HAM-TRAILS.txt APRS for TRAILS WB4APR and HAM RADIO PUBLIC SERVICE/OUTREACH ------------------------------------------------------------------------ HAM-TRAILS is an amateur radio project to provide health-&-welfare traffic for persons hiking the Appalachain Trail (or any other trail). It consists of small solar powered data entry boxes that collect traffic from hikers and then transmit a one packet summary every 15 minutes or so. These packets can also contain weather data as well. Just as NTS and other amateur radio services have offered the public a complementary communications service for brief messages to demonstrate our ability to handle health-and-welfare traffic, this HAM-TRAILS system provides a similar communications outreach and public education objective. Each HAM-Trail box has a descriptive plaquard which also has local HAM club information on it. Each device operates under automatic digital control usually from high places along the trail at very low power with only one hop. This way these data packets do not collide with any normal higher priority APRS packets, but do get relayed if the channel is clear. The hikers have no control over the operation of the packet system. They can only enter their personal data or view other's data to find friends along the trail. The sketch below shows the suggested front panel of the device: +----------------------------------+ | HAM-TRAIL COMMUNICATIONS | | +------------+ | | () UP | Welcome to | () BACK | <== a two-line by 16 character | () DN | Ham-Trails | () NEXT(OK)| <== screen and four buttons | +------------+ | | This comm service is provided | | by the local HAM radio club in | | this area. It accepts health- | | &-welfare messages from hikers | | and delivers them via HAM radio | | to www.aprs.net. Friends can | | see your messages there. | | Next device <---- 15 miles | | Next device -----> 10 miles | | | | Northern Maryland Amateur Radio | | Club. www.NMARC.org 410-293-6417 | +----------------------------------+ The menu system on the 16 character by-two-line display guides then through entering or viewing data. The APRS-TRAILS device reports the following items for each hiker in a single 5 byte ABCDE field. Up to 16 fields can be transmitted in a single report. If there are more than 16 active hikers being reported, then different packets are transmitted each cycle period on a rotating basis. FORMAT: Each hiker can select these data entry fields: ID - a three ID character field. (The person's initials) IN - An additional 1-7 ID (3 bits) (choose randomly) Dir - N/S/E/W,NE,SE,NW,SW (3 bits) (general direction of travel hrs-to-go - 0-13 hours to go (4 bits) (This field and Speed combined Speed - in MPH (0 to 15) (4 bits) (with time to transmit distnce Message - type (1 of 32) (5 bits) - Modifier (1 of 7) (3 bits) MESSAGE MODIFIFIER (1 of 7) ------------- --------------------------------------------------------- 1 Progress Way Ahead, ahead, OK, behind, way behind, giving up 2 Attitude Marvelous, Great, OK, alive, surviving, depressed, broken 3 Needs Money, food, clothes, supplies, mail, phone, radio 4 FRS Radio Ch 1,2,3,4,5,6,7 5 FRS Radio Ch 8,9,10,11,12,13,14 6 HAM freqs APRS, 144.39(PL100), 146.52, 446.00, 52.525 7 Meet@next Road, Shelter, Camp, town, creek, peak 8 Stopping at 1,2,3,4 5,6,7 (pre arranged possibilities) 9 Custom 1,2,3,4,5,6,7 ... 31 ....... POSITION: Since there can be no local clock at these sites, the time elapsed since entry is combined with the speed to predict a distance traveled in the direction indicated. This transmission is canceled when the hours-to-go has expired. Thus these two entries can be used to give 5 bits of distance in one-mile increments (32 miles maximum). Since each device knows the exact trail directions, it translates the hiker's rough cardinal direction into a more precise vector so that the future predicted direction can be fairly accurate. DATA ENTRY: The data entry device must be very robust and simple. For this reason a single 16 character by two line PROMPT window is used along with UP/DOWN and BACK/NEXT(OK) push buttons. The hiker is prompted through his data entry and he can also query the system about others along the trail. PLAQUARD: The plaquard associated with each HAM-TRAIL device is where the benefit to HAM radio is involved. It is a great opportunity for local clubs to proselitize about HAM radio. The sample text above might work for your club. In general, the entire device is probably no bigger than a 6" utility box and should be secrued from physical damage and weather as much as possible. LOCATIONS: For the physical sercurity and best utility of these devices, the following guidelines should be considered: 1) Locate them in the clear to minimize vandalism 2) Mount them to maximize southern sun exposure on solar panel 3) Northern facing LCD panel might be easier to read 4) Locate them on hill tops and crests to maximize comms 5) Locate them far from roads and camps and public access. They are for through-hikers and not day hikers and kids 6) Camoflage or hide the conduit and solar panel so that the device blends with nature except for the plaquard and display unit. POWER BUDGET: This system must be very low power to operate forever on the average sun from a 1/4 watt (3" square solar panel). This yields an average 24/7 available power of about 40 milliwatts. If the processor and display run on 40 mA at 10 volts but sleep most of the time when not in use, this gives the following power budget. Transmit 1W for 1 second every 12 minutes 2 mw User Entry (Processor running) 30/day * 3 mins 8% 30 mw Processor wake/sleep maintenance 2% 8 mw ---------------------------------------------------------- Total Average power 40 mw And to provide average power during up to 5 days of overcast the battery capacity can be met with 5 Watt hours of batteries or simply 6 AA NiMh cells. CUSTOM DATA: The following site-specific data will need to be programmed into each device: * APRS Position packet * Exact trail vectors in the two (or more) directions so that dead- rekoning of positions works out well * Distance to next device in each direction (if known) * Transmit rate (may need to be adjusted to match solar power) * Device NAME and CALLSIGN APRS PACKET FORMAT: The format for these packets will come from the experimental APRS data format "{HT" and uses the PRINTABLE subset of the ASCII code. That is, 8 bit values are permitted, but no bytes will be control codes. The overall packet format is as follows: MYCALL>AT1234,WIDE:{HTtswdrABCDEabcdeABCDEabcdeABCDEabcdeABCDE...... Where MYCALL is the license holder AT1234 is the Mile mark along the Appalachain Trail (or any trail) {HT is the format identifier for this application vtswdr is Volts, Temp, Solar flux, wind speed, direction, rain/Hr ABCDE are up to 16 fixed length 5 byte hiker reports Notice that the TOCALL may be just about anything to match the application and that this does not correspond with the standard APRS-TOCALL filters. This was done intentioanlly since this format is new and is not backward compatible with any existing code, and cannot be displayed meaningfully without NEW code. THus, new code can ignore the TOCALL filter for this new data type. WEATHER DATA: If additional instruments are added, then the once every 12 minute report can also report local weather data. The battery Voltage Temperature and Solar flux will be in every report (since they are only a thermister and a zenith pointing solar cell. These bytes use a (tbd) set of base 91 characters to give roughly 1% precision in the data. HIKER DATA: Hiker data consists of a 3 byte ID field and then two other bytes as follows: ABC bytes consist of 5 bits for the initials, and one bit that is always a "1" so that control characters are never generated. The remaining two bits are for the additional 3 bit "N" ID and the 3 bit DIRECTION which are encoded one bit per byte as follows: A bits are: N2, D2, "1", 5 bits (letters A through Z) B bits are: N1, D1, "1", 5 bits (letters A through Z) C bits are: N0, D0, "1", 5 bits (letters A through Z) Since the hiker's Initials, "N" ID and Direction do not change thoughtout his trip (in general), then these three bytes are unchanging and represent his full UNIQUE identification. On the Appalachain trail, for example, he is either going NE or SW no matter what his instantaneous direction might be... D The DISTANCE byte consists of the two lower-order direction bits followed by a "1" to avoid any control codes, followed by a 5 bit DISTANCE (0 to 32 miles) showing the predicted progress along the vector. D bits are: D1, D0, "1", 5-bits-of-distance E byte consists of 5 bits of message types and 3 bits of modifiers. But, again, to avoid embedded ASCII control characters, there are only 1-of-seven possible modifiers, as the 000 combination is not permitted. E bits are: M2, M1, M0, 5-bits-of-message-type