Cloud altimeter
The cloud altimeter is a device that is used on airfields to measure the cloud base.
The data obtained are used by the weather observer to create the current site weather. This information is made available to the air traffic control unit, which in turn can inform aircraft taking off and approaching about the measured cloud base. This gives the pilots an indication of the height from which entry into the clouds or the view of the earth can be expected.
Measurement method
Today laser cloud altimeters , so-called laser ceilographs, are mostly used for altitude measurement . Without a laser, the cloud base can be determined with a conventional ceilometer , consisting of a powerful headlight and a ground station, and with the help of trigonometry. However, this is only possible when it is cloudy or at night. A powerful headlight shines vertically upwards, the light spot on the underside of the cloud is measured by an observation station at a known distance from the headlight. The angle measured at the ground station between the horizontal and the line of sight to the light spot is used to calculate the height of the cloud base. It should be noted that the measurement is only carried out selectively. Since clouds rarely have an absolutely flat underside, an average value from several measurements is given as the cloud lower limit. The actual visibility conditions during an approach may differ.
Individual evidence
- ↑ Comprehensive documentation from the German Weather Service for determining the cloud base ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. (PDF; 371 kB)
