Patent Application
20130214975
The present invention in general relates to location measurement, and in particular to a device for providing spot location measurements of objects.
The Global Positioning System (GPS) is based on the fixed location base stations and the measurement of time-of-flight of accurately synchronized station signature transmissions. The base stations for the GPS are satellites and require atomic clocks for synchronization.
GPS has several draw backs including relatively weak signals that do not penetrate heavy ground cover and/or man made structures. Furthermore, the weak signals require a sensitive receiver. GPS also utilizes a single or narrow band of frequencies that are relatively easy to block or otherwise jam, and can easily reflect to surfaces, resulting in multi-path errors. The accuracy of the GPS system relies heavily on the use of atomic clocks, which are expensive to make and operate.
U.S. Pat. No. 7,403,783 entitled “Navigation System,” herein incorporated in its entirety by reference, improves the responsiveness and robustness of location tracking provided by GPS triangulation, by determining the location of a target unit (TU) in terrestrial ad hoc, and mobile networks. The method disclosed in U.S. Pat. No. 7,403,783 includes initializing a network of at least three base stations (BS) to determine their relative location to each other in a coordinate system. The target then measures the time of difference arrival of at least one signal from each of three base stations. From the time difference of arrival of signals from the base stations, the location of the target on the coordinate system can be calculated directly. Furthermore, the use of high frequency ultra-wide bandwidth (UWB) wireless signals provide for a more robust location measurement that penetrates through objects including buildings, ground cover, weather elements, etc., more readily than other narrower bandwidth signals such as the GPS. This makes UWB advantageous for non-line-of-sights measurements, and less susceptible to multipath and canopy problems. While existing RF (radio frequency) position tracking systems can determine the location of an antenna within a tracking space, this position is different from the location of the antenna that is in communication with the tracking devices.
However, it may be necessary to determine the relative position or distance of certain locations within an area of operation, or on an object of interest. If the area of operation or the object of interest is indoors, then GPS coordinates may not be available. In other cases, the locating device may be a sensor or a probe that has to be placed in close proximity to the location of interest, and there is no space available for the antenna to measure the location.
Thus, there exists a need for a device and method for providing spot location measurements of objects that are not readily accessible. Furthermore, it would also be advantageous to have a spot measurement system that overcomes the limitations of GPS technology. There also exists as need for the ability to known the exact location of a specific spot on the tracking module, which is not the same as the antenna position.
An inventive precision pinpoint tracking method and system is provided for devices that provide spot location measurements of objects. Embodiments of the location measuring device have a RF antenna, a tracking module in electrical communication with the RF antenna, and a tilt-compensated (TC) compass. In embodiments of the location measuring device, a measuring tip is offset at a distal end from the tracking module and the RF antenna is located at the proximal end of the tracking module. In embodiments, the TC compass provides data to calculate a translation of the position of the measuring tip with respect to the RF antenna to enable spot measurements of locations of a target object.
The tracking module, of embodiments of the location measuring device, includes in some embodiments at least one additional components of a three-dimensional (3D) accelerometer, a 3D compass, a 3D Gyroscopic sensors, a rechargeable battery, and microcontroller with software. The target location tracking module may also, in specific embodiments, a user interface capabilities such as a display, LED indicators, buttons, or an audio speaker.
In certain, the measuring tip of the location measuring device may be mounted on the end of an extending wand or telescopic extension, or the measuring tip may be formed with the crosshair intersection of two laser beams emanating from the inventive locating device.
An inventive precision pinpoint tracking method and device has utility in spot location measurements of objects. Embodiments of the inventive system may include a radiofrequency (RF) position tracking system, such as the tracking system disclosed in U.S. Pat. No. 7,403,783 with a target location tracking module that includes antenna, 3D accelerometer, 3D compass, 3D Gyroscopic sensors, a rechargeable battery, and microcontroller with software. The target location tracking module in some embodiments include user interface capabilities such as a display, LED indicators, buttons, or an audio speaker.
Existing RF (radio frequency) position tracking systems can determine the location of an antenna within a tracking space. However, it is often desirable to know the exact location of a specific location on the tracking module, which is different from the location of the antenna that is in communication with the tracking devices. In embodiments, the antenna of a tracking module is attached to a handheld device with a locating tip mounted on the end of an extending wand or telescopic extension. The tip of the device to then positioned at a reference location from which the 2D/3D position is measured. In this case, the device may be a sensor or a probe that has to be placed in close proximity to the location of measurement interest, and there is no space available for the antenna to measure the location. Furthermore, in order to acquire good radio signal from the antenna, such that good quality range measurements are collected, it is typically desirable to have clearance around the antenna, away from surfaces and objects. The antenna and tracking module can then be placed at an offset from the sensor or probe, and the translation from the antenna to the tip of the sensor or probe are in certain embodiments used to determine the location.
In another embodiment, the measurement tip is formed with the crosshair intersection of two laser beams emanating from the inventive locating device. The use of laser beams can serve as the pin-point measurement tip for the position tracking device when the desired measurement location is behind an optically transparent barrier such as glass; too far away to reach with the wand or telescopic extension absent cantilevered deformation; at an extreme condition as to a variable such as heat, radiation, cleanliness or combination thereof; or certain locations that may not be easily reachable or accessible. The angles of the laser beams are amenable to being dynamically adjusted to extend the crosshair that indicates the measuring tip.
In certain other embodiments, the tracking module first calculates the position of the antenna with RF tracking in a network, and subsequently calculates the position of the pointing tip by adding the translation from the antenna to the tip, translated in space by the roll, pitch and heading. The roll, pitch, and heading are measured with the 3D accelerometer, and 3D compass (3D magnetic sensors), configured as a tilt-compensated (TC) compass. A tilt compensated Compass is a device that can measure an object's horizontal orientation (i.e., direction within Earth's magnetic field) for any arbitrary orientation of that object in the vertical field (i.e., roll and pitch). In other words, for any forward or sideways rotation, a TC device will calculate the heading relative to the North Pole. The ability to acquire roll and pitch angles relative to gravity, and heading angle relative to earth magnetics' field are conventional knowledge as detailed for instance in AN3192 by STMicroelectronics. In instances where the reference frame of the RF position tracking system is orientated with a known orientation in the global coordinate system, then the heading from the TC compass can be related to the orientation within the RF reference frame. In general, the RF position tracking system in certain inventive embodiments is not related to the global coordinate system, but to an ad-hoc system of locating base stations, and a calibration procedure takes place to correlate the TC compass measurement to the orientation within the reference frame of the RF positioning system.
In other inventive embodiments, the translation from the antenna to the measuring tip of the tracking device must be known accurately and in the proper orientation to properly determine the location of an object or point in space. It is appreciated that the translation can be described in various coordinate systems, with the choice being often dictated by ease of computation or interface with other components or devices. These coordinate systems in 3D illustratively include Cartesian coordinates (x, y, z) spherical coordinates (azimuth, elevation, distance), or cylindrical coordinates (azimuth, elevation, z).
In certain inventive embodiments the device integrates the use of the TC compass with RF position tracking systems. As a result, with a relatively simple calibration process that integrates operation of these two different and unrelated systems that would otherwise operate in separate coordinate reference frames, to now provide accurate position tracking.
Calibration of the inventive location measurement device is readily accomplished by manually entering translation vectors for offsetting the location of the measuring tip, or by the following calibration sequence:
The translation distance may be expressed by the mathematical formulation as follows:
Where α is the roll, φ is the pitch, θ and is the yaw.
Referring now to
The orientation information of the handheld location measurement device 10 can now be used to enhance the accuracy of the RF position tracking system, depending on the operating scenario. Since the orientation of the handheld location measurement device 10 is typically associated with the location of the object or surface to be measured, it is possible to derive a reasonable estimation of the relative location of the object or surface to be measured relative to the handheld location measurement device 10. Depending on the material properties of the object or surface, it may be desirable to eliminate any range measurements that were acquired in the direction of the object or surface, since these measurements are likely to be non-line-of-sight, and therefore less accurate in terms of range determination. For example, it will be more likely that a range measurement was determined from an indirect path rather than the direct path, if the object or surface is opaque to the frequencies that are used by the RF position tracking system. With the knowledge of the current orientation and position, and with knowledge of the beacon locations for tracking, the system will be able to determine the direction of each of the range measurements to each of the beacons, and add a level of confidence to each of the measurements, depending on the reasonable estimation of the relative location of the object or surface to the handheld location measurement device.
The foregoing description is illustrative of particular embodiments of the invention, but is not meant to be a limitation upon the practice thereof. The following claims, including all equivalents thereof, are intended to define the scope of the invention.
This application is a non-provisional application that claims priority benefit of U.S. Provisional Application Ser. No. 61/541,529, filed Sep. 30, 2011 the contents of which are hereby incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61541529 | Sep 2011 | US |
