how many satellites does it take to give a 3 dimensional gps position?

Question

how many satellites does it take to give a 3 dimensional gps position?

Answer 1

With the technology of today 3 satilite can accomplish this but natturaly the more the better. with a system of satellites, computers, and receivers there able to determine the latitude and longitude of a receiver on Earth by calculating the time difference for signals from different satellites to reach the receiver.

Answer 2

FOUR!

NOT THREE!



Why? Because GPS measures the distance between you and the satellites to find your position. So:



If you had only one satellite, the locus of distance is a sphere.



If you had two satellites, the locus of distance from both would be a circle on that sphere.



If you had three satellites, the locus of distance from all three would be two points on that circle.



And you need a fourth satellite to distinguish between those last two points.



Since most people ignore altitude, the surface of the earth provides the necessary "fourth" sphere in 2-d applications, meaning you generally need only 3 satellites for most navigational problems. But for true 3-d, you need all four.

Answer 3

my gps only gives 3d fixes with a minimum of 4 satellites in view. I think three is technically enough for solving the problem on paper but that fourth one must somehow resolve time differences between the other three satellites (or rather, it's used by your GPS to evaluate the signals received from the other satellites - the satellites probably don't need to disambiguate anything).

Answer 4

Three. Think in 3 dimensions, the data from one GPS satellite and your receiver produce a distance from you to the satellite. Think of that as the radius of a sphere, and you're somewhere on the spere's surface. Add in a 2nd satellite -- two spheres intersecting give you a circle arcing through the earth and sky; you're on that circle. Add a 3rd satellite -- THAT sphere crosses the circle at two points. You are at one of those points. The system can eliminate one of those points as bogus (off in space, or deep underground), so at that point the GPS system can locate your position & altitude without ambiguity.

Answer 5

Earlier there were 4 satellites used for a single 3D GPS position. Today a single satellite can provide a 4D GPS position (Including different timezones in the world) with signal quality and resolution 150 times that of all 4 older satellites combined

Answer 6

you will get a rough fix off 2, based on time and distance of them away. 3 for accurancy. Ideally more.



IGNORE the first answer, its wrong. They don't measure the angle of the signal from the satellite, but calculate time and distance based on the speed of the signal. Satellite always transmit on a co-ordinated time between all 24 of them. Your hand held GPS that has no ability to tranmits knows this time, works out the satellite radius in the sky and calculates it's distance away.

Answer 7

two

if not then three

but i think two are quite effective using trigonometry

I can be able to get a 3d location of an object using two frequency emmitors and by calculating the reflected signal knowing how far and in what direction it is thus creating a three dimensional position of the object but for that to happen the traked object should be able to reflect back the sent signal thus completeng the triangle :

correct me if I am wrong but with mathematical proof.

Answer 8

It depends how long you have, two is enough if you can see them for a while, particularly if they are in favourable positions, three if you need a quick fix because you don't have an accurate time reference. The more you have ( if your GPS receiver can handle that many ) the quicker it is to get an accurate 3D fix.

Answer 9

3, its called triangulation, its the same if its 3D or 2D it still takes 3 satellites.. although obviously the more the better, more accurate. each satellite just takes a bearing and a distance, then sends that info into a different computer, and where all the lines cross is where you are...



simple really x



hope this is what you were after

Answer 10

Four is the THEORETICAL minimum for a 3-D fix. Even then, the accuracy and reliability of the fix is horrible.

Answer 11

Three are required to triangulate a position.

Answer 12

I would have thought a minimum of three.