Estimation of global position of a sensor node

• US 8,060,338 B2
• Filed: 02/04/2008
• Issued: 11/15/2011
• Est. Priority Date: 03/31/2005
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Damarla, Thyagaraju
• Primary Examiner(s): Lau; Tung S
• Application Number:
  US12/025,160
• Publication Number:
  US 20080228437A1
• Time in Patent Office: 1,380 Days
• Field of Search: 702/149
• US Class Current: 702/149
• CPC Class Codes: G01S 5/02213 Receivers arranged in a network for determining the position of a transmitter
• CPC Class Codes: G01S 5/0289 of multiple transceivers, e.g. in ad hoc networks
• CPC Class Codes: G01S 5/18 using ultrasonic, sonic, or infrasonic waves

Abstract

Methods and apparatuses for locating a sensor node are disclosed. A representative apparatus, among others, includes a processing unit that receives sensor node data and object trajectory information data for an object. The sensor node data is related to the object'"'"'s trajectory, and a data point in the object trajectory information data comprises a time stamp and the coordinates of a position. The position corresponds the location of the object at the given time. The processing unit is adapted to correlate at least a portion of the sensor node data with at least a portion of the object trajectory information data to determine an absolute position of the sensor node.

Claims

1. An apparatus for locating a non-GPS equipped stationary sensor node, said stationary sensor node having been haphazardly disbursed over a geographical area by a vehicle, the apparatus comprising:

a processing unit that receives stationary sensor node data and known source trajectory information data for a known source, wherein the stationary sensor node data includes but is not limited to normalized amplitude of the time domain data and is related to the trajectory information data of a known source, wherein a data, point in the trajectory information data thr a known source comprises a time stamp, which corresponds to a given time, and coordinates of the known source at the given time, wherein the processing unit is adapted to correlate at least a portion of the stationary sensor node data with at least a portion of the known source trajectory information data and the absolute position of the known source to determine an absolute position of the stationary sensor node,

said known source is a moving vehicle whose position at any given point is known and further comprises means for being detected by said stationary non-GPS equipped sensor node.

2. The apparatus of claim 1, wherein the non-GPS equipped stationary sensor node data includes a sensor node bearing angle, which is measured from a local reference axis to a ray extending from the stationary sensor node towards a given point, wherein the local reference axis is offset from a global reference axis by an offset angle, wherein the processing unit is adapted to synchronize the non-GPS equipped stationary sensor node data with the known source trajectory information data to eliminate the offset angle.

3. The apparatus of claim 1, wherein the processing unit is adapted to selectively exclude data points in the trajectory information data of the known source such that the portion of the trajectory information data that is correlated with the sensor node data is a subset of the entire trajectory information data.

4. The apparatus of claim 1, wherein the processor unit is adapted to determine a first estimate of the non-GPS equipped stationary sensor node coordinates, determine an offset angle using the first estimate of the sensor node coordinates, and determine a second estimate of the sensor node coordinates using the offset angle and at least a portion of the known source trajectory information data.

5. The apparatus of claim 1, wherein the processor unit is adapted to synchronize at least a second portion of non-GPS equipped stationary sensor node data with at least a second portion of the known source trajectory information data.

6. The apparatus of claim 1, further including:

a non-GPS equipped stationary sensor node that acquires data regarding the known source, wherein the sensor node is adapted to provide the sensor node data to the processing unit.

7. The apparatus of claim 2, wherein the processing unit is adapted to determine an estimate of the absolute position of the non-GPS equipped stationary sensor node using at least the difference in a pair of sensor node bearing angles and at least two data points included in the known source trajectory information data.

8. The apparatus of claim 3, wherein the processing unit excludes a data point of the trajectory information responsive to the data point corresponding to a first position that is less than a specific distance from a second position.

9. A program embodied in a non-transitory computer readable medium, the program comprising:

logic configured to receive known source trajectory information data for a moving vehicle whose absolute position is known at any given point, wherein the known source trajectory information data is collected over a first time span;

logic configured to receive sensor node data, wherein the sensor node data is acquired over a second normalized amplitude time span and is related to the object trajectory information data;

logic configured to determine several direction indicators, each direction indicator providing an approximate sensor node bearing from the non-GPS equipped stationary sensor node to the known source at given instant of time during the second normalized amplitude time span; and

logic configured to determine coordinates of the non-GPS equipped stationary sensor node using at least a portion of the collected trajectory information data and at least a portion of the acquired sensor node data.

10. The program of claim 9, wherein the trajectory information data includes multiple data points, each data point associates a specific instant of time with a position of the a moving vehicle whose position is known at any given point at the specific instant of time.

11. The program of claim 9, wherein the sensor node data includes multiple data points, further including logic configured to:

determine a first bearing angle for a first data point included in the trajectory information data;

determine a second bearing angle for a second data point included in the trajectory information data;

determine the difference between the first and second bearing angles;

determine whether the difference between the first and second bearing angles is greater than a predetermined amount; and

responsive to the difference being greater than the predetermined amount, determine not to use the second data point.

12. The program of claim 9, wherein the logic configured to determine coordinates of the sensor node further includes logic configured to:

determine a first estimate of the sensor node coordinates;

determine an offset angle using the first estimate of the sensor node coordinates;

determine a second estimate of the sensor node coordinates using the offset angle and trajectory information data.

13. The program of claim 9, wherein the logic configured to determine coordinates of the sensor node further includes logic configured to:

determine a first estimate of the sensor node coordinates;

determine a set of sensor node bearing angles from the sensor node data;

determine a set of object bearing angles using the first estimate of the sensor node coordinates and the trajectory information data;

define a grid about the first estimate of the sensor node coordinates;

determine for points on the grid the error between the set of sensor node hearing angles and the set of object bearing angles; and

determine a second estimate of the sensor node bearing angles based upon the determined errors.

14. The program of claim 10 wherein the logic configured to determine the coordinates further includes logic configured to:

choose a first data point from the trajectory information data and

selectively choose a second data point from the trajectory information data based upon a parameter and the first data point.

15. The program of claim 12, wherein the logic configured to determine a second estimate of the sensor node coordinates further includes logic configured to:

select data points of the trajectory information data in sets of points;

for each set of data points of the trajectory information data, use a set of data points of the trajectory information data to determine a third estimate of the sensor node coordinates; and

average the set of third estimates of the sensor node coordinates, wherein the average of the set of third estimates of the sensor node coordinates is the second estimate of the sensor node coordinates.

16. The program of claim 13, wherein the logic configured to determine a second estimate of the sensor node coordinates further includes logic configured to:

synchronize the sensor node data with the trajectory information data.

17. The program of claim 14, wherein the first data point is defined by a first position and a first time, the second data point is defined by a second position and a second time, the parameter corresponds to a specific distance, and the first and second positions are separated by a distance that is greater than the specific distance.