foresight-¹A point to which an instrument sighting is made for measuring or establishing its elevation and/or its horizontal position. ² For leveling the foresight is the visual intersection of the horizontal cross hair of du instrument with the foresight point or with a staff or rod held vertically over or under the foresight point when the instrument line of sight is level or when the vertical angle of the instrument line of sight is known or will become known from actual measurement. ³ For angle measuring or line prolongation, the foresight is the angle measurement on the graduate (horizontal circle of the instrument (set or to be read and recorded) when the vertical cross hair of the instrument is visually coinciding with the foresight point or with a marker in the vertical plane through the foresight point and the center of the instrument.

foresight, extra [LEVELING]—The rod measurement made at an instrument station in a line of levels and on a leveling rod standing on a bench marl or another point not in the continuous line of levels. In spirit leveling there may be one or more extra foresights from a single instrument station or setup, but there can be only one backsight and one foresight from any one instrument station.

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Source: NSPS “Definitions of Surveying and Related Terms“, used with permission.

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