|
This may just be lack of knowledge on my part... not sure if I have enough information to calculate this or not. I am googling right now, but not turning up anything on the specifics of my need but on all the side issues I alreay know.... 
Okay... first what I need to do is calculate current ocean level minus wave motion. In otherwords the gravitational surface including the moon. I have already the gravitational surface of the earth (geoid) from NASA, and have had it for a couple of years now. I am one of the few people who use it. But I need to add in the tidal effect in ocean height based on the lunar cycle. Not sure if atmospheric pressure affects sea height noticeably, but I basically have a ship that I need an accurate height on and the ship based GPS locations seem to be putting out a very poor +-20 meter location even from one end of the ship to the other.
Theoretically I have proposed the following:
Using knowns (lat lon location, lunar distance and viewing angle from location, sea level based on gravitational surface of earth):
Calculate height of ocean based on pull of the moon
use this in a more accurate position.
I am not asking you to do this for me, but if you can point me to the right location, I will do it. I will keep googling various terms hoping to stumble across the calculation. No homework, I am long since out of school.
Thanks!
Jeff
P.S. yes, I live in a desert, ocean tidal effects are something I never had to worry about before....
_________________________
Asu no koto o ieba, tenjo de nezumi ga warau.
Talk about things of tomorrow and the mice in the ceiling laugh. (Japanese Proverb)
|
|
|
|
|
I tried finding info on this sort of calculation some years back, but was told thata major factor in tidal heights vs time was the sloshing of water around terrain features that disrupted the simple newtonial effects that a water world would undergo, and that as a result there wasn't a theorectical model available.
|
|
|
|
|
dan neely wrote: and that as a result there wasn't a theorectical model available.
So I seem to be finding out... However, that in and of itself is good. This particular ship will not be sitting near terrain features, so I may be able to use the earth gravitational model with 1m effect from the sun, and 3m effect from the moon in the deep ocean. So I am not at a complete loss yet.
_________________________
Asu no koto o ieba, tenjo de nezumi ga warau.
Talk about things of tomorrow and the mice in the ceiling laugh. (Japanese Proverb)
|
|
|
|
|
Maybe. This was a few years back, but the impression I got was that the sloshing didn't just effect the hieghts of the tides, but offset the locations of the bulges as well. IIRC there was mention of a large bay(sea?) that ended up with a 24hr cycle instead of the normal 12.
|
|
|
|
|
dan neely wrote: Maybe. This was a few years back, but the impression I got was that the sloshing didn't just effect the hieghts of the tides, but offset the locations of the bulges as well. IIRC there was mention of a large bay(sea?) that ended up with a 24hr cycle instead of the normal 12.
about my biggest worry will be proximity to islands... This will be deep pacific, it will never (as far as I know) be in an inland sea like the gulf of Mexico.
_________________________
Asu no koto o ieba, tenjo de nezumi ga warau.
Talk about things of tomorrow and the mice in the ceiling laugh. (Japanese Proverb)
|
|
|
|
|
Jeffry J. Brickley wrote: calculate current ocean level minus wave motion
If you are referring ot wind driven waves, then, unless the boat is in a fairly fierce storm, and quite a small vessel, this fluctuation can be ignored.
Jeffry J. Brickley wrote: I need to add in the tidal effect in ocean height based on the lunar cycle
This will be almost impossible. Tides are extraordinarially complex. Some parts of the earth have virtually no tide (I mean in addition to the Med, which has no tide, some open ocean islands also have no tides). Other parts, like the channel islands, and th eBristol channel have as much as a 10 meter variation. Some places, like Southampton have two high tides.
This is all because water swirls and flows around the earth, dragged by the moon, and the way it moves is affected by land, and interfeerence wave paterns.
Additionally, when the sun and moon are in line larger tidal forces are generated.
I would say that calculating the height of a tide from the moons position would be almost impossible.
Instead I would refer to know tide heights around the world in relation to highwater Grenwich.
Truth is the subjection of reality to an individuals perception
|
|
|
|
|
fat_boy wrote: This will be almost impossible.
Very true... but at least in the process of learning it, I ruled out the need for it. This should be deep pacific only, even when they are around islands they should get only minor tidal forces. I am knew to tides (I live in a freakin' desert!), so I had to ask. Now I know, but that means one less calculation. 
_________________________
Asu no koto o ieba, tenjo de nezumi ga warau.
Talk about things of tomorrow and the mice in the ceiling laugh. (Japanese Proverb)
|
|
|
|
|
i am findisng myself unable to solve the following problem:
An equation of the tangent line to the curve
y=f(x)=x(8 cosx- 2 sinx)
at the point (4pi, f(4pi) is y =???
use pi=3.14(yes, approximate it to that), and ofcourse, cos(4pi) = 1, sin(4pi)=0.
any takers? i cant see why im getting it wrong. yes, this is for homework.
-- modified at 8:52 Wednesday 11th October, 2006
|
|
|
|
|
Umm...just pointing out that there is a Math[^] forum and you'd probably be better of getting an answer there.
"A democracy is nothing more than mob rule, where fifty-one percent of the people may take away the rights of the other forty-nine." - Thomas Jefferson
"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." - Benjamin Franklin
Edbert
Sydney, Australia
|
|
|
|
|
yeah, but no one posts there. so i would probably get more answers/ideas/nonsense here.
|
|
|
|
|
Anton Afanasyev wrote: yeah, but no one posts there. so i would probably get more answers/ideas/nonsense here.
Here you will get only 2-3 anwsers. How to know who is correct if they are not compatible?
Try sent emails to, say, 100.000 people. The most popular answer has to be the correct one.
|
|
|
|
|
He still has a better chance for an answer here, but the Math forum would give him less abuse and better karma.
We are a big screwed up dysfunctional psychotic happy family - some more screwed up, others more happy, but everybody's psychotic joint venture definition of CP
Linkify! || Fold With Us! || sighist
|
|
|
|
|
peterchen wrote: He still has a better chance for an answer here
Might as well open up the Lounge to programming questions then. 
Cheers,
Vikram.
"whoever I am, I'm not other people" - Corinna John.
|
|
|
|
|
peterchen wrote: but the Math forum would give him less abuse and better karma.
whoa whoa whoa. you mean the votes actually do something? like, make me Rise and Fall amongst the ranks of all the CPians?
|
|
|
|
|
Yes, at the end of the universe, The Great Maunder will count your fives and ones and theywill determine whether you come back as hamster. Or badger.
We are a big screwed up dysfunctional psychotic happy family - some more screwed up, others more happy, but everybody's psychotic joint venture definition of CP
Linkify! || Fold With Us! || sighist
|
|
|
|
|
Ah, but which one is better? Surely the most dedicated of CP members would like to give back something to CP (in the form of pedal power).
|
|
|
|
|
As you know, hamster run the servers (more responsibility, but then, Dave comes whipping you about daily), whereas badgers only run the signatures of.. some... members........ 
We are a big screwed up dysfunctional psychotic happy family - some more screwed up, others more happy, but everybody's psychotic joint venture definition of CP
Linkify! || Fold With Us! || sighist
|
|
|
|
|
|
Are you using the product rule when you take the derivative?
And I get on my knees and pray.
We don't get fooled again.
|
|
|
|
|
well the derivative itself is correct. i got a friend and a online thing to check that for me
and, i dont know what the right answer is. its an online submission thing, and it only says right/wrong  not which part.
|
|
|
|
|
nevermind. aparently, i dont know how to add 
|
|
|
|
|
y = (8 - 8pi)x + 32 pi<sup>2</sup> ??
|
|
|
|
|
yeah, correct. as i said above, i seem to not know how to add
|
|
|
|
|
I agree... as long as you mean the last term is 32(pi)^2 
Ryan "Punctuality is only a virtue for those who aren't smart enough to think of good excuses for being late" John Nichol "Point Of Impact"
|
|
|
|
|
As already pointed out, there's a maths forum but here goes
y = f(x)
slope M = dy/dx
You have one point on the line - (4PI, f(4PI)), and since it is the tangent to the curve, its slope will be -1/M it has the same slope. Just use the slope-point equation for the straight line (IIRC, it's y - y1 = m(x - x1)).
To find m at the point, simply substitute for x and y in dy/dx.
Please post in the maths forum in future. HTH.
Nostalgia is a very powerful emotion.
-- corrected slope of tangent, which I misread as normal. Thanks to Ryan. modified at 4:57 Wednesday 11th October, 2006
Cheers,
Vikram.
"whoever I am, I'm not other people" - Corinna John.
|
|
|
|
General 
News 
Suggestion 
Question 
Bug 
Answer 
Joke 
Praise 
Rant 
Admin 
Submit an article or tip
![Badger | [badger,badger,badger,badger...]](https://codeproject.global.ssl.fastly.net/script/Forums/Images/badger.gif)
![Badger | [badger,badger,badger,badger...]](https://www.codeproject.com/script/Forums/Images/badger.gif)
![Jig | [Dance]](https://www.codeproject.com/script/Forums/Images/jig.gif)
![Green Alien | [Alien]](https://www.codeproject.com/script/Forums/Images/alien.gif)
