[aprssig] FEMA - APRS Blackout data wanted...
bruninga at usna.edu
Thu Sep 8 19:16:45 CDT 2016
The Technology Office at FEMA asked me about using APRS data... THey want
DATA on anything they can get. For example, to visualize power blackouts.
I answered "It's in there!"
All we have to do is plot it.
Here is an approach I would try for any WEB based APRS map displays.
1) Keep at least 5 bits on every WX and HOME station and DIGIPEATER
2) Every 11 minutes decrement every such stations counter by 1
3) Every time a new packet is heard, increment the counter by 10
Now then any station with a count greater than 9 is considered a >90%
reliable 24/7/365 station (has been heard in the last 30 minutes too) We
can call these 24/7 stations.
Now when someone asks for a BLACKOUT PLOT, display two things:
All stations that have been heard in the last 10 minutes... (live stations)
AND *greyed-out* symbols for all of the 24/7 stations (blackout stations)
that have not been heard in 30 minutes.
BINGO, done. We have the data, just need to come up with the right
algorithm and the best way to display it.
The original APRSdos sort of did this by fading-to gray all stations not
heard in the last X minutes, This worked great locally because we each
generally knew all the symbols there were normally there 24/7 and conuld
instantly visualize something was wrong when they all faded to gray in an
area. (but were still on the map)
But for huge APRS-IS systems, there needs to be the algorithm to know which
stations area always on, so they can then indicate when the disappear..
Sure, lots of reasons why this is not going to be pergfect, but it does
give a QUICK indication that something has changed and eeds further
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