Determining position of a node based on aged position data

1. A method for determining a position of a node, the method comprising:

receiving first position data at the node from a first reference node and second position data from a second reference node, wherein the second position data comprises second position measurement information and a precision indicator which indicates accuracy of the second position measurement information;

generating a timestamp at the node which indicates when the second position data was received by node, associating the timestamp with the second position data and storing the second position data and associated timestamp at the node;

receiving updated first position data at the node from the first reference node;

determining, at the node, whether updated second position data has been received from the second reference node;

generating, at the node when the node determines that it has not received updated second position data from the second reference node, aged second position data by decreasing the precision indicator of the stored second position data as a function of an amount of time that has passed since a time indicated by the associated timestamp; and

determining a position of the node using both the aged second position data and the updated first position data.

2. A method according to claim 1 , wherein the step of decreasing the precision indicator of the stored second position data as a function of the amount of time that has passed since the time indicated by the associated timestamp comprises linearly decreasing the precision of the stored precision indicator as a function of the amount of time that has passed since the time indicated by the associated timestamp.

3. A method according to claim 1 , wherein the step of decreasing the precision indicator of the stored second position data as a function of the amount of time that has passed since the time indicated by the associated timestamp comprises exponentially decaying the precision of the stored precision indicator as a function of the amount of time that has passed since the time indicated by the associated timestamp.

4. A method according to claim 1 , further comprising:

determining, at the node, whether the node has moved since the time indicated by the associated timestamp; and

adjusting, when the node determines that the node has moved since the time indicated by the associated timestamp, a center position of the aged second position data based on a detected motion of the node to generate aged and moved second position data.

5. A method according to claim 4 , wherein the step of determining a position of the node using both the aged second position data and the updated first position data, comprises:

determining a position of the node using both (i) the aged and moved second position data and (ii) the updated first position data.

6. A method according to claim 1 , wherein determining the position of the node using both the aged second position data and the updated first position data comprises determining a geographic area comprising an intersection between the aged second position data and the updated first position data.

7. A node, comprising:

a receiver configured to receive first position data at the node from a first reference node and second position data from a second reference node, wherein the second position data comprises second position measurement information and a precision indicator which indicates accuracy of the second position measurement information;

a processor configured to generate a timestamp which indicates when the second position data was received by node and associate the timestamp with the second position data;

a memory configured to store the second position data and associated timestamp;

wherein the receiver is further configured to receive updated first position data from the first reference node, and

wherein the processor is further configured to determine whether updated second position data has been received from the second reference node, generate aged second position data by decreasing the precision indicator of the stored second position data as a function of an amount of time that has passed since a time indicated by the associated timestamp when the updated second position data has not been received, and determine a position of the node using both the aged second position data and the updated first position data.

8. A node according to claim 7 , wherein the processor is configured to decrease the precision indicator of the stored second position data as a function of the amount of time that has passed since the time indicated by the associated timestamp by linearly decreasing the precision of the stored precision indicator as a function of the amount of time that has passed since the time indicated by the associated timestamp.

9. A node according to claim 7 , wherein the processor is configured to decrease the precision indicator of the stored second position data as a function of the amount of time that has passed since the time indicated by the associated timestamp by exponentially decaying the precision of the stored precision indicator as a function of the amount of time that has passed since the time indicated by the associated timestamp.

10. A node according to claim 7 , further comprising:

a system designed to provide information regarding a detected motion of the node; and

wherein the processor is further configured to, when the node has moved since the time indicated by the associated timestamp, adjust a center position of the aged second position data based on the detected motion of the node to generate aged and moved second position data, and to determine a position of the node using both (i) the aged and moved second position data and (ii) the updated first position data.

11. A node according to claim 7 , wherein the processor is configured to determine the position of the node using both the aged second position data and the updated first position data by determining a geographic area comprising an intersection between the aged second position data and the updated first position data.

12. A method for determining a position of a node based on position data received from reference nodes, the method comprising:

receiving position data at the node from each of the reference nodes, wherein the position data from each node comprises position measurement information and a precision indicator;

generating a timestamp at the node for the position data from each node, and storing the position data and associated timestamps at the node;

determining, at the node upon receiving updated position data from one of the reference nodes, whether the node has received other updated position data from the other reference nodes;

generating, at the node, aged position data for each reference node that the node has not received updated position data from by decreasing the respective precision indicator of each aged position data for each reference node that the node has not received updated position data from as a function of an amount of time that has passed since a respective time indicated by the associated timestamp; and

determining a position of the node using both the aged position data and the updated position data.

13. A method according to claim 12 , further comprising:

determining, at the node, whether the node has moved since the time indicated by the timestamp associated with that stored precision indicator by detecting motion of the node; and

adjusting, when the node determines that the node has moved, a center position of the aged position data based on the detected motion of the node to generate aged and moved position data.

14. A method according to claim 13 , wherein the step of determining a position of the node, comprises:

determining a position of the node based on both of (i) the aged and moved position data and (ii) the updated position data.

15. A method according to claim 12 , wherein determining the position of the node using both the aged position data and the updated position data comprises determining a geographic area comprising an intersection between the aged position data and the updated position data.

16. A node, comprising:

a receiver designed to receive position data from different reference sources at different times, wherein the position data comprises: position measurement information and an associated precision indicator;

a memory designed to store the position data with an associated timestamp indicating a time at which the position data was received;

a processor designed to:

extrapolate the position measurement information based on the timestamp to generate extrapolated position data, wherein the extrapolated position data represents the stored position data extrapolated to a current time by (i) decreasing the associated precision indicator of at least one received position data as a function of an amount of time that has passed since a time indicated by the associated timestamp and (ii) adjusting a center position of at least one received position data as a function of a detected motion of the node; and

compute a position of the node based on the extrapolated position data.

17. The node according to claim 16 , wherein the processor is configured to compute the position of the extrapolated position data by determining a geographic area comprising an intersection between at least one extrapolated position data and at least one received position data.