utm vs lat/long - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > Skills and Seamanship > Seamanship & Navigation
 Not a Member? 

Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


Reply
 
LinkBack Thread Tools
  #1  
Old 11-25-2003
Member
 
Join Date: Jul 2001
Posts: 50
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 14
anneminix is on a distinguished road
utm vs lat/long

i have yet to see the use of universal transverse mercator (utm) vs lat/lon for marine navigation. since i use utm all the time on land and find it so much easier/faster that lat/lon i am wondering why its not used for marine purposes..tks GBA
Reply With Quote Share with Facebook
  #2  
Old 11-25-2003
Member
 
Join Date: Jul 2002
Posts: 56
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 13
pblais is on a distinguished road
utm vs lat/long

UTM and Lat/Long are almost interchangeable. It''s just the unit of measure.

What you find is that not all charts come in both units of measure. Sometimes they come only one way or another. The math by hand is a tad easier with the metric version and I can see why you would prefer it.

In the end if you feel more comfortable one way or the other then you''ll probably make fewer mistakes going with what you like.

FWIW, the conversion software to go between the two systems is far more accurate than the ability to make the chart.
Reply With Quote Share with Facebook
  #3  
Old 11-26-2003
Senior Member
 
Join Date: Jun 2003
Posts: 155
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 12
mcain is on a distinguished road
utm vs lat/long

Lat Long is a universal measurement of earth coordinates, in theory independent of map projection. A map projection (e.g. UTM, Albers Equal Area, etc) is a method of mapping the ellipsoid onto a flat surface. THere are probably 20 map projections in common use. Every mapping introduces distortions. Different kinds of distortions are present in the different projections. But all representations of the surface of the ellipsoid earth onto a flat surface will be distorted somewhere. Some distort angles, some areas, some distances. We have all seen the massive size of Greenland in grade school representations of the earth on a Mercator projection. For UTM, within a zone, the Northing and Easting coordinates are X-Y coordinates and can be used to make distance measurements, area measurements, and even direction measurements--all with some measure of inaccuracy and distortion. Going between zones is worse.
Lat Long is ideal for taking sights, etc (with a sextant). If you know very well what you are doing, the inaccuracies in a standard map projection are intended to be insignificant for normal use of the map.
Mathematical transformation between lat long and any map projection typically requires only the two axes of the earth as input--yes the two axes are different. Also, since the earth size has been measured many times, with different answers each time, you have to select the model of the earth ellipsoid you wish to use. Then the math transformation is trivial.
Normally N,E,Z are easier to scale off large scale topo maps, and if you have a handy computer, then transform to lat long or any other projection of interest.
All this said, I have seen the projection coordinates more often used in land mapping or map transformations for spacecraft imagery or high-altitude plane photo mapping, than for anything marine. If I were doing it, I''d stick with the standard marine stuff.
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On



All times are GMT -4. The time now is 11:51 PM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.