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Vehicle Based Estimation of Ground Elevations Disclosure Number: IPCOM000042881D
Publication Date: 2005-Feb-04
Document File: 4 page(s) / 87K

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For different x, y-positions along a road, an altitude parameter (z-coordinate) is determined as follows: 1) determine a total weight mtot of a vehicle at x, y, 2) determine a total resistance Fresist experienced by the vehicle, 3) calculate a road inclination alpha based on the total weight mtot and the total resistance Fresist, and 4) transmit a signal S(alpha) representing the calculated road inclination alpha to a central station. Based on reported road inclinations alpha at a number of segments of the road, the central station may determine an altitude function for this road. The altitude function is then used to calculate altitude levels for specific positions along the road. By taking into account several measurements performed by different vehicles and/or several passages of the same vehicle, the central station may gradually improve the precision of the altitude function, and thus also the altitude data for each x, y-coordinate.

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Vehicle Based Estimation of Ground Elevations

Today, many vehicles are equipped with a navigation system, which renders it possible to determine a geographical position for the vehicle, i.e. a set of x- and y-coordinates. Typically, such a naviga­tion system includes a GNSS receiver (GNSS = Global Naviga­tion Satellite System) and a map database. The most well known GNSS is probably the Global Positioning System (GPS; U.S. Government). However, the Galileo system (the Eu­ropean programme for global navigation services) and the Global Orbi­ting Navigation Satellite System (GLONASS; Russian Federation Ministry of Defense) represent two viable alter­native sys­tems thereto.

Based on the received satellite signals it is also possible to deter­mine an altitude, i.e. a z-coordinate, representing a dis­tance to the mean sea level. Nevertheless, the present systems can­not normally calculate this z-coordinate with sufficient preci­sion. Namely, a precision which may be adequate for determi­ning a relevant x, y-position for a vehicle is typically not suffi­cient for the altitude value z. It is envisioned that, in addition to geographical positio­ning, future navigation systems will also provide adjust­ment parameters for the vehicle’s internal func­tions and features, such as the suspension system, the gearbox and the cruise control. Variations in the z-coordinate have a major influence of these adaptations. Therefore the altitude parameter needs to be deter­mined relatively accurately.

Today’s GNSS:s are only capable of providing z-coordinates with a precision of several meters. This is inadequate to attain a useful control of the above-mentioned internal vehicle para­me­ters. As an alter­native to satellite signals, various atmo­spheric pressure sensors may be used for altitude measurements. How­ever, also these types of sensors fail to fulfill the accuracy require­ments. Only advanced accelerometers provide such accuracy. Still though, these high-precision sensors are too expensive to be included in civil vehicles, such as trucks, busses and passen­ger cars.

The patent document US 6,268,825 describes a solution wherein a vehicle-mounted navigation device registers road-shape data and reports this data to a detailed map database. Each time a vehicle passes a particular road segment, data pertaining to this road segment is reported to the detailed map database. Thus, the data therein become repeatedly improved. Amongst other things, the detailed map database includes inclination informa­tion for the roads on which the reporting vehicles travel.

However, there is no recording of altitude information in the database. It is therefore proposed that an apparatus located in one or more vehicles performs the below operations to provide a basis for determining an altitude parameter,...