[aprssig] Maryland CHART data on APRS

Jack Spitznagel frawg at frawg.org
Wed Nov 11 08:11:08 EST 2009

Hi Robin,

Contact Patrick Domack (K3PDK) who frequents this list. Patrick has
already got a big chunk of the task done. The road speed data was being
transmitted regularly earlier in the year. I have been inactive because
I have been out of the area too much to keep the APRS stuff online, but
a look this AM shows it does seem to be online. When there, info marker
signposts along the I-270 corridor, I-95, and the northern I-495 loop
area show on your favorite tracker map.

When I was active I tried to provide fill in for some of the Baltimore
area markers on I-695, I-97 and I-83. I see some speed signposts on 495
and 95 as I write this. They pop up around commuting times because
Patrick has them filtered not to show if traffic flow is normal.
Hovering the markers shows the traffic report data in AGWtracker and
other engines and it will show on a Kenwood 7/700/710 display. I am sure
it will show on some of the others too.

IIRC, the positional data for speed sensors, accidents, and hazards was
not being reported in geographic coordinates on the CHART map, but
rather in raster map coordinates (relative X-Y pixel position?). I
volunteered to help him get the GPS coordinates for the sensors on the
routes I travelled most frequently around Baltimore. There was no way in
the CHART reporting system to determine the GPS position of accident and
hazard markers. The only way I can think of to do that is to have an
exactly scaled proportionate map matrix that allows you to "guesstimate"
GPS coordinates from the pixel coordinates... that would be a bit messy.

Sorry for not being more up to date on this. I wound up with a new job
that has me flying out of the area frequently, so my APRS activity level
went to zero.

That about all the info I have on it.

Jack - KD4IZ

rfinesmith at aol.com wrote:
> I am in the process of programming packet server software that will
> send Maryland Coordinated Highways Action Response Team (CHART) data
> in APRS packet format.  For those unfamiliar with CHART, please see
> http://traffic.md.gov/, and click the Interactive Mapping link.  I
> wish to solicit thoughts from those living in or near Maryland about
> how to make this data available.  My first thought is to make this a
> directed query using APRSO.  There are numerous objects that could
> potentially be sent in response to this query - traffic incidents,
> road closures, hauling restrictions, weather, and dynamic roadway
> message signs.  I am thinking this information might need to be
> limited by a query footprint, but I don't know which APRS software
> allows the user to enter the target footprint in the query message, so
> I would appreciate this information from knowledgible persons. Should
> I require receipt of target footprint data to trigger sending any
> response?  Should these packets even be sent on 144.390, because it
> might have the potential to swamp the network? Finally, is there any
> interest among a large digi operator or IGate station in hosting this
> system? 
> Thanks,
> Robin, AA3NJ
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