PilotWolf
Well-Known Member
So a friend had just said he prefers DR to GPS
Most of my sea time bas required GPS accuracy.
Which do you prefer?
W.
Most of my sea time bas required GPS accuracy.
Which do you prefer?
W.
DR orGPS.
- Thread starter PilotWolf
- Start date
Portofino
Well-Known Member
Depends
Bit of both plus sometimes nothing .
If you are so familiar with your cruising grounds , happens easily with Med Boating then nothing .Like nipping to a favourite anchorage for a swim / lunch .
GPS plotter is on because it looks pretty.Serves no function typically.
How ever when venturing away from ( know it like the back of your hand territory) then a bit of both .
I like to check the accuracy of the boats compass against the GPS ,know the ETA , time to run to destination.
But on a offshore cruise I always have a paper chart out , under Perspex , cruise economically @ 27 knots on long passages, mentally that’s near enough 30 mph , along with the compass bearing , can work it all out by DR in my head . I find 30 at sea an easy number to quickly crunch about in my head , as an hour has 60;mins......2 mins a mile etc .
Sort of have a instant plan B running in my head parallel to plotter .
We have a navigation cupboard in the saloon with dividers and chart storage , protractor etc .
Tend to brief everyone the night before or morning on paper of a long day using the dividers on paper .
Also with a small leisure boat on a long passage there’s the range to calc .
Fortunately I have sight glasses ( cocked ) on the tanks , one tank for each engine @ 800 L + another 600 L long range tank which due to the plumbing I can divert to either “day tank “
27 knots burns approx 80 + L per side which with a 800 L tank makes that easy to understand we are dropping 10 % each hr . The glasses are graduated in 10 th s .So a quick glance I can see how many hrs I can go at 2 mins a mile .
So a quick visual in the morning while doing the daily checks is reassuring.
Having said that there are plenty of ports usually to refill , but some close @ lunch , others it’s a bun fight , prices vary significantly so it’s worth factoring in the fuel load before setting off .
Mentally I want a smooth transition to DR if the GPS and fuel guages were to fail .
If all this DR stuff sounds a bit alien to today’s tech kids
Cut my teeth navigating across the N sea , and Channel using DR and Decca , tide tables and current books .
So for me it’s a habit DR I can’t help it even though the plotter is on and fully route planned as well .
Bit of both plus sometimes nothing .
If you are so familiar with your cruising grounds , happens easily with Med Boating then nothing .Like nipping to a favourite anchorage for a swim / lunch .
GPS plotter is on because it looks pretty.Serves no function typically.
How ever when venturing away from ( know it like the back of your hand territory) then a bit of both .
I like to check the accuracy of the boats compass against the GPS ,know the ETA , time to run to destination.
But on a offshore cruise I always have a paper chart out , under Perspex , cruise economically @ 27 knots on long passages, mentally that’s near enough 30 mph , along with the compass bearing , can work it all out by DR in my head . I find 30 at sea an easy number to quickly crunch about in my head , as an hour has 60;mins......2 mins a mile etc .
Sort of have a instant plan B running in my head parallel to plotter .
We have a navigation cupboard in the saloon with dividers and chart storage , protractor etc .
Tend to brief everyone the night before or morning on paper of a long day using the dividers on paper .
Also with a small leisure boat on a long passage there’s the range to calc .
Fortunately I have sight glasses ( cocked ) on the tanks , one tank for each engine @ 800 L + another 600 L long range tank which due to the plumbing I can divert to either “day tank “
27 knots burns approx 80 + L per side which with a 800 L tank makes that easy to understand we are dropping 10 % each hr . The glasses are graduated in 10 th s .So a quick glance I can see how many hrs I can go at 2 mins a mile .
So a quick visual in the morning while doing the daily checks is reassuring.
Having said that there are plenty of ports usually to refill , but some close @ lunch , others it’s a bun fight , prices vary significantly so it’s worth factoring in the fuel load before setting off .
Mentally I want a smooth transition to DR if the GPS and fuel guages were to fail .
If all this DR stuff sounds a bit alien to today’s tech kids
Cut my teeth navigating across the N sea , and Channel using DR and Decca , tide tables and current books .
So for me it’s a habit DR I can’t help it even though the plotter is on and fully route planned as well .