generally shown on your unit as: <i><b> ddd.mm.ssss</b></i> which translates to degrees, minutes, seconds and hundredths of seconds. you'll generally have to change from the default to get this. </li>
<li>Decimal degrees, abbreviated <b><i>DD</i></b> and will be shown on your unit as: <i><b>ddd.dddd</b></i> which is just what it sound like, degrees, and ten thousandths of a degree. This is not commonly used. </li>
<li>Degrees, decimal Minutes, this is the most commonly used, and translates to degrees, minutes, ten thousandths of a minute, it's abbreviated as <b><i>DM</i></b> and will be shown on your unit as <i><b>ddd.mm.mmmm</b></i>. On my Garmins (I have three), this is the default display. </li></ul>

If you make sure that all of the participating GPS units are all on the same abbreviation, they should all display the same.

Also bear in mind that there are lots of other ways to display the coordinates, these are the most common. You should also make sure that everyone is on [url="http://en.wikipedia.org/wiki/WGS84"]WGS 84[/url] (this is the most common, and is always the default, at least in North America, other countries this may not be so). If they are not on WGS84, they have no hope of ever finding anything in your competition.

Hopefully this was helpful.
Edited by - delliottg on 12/12/2007 12:47:19
Go to Top of Page

AADIVER
Admiral

Members Avatar

USA
966 Posts
Response Posted - 12/12/2007 :  12:39:52  Show Profile  Visit AADIVER's Homepage
David, that sounds like our solution, we'll check it out. Thanks.
Edited by - on
Go to Top of Page

delliottg
Former Mainsheet C250 Tech Editor

Members Avatar

USA
4479 Posts
Response Posted - 12/12/2007 :  12:43:55  Show Profile  Visit delliottg's Homepage
Frank,
I edited my post to give you more information on other sites.
Edited by - on
Go to Top of Page

glivs
Admiral

Members Avatar

USA
836 Posts
Response Posted - 12/12/2007 :  19:09:48  Show Profile
Frank,
David nailed the two most common "user errors", i.e. incorrect format and datum settings. Depending on your location, the latter can result in errors upwards of 100's of feet or more. In addition, there are some feature differences between models that could result in differences on the order of 10's to 100's of feet, such as WAAS capability, electronics (antenna's etc.) and software. On open waters, the software is not going to result in big differences but on land under forest canopies, in particular, it can. Another source of accuracy is the number of satellite observations used to make a position estimate. When tracking your course obviously a single observation is a single position reading. Generally models in the $200+ range allow you to average any number of observations usually resulting in notably accuracy for marking, for example, the entrance buoy to your harbor or that big rock you spotted when the water was low last season. ;)
Edited by - on
Go to Top of Page
  Previous Topic Topic Next Topic  
 New Topic  Topic Locked
 Printer Friendly
Jump To:
Association Forum © since 1999 Catalina Capri 25s International Association Go To Top Of Page
Powered By: Snitz Forums 2000 Version 3.4.06
Notice: The advice given on this site is based upon individual or quoted experience, yours may differ.
The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.