Boots – shoes – and leggings
Patent
1980-11-17
1983-12-06
Krass, Errol A.
Boots, shoes, and leggings
343 5W, 356 4, 364433, G01C 308, G06F 1548
Patent
active
044197314
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to apparatus for estimating the slant visibility in obscured atmospheres such as fog, falling snow and rain, and in particular for providing an indication for use by aircrew and air traffic controllers as to when, during an aircraft landing approach in fog conditions, the pilot is likely to be able to see the runway lights and a extent to which airport lighting pattern or marking will be capable of being viewed by the pilot as the runway approach progresses. The mode of development of this extent during the course, say, of an aircraft landing run, is called a visual sequence.
Hitherto operational measurements of low visibility for assisting air traffic control have almost always been made by human observers or instruments, such as transmissometers, close to the ground. These measurements are reported as `runway visual range`. This technique cannot usually give a reliable indication of any vertical element to visibility, and this vertical element has a profound effect upon what is called the slant visual range, that is for example, the distance an aircraft pilot can actually see when looking toward the ground, anywhere between directly below and the horizon. The ground measurement derived runway visual range then is used to estimate the probability of a landing success. The shortcomings of this ground measurement deviation method is that in the interest of safety, visual landing attempts are prohibited more often than might have really be necessary. This is because the majority of low visibility situations are those involving a deep mature fog or a low cloud, and since fog density increases with altitude (up to a relatively instantaneous ceiling), once a pilot has made visual contact with a runway lighting pattern he will be able to maintain it down to the landing. The ground measurement deviation method does not, of course, endeavour to imply any actual estimate either of the visual contact height or of the visual sequence. Moreover it can not made allowance for shallow, developing, dispersing or lifting fogs, which although being perhaps less prevalent than deep mature fogs are nevertheless frequently encountered.
Drawbacks also exist in the measuring technique per se. This has customarily comprised deploying transmissometers with horizontal measuring paths at a standard measuring height of 5 m above the ground (5 ft in the UK). Shallow ground radiation fog the ceiling of which is below transmissometer level will not be detected. A fog ceiling slightly above transmissometer level will result in an unduly severe fog indication and an unnecessary refusal being issued to the pilots of tall aircraft, (eg those where the cockpit is over 10 m from the ground). Furthermore a fog ceiling intermittently penetrating the measurement path of the instrument will result in large and quite illusory fluctuations of the reported values.
It will also be appreciated that there are, to say the least, constraints pertaining to the deployment in the vicinity of airfields of instrumentation operating at significant heights, especially heights where at instrumentation could be employed to simulate meaningfully slant visual range.
What has now been discovered is that by making a small number of slant or vertical measurements (typically three in number) from various heights to the ground sufficient information is available which by the judicious application of predetermined models of mean extinction coefficient profile allow estimation of the actual profile over a range of heights not less than that of the measurements with a useful accuracy. (Extinction coefficient (.sigma.) is the reciprocal of the distance over which light falls, due exclusively to obscuration, to 1/e times its original intensity.
Accordingly, in those circumstances where the fog or cloud extends considerably above the ground (several hundreds of feet) then the mean extinction coefficient profile in the bottom one hundred or so feet may be adequately described by the use of a polynomial of order two or less such that ##EQU1## where
REFERENCES:
patent: 3650627 (1972-03-01), Noxon
patent: 3702565 (1972-11-01), Moses et al.
"Opto-Electronics Signal Processing Techniques" Lasers for Measuring Slant Visual Range by E. T. Hill, pp. 35-35-9.
Krass Errol A.
The Secretary of State for Defence in Her Britannic Majesty's Go
LandOfFree
Apparatus for estimating slant visibility in fog does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus for estimating slant visibility in fog, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus for estimating slant visibility in fog will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2032704