Self-calibrating electronic distance measurement instrument

• US 6,614,395 B2
• Filed: 05/20/2002
• Issued: 09/02/2003
• Est. Priority Date: 07/24/1998
• Status: Expired due to Term

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: McCusker, Michael V., Talbot, Nicholas C.
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US10/153,201
• Publication Number:
  US 20020135509A1
• Time in Patent Office: 470 Days
• Field of Search: 342/357.17, 342/357.14, 342/127, 342/357.12, 356/5.1, 331/25
• US Class Current: 342/357.31
• CPC Class Codes: G01C 15/002 Active optical surveying means optical plumbing G01C15/105
• CPC Class Codes: G01S 17/86 Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
• CPC Class Codes: G01S 19/14 specially adapted for specific applications
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain
• CPC Class Codes: G01S 7/4021 of receivers
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

A combined satellite positioning and electro-optical total station system includes a reference oscillator that provides local oscillator signals for a satellite navigation receiver and a precision frequency source for use by an electronic distance meter. When the satellite navigation receiver is locked onto and tracking orbiting navigation satellites, the highly precise cesium-rubidium clocks in the navigation satellite system can be used as standards to control the reference oscillator in the combined satellite positioning and electro-optical total station system. Baseline measurements made by the electronic distance meter are therefore not subject to mis-calibrations and drift as long as the satellite navigation receiver is locked onto and tracking the orbiting navigation satellites.

Claims

1. A combined satellite positioning and electro-optical total station system in which the total station is automatically and precisely calibrated, comprising:

a global positioning system receiver including a navigation computer configured to receive a navigation message and a PRN-code measurement and to determine carrier phase and frequency of at least one satellite signal, a local reference oscillator for generating a signal that is referenced to the phase of at least one cesium-rubidium clock on board a satellite in the GPS satellite system, said reference oscillator providing a precision reference frequency and oscillator control to an electronic distance measurement system (EDM) to automatically and precisely calibrate said EDM;

an electronic distance measurement (EDM) system with a phase measurement subsystem connected to a transmitter for sending an out-bound signal through a telescope to a distant target, and adapted to receive back an in-bound signal through said telescope, and adapted to use said precision reference frequency to conduct at least one of pulse time-of-flight and carrier phase measurements to determine a line-of-sight distance to said distant target, wherein said reference oscillator provides a time base accuracy for said distance measurement comparable to the accuracy of the cesium-rubidium clock on at least one GPS satellite.

2. The system of claim 1, further comprising:

a theodolite in which said telescope is mounted to an angle measurement instrument connected to a servo actuator, and that receives a space-vector-to-target signal computed by the navigation computer from a target position seed input, and providing for target signal commands to said servo that can move said telescope to be pointed at said distant target;

wherein, said target location seed is computed using differential satellite position calculations.

3. A combined satellite positioning and electro-optical total station system in which the total station is automatically and precisely calibrated, comprising:

a global positioning system receiver including a navigation computer configured to receive a navigation message and a PRN-code measurement, and providing a local oscillator signal that is referenced to the frequency and phase of a cesium-rubidium clock on board a satellite in the GPS satellite system, the computer further providing a three-dimensional position reading of the system;

an electronic distance measurement (EDM) phase measurement subsystem connected to the computer to receive said local oscillator signal and automatically and precisely calibrate the time base of the EDM, the EDM connected to a transmitter for sending an out-bound signal through a telescope to a distant target, and connected to receive back an in-bound signal through said telescope, and adapted to use at least one of pulse time-of-flight and carrier phase measurements to determine a line-of-sight distance to said target; and

a target range measurement output connected to the EDM phase measurement subsystem and adapted to provide time-of-flight data information related to said line-of-sight distance to said distant target;

wherein, the navigation computer computes the three-dimensional position of the system based on said code measurement, said time measurement and said navigation message and once said position is determined only one satellite is required to calibrate the time base of the EDM; and

wherein said local oscillator signal provides a time base accuracy for said EDM comparable to the one GPS satellite.

4. The system of claim 3, further comprising:

a radio receiver connected to receive a radio transmission from other than a GPS satellite, and which radio transmission includes a precise and stable transmitted signal that is used to train the reference oscillator during periods the navigation computer is not able to directly track GPS transmissions.