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[aprssig] aprs.fi web vs APRS-IS (was: WiFi APRS traveler)

Heikki Hannikainen hessu at hes.iki.fi
Sun Dec 12 11:19:23 UTC 2010


On Sat, 11 Dec 2010, Lynn W. Deffenbaugh (Mr) wrote:

> Isn't there something we should be aware of related to name-spaces between 
> the web-submitted position and positions received from APRS-IS for the same 
> callsign-SSID?  Aren't those actually two different stations on aprs.fi?  And 
> how can we tell one vs the other?

Right, they're different stations. There aren't SSIDs on the web, or in 
the AIS world, just on APRS.

The web-originated stations on aprs.fi have names, and random, unique ID 
numbers assigned to them by aprs.fi. The names do not need to be unique, 
so there can be multiple web stations named 'Lynn' or 'Joe'. The first 
'Joe' on aprs.fi doesn't get exclusive rights to show his name on the 
site. Links to these stations use the ID numbers, and a station class 
prefix 'w': http://aprs.fi/info/w/4225895793 is the web station "oh7lzb 
föni". The info page says it's "Web station oh7lzb föni" as opposed to 
"APRS station OH7LZB" or "APRS object Aurora" or "APRS item Foo". The 
"packet path" in the info balloon says "[aprs.fi via Web]" instead of 
something like "[APRS via via TRACE2-2,qAR,OH2KXH]".

AIS ships have unique MMSI numbers, assigned by the maritime / 
communications authorities. And names, which, again, are not unique at 
all. You can look them up by the MMSI number (which will always give you 
the correct ship) or by name (in which case you might end up picking one 
from a list, if there are many ships with that name). The links to these 
use the station class prefix 'i' and the MMSI number: 
http://aprs.fi/info/i/209627000 is just one of the ships named Aurora.

The APRS stations have their names and source callsigns. The object&item 
names and the APRS stations live in the same namespace, so there can be 
only one 'OH7LZB' which can be either an APRS station, an object or an 
item. These use the station class prefix 'a' with the name: 
http://aprs.fi/info/a/Aurora or http://aprs.fi/info/a/OH7LZB-9

You can still look up stations as before, by entering a callsign, or 
object / item name. If it's unique, the lookup will work as before. If 
the name isn't unique (it exists in multiple target classes), or if there 
are multiple stations having the same name (which is possible on the web 
and in AIS), you'll get a list of the stations to pick from: 
http://aprs.fi/info/Aurora

Old links pointing to aprs.fi, not having the class prefixes, work in the 
same way. If there are multiple matches for the same name, you get a list 
to pick from. http://aprs.fi/info/OH7LZB-9 or http://aprs.fi/OH7LZB-9 will 
work directly, since the name is unique.

http://blog.aprs.fi/2010/07/class-based-links-transmit-rate-advisor.html

   - Hessu


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