1. A measuring method for performing monitoring measurement on a plurality of objects to be measured by a measuring instrument, which comprises a telescope for performing sighting on the objects to be measured, a distance measuring unit for measuring a distance to each of the objects to be measured by projecting a distance measuring light through said telescope, an image pickup unit for taking an image in sighting direction and for acquiring a digital image, angle detecting units for detecting a vertical angle and a horizontal angle in the sighting direction of said telescope, and an automatic sighting unit for making said telescope perform automatic sighting to the objects to be measured, comprising a step of rotating said telescope in horizontal direction and in vertical direction and of scanning over a predetermined range as set so that a plurality of objects to be measured are included, a step of acquiring digital images with a predetermined time interval in the process of scanning, a coarse measuring step of detecting the objects to be measured in said digital image and of calculating a vertical angle and a horizontal angle of each of the objects to be measured based on a deviation of the objects to be measured on said digital image from sighting axis, and also, based on the results of detection from said angle detecting unit, and a step of associating said calculated vertical and horizontal angles with each of the objects to be measured and of storing the vertical and horizontal angles as target values for automatic sighting.