Thursday, November 24, 2016

Tracking birds with 5 radars from 200 m and up suggests flat earth model

To know where birds are the KNMI has developed a method using 5 radars in the Nederlands and Belgium, so that they scan from 200 m till 1,6 km (first layer, divided in layers of 100 m). Second layer is from 1,6 km and up. This is actually a very useful tool, so that birds can be avoided by planes. So how does this registration of birds go on a globe or a flat earth as the radar beam can only go in a straight , and what kind of conclusion can we make out of these facts?

5 Radars used

For the Nederlands they used Radar ID 6234 Den Helder and Radar ID 6260 De Bilt and for Belgium Radar ID 6410 Jabbeke, Radar ID 6451 Zaventem and Radar ID 6477 Wideumont (1).


Principles of a radar on a globe

A big problem for radars on a globe is that they can only register what is above their line of sight. For-instance if the radar is approximately 50 m high, their line of sight crosses the horizon at (6371050^2-6371000^2)^91/2) = 25,2 km. From that point on the radar cannot see what is below their line of sight, behind the horizon. In that case for more information they will need to use other radars as well. A high grid of radars would be required.

Radar on a flat earth

If a radar is located on a flat earth, it would work the best. Beams from the radar are send out and come back with the required information on weather, planes and in this case birds. As the radar beam goes in a straight line and comes back it can give much information from ground-level to several km high. A low grid of radars is needed.

Radar Den Helder and bird tracking near Eemshaven

For the Nederlands and Belgium they have full coverage of the 2 lands and can track all the birds from 200 m and up (2). If we for-instance look at Eemshaven, it is located at 148,4 km (3) from the nearest radar being Den Helder. With a horizon distance for the approximately 50 m high radar of 25,2 km, the earth still would over 148,4-25,2 = 123,2 km have a curvature drop of: (6371^2+123,2^2)^(1/2)-6371 = 1,19 km. As the radar beam cannot turn and see over the curvature, how come you can see bird-movement from 200-1600 m in source (4) whilst at Eemshaven you can only see birds above 1,19 km height. This would be on a globe an impossibility as radar beams go in a straight line, so you cannot see over the horizon. Unless it isn't a globe model, but a flat earth model. You judge for yourself, but this surely suggests a flat plane.

Sources:
(1) https://github.com/enram/case-study/blob/master/data/radars/radars.geojson
(2) https://github.com/enram/case-study/tree/master/data/bird-migration-altitude-profiles
(3) http://www.afstand-berekenen.com/zoeken?from=den+helder&to=Eemshaven%2C+Netherlands
(4) http://enram.github.io/bird-migration-flow-visualization/viz/2/nl-be/

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