# RE: Compute Elevation

Lance -

Let me give you some insight as to how we handle this problem in software
used by the Air Force Satellite Control Network (AFSCN) and others -- I am a
consultant for a company located in your neck of the woods.

What we have is an "Obscura" table for each of the Remote Tracking Sites
(RTSs) -- a single site would be analogous to your antenna farm.  An obscura
table is a discrete listing (from 0 to 359 degrees of Azimuth in one degree
increments) of the minimum unobscured elevation for the particular site.
The rough visibility computations are performed using the lowest unobscured
elevation to get the approximate horizon break time.  These times are then
adjusted the obscura Elevation corresponding to the Azimuth of the horizon
break.  This is perhaps more elaborate than you might want to code into your
software.

There are more elegant ways I've developed if you don't need a precise
answer and have only a few blocking obstructions.

73, Ken N2WWD
n2wwd@amsat.org

-----Original Message-----
From: owner-AMSAT-BB@amsat.org [mailto:owner-AMSAT-BB@amsat.org]On
Behalf Of Murphy, Lance
Sent: Friday, August 09, 2002 12:26 PM
To: 'amsat-bb@AMSAT.Org'
Subject: [amsat-bb] Compute Elevation

Hello all,
I have been using Satscape to track the birds. So the info I have found out
I am surrounded by mountains.( I knew this with out Satscape <grin>) I have
calculated by using the sun and some of the birds that my
minimum horizon is between 18-25 deg. I am lucky from azimuth 170-230 it
goes down to 8 deg. So what I am
looking for is away to figure out the time and how long the birds are above
these minimums. I also live in a town house
which makes planning for my antenna farm more fun. I was able to copy
signals last night on AO-10 with my new Kenwood
TS-2000 and my Diamond GP-6. I live on the coast in Pacifica Ca, 12 miles
south of San Francisco.
Lance Murphy
KG6DSN

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