Communications: directive radio wave systems and devices (e.g. – Directive – Including a satellite
Reexamination Certificate
2000-04-18
2001-11-13
Blum, Theodore M. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a satellite
C342S357490, C342S357490, C701S215000
Reexamination Certificate
active
06317079
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a system that permits an operator to safely navigate a vessel in a water channel or harbor by using the Global Positioning System (GPS). The GPS is used to determine position (3-dimensionally) on earth by using a set of 24 geo-synchronous, earth-orbiting satellites broadcasting precisely timed signals. A GPS signal receiver (or GPS receiver) on earth is able to simultaneously read transmissions from at least four of these satellites to determine global latitude, longitude, time and elevation. The most widespread use, and the purpose of the GPS creation, is global navigation. Inexpensive GPS signal receivers are capable of providing one's location to within about 300 feet horizontally and 50 feet vertically. Greater accuracies are currently disabled or non-military receivers by the U.S. Department of Defense.
To obtain the water depth while on a ship, various types of Instruments and systems have been used to inform personnel of the water depth in channel and harbors. One common method is to rely on previously made measurements from the keel to the bathymetry (sea bottom topography). However, in doing so it must be recognized that the bathymetry changes with sediment transport from upland rainfall, runoff and shifting sand from long shore transport and coastal storms. As a result the previous measurements may not reflect the true conditions at the time the operator is in the channel.
Another prior art patented system discloses a signal processor which receives signals from an array of transponders to determine and record ranges to specific transponders, with the information received being recorded in a computer which transfers the information to a visual display.
With another prior art system used to measure ocean depths, acoustical sounding from a ship is used with pulses of different frequencies. The echoes are received at the ship and sorted by specific frequency. By doing so the user is assured that the determination of the transit time of a pulse of one frequency is not confused by the receipt of an echo at another frequency.
Still another prior art system discloses a system for locating a bottom cable which uses transponders connected to the cable and a master transponder which broadcasts an interrogation pulse from each transponder. Slave transponders send encoded signals to the master transponder and the time between the pulses is measured to constitute a range measurement to the slave transponder.
DESCRIPTION OF THE PRIOR ART
System used to provide for the on board measurement of water depth are known. For example, in the U.S. Pat. No. 3,432,851 to Cox, Jr. et al. there is disclosed a system with a signal processor which receives signals from an array of transponders to determine and record ranges to specific transponders, with the information received being recorded in a computer which transfers the information to a visual display.
U.S. Pat. No. 4,259,734 to Harmel discloses a system used to measure ocean depths with acoustical sounding from a ship using pulses of different frequencies. The echoes from these pulses are received at the ship and sorted by specific frequency. By doing so, the user is assured that the determination of the transit time of a pulse of one frequency is not confused by the receipt of an echo at another frequency.
U.S. Pat. No. 5,497,356 to Norton, Jr. et al. discloses a system for locating a bottom cable which uses transponders connected to the cable and a master transponder which broadcasts an interrogation pulse from each transponder. Slave transponders send encoded signals to the master transponder and the time between pulses is measured to constitute a range measurement to the slave transponder.
In a preferred embodiment of the present invention a Global Positioning System (GPS) reference signal receiving station located on land broadcasts information to a ship with its own GPS signal receiver system. Using the information from the reference station and the information on the ship, a level position of the ship can be computed. This allows the determination of keel clearance relative to the published channel template in lieu of a reference to the bathymetry. An on board computer, using a interpolated channel grid, is able to compute the height at a given position, using predetermined ellipsoid height tidal measurements, that are adjusted by subtracting the distance from the phase center of the onboard GPS antenna to on the bottom of the keel as is detailed in the following.
SUMMARY OF THE INVENTION
A preferred embodiment of the present invention relates to a system to permit the navigation of a channel or harbor having a reference GPS signal receiving station that sends information to a ship with its GPS signal receiving system.
It is an object of the present invention to provide for a system to determine height relative to a reference.
Another object is to provide for such a system in which the GPS systems at a reference position and on a ship are used with a computer to calculate the desired result.
FIG. 1
is a cross sectional schematic view showing a ship in a channel and the parameters and components of interest. No scale is used for any of the components or their perspective distances apart. A ship or vessel
1
—the terms are used interchangeably herein—is positioned in a body of water or channel
3
located between the two spaced shorelines
4
. The keel
5
of the ship has published channel depth keel clearance
7
. In one embodiment, on the ship
1
there is a first GPS signal receiving system
9
with an antenna
11
. Included in a system
9
is a radio signal receiver with an antenna
13
. The system
9
also has a computer which permits vertical positions to be determined to within 0.15 feet accuracy using differential GPS (DGPS). To do so a second GPS signal receiving system
15
located on shore is used as a reference and has a second GPS antenna
17
and a radio transmit antenna
19
. In
FIG. 1
, the two space vehicle (SVs) SV
1
and SV
2
represent two of the 24 earth orbiting satellites in the GPS. Each GPS space vehicle is in communication with the two GPS signal receiving antennas
11
and
17
.
REFERENCES:
patent: 3432851 (1969-03-01), Cox
patent: 4259734 (1981-03-01), Harmel
patent: 5202829 (1993-04-01), Geier
patent: 5491636 (1996-02-01), Robertson et al.
patent: 5497356 (1996-03-01), Norton, Jr. et al.
patent: 5689475 (1997-11-01), Chaumet-Lagrange
patent: 6185504 (2001-02-01), Berstis et al.
International Symposium on Marine Positioning, INSMAP pp. 432-441, inclusive Nov. 30-Dec. 4, 1998.
Baugher Jr. Earl H.
Blum Theodore M.
U.S. Army Corps of Engineers as represented by the Secretary of
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