Trimble Navigation Limited

Peter Raby

Michael V McCusker

Stuart Riley

James L Sorden

Method and apparatus for synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, such as a GPS or GLONASS signal, that consists of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point, such as the preferred signal time of arrival. A first autocorrelation function AC,(&tgr;) is generated between the preferred, interference-free signal and a reference signal that replicates the preferred signal, as a function of the time shift &tgr; between the two signals. A second autocorrelation signal AC,(&tgr;) is measured between the reference signal and the incoming signal. Three amplitudes AC,(&tgr;,), AC,(&tgr;,) and AC,(&tgr;,) of the second autocorrelation function and the corresponding code phase time shift values &tgr;,, &tgr;,and &tgr;,are selected that satisfy at least one of the relations 0<&tgr;,&minus;&tgr;,&equals;f1&Dgr;&tgr;,and 0<&tgr;,&equals;f2&Dgr;&tgr;,, (0<f1, f2&lE;0.5). A shift PRC(t;j;rcv) in a pseudorange value associated with the incoming signal, measured at the user receiver, from at least one SATPS signal source, number j, is determined by a ratio of a first linear combination of the amplitudes AC,(&tgr;,), AC,(&tgr;,) and AC,(&tgr;,), multiplied by a selected parameter K&prime; and divided by a second linear combination of these amplitudes, plus a second selected parameter K&Prime;. The parameters K&prime; and K&Prime; are determined by examination of the first correlation function AC,(&tgr;) and are independent of the values AC,(&tgr;,), AC,(&tgr;,), AC,(&tgr;,), &tgr;,, &tgr;,and &tgr;,, but may depend upon the selected fractions f1 and f2, upon the SATPS satellite number j, upon the characteristics of the receiver, and upon one or more of the coefficients in the linear combinations.

Multipath compensation for pseudorange signals

A tilt predictor incorporated into a total station to predict the degree of tilt of the rotational alidade portion of a total station corresponding to the rotational orientation of the rotational alidade portion. In one embodiment, the present invention defines the plane of rotation for the rotational alidade portion with the rotational alidade portion disposed in a first rotational orientation. The rotational alidade portion is then rotated to the desired rotational orientation. This embodiment then predicts the degree of tilt of the rotational alidade portion at the desired rotational orientation.

Tilt prediction for total station

An audible signal generator incorporated into a total station to audibly indicate to the user the rotational orientation of the total station, and a method for using the audible indication to perform the tilt sensor calibration. In one embodiment, the present invention indicates to the user of the total station when the tilt sensor has been calibrated with the total station in a first rotational orientation. This embodiment then audibly indicates to the user when the rotational alidade portion of the total station has been rotated to a second rotational orientation. This embodiment then audibly indicates to the user when the tilt sensor has been calibrated with the total station in the second rotational orientation.

Audible tilt sensor calibration

An electronic distance meter comprises an integrated circuit from a GPS navigation receiver having a local pseudo-random number code generator for code demodulation that is connected to modulate either a polychromatic or a monochromatic light source. An optical system focuses the light on a distant target with an unknown range. Reflections from the distant target are focused on a light detector that produces a phase-delayed copy of the original pseudo-random number code. The time-of-flight to and back from the distant target is a function of the distance. The GPS receiver integrated circuit computes the range based on the code-phase delay to a precision better than one centimeter. The position of a remote target can be triangulated from several electronic distance meters each having known positions, e.g., determined by included GPS navigation receivers. Conversely, the position of a single electronic distance meter can be determined by triangulation by ranging to several remote targets each having known positions.

Code-space optical electronic distance meter

The present invention provides a method and apparatus for expediently determining the azimuthal orientation of a total station. In one embodiment, the present invention is comprised of a total station having a vertical axis. The total station also includes a rotational alidade portion adapted to rotate about the vertical axis, and an electronic distance measuring portion. The present invention also includes a satellite-based position determining system antenna coupled to the total station. In the present invention, the satellite-based position determining system antenna is offset from the vertical axis. That is, in the present invention, the satellite-based position determining system antenna is not disposed coincident with the vertical axis of the total station.

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London, United Kingdom

Peter Raby