Method for measuring heliostats, and method for calibrating heliostats

A method for measuring heliostats in a heliostat field that has a plurality of heliostats and is part of a solar tower power plant that has a solar tower, the heliostats each having at least one reflector having a mirror surface, said method comprising the following steps:

• a) providing a light source;
• b) aligning at least some heliostats to be measured in order to reflect light from the light source onto a predefined target point or target area in the sky or in the vicinity of the solar tower;
• c) moving a flying apparatus having at least one camera along a predefined flight pattern around and over the target point or target area, and simultaneously capturing images of one of the one or more heliostats to be measured by the camera at a predefined time interval;
• d) evaluating the images, wherein, for each of the heliostats to be measured in at least some of the images, it is determined whether light from the light source has been reflected into the camera, and wherein a virtual target is calculated from the images by a previously determined or stored capturing position of the corresponding image, wherein the focal point for each heliostat to be measured is determined on the virtual target;
• and
• e) determining, by the focal point on the virtual target, a target vector of each of the heliostats to be measured and comparing it with a target value in order to determine a target/actual deviation,
• wherein at least steps a) to c) are carried out at a time with low solar radiation or at night.