Abstract: A measurement agent for measuring a distance from the agent to a tag may include a transmitter and receiver for transmitting and receiving radio wave signals. The agent is arranged for changing the agent transmitter from a particular state wherein the agent transmitter transmits a particular radio wave interrogation signal towards a further state determined by the agent wherein the agent transmitter transmits a further radio wave interrogation signal when a signal behavior of a received radio wave response signal changes. Further, the measurement agent includes a counter for determining a time period between transmittance of a first radio wave interrogation signal and receipt of a radio wave response signal having a predetermined signal behavior. The agent also includes a processor for computing a distance between the agent and the tag, based on the determined time period and a multiple number of radio wave interrogation signals.

Abstract: A measurement agent for measuring a distance from the agent to a tag may include a transmitter and receiver for transmitting and receiving radio wave signals. The agent is arranged for changing the agent transmitter from a particular state wherein the agent transmitter transmits a particular radio wave interrogation signal towards a further state determined by the agent wherein the agent transmitter transmits a further radio wave interrogation signal when a signal behaviour of a received radio wave response signal changes. Further, the measurement agent includes a counter for determining a time period between transmittance of a first radio wave interrogation signal and receipt of a radio wave response signal having a predetermined signal behaviour. The agent also includes a processor for computing a distance between the agent and the tag, based on the determined time period and a multiple number of radio wave interrogation signals.

Abstract: A method of determining ground properties comprises the steps of transmitting magnetic waves through the ground from a first location (A) to a second location (B), comparing the magnetic waves received at the second location with the magnetic waves transmitted at the first location so as to determine the attenuation of the ground, and deriving the ground properties from the attenuation thus determined. The magnetic waves are transmitted at multiple frequencies so as to determine a frequency dependency of the attenuation.