# US 8,788,128 B1 · Precision navigation for landing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,788,128 B1 - Document ID: US8788128B1 - Status: Granted - Kind: B1 - Application number: 12/221,354 - Filed: 2008-08-01 - Granted: 2014-07-22 - Earliest claimed: 2008-08-01 - Assignees: Rockwell Collins, Inc. - Applicants: Patrick D. McCusker - Inventors: Patrick D. McCusker - Web page: https://patentgrep.com/patent/US8788128B1 ## CPC - G08G 5/54: for approach or landing - G01S 13/882: {for altimeters (measuring height using barometric means G01C5/06)} - G01S 13/935: for terrain-avoidance - G05D 1/0676: {specially adapted for landing} - G01S 13/953: {mounted on aircraft} - Y02A 90/10: Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation - G08G: TRAFFIC CONTROL SYSTEMS (guiding railway traffic, ensuring the safety of railway traffic B61L; arrangement of road signs or traffic signals E01F9/00; radar or analogous systems, sonar systems, lidar systems specially adapted for traffic control G01S13/91, G01S15/88, G01S17/88; {radar or analogous systems, sonar systems, lidar systems specially adapted for anti-collision purposes G01S13/93, G01S15/93, G01S17/93}) - G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES - G05D: SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES - Y02A: TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE ## Abstract In the examples described the forward-looking radar generated real-time terrain model (or in an alternative example in combination with a terrain database), can allow the use of a radio altimeter to compute aircraft vertical position relative to the runway threshold. Such a system typically provides improved accuracy for precision landings. ## Claims ### Claim 1 A method of precision navigation for an aircraft, the method comprising: determining aircraft height during initial and intermediate approach utilizing a real time terrain elevation database, wherein the real time terrain elevation database is derived from data from a forward looking radar on board the aircraft; providing a validated terrain elevation model by comparing or combining a database terrain elevation model and the real time terrain elevation database; determining the aircraft height during a final approach utilizing the validated terrain elevation model. ### Claim 2 (depends on 1) The method of precision navigation of claim 1 in which determining aircraft height during initial and intermediate approach utilizing the real time elevation model further comprises: determining a horizontal and vertical position of the aircraft; determining an expected location of a touch down zone relative to an aircraft position; verifying aircraft parameters relative to the aircraft position; and generating a real time elevation model of a terrain swath along a final approach path. ### Claim 3 (depends on 2) The method of precision navigation of claim 2 in which determining horizontal and vertical position of the aircraft is done with a GPS system. ### Claim 4 (depends on 2) The method of precision navigation of claim 2 in which determining horizontal and vertical position of the aircraft is done with a space based augmentation system-enabled GPS system. ### Claim 5 (depends on 2) The method of precision navigation of claim 2 in which determining horizontal and vertical position of the aircraft is done with a WAAS-enabled GPS system. ### Claim 6 (depends on 2) The method of precision navigation of claim 2 in which the aircraft parameters include slant range, azimuth angle and elevation angle relative to aircraft position. ### Claim 7 (depends on 1) The method of precision navigation of claim 1 in which generating the real time elevation database further comprises: collecting terrain elevation data; selecting hilltops likely to produce accurate altimeter readings; and correlating measurements to the terrain elevation database. ### Claim 8 (depends on 7) The method of precision navigation of claim 7 further comprising: determining if terrain is sufficiently flat; determining if there is sufficient time before landing; and measuring valleys likely to produce accurate altimeter readings. ### Claim 9 (depends on 7) The method of precision navigation of claim 7 in which collecting terrain elevation data is performed with X-Band Radar. ### Claim 10 (depends on 7) The method of precision navigation of claim 7 in which collecting terrain elevation data is performed with a weather radar system. ### Claim 11 A method of determining a final approach for an aircraft, the method comprising: determining a horizontal aircraft position; computing vertical position of the aircraft from a validated terrain elevation model and radio altimeter data, wherein the validated terrain elevation model is generated by comparing or combining a data base terrain elevation model and a real time terrain elevation database, wherein the real time terrain elevation database is derived using data from an active forward looking radar aboard the aircraft; and confirming aircraft position relative to a runway. ### Claim 12 (depends on 11) The method of determining a final approach for an aircraft of claim 11, in which confirming aircraft position includes confirming a runway centerline position and the aircraft position relative to the centerline. ### Claim 13 (depends on 11) The method of determining a final approach for an aircraft of claim 11 in which computing vertical position of the aircraft from a validated terrain elevation model and radio altimeter data further comprises: tracking distance from a touch down zone; sampling altitude with a radio altimeter at a collection of hilltop points; coasting between samples; and increasing sampling as the aircraft approaches a runway threshold. ### Claim 14 (depends on 13) The method of determining a final approach for an aircraft of claim 13 in which coasting between samples further comprises: retrieving inputs from other airborne systems; and combining retrieved inputs with radio altitude data. ### Claim 15 (depends on 11) The method of determining a final approach for an aircraft of claim 11 in which computing vertical position of the aircraft from a validated terrain elevation model and radio altimeter data further comprises a water/mountain approach procedure. ### Claim 16 (depends on 11) The method of determining a final approach for an aircraft of claim 11 in which computing vertical position of the aircraft from a validated terrain elevation model and radio altimeter data further comprises a circle to land approach procedure. ### Claim 17 A precision navigation system comprising: a GPS unit; a stored terrain data base having a first terrain model; a real time terrain data base having a second terrain model; a processor including a precision landing process and coupled to the GPS unit, wherein the precision landing process uses a validated terrain model using the first terrain model and the second terrain model on final approach for a height determination, the validated terrain model generated by comparing or combining the first terrain model and the second terrain model; a WAAS correction device providing WAAS correction signals to the processor; and a forward looking radar, wherein the real time terrain data base is derived at least in part from data from the forward looking radar. ### Claim 18 (depends on 17) The precision navigation system of claim 17 in which the precision landing process further comprises a real time elevation model process. ### Claim 19 (depends on 17) The precision navigation system of claim 17 in which the forward looking radar is a weather radar. ### Claim 20 (depends on 17) The precision navigation system of claim 17, in which the forward looking radar scans ahead of an aircraft to determine a height of prominent geographical features.