Patent ID: 8798319

Claim:
A method for verifying a surveying instrument's external orientation during a measurement process, wherein the surveying instrument is at least provided with imaging means and angle measurement means for detecting an internal photographing direction of the imaging means relative to a base of the surveying instrument, the method comprising the initialization steps of: directing the imaging means onto a reference object and detecting a first photographing direction of the imaging means; taking a first image of the reference object in the first photographing direction; memorizing the first image and the first photographing direction as being indicative of the surveying instrument's external orientation, and in a proceeded state of the measurement process the further, verifying steps of: re-directing the imaging means onto the reference object and detecting a second photographing direction of the imaging means; taking a second image of the reference object in the second photographing direction; and comparing a first with a second imaged position of the reference object in the first respectively the second image by image processing as well as the first with the second photographing direction and verifying the surveying instrument's external orientation based on disparities between the first and the second imaged position and/or between the first and the second photographing direction, wherein the surveying instrument comprises a telescope defining an aiming-axis and having integrated the imaging means, wherein crosshairs are superimposable indicating the aiming-axis in the image; and the predetermined area is defined around the crosshairs in the first image as the template and the centre of the crosshairs representing the aiming-axis in the first image is set as a reference point of the template; the template is matched within the second image; and a pixel offset between: the position of the centre of the crosshairs in the second image; and the position of the reference point of the matched template in the second image, is determined indicative of a disorientation of the surveying instrument.