Topic: First a math question, then... - page 2. (Read 3267 times)

What you are describing is called "Triangulation", it works to find a point in a plane if the three given points are not in a line. If you have three dimensions you would need a fourth point, as you will get two possible solutions from three points unless the given point is coplanar with the three.

You don't have to worry too much over short distances, but for longer distances you might need to know whether the distance follows the surface of the earth or goes through it?

I've coined a name for the device, stemming from the following:



It currently has only one mundane result via Google and is easy to pronounce, coupled with having other attributes.

I'm going to purchase the domain name later today.

To be clear, the Voynich Manuscript was only used for inspiration in naming the device and gleaning an example symbol. I sure the hell don't desire to be sued by descendants of its author.

~Bruno K~

That's pretty trippy.

It will be up to the giver of the device and how that person programmed it as to what's at the final destination. The possibilities are endless: the geocaching crowd could find a use for it; lovers could give it to their sole mates, where its only purpose is to read out how far away they are from the location of their first kiss, date, sex, met, etc.; B & M businesses could use it for some creative marketing campaign; among others I've thought of and, given time, a myriad more examples would manifest themselves. Bottomline, let the end users decide its purpose.

Putting aside the marketing aspect to create a demand for the device (just had a vision of Atlas when I penned 'device' that time--weird!), what would be paramount is that the device works properly, and the website function seamlessly with little effort on the user's part. I further propose that the device be manufactured in the US as cost efficient as possible, not worrying too much of its final price point, for it's a gift, not a necessity. As a gift, the device should have aesthetic qualities in its design and packaging, albeit it's possibly just a box-like structure.

For sake of argument, we'll just safely assume that one coordinated is possible when only three coordinates are inputted. Any bugs regarding this fact can be worked out during the coding stage of the accompanied website.

More to come.

~Bruno K~

Some say the Voynich manuscript is a hoax, and contains no real meaning.

I'm fascinated by your idea, Phinnaeus. When the user gets to the final point, would the item do or reveal anything? If not... what a joke!

Oh, and I can second what SgtSpike and myrkul are saying: because GPS confines all coordinates to MSL (Mean Sea Level) + elevation, and elevation is always much smaller than the diameter of the sphere, then we can say elevation is always (approximately) zero.

This means a triangle formed by three GPS coordinates is either degenerate (it's a straight line) – or, the points and the length from each point will exactly resolve to one "solution." Since elevation is not truly zero, there are actually two solutions if elevation is included in the calculation; but both solutions need to be averaged together to get the best Latitude and Longitude reading for the real solution (that is, use Newton's method to approximate a more accurate solution along the line between the two mathematical solutions).

FDFY!  

http://en.wikipedia.org/wiki/Voynich_manuscript

In fact, this is what's going to give us the inspiration as to what to name the damn thing.

~Bruno K~

Dafuq is that?

The small device (for sake of design, consider it box-shaped) only has a display that reads out in miles or kilometers (automatically adjusts to the region it's in) while in default mode, a single button, and an image, similar to one below.



Would have a USB port for programming and a port for a charger (included), for it runs on replaceable rechargeable batteries, located behind a screwed in panel.

Almost forgot something. A very small speaker is inside the device, or another unmarked port is provided that would accommodate a headphone cord, which may prove to be the better option.

Well, Let's say I gave you such a device, and you immediately used it from home, then proceeded to plug in that info into the website. As a helpful aid to your locating the target spot, it throws up this image:


So, you then decide to go into Chicago and check from there:


So now we have 2 points, one down in central Illinois, and one in southern Wisconsin (just outside the scope of this map, sadly, but you can see where it would be), and it is now time for a bit of a road trip. Hitting the button and inputting the information once you get to Peoria results in this image:



And we're left with only one point remaining that matches the distances from the three points. I was sending you to Lincoln. As long as your three points are not in a straight line, this will always happen.

Well, sure, they should be exactly.  I didn't bother to make them exact when I drew them, because the point still stands.  If you picture the points mirrored from each other whilist the triangle is perfectly flat, then you should also be able to picture the points in different X,Y positions (if X,Y can be assumed to be a point on the surface of the earth) if the triangle is tilted (relative to the surface of the earth).  In the case of a tilt, one point would stay on the surface, and the other point would be underground, but you would have to have some way of determining which point is the one underground and which point is the one on the surface.

I am certain the math would be elementary with someone familiar with these sorts of calculations.  The only point I was making is that there are two valid and legitimate answers for the question "what point in space, relative to the triangle's location, matches the length of A, B, and C?"  When calculating what the X,Y on the surface of the earth must be, a person must take this into account and be certain to choose the correct answer to the question out of the two possible answers.  If you have a machine to do this automatically, then all the better - it should be able to easily determine which point is the legitimate point.  But I was under the impression that no such machine existed, and Phinnaeus was attempting to do this the old fashioned way, in which case, more care should be taken.

That's what I figured, whereupon a layperson would just imagine it as a beeline.

Allow me to re-ask the original question differently, given:

Suppose there's a site on the internet that allows the user to plug in a GPS coordinate and a distance into some provide fields. Then they are asked to provide two different sets of the same into another pair of fields. Then asked to do it one more time, making that three different GPS coordinates and three different distances. Would the resulted GPS coordinate be of one location or two?

Bear in the mind that this imaginary device does not read out any GPS coordinates, and must be provided with the use of a secondary device, presumably a smart phone. More on this later, but first let's make sure we're on the same page as it pertains to the question.

~Bruno K~

That's how it's calculated when the GPS is figuring out where you are, in relation to the satellites. The GPS knows it's on the surface of the earth, though, so when it calculates distance, it does it along the surface, since it knows how many miles or kilometers it is, roughly, per degree or longitude and latitude. It's not a straight line through the earth that it uses, but a curved one along the surface. That's how it defines the circle. That little box is smarter than you might think.

Is it safe to assume that that is how the distance is calculated using GPS? I see that it wouldn't be a pure straight line through the crust of the Earth.

That image isn't very clear. Are lines B₁ and B₂ identical in length? Same for C₁ and C₂, and A₁ and A₂? They need to be.

Remember, what you're actually reading when you press the button is a sphere, placed on the surface of a much larger sphere, with it's center at your location, and it's surface intersecting your destination. Sine we're pretty sure the desired location is not in space, or deep within the crust, most of those points are discarded, leaving only a circle on the surface of the larger sphere.

Nice name, but won't work: About 23,200 results (0.36 seconds)

Now on to reading the other posts, and it looks like math is evolved, for I glimpsed triangulation images.

EDIT: Now I'm back at square one, not knowing if two points or one is possible. Google, here I come!

i couldn't decipher this image.

perhaps you could mark the points, instead of the lines, and say which 3 points form the initial triangle

then mark the two perfectly legitimate positions as X and Y

Fair enough.

I'm going to try to illustrate my argument with a couple of crudely-drawn paint images.

This first image shows a triangle perpendicular to the earth.  I am only really showing it to help people better visualize what I am attempting to represent in the second picture.  As you can see, two perfectly legitimate positions can be derived from the calculations of the triangles.



In the second image, I attempt to demonstrate a triangle slightly tilted (due to difference in elevation when taking the readings).  With the tilt of the triangle, the mirror images of the triangle don't overlap with each other, and you still end up with a difference in calculated position. The horizontal dotted black line attempts to show that difference.

If the triangle is perpendicular to the surface of the earth, then you have committed exactly the error I warned against earlier: discounting elevation, all your points are in a straight line. That's why you have two valid surface points, not the elevation.

Picture it this way:  If a triangle is perpendicular to the earth, and you are trying to do this sort of analysis, then you would have two very viable points for the same calculation - one on each side of the triangle.

Eh, maybe it's hard to explain without a picture.  I'll see if I can come up with one.