[aprssig] Draft Copy of Thesis on APRS - Thoughts

WD8ARZ wd8arz at ix.netcom.com
Tue Dec 9 19:20:43 EST 2014

Just a minor note in case this information fits in with your project 

It is easy to accept an APRS position on a map as a given. That is that 
it is in fact valid information from the GPS data stream. However there 
are circumstances where that can be questionable. At times solar events 
can disrupt the GPS signal causing loss in accuracy. Users can also 
configure their gps units to intentionally not provide as accurate 
information as it is possible to do while they are mobile.

Many hardware APRS radios and APRS programs allows for truncating the 
last few digits of the Lat / Lon coordinates data so as to not provide 
exact coordinates even while providing real time data streams. The real 
location of the moving APRS symbol on the map could be some distance 
away. Frequently when I am out and about and using APRS, I choose 
settings that restricts the last several digits of the Lat / Long data 
so my exact location is not discernible. This is to protect my vehicle 
from theft of my gear while I am away from it at various stops. But it 
also allows me to use the benefits of APRS to communicate with other 
APRS users.  When I am on a trip I frequently allow exact GPS 
coordinates to appear as I am a moving target anyway ..... but at those 
times I dont turn on aprs when at my home, place of work, stopped for 
gas or a rest stop, or at my intended destination.

It is also possible for the user to put in manual location data that has 
nothing to do with their location at all .... even show up out of the 
country .....

Today I noticed that my APRS call sign shows me in a drive way at home 
that appears as if I live there. Actually I did a U turn and turned off 
my APRS before heading home and didnt realize it had beaconed in that 
drive way ...... also having our APRS station relayed to the network 
isnt one hundred percent .... there will be gaps.

Another concern is that many hams have their real home address listed 
with their amateur radio call signs in public internet databases. For 
example looking up a hams callsign on QRZ  frequently gives a home 
physical address .... but it doesnt have to. It is also why a lot of 
hams wont do APRS as they want to protect their privacy. The FCC 
application form for your license allows listing your real home address 
in a section on the form that is required for FCC use, but there is 
another section where you can put in a post office box address that is 
only seen by the public such as when looked up on Qrz and other sites. 
That keeps us legal and helps reduce our risk for our vehicles or homes 
being targeted ... after all when your APRS signal shows you out and 
about, your not at your home during that time .....

Hope this wasnt a distraction, as it wasnt intended to be.

73 from Bill - WD8ARZ
WD8ARZ        Base Station (with 'off set' coordinates)
WD8ARZ-9    Mobile TM-D700AG
WD8ARZ-10  Android Smart Phone - APRSdroid  and U2APRS
APRS Viewer on Android for displaying APRS stations only, no beacon / 

On 12/6/2014 6:43 PM, Kenneth Finnegan wrote:
> Ladies and Gentlemen,
> I am preparing to defend my thesis at Cal Poly SLO next week, and
> thought some readers of this list might enjoy seeing a draft copy of
> my thesis. I'd appreciate feedback on any glaring quantifiable errors
> in the document.
> http://thelifeofkenneth.com/files/draft_finnegan_aprs_thesis.pdf
> I'd like to say once again thanks for all the help offered by many of
> you as I've worked on my thesis for the last year.
> If you happen to be in the SLO area, my defence will be on Friday Dec
> 12 at 9am in the EE department conference room, and you are welcome to
> attend.
> --
> Kenneth Finnegan
> http://blog.thelifeofkenneth.com/

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