GPS device with compass and altimeter and method for displaying navigation information

• US 6,381,540 B1
• Filed: 09/14/2001
• Issued: 04/30/2002
• Est. Priority Date: 11/01/1999
• Status: Expired due to Term

• Current Assignee: Garmin Corporation (Garmin Limited)
• Original Assignee: Garmin Corporation (Garmin Limited)
• Inventors: Laverick, David J., Olivier, Tracy, Beason, Lawrence W., Burgett, Scott
• Primary Examiner(s): Beaulieu, Yonel
• Application Number:
  US09/952,783
• Time in Patent Office: 228 Days
• Field of Search: 701/213, 701/4, 701/8, 342/357.06, 342/120, 733/84
• US Class Current: 701/213
• CPC Class Codes: G01C 21/20 Instruments for performing navigational calculations G01C21/24, G01C21/26 take precedence
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38
• CPC Class Codes: G01C 5/06 by using barometric means
• CPC Class Codes: G01S 19/45 by combining measurements of signals from the satellite radio beacon positioning system with a supplementary measurement

Abstract

A portable, handheld electronic navigation device includes an altimeter, a compass, and a GPS unit. An internal memory stores cartographic data, for displaying the cartographic data on a display of the navigation device. Accordingly, the device is capable of displaying cartographic data surrounding a location of the unit as determined by GPS, heading information as determined by the compass, and altitude information as determined by the altimeter. Additionally, through operation of an input, a user can cause the display to move, and thus display additional cartographic information, in the direction of the compass heading even when the user of the device is standing still. Furthermore, through utilization of a clock, such as the GPS clock, a user can determine altitude changes over time. Also, the altimeter of the navigation may be calibrated with altitude information entered by a user, with altitude information obtained from the cartographic or with altitude information derived from GPS.

Claims

1. A method of calibrating an altimeter, said method comprising:

calculating altitude based upon sensed barometric pressure;

calculating altitude based upon GPS; and

comparing said calculated barometric-pressure based altitude with said calculated GPS based altitude and, when said calculated barometric-pressure based altitude differs from said calculated GPS based altitude by at least a selected amount, then selecting not to rely upon said calculated barometric-pressure based altitude.

2. A method of calibrating an altimeter, said method comprising:

calculating altitude based upon sensed barometric pressure;

calculating altitude based upon GPS; and

comparing said calculated barometric-pressure based altitude with said calculated GPS based altitude and, when said calculated barometric pressure based altitude differs from said calculated GPS based altitude by at least a selected threshold amount, providing an indication to a user of said difference.

3. The method as set forth in claim 2, further comprising the step of permitting said user to select the basis for determining said altitude when said difference exceeds threshold.

4. A method of calibrating an altimeter, said method comprising:

calculating altitude based upon sensed barometric pressure and information entered and stored into a memory;

calculating altitude based upon GPS; and

comparing said calculated barometric-pressure based altitude with said calculated GPS based altitude and, when said calculated barometric pressure based altitude differs from said calculated GPS based altitude by at least a selected amount, then determining a time duration associated with said stored information.

5. The method of calibrating an altimeter as set forth in claim 4, further comprising:

when said time duration is greater than a selected threshold, then automatically selecting not to rely upon said barometric-pressure based altitude.