Method of transmitting postion data from a mobile unit
First Claim
1. A method of transmitting from a mobile unit position data derived from a grid coordinate system and defining unambiguously to a desired resolution a position of said unit within said coordinate system, wherein said position data is transmitted in the form of two messages spaced in time, one message comprising coordinate position data from which a lower order of data has been truncated whereby the one message defines an unambiguous position within said coordinate system at a resolution lower than said desired resolution, and the other message comprising coordinate position data from which a higher order of data has been truncated whereby the other message defines to the said desired resolution a position within said coordinate system that is ambiguous, the degree of truncation of the position data in each message being determined in accordance with a predetermined factor corresponding to a given distance within said coordinate system that is greater than the distance travelled by said mobile unit in the time space between said messages, whereby from the data of the two transmitted messages and the said predetermined factor, the position of the unit at the time of transmission of the said other message can be determined to said desired resolution.
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Abstract
A method of transmitting position data from a mobile unit comprises determining a coordinate position of the mobile unit and transmitting position data in two messages spaced in time one message having higher order data truncated and the other having lower order data truncated whereby both messages can be transmitted over a lower bandwidth and the position data can be reconstructed at a receiving station from the two messages.
24 Citations
12 Claims
- 1. A method of transmitting from a mobile unit position data derived from a grid coordinate system and defining unambiguously to a desired resolution a position of said unit within said coordinate system, wherein said position data is transmitted in the form of two messages spaced in time, one message comprising coordinate position data from which a lower order of data has been truncated whereby the one message defines an unambiguous position within said coordinate system at a resolution lower than said desired resolution, and the other message comprising coordinate position data from which a higher order of data has been truncated whereby the other message defines to the said desired resolution a position within said coordinate system that is ambiguous, the degree of truncation of the position data in each message being determined in accordance with a predetermined factor corresponding to a given distance within said coordinate system that is greater than the distance travelled by said mobile unit in the time space between said messages, whereby from the data of the two transmitted messages and the said predetermined factor, the position of the unit at the time of transmission of the said other message can be determined to said desired resolution.
Specification