Compass vs. GPS

[H20Rat]

Re: Compass vs. GPS

I fish a river so a compass would do me no good at all.

Kinda hard to get lost on a river, you go this way or that way.

same here, the river is maybe 1/4 a mile wide at the VERY widest point. A compass would be completely pointless.

A GPS on the other hand... I use mine fairly often. i've got 'safe' trails marked that are clear of sandbars, and I drive exclusively with those if I'm out after dark.

 

[Ned L]

Re: Compass vs. GPS

"Sexton" - You need a church official in order to navigate around the world?? I think you mean sextant (& you need a chronometer with it to be of any value).

 

[drrpm]

Re: Compass vs. GPS

I have a compass but don't really need it. No GPS either. While my main boating lake is quite large, land is always in sight, I have a chart and there are plenty of marker buoys. If I were to boat out of sight of land, I'd want both the compass and GPS.

 

[mphy98]

Re: Compass vs. GPS

Up in Canada if you do not have a gps on some lakes, you will get lost. There are way to many islands and bays that are just downright huge. Eagle lake by Dryden is about 60 miles long and not a straight part in it. Lake of the woods and others same thing. A compass just won't cut it. I even bought a chip from Navonics that is the best!

 

[Mike Robinson]

Re: Compass vs. GPS

What about the wind?

Good point. That's known as leeway.

 

[Ned L]

Re: Compass vs. GPS

Current will affect a power boat far more than the wind. (The effect of wind is pretty negligible, esp. on a fast power boat where the apparent wind is pretty much always from forward.) A cross current will cause a much great affect than many people will realize. If you plot a one hour run on a chart from point "A" to point "B", and have a 3 knot cross current the whole run, you will miss your end mark by three nautical miles if you don't compensate for that current.

 

[Blackacid]

Re: Compass vs. GPS

I use the gps on my phone. our lakes are tiny though. I don't really have much to worry about.

 

[boatmanalso]

Re: Compass vs. GPS

what do you need a compass for if you have gps/ I assume chart plotter?

 

[nofuss]

Re: Compass vs. GPS

I generally use the gps for navigation, however i regularly check the compas calibration with it.
When on long trips I navigate using the GPS however I keep taking note of changes in bearing required to stay on course, (changes created due to drift wind or current caused) as this would be the compensation i would have to use if i lost the GPS for some reason. I would then be able to use the compas and compensate for the changes.
However since there are constantly changes in wind and current in the oceans where i boat, the compensation is not as exact a science as the GPS correction. as such if i lose the GPS I would tend to use a more conservative course.
Another one on here who could correct for "set and drift" when navigating with a compas alone. However a multiple satilite system (GPS) will always be more acurate as it considers your exact position.

 

[Ned L]

Re: Compass vs. GPS

OK, a dumb question here. (I'll preface by saying that when I have access to a GPS on a boat it is when we are aboard our friends boat (out regularly & I'm always at the helm), so I haven't been able to read the manual).... So, ... When navigating by GPS (no autopilot) am I correct that you have two choices for steering on a heading 1) play like it is a video game so to speak & keep the 'boat curser' aimed at your destination, or 2) steer by the heading indicated digitally on the GPS. I suspect there are more options I just don't know about. As I said earlier I grew up with a compass & much prefer steering by one.

 

[boatmanalso]

Re: Compass vs. GPS

OK, a dumb question here. (I'll preface by saying that when I have access to a GPS on a boat it is when we are aboard our friends boat (out regularly & I'm always at the helm), so I haven't been able to read the manual).... So, ... When navigating by GPS (no autopilot) am I correct that you have two choices for steering on a heading 1) play like it is a video game so to speak & keep the 'boat curser' aimed at your destination, or 2) steer by the heading indicated digitally on the GPS. I suspect there are more options I just don't know about. As I said earlier I grew up with a compass & much prefer steering by one.

I look at my position and steer towards where I want to go not to run over or into something. When I let someone else steer they tend to look at the gps chart plotter for extended amounts of time and seem to rarely look where they are going. A plotter is better . Even though they have a disclaimer for legal reasons, You can tell where you are within 12 feet in most cases at a glance . If you pull out your chart and find you position and then confirm it , minutes go by. Depending on your speed, that can be dangerious!

 

[themaniam1]

Re: Compass vs. GPS

OK, a dumb question here. (I'll preface by saying that when I have access to a GPS on a boat it is when we are aboard our friends boat (out regularly & I'm always at the helm), so I haven't been able to read the manual).... So, ... When navigating by GPS (no autopilot) am I correct that you have two choices for steering on a heading 1) play like it is a video game so to speak & keep the 'boat curser' aimed at your destination, or 2) steer by the heading indicated digitally on the GPS. I suspect there are more options I just don't know about. As I said earlier I grew up with a compass & much prefer steering by one.

If you use the GPS to steer by course(meaning you have it show only the compass and not the map) it is the same as a compass. The currents can be moving you sideways while all the time you are pointing the bow to the correct course and you will miss your destination.

When using the map option of the GPS to steer (meaning you do not have a visual to recon from) is like being in a video game. I have many times on a couple of lakes around here did that at night where I could not see a thing and there were cliffs and submerged rocks. I just keep the boat cursor on the submerged river course and that way I would never run into any rocks since a river never goes through a rock but around it. It usually a lot longer since the lake covers a much broader area but it is SAFE. By the way one lake is 91 miles long and the other is 186 miles long with many side canyons and would be a nightmare to do at night. I have a hand held GPS as backup.

 

[paultjohnson]

Re: Compass vs. GPS

I learned out in the woods deer hunting once that a GPS has its faults. If I would have stuck with what that thing was telling me I would still be out there !! And that was years ago J K I still use a GPS often on my boat, on the Mississippi Its a Lowrance and even with its preloaded map looking back at my track, it shows me up on land, going thru parking lots etc. Reminds me of the old saying KISS [ keep it simple stupid] I go by my GPS, but verify it with a compass. I would not trust my gps on its own. They do get better every year, but............ My 1 1/2 cent worth

 

[Drowned Rat]

Re: Compass vs. GPS

I learned out in the woods deer hunting once that a GPS has its faults. If I would have stuck with what that thing was telling me I would still be out there !! And that was years ago J K I still use a GPS often on my boat, on the Mississippi Its a Lowrance and even with its preloaded map looking back at my track, it shows me up on land, going thru parking lots etc. Reminds me of the old saying KISS [ keep it simple stupid] I go by my GPS, but verify it with a compass. I would not trust my gps on its own. They do get better every year, but............ My 1 1/2 cent worth

This is a problem with the mapping software you are using, not the GPS. It is true you cannot rely on some electronic charts to show your position accurately, BUT your GPS position charted on a paper chart will be dead on accurate every time. If you're using your GPS on waters you cross frequently, leave the trail feature engaged so you can follow known safe paths, even if it shows you crossing a mountain or something.

 

[dingbat]

Re: Compass vs. GPS

So, ... When navigating by GPS (no autopilot) am I correct that you have two choices for steering on a heading 1) play like it is a video game so to speak & keep the 'boat curser' aimed at your destination, or 2) steer by the heading indicated digitally on the GPS. I suspect there are more options I just don't know about. As I said earlier I grew up with a compass & much prefer steering by one.

Different GPS have different navigation features.

I have the option to use a digital compass, steer to a track on the screen, steer to a 3D perspective view or steer by keeping the pointer centered on a ?track bar? that is displayed at the top of the screen along with the chart.

My preference is steer to the track bar unless on auto pilot.

 

[Ned L]

Re: Compass vs. GPS

Thank you for the input everyone. So it seems the options are pretty much what I thought (except apparently it can be set to show only a compass card - & be used just like a magnetic compass). I'll say that it does drive me crazy when I see someone basically steering a boat like a video game, with their face looking at the GPS & steering intently by the curser. If my next waypoint is out of view, I use the GPS to get my heading & then steer by compass. I think you can hold a straighter course that way. It makes me nervous watching someone running the boat who's head isn't up on the horizon.

 

[Mike Robinson]

Re: Compass vs. GPS

The heading the GPS displays is not necessarily the direction your vessel is pointed, but the direction your vessel is travelling in, also known as "course made good".

Your GPS doesn't know which way your vessel is pointed, only which direction you are travelling. When travelling at speed, especially on a planing hull, the heading displayed by the GPS will normally be the same as which your boat is pointed, but if you are travelling slowly with a cross current or wind the heading displayed by your GPS can be very different from which your boat is pointed.

As an experiment, try going ahead on a straight course then without changing your heading, go astern and watch the display on your GPS.

A compass will show the direction that your vessel is pointed in, which is not neccessarily the direction in which your vessel is travelling.

 

[Mike Robinson]

Re: Compass vs. GPS

This is a problem with the mapping software you are using, not the GPS. It is true you cannot rely on some electronic charts to show your position accurately, BUT your GPS position charted on a paper chart will be dead on accurate every time. If you're using your GPS on waters you cross frequently, leave the trail feature engaged so you can follow known safe paths, even if it shows you crossing a mountain or something.

Partly this depends on the horizontal "Datum" used by the publisher of the chart you are using, regardless of whether the chart is electronic or paper. (Many electronic charts are scans of paper ones) Many older charts around here (West Coast Canada) use NAD 27 (North America 1927) and don't work well with GPS, a better choice is a chart using NAD 83.

Another factor is the type of chart projection used, a chart is a flat surface and the earth is curved so some distortion is inevitable.

 

[Art Bernard]

Re: Compass vs. GPS

When fishing offshore, I use both GPS and a compas as a back up if for nothing else than to point me in the direction of land if the gps dies.

Art

 

[GMIslander]

Re: Compass vs. GPS