2.0 javAPRSFilter Users Guide.

 Introduction:
 The APRS-IS full feed today have a lot of traffic and require a high
bandwidth, in particular for the APRS-IS server sites, but also for some of
you that connect that are only interested in the particular traffic. To
accommodate this a number of servers have special regional feeds which
filter the traffic. There are also some weather specific feeds available.
But all these are setup according to what the server operator "thinks" will
be good for the users. Now we can take this one step further.

 Now will each of you be able to select what traffic you are interested in
and the server will create a unique feed for you. There is great flexibility
to construct your personal feed.


 How does it work?
 Pete Loveall AE5PL have written the APRS-IS server software javAPRSSrvr in
java which is used by a number of servers. Pete has been kind to create some
hooks into his server software so I have been able to write a filter add-on,
javAPRSFilter (also in java). These 2 applications work together to provide
this filtering. Status on the APRS-IS servers can be found here:
http://ahubswe.net/aprs_stat.asp

 You define the filter by doing the following:

        1. Connect and logon to a filter enabled port on a server
        2. Send an APRS message to the server requesting the filter you want


 Filter commands
 There are 10 different kinds of filters that can be used in any combination.
Each filter is working independent and is additive to the feed. This mean if
the filter finds a match it will be passed to you. The filter commands in
the APRS message to the servers call is starting with the word 'filter'
(without quotes) and each filter command is delimited by a single space. A
message with just 'filter?' (without quotes) will return the current filter
definition.


 #1 Range filter
 The range filter will pass all stations and objects within a distance from
a set location. It will also pass messages to stations within the filter and
positions of the message sender even if they are outside the range. Up to 3
range filters can be used at the same time to extend the areas when you have
problem to find a good circle match.

 Syntax:        r/lat/lon/dist [r/lat1/lon2/dist2 [[r/lat2/lon2/dist2]]

 Where:         r = range command
                lat = latitude in degrees (no decimals). Negative for south
                lon = longitude in degrees (no decimals). Negative for west
                dist = distance in kilometers from lat/lon.
                        I'm sorry we don't use miles here in Sweden ;-)

 Samples:       r/55/-4/600     This will pass all traffic for UK
                r/37/-81/1500   This will pass all east cost US traffic


 #2 Prefix filter
 Note: This filter is kept for backwords compatibility. The Budlist filter now
support this functionality. (from V 1.4)

 The prefix filter will pass traffic based on if the sender’s call starts
with a specific pattern.

 Syntax:        p/p1/p2/p3...

 Where:         p = prefix command
                p# = The prefix (starting) pattern

 Samples:       p/K             This will pass all traffic from stations
				starting with K
                p/SK/F  	This will pass stations starting with either SK or F
                p/SM5NRK        This will pass all traffic from SM5NRK and any
				SSID at the end


 #3 Budlist filter
 The budlist filter will pass traffic based on exact match of the sender’s
call or call starts with a specific pattern (from V 1.4). Also the SSID is part 
of the exact match.

 Syntax:        b/call1/p1*/call3/p2*...

 Where:         b = budlist command
                call# = The prefix (starting) pattern
                p# = The prefix (starting) pattern

 Samples:       b/SM5NRK                This will pass all traffic from SM5NRK
					without any SSID
                b/SM5NRK-5/SK5UM        This will pass all traffic from SM5NRK-5
		b/K*    	        This will pass all traffic from stations
					starting with K
                b/SM5NRK/F*	  	This will pass all traffic from SM5NRK and
					stations starting with F


 #4 Type filter
 The type filter will pass traffic depending on the packet type. More than
one type can be defined in one single command.

 Syntax:        t/type

 Where:         t = type command
                type = is one or more of the following letters
                        p = Position packets
                        o = Objects
                        i = Items
                        m = Message
                        n = NWS Weather and NWS Area Objects
                        w = Weather
                        t = Telemetry
                        q = Query
                        s = Status
                        u = User-defined

 Samples:       t/p             This will pass all traffic with a position
                t/w             This will pass all weather traffic. For
				positionless weather objects the corresponding
				position packet will also be sent when it is
				next heard
                t/mos           This will pass all messages, objects and status
				traffic


 Remeber that the APRS message must start with the word filter and the the
commands.

 The above filters can be combined as explain above. Each filter will
however working independent of the others, for example:

        filter r/63/16/1000 r/55/-4/600 p/F b/AE5PL t/s

 The above filter will pass all traffic within Nordic (range#1) AND UK
(range#2) AND stations starting with F (prefix) AND from AE5PL (budlist) AND
all status traffic (type).


 #5 Symbol filter
 The symbol filter will pass traffic based on the symbol in the packet.

 Syntax:        s/pri/alt/over

 Where:         s = symbol command
                pri = symbols in primary table
                alt = symbols in alternate table
                over = overlay character (case sensitive)

 Samples:       s/->       This will pass all House and Car symbols
			   (primary table)
                s//#       This will pass all Digi with or without overlay
                s//#/T     This will pass all Digi with overlay of capital T


 #6 Digipeater filter
 The digipeater filter will pass all packets that have been digipeated by a
particular station(s). Remember that a packet can many time go different routes
to get to APRS-IS and might be digipeated by other stations that is shown. These
packets are filtered out by various filters/application as duplicates. More that
one digipeater can be entered and each are OR together.

 Syntax:        d/digi1/digi2...

 Where:         s = digipeater command
                digi# = digipeater call

 Samples:       d/SM5NRK-2              Pass all packets digipeated by SM5NRK-2
                d/SM5NRK-2/SK5UM        Pass all packets digipeated by SM5NRK-2
					or SK5UM


 #7 Area filter
 The area filter works the same as range filter but the filter is defined as a
box of coordinates. The coordinates can also been seen as upper left coordinate
and lower right. Lat/lon are integer (no decimal) degress. South and west are
negative. Up to 3 area filters can be defined at the same time.

 Syntax:        a/latN/lonW/latS/lonE

 Where:         a = area command
                latN = North latitude border (-90 to 90)
                lonW = West longitude border (-180 to 180)
                latS = South latitide border (-90 to 90)
                lonE = East longitude border (-180 to 180)

 Sample:        a/50/-130/20/-70        This will pass all traffic in US


 #8 q Contruct filter
 The q Construct filter will base all filtering on the q Construct used on the
APRS-IS. For more information about q Contract look here:
http://www.aprs-is.net/q.htm

 Syntax:        q/con/ana

 Where:         q = q Construct command
                con = list of q Construct to pass (case sensitive)
                ana = analysis based on q Construct.
                        i = Pass positions from IGATES identified by qAr or qAR.

 Sample:        q/C             Pass all traffic with qAC
                q/rR            Pass all traffic with qAr ot qAR
                q//i            Pass all position packets from IGATES
				indentified in
                                other packets by qAr or qAR

 #9 Object filter (from V1.4)
 Same as BudList but acts on the object names instead of sender's call. 

 Syntax:	o/name1/n2*/name3/n3*...

 See Budlist for more information

 #10 My Range filter
 The my range filter will pass all stations and objects within a distance from
your own station. It will use the location sent for the same call as you used
when you logged onto the server. This is useful if you have an mobile station
with internet connection. It will then always pass the local stations no matter
of where you are.

 Note: This will not work until a valud position has been sent from the same
 call-ssid you used when you logon to the server.

 Syntax:        m/dist

 Where:         m = my range command
                dist = distance in kilometers from lat/lon.

 Samples:       m/500     This will pass all traffic within 500 km from my location

 #11 Friend Range filter
 The friend filter works the same as My range filter, except you define which
call-ssid should be used (see more above). Up to 3 friend filters can be defined.
This is a moving filter so it is following the call-ssid last known position.


 Note: This will not work until a valud position has been sent from the
 call-ssid defined.

 Syntax:        f/call/dist

 Where:         f = friend range command
 		call = call to be used as center of the range
                dist = distance in kilometers from lat/lon.

 Samples:       f/SM5NRK/500     This will pass all traffic within 500 km from
                                 SM5NRK's last position.


 Support
 I do monitor the aprssig, UI-View and Xastir mailing lists so please post any
questions there.

 73 de sm5nrk/Roger
