Abstract: A method for transmission to a receiver of a geographic coordinate ? of a transmitter positioned in a spherical coordinate system ?, ?, at least a portion of one hemisphere of the Earth's sphere being divided into N sections each bounded by a minimum ? and a maximum ?, each section being subdivided into X cells each bounded by a minimum ? and a maximum ?, X varying depending on the section, includes at least the following steps: partitioning all of the latitude sections into M+1 classes, M sections being interspersed between two sections of the same class; transmitting, in one and the same message, the coordinate ? of the transmitter referenced relative to the cell in which the transmitter is located and the class of the latitude section in which the transmitter is located, the range of the receiver being at the most equal to the width of a cell along the axis of variation of the coordinate ?.

Abstract: A method for transmission to a receiver of a geographic coordinate ? of a transmitter positioned in a spherical coordinate system ?, ?, at least a portion of one hemisphere of the Earth's sphere being divided into N sections each bounded by a minimum ? and a maximum ?, each section being subdivided into X cells each bounded by a minimum ? and a maximum ?, X varying depending on the section, includes at least the following steps: partitioning all of the latitude sections into M+1 classes, M sections being interspersed between two sections of the same class; transmitting, in one and the same message, the coordinate ? of the transmitter referenced relative to the cell in which the transmitter is located and the class of the latitude section in which the transmitter is located, the range of the receiver being at the most equal to the width of a cell along the axis of variation of the coordinate ?.

Abstract: A method for transmitting data between a responder and an interrogator communicating in a secure mode includes the interrogator transmitting an interrogation signal comprising an authentication sequence to the responder which replies to the interrogator with a signal subjected to a time delay depending on said authentication sequence. A message for selection of the type of data to be transmitted is inserted into said interrogation signal, the responder decoding said selection message in order to transmit the selected data to the interrogator, said data being formatted in the form of standard identification codes so as to be masked.