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If the GPS says 85mph, how fast am I going?

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Old 12-16-2005, 12:51 PM
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Default Re: If the GPS says 85mph, how fast am I going?

I just re-read my post (#40) and I completely forgot to factor in whether the boat has shorepower or not.
I'm an idiot and I apologize to you gentlemen for this gross oversight.

Whether the boat is rigged with or without shorepower, has no effect on any of my previous calculations or observations. However, if it has a GENERATOR, well, that changes everything...
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Old 12-16-2005, 12:57 PM
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Default Re: If the GPS says 85mph, how fast am I going?

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Originally Posted by Edward R. Cozzi
I just re-read my post (#40) and I completely forgot to factor in whether the boat has shorepower or not.
I'm an idiot and I apologize to you gentlemen for this gross oversight.

Whether the boat is rigged with or without shorepower, has no effect on any of my previous calculations or observations. However, if it has a GENERATOR, well, that changes everything...

Understood...it can be normally over looked....especially dealing with all the intangables
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Old 12-16-2005, 01:05 PM
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Talking Re: If the GPS says 85mph, how fast am I going?

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Originally Posted by enticer
Understood...it can be normally over looked....especially dealing with all the intangables
I can plainly see that YOU understand.
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Old 12-16-2005, 01:08 PM
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Default Re: If the GPS says 85mph, how fast am I going?

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Originally Posted by bojoe2
Well Reggie won most of world speed records with one of those gps units your talking about, it said 161 mph but the jet ski passing him said 54 so I CANT FIGURE
THATS FUNNY I DONT CARE WHAT ANY ONE SAYS THATS FUNNY.
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Old 12-16-2005, 01:31 PM
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Default Re: If the GPS says 85mph, how fast am I going?

Depends on the water temperature. Don't forget, centigrade will throw off the equation. Wait, is the river in Canada? If it is in Canada, then there are other metric factors. Forget about it...This is way beyond me.
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Old 12-16-2005, 01:37 PM
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Default Re: If the GPS says 85mph, how fast am I going?

Your GPS will read faster going down stream and slower upstream compared to boating on a lake. I boat on the Missouri River and it flows around 6 mph. Based on speeds at certain rpms obtained from LOTO which is not flowing, GPS readings on a flowing river are inaccurate, once again compared to a lake. Think of it as walking on a tread mill. Tread mill says 5 mph, but your actually going nowhere based on fixed ground speed. On the Missouri, I have to idle upstream at 6 mph just to stay even with the bank.

My guestimate on your 85 mph GPS reading is that your actually going 82-83.

Last edited by Harper220; 12-16-2005 at 01:41 PM.
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Old 12-16-2005, 01:44 PM
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Default Re: If the GPS says 85mph, how fast am I going?

Quote:
Originally Posted by Harper220
Your GPS will read faster going down stream and slower upstream compared to boating on a lake. I boat on the Missouri River and it flows around 6 mph. Based on speeds at certain rpms obtained from LOTO which is not flowing, GPS readings on a flowing river are inaccurate, once again compared to a lake. Think of it as walking on a tread mill. Tread mill says 5 mph, but your actually going nowhere based on fixed ground speed. On the Missouri, I have to idle upstream at 6 mph just to stay even with the bank.

My guestimate on your 85 mph GPS reading is that your actually going 82-83.
how does GPS know your going 6 if your not moving?
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Old 12-16-2005, 01:52 PM
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Default Re: If the GPS says 85mph, how fast am I going?

Quote:
Originally Posted by Harper220
Your GPS will read faster going down stream and slower upstream compared to boating on a lake. I boat on the Missouri River and it flows around 6 mph. Based on speeds at certain rpms obtained from LOTO which is not flowing, GPS readings on a flowing river are inaccurate, once again compared to a lake. Think of it as walking on a tread mill. Tread mill says 5 mph, but your actually going nowhere based on fixed ground speed. On the Missouri, I have to idle upstream at 6 mph just to stay even with the bank.

My guestimate on your 85 mph GPS reading is that your actually going 82-83.
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Old 12-16-2005, 02:07 PM
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Talking Re: If the GPS says 85mph, how fast am I going?

Quote:
Originally Posted by Harper220
Your GPS will read faster going down stream and slower upstream compared to boating on a lake. I boat on the Missouri River and it flows around 6 mph. Based on speeds at certain rpms obtained from LOTO which is not flowing, GPS readings on a flowing river are inaccurate, once again compared to a lake. Think of it as walking on a tread mill. Tread mill says 5 mph, but your actually going nowhere based on fixed ground speed. On the Missouri, I have to idle upstream at 6 mph just to stay even with the bank.

My guestimate on your 85 mph GPS reading is that your actually going 82-83.
I'm sorry, but you are incorrect.

The GPS is measuring the speed AFTER all the conditions you mentioned are factored in. Aren't you reading the posts?

Who are you, anyway? Do YOU know Dr. Von Braun and DR. Sagan like WE do? What are your credentials?
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Old 12-16-2005, 02:29 PM
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Default Re: If the GPS says 85mph, how fast am I going?

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Originally Posted by dockrocker
Don't forget to account for the orbital speed of the satellite, and since not all GPS satellites orbit at the same rate, you'll need to know:

1. Which satellites you're locked in to,
2. The geospatial relationship between said satellites,
3. The speed of the current,
4. Your lattitude,
5. The airspeed velocity of an unladened swallow,
6. The circumference in centimeters of Pam Anderson's orginal boobs.

At that point, hire Carl Sagan to do the math and Voila! - an accurate reading of your speed.

And people say technology is so hard.
Is that an African or European Swallow?
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