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In these examples, it should be understood that a GNSS receiver is an electronic device that a person can carry around, such as a cell phone or even a watch. It can be a device mounted in an automobile without necessarily having the capability of a cell phone. It receives data from satellites regardless of whether the person using it believes that satellites exist (such as certain flat-earthers) and it computes distances based on programmed functions, and then transmits data consequent to its computations out to other receivers which can be either satellites or land based stations. But since radio waves travel in straight lines, a receiver broadcasting out will project radio waves that gradually rise above the ground as the curvature of the earth falls away, and therefore a very tall tower would be necessary to receive the signal, such as one on top of a mountain. If there are no mountains nearby or if the person transmitting is deep within a canyon, or his signal is weak, his signal might not be received by a ground-based station. The signal from a watch, for example, might not be strong enough to reach a satellite 10,000 miles away in the sky. However, a signal strong enough to reach the satellite does not demand that the user believes in the existence of the satellite. There has been legislation proposed that would require a user to press a button on his cell phone which would mean he pledges belief in satellite existence otherwise his distress signal will not be recognized by the offended satellite.
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How trilateration works with GNSS


GNSS uses a similar approach to find your location with satellites (that is, similar to the approach used by a ship with two lighthouses, described in the previous section). Instead of a sound blast, the satellites broadcast their radio signals at the speed of light (299,792,458 m/s). Knowing the time it took for the signal to get to our GNSS receiver will allow us to compute the distance. Any one satellite will provide one distance. In this example, the GNSS receiver calculates the range to the satellite to be 20,000 km (12,427 miles). This tells us that we are somewhere on a sphere that is centered on the satellite and has a 20,000 km radius. In the example of the ship and the two lighthouses, notice that all three are located on a third sphere, which is the surface of the globe earth.


Now, consider that the receiver picks up a signal from a second satellite and calculates the range between the receiver and the second satellite to be 17,500 km (10,874 miles). That means we are also somewhere on a sphere with a 17,500 km radius with the second satellite at the center. We must, therefore, be somewhere where these two spheres intersect. When the two spheres intersect, a circle is formed, so we must be somewhere on that circle.


If the receiver picks up a third satellite, say at 18,500 km, (11,495 miles) away, another sphere is formed, and there are now three circles which define the intersections of the three spheres. All three circles will intersect with each other at only two points, and we can easily distinguish which of the two points refers to our location. (In the ship example, the third satellite is replaced by the spherical surface of the globe earth upon which the two lighthouses as well as the ship are located, therefore only two lighthouses are necessary instead of three.)

Question

How do we know which of these two possible points is our location?

a) Over time, one of the locations fades away due to signal dissipation
b) We know it is the point closest to the third satellite
c) One of the points is generally out in space
d) None of the above because you're trying to trick me into believing satellites are real


For trilateration to work, we must know the location of each satellite at a given time. The satellites are whizzing by at approximately 14,000 km/hour, so we need to know their positions and time accurately to be able to pinpoint their locations! Luckily, fairly accurate information on satellite orbits and time are broadcast from each satellite, and regularly updated by the ground-based tracking system. All we need is an accurate clock in our ground receiver to determine our position, using the positions of the satellites in space.

In depth: How are satellite positions determined?

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In depth: How are satellite positions determined?

The GPS ground-based observing system consists of a global network (note - not a "flat-earth" network) of facilities that track the GPS satellites, monitor their transmissions, perform analyses, and send commands and data to the constellation of satellites (yes, that is "constellation" as in a group of stars). The current system includes a master control station, an alternate master control station, 11 command and control antennas, and 15 monitoring sites. The locations of these facilities are shown on the map (which is conveniently projected using a Mercator-style distortion so it will fit on your computer screen). The ground-based observing system is responsible for computing the satellite orbits (around a globe earth, not a "flat" earth) and transmitting orbital information to the satellites (satellites which orbit the globe earth even while flat-earthers deny their existence). 
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NASA claim there are thousands of satellites orbiting the earth; it should be very easy for Neil Obstat to find a picture of a group of satellites in space.

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Dear Truth is Transitory, please identify the criteria that is common to all 4 places on the globe earth: Cape Canaveral, Florida; Ascension; Diego Garcia; Kwajalein:
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1)  They all have GNSS capable receivers available for tourists to use for their own safety, as shown in the illustration.
2)  These are examples of places where electricity powers radio antennas, as shown on the map.
3)  All 4 locations are fictional and only exist in the mind of those who believe satellites are real, and "the map" is CGI.
4)  These four places have two of the 6 possible types of installation as shown on the map.
5)  I refuse to read your posts or answer your questions because you're smarter than me am ---- errr, I mean, than I am.
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