Abstract: In a surveying instrument including an instrument height measuring unit the instrument height measuring unit includes a light transmitting unit configured to emit light, a beam splitter configured to be incident with light emitted from the light transmitting unit, split the incident light into reference light and distance-measuring light, send the reference light to a reference light path, and send the distance-measuring light to a distance-measuring light path, a first light receiving unit configured to receive the reference light, a second light receiving unit configured to receive light being the distance-measuring light that has been emitted toward a position below the vertical axis of the surveying instrument main body and returned by being reflected by a distance-measuring object, and an arithmetic unit configured to calculate the instrument height based on a difference between light reception signals generated by the first light receiving unit and the second light receiving unit.

Abstract: A surveying instrument capable of irradiating a spotlight as visible light for centering toward a position below a vertical axis of a surveying instrument main body is configured such that that an irradiation shape of the spotlight is a toric shape. When visible light for centering which passes through a center point of the surveying instrument and is projected on a position right below the surveying instrument is projected in a toric shape having a hole opened at a center like a donut shape, both of an inner circle and an outer circle can be recognized, so that many guides are provided, and it is easier for a worker to align the toric shape with the target point than a point shape, so that the burden of a centering work on the worker is reduced.

Abstract: In a surveying instrument including an instrument height measuring unit configured to make a distance measurement by emitting distance-measuring light to a distance-measuring object below a vertical axis of a surveying instrument main body, and an arithmetic unit configured to calculate a distance to the distance-measuring object by analyzing light being the distance-measuring light that has returned by being reflected by the distance-measuring object, and calculate an instrument height, the instrument height measuring unit is configured to make a distance measurement by irradiating the distance-measuring light toward a predetermined region of the distance-measuring object centered on a point below the vertical axis of the surveying instrument main body, and the arithmetic unit is configured to calculate the instrument height by operating an average value of distance-measurement values in the region.

Abstract: A phase difference frequency generating method comprising: cutting out a reference signal, which is a continuous signal with a predetermined frequency, in a predetermined time and at a predetermined time interval by a signal for intermitting and creating a first intermittent signal, shifting the signal for intermitting by a time corresponding to ?/a (a=natural number) of a fundamental frequency of the reference signal, cutting out the reference signal in the predetermined time and at the predetermined time interval by the signal for intermitting as shifted and creating a second intermittent signal, and carrying out a restoration processing for restoring the second intermittent signal by a time as shifted.

Abstract: A phase difference frequency generating method comprising: cutting out a reference signal, which is a continuous signal with a predetermined frequency, in a predetermined time and at a predetermined time interval by a signal for intermitting and creating a first intermittent signal, shifting the signal for intermitting by a time corresponding to ?/a (a=natural number) of a fundamental frequency of the reference signal, cutting out the reference signal in the predetermined time and at the predetermined time interval by the signal for intermitting as shifted and creating a second intermittent signal, and carrying out a restoration processing for restoring the second intermittent signal by a time as shifted.