US4965586A — Position determination and message transfer syste…

Claim 1

Independent Claim 152 words

A system for determining the position of a user located on the earth's surface, comprising: a user-carried transceiver for receiving an interrogation signal and transmitting a reply signal in response to said interrogation signal; two satellites at spaced orbital locations above the earth, each of said satellites carrying repeater means for receiving and retransmitting the reply signal transmitted by the user-carried transceiver; and a ground station for periodically transmitting the interrogation signal and for receiving and processing the retransmitted reply signals from the two satellites, said ground station including means for calculating the user position based on the arrival times of the retransmitted reply signals at the ground station, the transmission time of the interrogation signal from the ground station, and the elevation of the user on the earth's surface, said elevation being derived form a stored terrain map providing local terrain elevations at a plurality of points on the earth's surface.

Claim 2

Independent Claim 152 words

A system for determining the position of a user located on the earth's surface, comprising: a user-carried transceiver for receiving an interrogation signal and transmitting a reply signal in response to said interrogation signal; two satellites at spaced orbital locations above the earth, each of said satellites carrying repeater means for receiving and retransmitting the reply signal transmitted by the user-carried transceiver; and a ground station for periodically transmitting the interrogation signal and for receiving and processing the retransmitted reply signals from the two satellites, said ground station including means for calculating the user position based on the arrival times of the retransmitted reply signals at the ground station, the transmission time of the interrogation signal from the ground station, and the elevation of the user on the earth's surface, said elevation being derived form a stored terrain map providing local terrain elevations at a plurality of points on the earth's surface.

Claim 3

Dependent Claim 31 words

A system as claimed in claim 1, wherein the two satellites are in geostationary orbit about the earth, each of said satellites being located in a different position in said orbit.

Claim 4

Dependent Claim 27 words

A system as claimed in claim 2, wherein said terrain map provides terrain elevations directly above input reference points on a reference ellipsoid approximating the earth's surface.

Claim 5

Dependent Claim 26 words

A system as claimed in claim 2, wherein the interrogation signal is relayed from the ground station to the user-carried transceiver through one of said satellites.

Claim 6

Dependent Claim 42 words

A system as claimed in claim 1, wherein the reply signal transmitted by the user-carried transceiver is coded with information uniquely identifying the user, and wherein the ground station includes means for detecting the user identifying information in the received reply signals.

Claim 7

Dependent Claim 38 words

A system as claimed in claim 1, wherein the ground station further includes means for transmitting calculated position information to the user-carried transceiver, and wherein the user-carried transceiver further includes means for receiving and displaying said position information.

Claim 8

Independent Claim 148 words

A method for determining the position of a user located on the earth's surface using two relay satellites at spaced orbital locations above the earth, said user carrying a transceiver for transmitting a reply signal in response to a received interrogation signal, said method comprising the steps of: transmitting an interrogation signal to the user at a known or measured time; receiving a reply signal from the user through each of the two satellites; measuring the arrival times of the reply signals received through the two satellites; calculating a line of position for the user based on the arrival times of the reply signal through the two satellites and the transmission time of the interrogation signal; determining the intersection of the line of position with the earth's surface by reference to a stored terrain map providing local terrain elevations at a plurality of points on the earth's surface.

Claim 9

Independent Claim 148 words

A method for determining the position of a user located on the earth's surface using two relay satellites at spaced orbital locations above the earth, said user carrying a transceiver for transmitting a reply signal in response to a received interrogation signal, said method comprising the steps of: transmitting an interrogation signal to the user at a known or measured time; receiving a reply signal from the user through each of the two satellites; measuring the arrival times of the reply signals received through the two satellites; calculating a line of position for the user based on the arrival times of the reply signal through the two satellites and the transmission time of the interrogation signal; determining the intersection of the line of position with the earth's surface by reference to a stored terrain map providing local terrain elevations at a plurality of points on the earth's surface.

Claim 10

Independent Claim 132 words

A method for providing approach guidance to a landing aircraft using two relay satellites at spaced orbital locations above the earth, said aircraft carrying a transceiver for transmitting a reply signal in response to a received interrogation signal, said method comprising the steps of: transmitting an interrogation signal to the aircraft transceiver at a known or measured time; receiving a reply signal from the aircraft transceiver through each of the two satellites; calculating a line of position for the aircraft based on the arrival times of the reply signal through the two satellites and the transmission time of the interrogation signal; estimating the aircraft location from the intersection between the line of position and a predetermined glide slope; and providing the aircraft with altitude information representing desired altitude on the glide slope.

Claim 11

Independent Claim 132 words

A method for providing approach guidance to a landing aircraft using two relay satellites at spaced orbital locations above the earth, said aircraft carrying a transceiver for transmitting a reply signal in response to a received interrogation signal, said method comprising the steps of: transmitting an interrogation signal to the aircraft transceiver at a known or measured time; receiving a reply signal from the aircraft transceiver through each of the two satellites; calculating a line of position for the aircraft based on the arrival times of the reply signal through the two satellites and the transmission time of the interrogation signal; estimating the aircraft location from the intersection between the line of position and a predetermined glide slope; and providing the aircraft with altitude information representing desired altitude on the glide slope.

Claim 12

Independent Claim 177 words

A system for determining the position of a user located on the earth's surface, comprising: a user-carried transceiver for receiving an interrogation signal and transmitting a reply signal in response to said interrogation signal; two satellites at spaced orbital locations above the earth, each of said satellites carrying repeater means for receiving and retransmitting the reply signal transmitted by the user-carried transceiver; and a ground station for periodically transmitting the interrogation signal and for receiving and processing the retransmitted reply signals from the two satellites, said ground station comprising: means for calculating the user position based on the arrival times of the retransmitted reply signals at the ground station, the transmission time of the interrogation signal from the ground station, and the elevation of the user on the earth's surface; and a stored terrain map providing local terrain elevations at the plurality of points on the earth's surface, said user elevation being obtained from said stored terrain map by said calculating means in response to input information derived from the arrival times of said retransmitted reply signals.

Claim 13

Independent Claim 177 words

A system for determining the position of a user located on the earth's surface, comprising: a user-carried transceiver for receiving an interrogation signal and transmitting a reply signal in response to said interrogation signal; two satellites at spaced orbital locations above the earth, each of said satellites carrying repeater means for receiving and retransmitting the reply signal transmitted by the user-carried transceiver; and a ground station for periodically transmitting the interrogation signal and for receiving and processing the retransmitted reply signals from the two satellites, said ground station comprising: means for calculating the user position based on the arrival times of the retransmitted reply signals at the ground station, the transmission time of the interrogation signal from the ground station, and the elevation of the user on the earth's surface; and a stored terrain map providing local terrain elevations at the plurality of points on the earth's surface, said user elevation being obtained from said stored terrain map by said calculating means in response to input information derived from the arrival times of said retransmitted reply signals.

Claim 14

Dependent Claim 30 words

A system claimed in claim 9, wherein the two satellites are in geostationary orbit about the earth, each of said satellites being located in a different position in said orbit.

Claim 15

Dependent Claim 82 words

A system as claimed in claim 10, wherein: said terrain map provides terrain elevations directly above input reference points on a reference surface approximating the earth's surface; said input information comprises an approximate user position defined by the intersection between said reference surface and a line of position established by said signal arrival times; and said calculating means is effective to calculate a corrected user position based on the elevation obtained from said stored terrain map in response to said input information.

Claim 16

Dependent Claim 26 words

A system as claimed in claim 10, wherein the interrogation signal is relayed from the ground station to the user-carried transceiver through one of said satellites.

Claim 17

Dependent Claim 42 words

A system as claimed in claim 9, wherein the reply signal transmitted by the user-carried transceiver is coded with information uniquely identifying the user, and wherein the ground station includes means for detecting the user identifying information in the received reply signals.

Claim 18

Dependent Claim 38 words

A system as claimed in claim 9, wherein the ground station further includes means for transmitting calculated position information to the user-carried transceiver, and wherein the user-carried transceiver further includes means for receiving and displaying said position information.

Claim 19

Independent Claim 225 words

A method for determining the position of a user located on the earth's surface using a ground station and two relay satellites at spaced orbital locations above the earth, said user carrying a transceiver for transmitting a reply signal in response to a received interrogation signal, said method comprising the steps of: transmitting an interrogation signal from the ground station to the user at a known or measured time; receiving a reply signal from the user at the ground station through each of the two satellites; measuring the arrival times at the ground station of the reply signals received through the two satellites; calculating at the ground station a line of position for the user based on the arrival times of the reply signal through the two satellites and the transmission time of the interrogation signal; determining at the ground station the intersection point between the line of position and a reference surface approximating the earth's surface; using said intersection point as an input to a stored terrain map at the ground station in order to obtain a local terrain elevation, said ground station providing local terrain elevations at a plurality of points on the earth's surface; and using the local terrain elevation obtained from the stored terrain map and said line of position to determine at the ground station the position of the user.

Claim 20

Independent Claim 225 words

A method for determining the position of a user located on the earth's surface using a ground station and two relay satellites at spaced orbital locations above the earth, said user carrying a transceiver for transmitting a reply signal in response to a received interrogation signal, said method comprising the steps of: transmitting an interrogation signal from the ground station to the user at a known or measured time; receiving a reply signal from the user at the ground station through each of the two satellites; measuring the arrival times at the ground station of the reply signals received through the two satellites; calculating at the ground station a line of position for the user based on the arrival times of the reply signal through the two satellites and the transmission time of the interrogation signal; determining at the ground station the intersection point between the line of position and a reference surface approximating the earth's surface; using said intersection point as an input to a stored terrain map at the ground station in order to obtain a local terrain elevation, said ground station providing local terrain elevations at a plurality of points on the earth's surface; and using the local terrain elevation obtained from the stored terrain map and said line of position to determine at the ground station the position of the user.

Claim 21

Dependent Claim 37 words

A method as claimed in claim 15, wherein said intersection point corresponds to an approximate position of said user, and wherein the actual user position is determined by correcting said approximate position using said local terrain elevation.

Claim 22

Independent Claim 146 words

A system for determining the position of a user located on the earth's surface, comprising: a user-carried transmitter for transmitting a signal; a plurality of satellites at spaced orbital locations above the earth, each of said satellites carrying repeater means for receiving and retransmitting the signal transmitted by the user-carried transmitter; and a ground station for receiving and processing the retransmitted signals from the satellites, said ground station comprising: means for calculating the user position based on the arrival times of the retransmitted reply signals at the ground station and the elevation of the user on the earth's surface; and a stored terrain map providing local terrain elevations at a plurality of points on the earth's surface, said user elevation being obtained from said stored terrain map by said calculating means in response to input information derived from the arrival times of said retransmitted replay signals.

Claim 23

Independent Claim 146 words

A system for determining the position of a user located on the earth's surface, comprising: a user-carried transmitter for transmitting a signal; a plurality of satellites at spaced orbital locations above the earth, each of said satellites carrying repeater means for receiving and retransmitting the signal transmitted by the user-carried transmitter; and a ground station for receiving and processing the retransmitted signals from the satellites, said ground station comprising: means for calculating the user position based on the arrival times of the retransmitted reply signals at the ground station and the elevation of the user on the earth's surface; and a stored terrain map providing local terrain elevations at a plurality of points on the earth's surface, said user elevation being obtained from said stored terrain map by said calculating means in response to input information derived from the arrival times of said retransmitted replay signals.

Claim 24

Dependent Claim 30 words

A system as claimed in claim 17, wherein said satellites are in geostationary orbit about the earth, each of said satellites being located in a different position in said orbit.

Claim 25

Dependent Claim 40 words

A system as claimed in claim 17, wherein the signal transmitted by the user-carried transmitter is coded with information uniquely identifying the user, and wherein the ground station includes means for detecting the user identifying information in the received signals.

Claim 26

Dependent Claim 38 words

A system as claimed in claim 17, wherein the ground station further includes means for transmitting calculated position information to the user-carried transmitter, and wherein the user-carried transmitter further includes means for receiving and displaying said position information.

Claim 27

Independent Claim 154 words

A method for determining the position of a user located on the earth's surface using a ground station and a plurality of satellites at spaced orbital locations above the earth, said user carrying a transmitter for transmitting a signal to the ground station through said satellites, said method comprising the steps of: receiving a signal from the user at the ground station through each of said satellites; measuring the arrival times at the ground station of the signals received from said satellites; and calculating at the ground station the position of the user based on the arrival times of the signals received from the satellites and the elevation of the user on the earth's surface, said elevation being derived from a stored terrain map a the ground station in response to input information derived from said arrival times, said terrain map providing local terrain elevations at a plurality of points on the earth's surface.

Claim 28

Independent Claim 154 words

A method for determining the position of a user located on the earth's surface using a ground station and a plurality of satellites at spaced orbital locations above the earth, said user carrying a transmitter for transmitting a signal to the ground station through said satellites, said method comprising the steps of: receiving a signal from the user at the ground station through each of said satellites; measuring the arrival times at the ground station of the signals received from said satellites; and calculating at the ground station the position of the user based on the arrival times of the signals received from the satellites and the elevation of the user on the earth's surface, said elevation being derived from a stored terrain map a the ground station in response to input information derived from said arrival times, said terrain map providing local terrain elevations at a plurality of points on the earth's surface.

Claim 29

Independent Claim 188 words

A method for determining the position of a user located on the earth's surface using a first transmitter, a second transmitter carried by said user, and a plurality of satellites at spaced orbital locations above the earth, said method comprising the steps of: placing said first transmitter at a first location on the earth's surface at which one or more of the latitude, longitude and elevation of the first transmitter are unknown; receiving a signal form said first transmitter through one or more of said satellites; calculating the unknown latitude, longitude and/or terrain elevation of the first transmitter based on the arrival times of the signals received from said satellites; entering said terrain elevation into a terrain map memory as a function of latitude and longitude; moving a user carrying said second transmitter to a second location on the earth's surface in relative proximity to said first location; receiving signals from said second transmitter through one or more of said satellites; and calculating the position of said user based on the arrival times of the signals from said satellites and elevation data stored in said terrain map memory.

Claim 30

Independent Claim 188 words

A method for determining the position of a user located on the earth's surface using a first transmitter, a second transmitter carried by said user, and a plurality of satellites at spaced orbital locations above the earth, said method comprising the steps of: placing said first transmitter at a first location on the earth's surface at which one or more of the latitude, longitude and elevation of the first transmitter are unknown; receiving a signal form said first transmitter through one or more of said satellites; calculating the unknown latitude, longitude and/or terrain elevation of the first transmitter based on the arrival times of the signals received from said satellites; entering said terrain elevation into a terrain map memory as a function of latitude and longitude; moving a user carrying said second transmitter to a second location on the earth's surface in relative proximity to said first location; receiving signals from said second transmitter through one or more of said satellites; and calculating the position of said user based on the arrival times of the signals from said satellites and elevation data stored in said terrain map memory.

Claim 31

Dependent Claim 33 words

A method as claimed in claim 22, wherein said first transmitter is moved to a series of locations in order to store the terrain elevations at said locations in said terrain map memory.

Claim 32

Dependent Claim 27 words

A method as claim in claim 22, wherein the signal transmitted by said first transmitter includes altitude information obtained from an altitude-sensing device associated with said transmitter.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1993-10-22	1994-04-23	1994-10-23	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1997-10-22	1998-04-23	1998-10-23	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2001-10-22	2002-04-23	2002-10-23	$7700.00	Window Closed / Lapsed

Position determination and message transfer system employing satellites and stored terrain map

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