APRS-AT.TXT APRS on the Appalachian Trail! =========================================================================== Document version: 002 Document dated: 5 May 2003. Author(s): Bob Bruninga, WB4APR APRS-AT was written to run in APRS Kiosks along the Appalachian Trail wherever we can find power and a sheltered location for an old DOS PC. APRS-AT runs under automatic control to report the movement of hikers along the trial. Hikers may either be HAMS with APRS portable gear, or regular hikers who have placed themselves on the map at one of these APRS Kiosks along the trail. Their movements are dead-reckoned based on their estimated speed and direction. HIKER DATA ENTRY: Each hiker is identified by his initials, direction of travel, icon, and type of hiker (Day, Through, Weekend, etc). He also enters additional data that will show up in his object report: *Initials for ID AAA *Direction North or South *Type Day, Section, Through, or Weekend Starting point Where he entered the trail Destination His ultimate destination ICON Hiker, Bike, Horse, Circle, Sqare, Triangle Speed Speed in Miles per day... The first three are used to give him his unique ID such as "AAANT" for a North bound Through hiker with the initials of AAA. NIGHTIME OPS: All such hikers are dead reckoned every hour or so between the hours of 7 AM to 7 PM. After those hours, all objects are transmitted at their last predicted position and their ICON is converted to the "tent" icon. Whenever an object has not been updated in a week or reaches its final destination, it is removed from the system. DEAD RECKONING and APRS: Although all APRSdos programs dead reckon all moving objects to their estimated current positions based on elapsed time since the last position report, APRS-AT (derived from APRSdr) does this movement at the point of transmission, not at reception. Thus, to all other APRS programs of any kind, whether DR is enabled or not, they see the new estimated positions only. This includes the WEB FINDU.COM as well! This is a very powerful technique which can provide the same measure of tracking but without attaching a GPS to every hiker! The concept is simple, the position of the hiker at least for the purpose of knowing approximaely what section of trail he is on is completely predictible from his last known point as long as he makes a reasonable entry of his estimated speed over the next section... APRS ALT-NET: To avoid cluttering normal APRS screens in states along the trail, all APRS-AT stations use the special ALT-NET of ATxxxx. This should not be displayed by properly configured software. By the same token, the APRS-AT stations will not display anything on the maps except other ATxxxx stations. But APRS-AT does have two other exceptions. First, any Kenwood HT using the Hiker ICON will be captured. This is necessary, since the Mic-E format cannot designate an ALT-NET. Second, all weather stations are accepted since weather information should be useful to Hikers. THE TRAIL: The Appalachian Trail is added to a DOS map as a purple line in the map file USA-AT.MAP. This is one map that covers the entire 2000+ mile range of the trail. Just as in APRSdr, the trail begins in Georgia and runs to Maine and BACK so that Hikers may be placed on the trial going either direction. North bound hikers use LEG 1 and southbound hikers use LEG 2. BEGINNING A HIKER: The INPUT-ADD-OBJECT command in APRSdr has been completely customized for APRS-AT. The hiker only needs to enter the appropriate information above, and he is placed on the map at the present location of the APRS Kiosk he is using. To make this work the APRS-AT must be customized with these parameters: 1) The location of the Kiosk 2) The immediate direction of the first leg north and south 3) The difficulty of the next 60 miles north and south Whenever the destination of a hiker is reached, his SPEED is set to zero so that no further DR occurs and his ICON remains in the system for a day before it is deleted... Hikers that APRS-AT is dead-reckoning will show in CYAN. Any other of your uplinked Objects will be the usual Yellow. APRS-AT keeps the map USA-AT in memory at all times 4 APRS-AT will not let you zoom below 1 mile. This is because the DR algorithm fails due to map scale problems below that range. See APRSdr.txt on how the USA-AT map is made using color 13 and no leg is shorter than what a Hiker would cover in one hour (about one mile) REDRAW: APRS-AT has an automatic recenter and redraw routine whenever keyboard has been in active for 3 minutes. This time is settable with the alt-S-OTHER-REDRAW command. By default, APRS-AT sets the special APRS ALT-NET of ATxxxx. Thus this software will only show the location of other APRS-AT systems. But since the Kenwood's cannot do alt-Nets, all Kenwoods showing the HIKER ICON will be displayed too. Enjoy! Bob Bruninga