US 6,182,372 B2 · Interpolation using digital means for range findings in a total station

Abstract

A distance interpolator incorporated into a total station and a method for digitally interpolating a distance measurement from the total station to a target, such that the distance interpolator measures the distance from the total station to the target using primarily digital electronics and statistical analysis. In one embodiment, the total station transmits an energy pulse from the electronic distance measuring portion of the total station, with the energy pulse directed at the target. This embodiment then receives at the electronic distance measuring portion the energy pulse reflected from the target. This embodiment also contains a reference oscillator and digital counter, which counts the number of reference oscillator clock pulses that elapse from the time the energy pulse is transmitted to the time the reflection of the energy pulse is received. This embodiment further accumulates counts for a number of additional energy pulses, and then calculates the average value of the counts over all energy pulses transmitted. This embodiment then calculates the distance between the total station and the target using the average value of the counts, the frequency of the reference oscillator, and the speed of light in the environment in which the counts were obtained.

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Drawings

Claims17

Dependent claims

A measurement apparatus comprising:

a total station, said total station further comprising:
a rotational alidade portion,
an electronic distance measuring portion coupled to said rotational alidade portion, said electronic distance measuring portion adapted to transmit an energy pulse directed at a target and to receive said energy pulse reflected from said target,
a distance interpolator coupled to said electronic distance measuring portion, said distance interpolator adapted to digitally interpolate between distance measurements obtained using said total station such that said total station more precisely measures distance from said total station to said target, and
a reference oscillator coupled to said electronic distance measuring portion, said reference oscillator adapted to generate a plurality of clock pulses independent of said energy pulse, wherein said plurality of clock pulses are for measuring time of flight of said energy pulse.

2 more elements

In a total station, a method for digitally interpolating a distance measurement from a total station to a target such that said total station more precisely measures distance from said total station to said target, said method comprising the steps of:

a) transmitting an energy pulse from an electronic distance measuring portion of said total station, said energy pulse directed at said target;
b) receiving at said electronic distance measuring portion said energy pulse reflected from said target;
c) generating a plurality of clock pulses, said plurality of clock pulses generated by a reference oscillator, wherein said plurality of clock pulses are generated independent of said energy pulse, and wherein said plurality of clock pulses are for measuring time of flight of said energy pulse;
d) determining a count of said plurality of clock pulses between a start time when said count of said plurality of clock pulses is to start, and a stop time when said count of said plurality of clock pulses is to stop, said start time and said stop time corresponding to said energy pulse;
e) determining said count of said plurality of clock pulses between said start time and said stop time for each of a selected number of different energy pulses;
and
f) calculating the mean of said count of said plurality of clock pulses for said selected number of different energy pulses.

4 more elements

Dependencies are inferred from the claim text.

Description3,563 words

Summary751 words

#The present invention relates to survey instrumentation. In particular, the present invention pertains to a total station.

#Modern total stations are typically required to electronically measure distances with an accuracy of five (5) mm or better. One method used to measure these distances is the time-of-flight method, where a short (<10 nano-seconds) pulse of light is emitted by the instrument, and a careful measurement is made of the time-of-flight between when the pulse leaves the instrument and when an echo pulse is received from the object to be measured.

#The speed of light (which is 3×10{circumflex over ( )}8 meters/second), coupled with the desire to measure distances to within 5 mm, leads to a requirement that the time-of-flight be measured with a precision of less than 40 pico-seconds. This, in turn, leads to a requirement in the hardware to either have a temperature-stable, precision reference oscillator with a frequency of 25 gigahertz (which is currently not practical), or a method of interpolating between the clock pulses of a slower reference oscillator.

Brief description of the drawings6 figures

#The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention:

#FIG. 1 is an illustration of a method for measuring time-of-flight of an energy pulse in accordance with a prior art total station.

#FIG. 2 is a perspective view of a total station in accordance with one embodiment of the present invention.

Detailed description2,649 words

#Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be obvious to one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present invention.

#With reference now to FIG. 2, a perspective view of one embodiment of a total station used in accordance with the present invention is shown. Total station 200 is comprised of base portion 206, rotational alidade portion 208, and electronic distance measuring portion 210. Rotational alidade portion 208 rotates on base portion 206 about the vertical central axis represented by arrows 212a and 212b. That is, rotational alidade portion 208 is able to rotate 360 degrees on base 206.

#Electronic distance measuring portion 210 then rotates within rotational alidade portion 208 about a horizontal axis represented by arrows 211a and 211b. Given the rotation of the electronic distance measuring portion 210 around axis 211 and the rotation of rotational alidade portion 208 around axis 212, it is possible to point electronic distance measuring portion 210 at any target so that the distance between the instrument and the target can be measured.

Facts

Application

09/139,535Filed 25 Aug 1998

Granted

6 Feb 2001

Term ended

25 Aug 2018

Estimated · how

20 years from earliest known nonprovisional domestic filing. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination. Patent term adjustment is unavailable; no adjustment was added.

Classification2 codes

G01C 1/02
Measuring angles: theodolites
G01C
Measuring distances, levels or bearings

Description3,563 words

Summary751 words

#The present invention relates to survey instrumentation. In particular, the present invention pertains to a total station.

Brief description of the drawings6 figures

#FIG. 1 is an illustration of a method for measuring time-of-flight of an energy pulse in accordance with a prior art total station.

#FIG. 2 is a perspective view of a total station in accordance with one embodiment of the present invention.

Detailed description2,649 words

Interpolation using digital means for range findings in a total station

Life of this patent

Interpolation using digital means for range findings in a total station

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims17

Description3,563 words

Drawings

Classification2 codes

Life of this patent

Description3,563 words