[aprssig] Does GPS work in space ?

Wes johnston wes at kd4rdb.com
Sun Apr 23 08:42:46 CDT 2006

Yes and no.... 

Yes, with the proper GPS receiver.  "Da Rules" say that a gps unit can give position reports if it is >18Km (I forget the exact number) as long as it is not moving faster than 500m/s.  You can do one or the other, but not too high and not too fast at the same time.  So since it impossible to go into orbit at less than 17,000mph, when your garden variety GPS gets to 18Km altitude, it will stop reporting positions.  Note that most GPS manufacturers read the rules as EITHER 18km or 500m/s, hence there are MANY MANY gps units that won't go higher than 18k/m... the GPS18 from garmin interprets the rules correctly thrus is good for balloon use over 18km up.

PCSat has a GPS on board and for a while did report it's position because it had an exempted GPS receiver.  Even though it's in orbit, it's in a lower orbit than the GPS satellites, so they are still overhead relative to PCSAT.  

Anyone know if these rules apply to the new european gps system?

Does anyone know if the GPS system will work when a receiver it higher than the GPS satellites?  Seems like it should from a purely mathematical standpoint.

  ----- Original Message ----- 
  From: Andrew Rich 
  To: TAPR List 
  Sent: Sunday, April 23, 2006 5:44 AM
  Subject: [aprssig] Does GPS work in space ?

  Andrew Rich
  Amateur radio callsign VK4TEC
  email: vk4tec at tech-software.net
  web: http://www.tech-software.net
  Brisbane AUSTRALIA 


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