What's more accurate gps or speedometer gauge ??

[tdt91]

Some of you guys still don't get it. If you get clocked doing 65MPH it don't matter about a head wind or a conveyor belt etc. Your still doing 65. I don't care if you have a V12 and the peddle is to the floor, if your doing 65 then your doing 65. Same for a boat, GPS and radar don't give a rats azz what the current of the water is, it has no bearing on how fast the vehicle is moving over the face of the earth.
I understand what you guys are saying but it plays no part when being shot with a radar or using GPS for speed. The way you guys are rationalizing this, you would need to take into account the rotation of the earth too.
You guys are probably teachers and now we know why kids graduate HS and cannot read or write. You probably buy into the Commie math too.

[basser38]

Are you all saying my old ranger didn't really run 82?

[ECobb91]

Some of you guys still don't get it. If you get clocked doing 65MPH it don't matter about a head wind or a conveyor belt etc. Your still doing 65. I don't care if you have a V12 and the peddle is to the floor, if your doing 65 then your doing 65. Same for a boat, GPS and radar don't give a rats azz what the current of the water is, it has no bearing on how fast the vehicle is moving over the face of the earth.
I understand what you guys are saying but it plays no part when being shot with a radar or using GPS for speed. The way you guys are rationalizing this, you would need to take into account the rotation of the earth too.
You guys are probably teachers and now we know why kids graduate HS and cannot read or write. You probably buy into the Commie math too.

No we get it. it’s Also obvious that while you keep trying to continue efforts to win some online debate that means nothing other than whose dinger is 1mm bigger, you also completely ignore the other parts of posts where people agreed with you (me include) that gps speed is accurate regardless of outside conditions.

[Highcentered]

Are you all saying my old ranger didn't really run 82?

It did over land with the help of the current and possibly a shot of nitrous!

[Highcentered]

Thinking further, this debate is beyond stupid. A 67mph boat running 72 with a 5mph current is still technically slower than a 70mph boat running without current if you put both boats on the same body of water side by side. Can we at least agree on that?

[Smokeyr67]

Are you all saying my old ranger didn't really run 82?

It probably did a bit more than that, if you use KPH

[Smokeyr67]

I get it, you don't want to accept the point of the debate, thats cool, we all have our comfort zone, yours seems to be somewhere south of a certain Egyptian river.

Your quite correct that GPS and radar don't care about your true speed, just your ground speed, but when talking about boats or planes being operated in a fluid your either just being willfully ignorant or you just can't understand the concept. Either / or, I don't care, I know that I'm correct and you probably know that too, but are trying to play the Devils Advocate, bravo!

[all4s]

So when in current in a boat, do this. Shut the boat off and drift. Look at your accurate gps and see what the current is. Now, running with the current or against the current it only takes simple math to figure out your “true” speed. Whatever you want to call “true” speed. Since some of us differ on what it is.

[PMantle]

but when talking about boats or planes being operated in a fluid your either just being willfully ignorant or you just can't understand the concept.

No one is doing this.

[Highcentered]

No one is doing this.

No one is talking about something operating in a fluid such as water like a boat does?

[PMantle]

No one is talking about something operating in a fluid such as water like a boat does?

Of course they are.

[billnorman1]

So when in current in a boat, do this. Shut the boat off and drift. Look at your accurate gps and see what the current is. Now, running with the current or against the current it only takes simple math to figure out your “true” speed. Whatever you want to call “true” speed. Since some of us differ on what it is.

That's kind of true but aircraft don't subtract or add wind to GPS when reporting their speed. Although there is water speed, the only thing we care about is speed relative to the Earth, third rock from the Sun.

If you were doing 50 in 50 MPH current, you would not be doing 100, even in a Ranger.

[avidbasser]

[Smokeyr67]

That's kind of true but aircraft don't subtract or add wind to GPS when reporting their speed. Although there is water speed, the only thing we care about is speed relative to the Earth, third rock from the Sun.

If you were doing 50 in 50 MPH current, you would not be doing 100, even in a Ranger.

Ive given examples of when speed through water IS something (at least some of us) care about.

When prop testing your true speed through water is critical if you want to get good, reliable consistent data and when trolling lures it’s important to have an accurate speed to get into the lures best working range.

[billnorman1]

Ive given examples of when speed through water IS something (at least some of us) care about.

When prop testing your true speed through water is critical if you want to get good, reliable consistent data and when trolling lures it’s important to have an accurate speed to get into the lures best working range.

I kinda agree.

Except boat speedometers are notoriously inaccurate, and any Bourdon tube gauge is generally inaccurate in the first 25% or so of its range.

[Pulsare2020]

My iPhone with Speed Box app shows identical speed to my Lowrance GPS.

This is an old thread, but I have a Livorsi GPS speedometer on my 2400 Checkmate. I also have the Livorsi Vantage View / Smartcraft system that will recall engine rpm and GPS speed. The other day I swore the speedo needle showed 75 mph but the digital recall for GPS speed showed 73 mph. I called Livorsi and they said to trust the digital recall, that the needle on the GPS speedo might not be exactly at 0 or move slightly more. So I try it again and this time my wife has the Speedometer app turned on her cell phone and is calling out the speeds to me. Once she said 75 mph, I got out of it, but I glanced at the needle on the GPS Speedo and it was close to 75 / 75.5 mph. When I got back to our dock I checked the recall and it said 73 mph again and I did not forget to clear the rpm and mph recalls. So the GPS phone app, the GPS speedo and the GPS recall do not agree. The Speedo updates 10 times / second and I think the phone 1 time per second so for a while, especially if you are accelerating, the phone always lags the speedo. Once you are a set speed, after perhaps 5 seconds the phone readout stays constant.

[BOATS]

But isn’t there a +/- on the readings from gps satellites? All things equal I would think that a radar gun would pretty dang close to gps accuracies.

I’m just spitballing here, so I really have no idea if I’m even in the ball park.

Can be as much as + or - 5mph depending on the number of satellites that the unit is receiving.

[John_6788]

Well, I'm sure this will be looked at as BS,,, but my 88 Tracker with its original speedometer reads pretty much within' 1 to 2 mph of my Garmin

[Coach185]

After receiving signals from at least four different GPS satellites, the receiver can calculate its position in all three dimensions (based on time delays between signals). Once the receiver knows exact position at any given time, the internal electronics tracks that position in time and calculates ship's speed.

I still like my speedos, they always show I'm going faster

[DaveBrabec]

I havent had a boat speedo work for very long in the last 3 boats,GPS