What is minimal drift?

[hungupthespikes]

A normal ground vehicle in nearly always in line with the direction of travel, and when it isn't, it must necessarily be skidding, and skidding sideways.
.

Or just the opposite, Going around a turn the heading (the way the nose is pointing) is off road, the front wheels are trying to keep the intended bearing.
Even when going down a straight highway the crown of the road will make the operator change the heading to get back on bearing.
Boat, car. plane...almost never are the heading and the bearing going to be the same for any reasonable length of time.
lol Hence, I guess there is always "minimal drift". :doh:

:yield:huts

 

[dingbat]

Inertial navigation is just knowing where you started, and using your speed (from a 'log'), course (from a gyro) and set and drift, estimating where you should be... And that is not used by auto-pilots. What's used by auto-pilots is heading, or a GPS (or Loran) input (which adjusts the heading fed to the AP according to the current position and the selected waypoint).

Chris.....

Your AP doesn't use a gyro for position and velocity compensation?

An autopilot has to "predict" course and heading to feed the servo. You can't get there using the 1 second update rate of GPS, not to mention the inherent position errors. The only way to "predict" is using a real time input from a gyro for position and velocity compensation. This compensation in itself, meets the definition of "Inertial Navigation"

 

[southkogs]

LOL ... This is all my fault! I used the phrase minimal drift at one point in a topic. I can't find it now, but it was with regards to how a bow rider comes to a stop (I think).

My use of the term "minimal drift" was not as a term that sailors/boaters use specific to a particular property of boating. Rather, it was an adverb + a verb to describe a situation.

And Myrtonos, in order for anything to be "minimal" (drift, angle, distance, etc.) it, by nature of the language itself, must be relative to something. So, minimal drift (in the case of what we're talking about) must be relative to either the fixed point or the flowing point. It can't be in relationship to both simultaneously. That's a limitation of language and science ...

... and a problem in most of our social understandings of morality and ethics. But that would close the topic 'fer sure.

 

[smokeonthewater]

D^MN YOU Scuba Steve!!!!

 

[Myrtonos]

Or just the opposite, Going around a turn the heading (the way the nose is pointing) is off road, the front wheels are trying to keep the intended bearing.
Even when going down a straight highway the crown of the road will make the operator change the heading to get back on bearing.
Boat, car. plane...almost never are the heading and the bearing going to be the same for any reasonable length of time.
lol Hence, I guess there is always "minimal drift". :doh:

Even when turning, a land vehicle is still in line with the direction of travel, rotating in sychronism with the change in direction, boats tend to slide through turns, and I do wonder whether ships tend to slide anymore through turns than smaller craft with similar hull designs. I believe it's because of this tendency that canal junctions are never configured as roundabouts.
Not all roads are crowned and many wide ones are only crowned near the gutter, and that only puts the vehicle on a list, not yaw, and it doesn't pull on their field of view.

So, minimal drift (in the case of what we're talking about) must be relative to either the fixed point or the flowing point. It can't be in relationship to both simultaneously.

Of course it's possible for a vessel to drift relative to both the water and the ground. What are fixed and flowing points?

 

[thumpar]

Even when turning, a land vehicle is still in line with the direction of travel, rotating in sychronism with the change in direction, boats tend to slide through turns, and I do wonder whether ships tend to slide anymore through turns than smaller craft with similar hull designs. I believe it's because of this tendency that canal junctions are never configured as roundabouts.
Not all roads are crowned and many wide ones are only crowned near the gutter, and that only puts the vehicle on a list, not yaw, and it doesn't pull on their field of view.

So, minimal drift (in the case of what we're talking about) must be relative to either the fixed point or the flowing point. It can't be in relationship to both simultaneously.

Of course it's possible for a vessel to drift relative to both the water and the ground. What are fixed and flowing points?

I guess you have never watched Nascar or me in the winter. I like to get sideways in the snow. My van has AWD so it is fun.

Where we boat there is pretty much 0 current. The only thing that will make us drift is the wind. We can sit for hours in a cove on a calm day without having to move.

 

[southkogs]

Of course it's possible for a vessel to drift relative to both the water and the ground. What are fixed and flowing points?

Actually, that's true ... I misspoke.

Let's try it this way: You're in a boat on a river that is flowing past you (so, you're in the current). You've let down anchors properly and the boat is perfectly stationary relative to the fixed points (riverbed & ground/land). However, if you were to have a pitot tube on that boat you may still be registering a couple knots of speed because relative to the water that's flowing past you (a flowing point - my own made up term) there is motion. (Technically the water is moving, and that's where all of the energy is.)

But the boat in the scenario above isn't in "drift" relative to both the fixed points and the flowing points at that time. It's not in motion relative to one, and in motion relative to the other.

And again, technically the water (floating point - my own made up term) is doing the moving. The boat is "at rest" with it's anchors acting equally against an opposing force (the water).

Though, we could make this really academic and try to calculate in that the earth is rotating at 1,070 MPH making our boat in the example above technically moving at a rate just shy of supersonic ...

... but that would probably get me banned from the forum.

 

[achris]

Ok, here's a 'drift' scenario to throw those both out the window. Where we fish we often have a current setting to the south (I prefer to use recognised terms, and not make up my own as this leads to confusion, and threads like this one :facepalm. We also have the wind from the south west. We drift to the east.... So we are moving relative to all three; Wind, current and seabed.

...Though, we could make this really academic and try to calculate in that the earth is rotating at 1,070 MPH making our boat in the example above technically moving at a rate just shy of supersonic ...

... but that would probably get me banned from the forum.

Not at all... And this is where I was going from one of my early posts in this thread. Questions like this have to have a 'frame of reference', or they are totally meaningless.

Want to go the the extreme? Let's have a look at the speed the earth is travelling through space as it revolves around the sun, or how fast we're travelling through space WITH the sun as our solar system revolves through the galaxy.... Ad nauseum...

Chris.......

 

[nwcove]

this was a fun read!! but im a bit confused.....if i am drifting south, and cast a lure north, will that effect my relative position on a body of water??

 

[southkogs]

this was a fun read!! but im a bit confused.....if i am drifting south, and cast a lure north, will that effect my relative position on a body of water??

42

LOL - achris: I've been sitting here through the whole thing knowing the way you can calculate those sorts of things is using triangular equations (pythagorean theorem). But I'm kinda' afraid that was just going to confuse things even a little more

... and now our poor anchored boat is doing around 68,000 MPH.

 

[smokeonthewater]

in the automotive world "minimal drift" is the amount that I can lay my lil beemer sideways in the rain making a turn with a cop watching me without getting pulled over.... can't let it hang out way out but I CAN get away with minimal drift LOL

 

[roscoe]

why

 

[hungupthespikes]

this was a fun read!! but im a bit confused.....if i am drifting south, and cast a lure north, will that effect my relative position on a body of water??

If the lure hooks a relative then your position will most likely be in the water. :laugh:

" the devil made me do it" Flip Wilson

 

[achris]

42

Ahhh, the answer to the ultimate question of life, the universe and everything... Long time since I've heard reference to that...

LOL - achris: I've been sitting here through the whole thing knowing the way you can calculate those sorts of things is using triangular equations (pythagorean theorem). But I'm kinda' afraid that was just going to confuse things even a little more

Just vector analysis...

... and now our poor anchored boat is doing around 68,000 MPH.

It's worse than that... With reference to the centre of our galaxy, your anchored boat is doing roughly 490,000mph.... (I wonder if that's 'minimal drift'?)

Chris....

 

[southkogs]

Ahhh, the answer to the ultimate question of life, the universe and everything... Long time since I've heard reference to that...

Glad it got caught.

Myrtonos - we're having a little fun, somewhat to your expense. No offense intended. Hope you got to laugh at it a bit too.

 

[NYBo]

Myrtonos - we're having a little fun, somewhat to your expense. No offense intended. Hope you got to laugh at it a bit too.

Somewhat? Completely at his expense. One of the forum rules is that he who starts a topic like this has to buy a round!:very_drunk:

 

[tomhath]

It's worse than that... With reference to the centre of our galaxy, your anchored boat is doing roughly 490,000mph.... (I wonder if that's 'minimal drift'?)
Chris....

And of course that depends on whether the observer is in your anchored boat or in the center of the galaxy. Dr. Einstein's Theory of Relativity told us that both distance and time as measured by observers moving relative to each other are different.

 

[nwcove]

42

LOL - achris: I've been sitting here through the whole thing knowing the way you can calculate those sorts of things is using triangular equations (pythagorean theorem). But I'm kinda' afraid that was just going to confuse things even a little more

... and now our poor anchored boat is doing around 68,000 MPH.

have no clue what "42" means, but i do need to know how travelling at at 68000 mph while anchored affects my gallons per hour calculations for a day trip? :faint2:

 

[achris]

have no clue what "42" means, but i do need to know how travelling at at 68000 mph while anchored affects my gallons per hour calculations for a day trip? :faint2:

Have a read of Douglas Adams's trilogy, "The Hitchhikers' Guide to the Galaxy", "Restaurant at the End of the Universe", "Life, the Universe and Everything", "So Long and Thanks for all the Fish", and "Mostly Harmless"....

Chris......

 

[roscoe]

Have a read of Douglas Adams's trilogy, "The Hitchhikers' Guide to the Galaxy", "Restaurant at the End of the Universe", "Life, the Universe and Everything", "So Long and Thanks for all the Fish", and "Mostly Harmless"....

Chris......

Ah yes, the trilogy of 5.

I believe that's why I dropped out of college and got a technical degree.