Vehicle Based Estimation of Ground Elevations
Publication Date: 2005-Feb-04
The IP.com Prior Art Database
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.
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,...