>
> If you are using the calculator within Windows, for example, you
will see a
> button for COS and also another for INV. If you want the arccos, ie. the
inverse of
> the cosine, enter your value, hit the INV box to check it off and then hit
COS.
>
Mathematically, arccos returns a value in radians = 180 degrees / PI() =
57.29578
The formula given assumes it is returned in degrees, which is the default in
Windows' Calc, but not in Excel and other programming systems - be careful
about that (also you should select menu View / Scientific to SEE the
functions - in Standard cos and arccos can be used by TYPING o and io)
Anthony also asked 'at what altitude is the object '- this formula is for 0
degrees, on (see-level) horizon.
To find the ground range for another value, use the same formula for another
Earth radius, then subtract the distance corresponding to the elevation you
want (a).
With R=6371 km and a in degrees:
DIST = R * {arccos[cos(a)*R/(R+HEIGHT)] / 57.29578} - a * R / 57.29578
assuming your calculator works completely in degrees. If using radians, use
DIST = R * arccos[cos(a / 57.29578)*R/(R+HEIGHT)] - a * R / 57.29578
With HEIGHT = 200 km, this gives for
a=0 DIST=1576
a=5 DIST =1113
a=10 DIST = 810 ...
a=85 DIST = 17
-----------------------------------------------------------------
Unsubscribe from SeeSat-L by sending a message with 'unsubscribe'
in the SUBJECT to SeeSat-L-request@lists.satellite.eu.org
http://www2.satellite.eu.org/seesat/seesatindex.html
This archive was generated by hypermail 2b29 : Tue May 01 2001 - 01:24:21 PDT