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To compute the greatest distance D BL at which an observer B can see the top of an object L above the horizon, simply add the distances to the horizon from each of the two points: D BL = D B + D L For example, for an observer B with a height of h B =1.70 m standing on the ground, the horizon is D B =4.65 km away.
When the prevailing visibility is less than 4 miles, or goes from less than 4 miles to four miles or greater, tower personnel are required to take a prevailing visibility reading. If this reading differs from the ground reading (i.e., different readings for different heights ), the lower value of the two is used for aircraft operations.
By subtracting this from 90°, he would find that the zenith distance is 90°, which is his latitude. Observer C at the same time is at latitude 20°N on the same meridian, i.e. on the same longitude as Observer A. His measured altitude would be 70°, and subtracting this from 90° gives a 20° zenith distance, which in turn is his latitude. In ...
This is worked out by applying the distance from that position either by log or by the estimated speed over time with the course steered. A sight is taken, that is the distance above the horizon of a heavenly object, in this case nearly always the sun, is measured with a sextant and the exact time noted in UTC. The sextant angle obtained is ...
Azimuth is measured eastward from the north point (sometimes from the south point) of the horizon; altitude is the angle above the horizon. The horizontal coordinate system is a celestial coordinate system that uses the observer's local horizon as the fundamental plane to define two angles of a spherical coordinate system: altitude and azimuth.
The effect of progressively shifting Sun angle on the appearance of a vista as seen from Canyonlands National Park. In each image air quality is the same. 1, 2 – represents a moment after sunrise; 3, 4 – a vista around noon, when the angular distance to the Sun is the biggest, hence visibility is the best (Malm, 2016).
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In navigation the instrument is also called a cross-staff and was used to determine angles, for instance the angle between the horizon and Polaris or the sun to determine a vessel's latitude, or the angle between the top and bottom of an object to determine the distance to said object if its height is known, or the height of the object if its distance is known, or the horizontal angle between ...