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Re: Differences in tracking software



Chris,

Your answer is a good one, and from the differences I see, probable.

All should bear in mind the differences are minor, but compound into
requiring the operator to do some software gymnastics in some instances.

I use Station to control my rig and rotor for the analog birds.  It
appears to be most accurate for birds to the east.  I also run Logsat to
graphically track the bird.  It seems to be most accurate for birds to
the west.  I also run PocketSat on my PalmPilot so I can see where the
birds are located while I'm out and about.  NONE of them EVER show the
same statistics.  Earlier, I also loaded WINORBIT 3.5, and WISP on the
desktop, and Predict on my HP Palmtop.  That's 6 programs total.  NONE
agreed.

I have learned to "fool" all of the programs by stating my height to be
300 meters higher than I actually have antennas mounted.  This helps. 
Station will not predict a pass which is less that 3 degrees.  Logsat
will only predict at around 1 degree.  My antennas are in the clear, and
because I live on a peninsula with large bodies of water on each side, I
REGULARLY can work the birds at or below the horizon.  In fact, today I
worked the western pass of FO20, and talked to Jerry, W0SAT, when Logsat
showed the bird 2.2 degrees below and Station 3.5 degrees below the
horizon.

It probably goes against logical thinking, but ground effect, knife edge
propagation, and some tropo enhancement extend the range of satellites
to below the horizon.  Maybe the software authors will program
predictions to begin at a user selected horizon, INCLUDING negative
numbers!

Thanks for your thoughts Chris.

73, Mike in Fort Myers, FL



Chris Jackson wrote:
> 
> Depending on how far out they are, the differences may be explained by the
> orbit propagator used.  Most amateur programs (and many others) use a
> simplified version of the SGP4 propagator that doesn't account for many of
> the smaller disturbances.  This is generally fine for amateur use and if the
> keps are kept reasonably up to date there is very little difference in any
> case.  NORAD keps are designed to work with the full SGP4 model, and
> therefore the best answer will be obtained using a program that uses this
> model.

>                                        __\/__
>     |                              .  / ^  _ \  .
>     |                              |\| (o)(o) |/|
>     ^    ---   * -----------------.OOOo--oo--oOOO.------------------- *
>    |||   | |   * Mike Gilchrist - KF4FDJ ..... AMSAT Area Coordinator *
>    |X|   | |   * P.O. Box 763 ................ AMSAT  member   #31884 *
>    [X]~~~|k|   * Fort Myers, FL  33902 ....... ARRL  member  #1781549 *
>   /   \  |f|   * http://www.gate.net/~seven77  telephone 941.772.7907 *
>  |     | |4|   * kf4fdj@amsat.org ............................ EL96ap *
>  |  P  | |f|   * I.S. Professional ..... CNA .... Computer Consultant *
>  |  3  |=|d|   *   AO10, AO27, FO20, FO29, RS13, RS15, MIR, E Layer   *
>  |  D  | |j|   *    Bringing Oscar demos to the Lee County Schools.   *
>  |_____|=| |   * * * * * * * * * * * * * *  * * * * * * * * * * * * * *
>   /*X*\  | |   *  Black holes were created when God divided by zero.  *
>  ________|_|______________________________Oooo.________________________
>                                   .oooO   (   )
>                                   (   )    ) /
>                                    \ (    (_/
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-- 
                                       __\/__ 
    |                              .  / ^  _ \  . 
    |                              |\| (o)(o) |/|
    ^    ---   * -----------------.OOOo--oo--oOOO.------------------- *
   |||   | |   * Mike Gilchrist - KF4FDJ ..... AMSAT Area Coordinator *
   |X|   | |   * P.O. Box 763 ................ AMSAT  member   #31884 *
   [X]~~~|k|   * Fort Myers, FL  33902 ....... ARRL  member  #1781549 *
  /   \  |f|   * http://www.gate.net/~seven77  telephone 941.772.7907 *
 |     | |4|   * kf4fdj@amsat.org ............................ EL96ap *
 |  P  | |f|   * I.S. Professional ..... CNA .... Computer Consultant *
 |  3  |=|d|   *   AO10, AO27, FO20, FO29, RS13, RS15, MIR, E Layer   *
 |  D  | |j|   *    Bringing Oscar demos to the Lee County Schools.   *
 |_____|=| |   * * * * * * * * * * * * * *  * * * * * * * * * * * * * *
  /*X*\  | |   *  Black holes were created when God divided by zero.  *
 ________|_|______________________________Oooo.________________________ 
                                  .oooO   (   ) 
                                  (   )    ) / 
                                   \ (    (_/ 
                                    \_)
----
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To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



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