NAVITRA to APRS J-Gate DRAFT SPECIFICATION 8 Apr 2003 ----------------------------------------------------------------------- WB4APR This spec suggests a mechanism for exchanging messages and data between APRS users and Japanese NAVITRA users via the worldwide APRS Internet System. NAVITRA is an AX.25 Mobile position reporting system used in Japan on their domestic model D7 and D700 equivalent radios. Although it has no specific messaging capability, it does have the same 40 character DX-LIST that we have in our radios. Thus we can convert APRS messages to something they can receive. They can communicate back using the 20 character text in their position reports or eventually start using APRS client software to send standard APRS messages. By definition, all packets on the APRS-IS will be APRS formatted. Japanese users desiring to view this data on the actual internet will use normal APRS client software. This spec defines only how packets cross the NAVITRA(RF)-to-APRS(IS) interface before being sent to or from the APRS-IS. I will call this a "JGate" to distinguish it from an "Igate" although they are otherwise identical processes in client software. In other words, how NAVITRA RF packets will be converted to APRS format and how APRS packets will be converted to NAVITRA on RF. POSITION DATA: This is easy. JGate authors simply add the $PNTS NAVITRA format to their list of existing APRS formats they parse. This simple step immediately makes an APRS program NAVITRRA compliant as far as being able to monitor RF in Japan and the worldwide APRS-IS. This is the EASY and the MOST REWARDING step in integrating NAVITREA users into APRS. If authors put $PNTS into all their software, then even visiting Japanese hams elsewhere int he world can be seen on APRS! MESSAGES: APRS messages that need to go through a JGate will be converted to DX-LIST format before transmission back to RF in Japan. This makes them receivable on any D7 and D700 in Japan. ALthough the mobile user in Japan cannot send back a message or DX list format, NAVITRA users can communicate with each other by adding ">TOCALL" at the end of the 20 byte text. Sometimes only a callsign suffix is used ">XXX". This should be easy to identify and parse back into a brief APRS message at the JGate. POSITION DATA NAVITRA(RF)-TO-APRS(IS): -------------------------------------- But before we get into the details of the text or "message" bytes, we must first define the standard conversion for position data. In the NAVITRA data, there is only ONE packet format. BUT it has a single byte "I" which can indicate the "type" of position report as shown below. It can either be the station's present position, a Waypoint, a Starting point or an Ending point. But almost all packets are of the "O" type. The others are RARELY used: NAVITRA FORMAT: $PNTS,V,I,DD,MM,YYYY,HHMMSS,LAT,N,LONG,W,$ Here is then how to convert the $PNTS to APRS format based on the "I" byte: APRS(I=0): @DDHHMMzDDMM.HHN/DDDmMM.hhW$CSE/SPD/xxxxxx... A posit APRS(I=S): ;XXX-START*DDHHMMzDDMM.HHN/DDDmMM.hhW$xxxxxx... Start Pt APRS(I=E): ;XXX-END *DDHHMMzDDMM.HHN/DDDmMM.hhW$xxxxxx... End Pt APRS(I=I): ;XXX-WAYPT*DDHHMMzDDMM.HHN/DDDmMM.hhW$xxxxxx... Waypoint APRS(I=P): ;XXX-OBJCT*DDHHMMzDDMM.HHN/DDDmMM.hhW$xxxxxx... Object Where XXX is the sending station's callsign suffix. These suffixes are only used as the object NAME in the object formats. J-GATE NAVITRA to APRS-IS MESSAGE FORMAT: ----------------------------------------- Common usage in Japan has users placing ">TOCALL" at the end of any position text when it is intended for another station. Sometimes this is only a sufFIX. Our conversion is easy. 1) If the ">TOCALL" exists, then TOCALL becomes the APRS message address and the TOCALL is added to a TOCALL-buffer in the JGate 2) If ">xxx" is 3 bytes and it matches the suffix of a call in the TOCALL-buffer then it is sent to that call. If there is no match, then it is sent to ALL with the entire 20 bytes included in the message as is... Here are the examples that we can use for APRS conversions: NAVITRA 20 byte TEXT Converted to APRS FORMAT NOTES -------------------- -------------------------------------------- ---------- message text >TOCALL :TOCALL...:NAVITRA MSG: message text Normal MSG More message txt>XXX :ALL......:NAVITRA MSG: More message txt>xxx Suffix msg any other text, etc [is not a message because the ">" is missing] In these examples, the ">" character indicates it is a NAVITRA message for injection into the J-GATE. WHat follows the ">" can be 4 things: >TOCALL in this case, the conversion is to a personal message >XXX In this case, the conversion is to a personal message or to ALL if there is no immediate match ># This will be a Bulletin Number # > This will be an Email TOCALL is variable length, from 4 to 6 characters. There is no provision for SSID, since just like in APRS, a message to the root call will be accepted by all SSID's of the same call. And since there is no ACK capability in NAVITRA, then there is no reason to specify or require an exact SSID match. APRS(IS)-TO-NAVITRA(RF) Message Conversion: -------------------------------------------- Going from APRS-IS to RF requires the J-Gate to convert it to DX-LIST format. This gives us a 30 to 40 character message capability. But since there are no ACKS, the message is transmitted 'n' times and it times-out. Here is how we can use the DX-list format to send messages to the Japanese model D7 and D700 in Japan: D7 Display: +--------------+ +--------------+ | DxXYZ>ABCDEF | | DxXYZ>ABCDEF | | 222222222_ | | 3333333333 | | [MSG] | | 4444444444 | +--------------+ +--------------+ D700 Display: +---------------------------+ | 1:XYZ>ABCDEF** [MSG]| | 222222222 | | 333333333344444 | | 444445555555555 | +---------------------------+ D700 DX-list: +---------------------------+ | 1:XYZ>ABCDE 222222222[MSG]| <== note only 5 chars of TOCALL +---------------------------+ URCALL>RESORC:DX de IGATECALL.222222222_XYZ>ABCDEF***33333333334444444444 5555555555*[MSG] Notice that all the fields are fixed length: IGATECALL 9 bytes valid call format 2222... This is 10 chars, but the last (_) is not shown on the D700 XYZ>ABCDEF The FROM (suffix) and full TOCALL 3333... 10 bytes of free text 4444... 10 bytes of free text 5555... 10 more bytes not shown on the D7 Notice that since this is an APRS-IS to RF conversion process, this process is only performed if the "TOCALL" of the message matches a locally received NAVITRA station just like any IGate. But to allow for an intial means to communicate with the small number of Japanese using NAVITRA, there needs to be a backdoor. THis will be via a bulletin such as BLN#JAPAN or BLN#NIHON. NAVITRA GROUP CALLS: There is another feature in NAVITRA that allows GROUP calls. These can be used to send packets to certain 3 digit groups. We could use one such GROUP call as a way to automatically pass APRS packets through the JGate that are intended for JAPAN only. The default wildcard is "000". SO, for example, only bulletins originated on APRS specifically intended for NAVITRA users by these group calls would be J-Gated to RF in Japan. I need to work on the GROUP code some more, because I am not sure if it is only an outgoing indicator or if there is a filter on the NAVITRA incoming... DETAILS of the NAVITRA PROTOCOL: -------------------------------- Data in AX.24 packet: $PNTS,VER,ID,dd,mm,yyyy,hhmmss,LAT,NS,LON,EW, DIR,SPD,ICON,COMMENT,GROUP,STATUS*SUM VER Version of this $PNTS format. '1' is the most recent ID Shows what kind of data this is. '0': normal position data 'P': location of object 'R': ack for 'P' receiving. 'S': start point of Route 'I': intermediate waypoint of Route 'E': goal point of Route DIR moving direction '00' to '63' SPD moving speed 'xxx.x' km/h ICON icon dat '0-9, A-E' See table below COMMENT Up to 20 digits comment GROUP group code. '000' to 'ZZZ' STATUS gps status '1' if gps data is OK SUM check sum NAVITRA to APRS ICON CONVERSIONS -------------------------------------------- APRS SYMBOL NAVITRA ICON -------------- ---------------------------------------------- 0n 0 Triangle 0 - Triangle Yn Y Triangle 1 - Triangle with a "Y" on it (Yellow I think) Bn B Triangle 2 - Triangle with a "B" on it (Blue I think) Gn G Triangle 3 - Triangle with a "G" on it (Green I think) Rn R Triangle 4 - Triangle with a "R" on it (Red I think) /r Vertical 5 - vertical antenna with groundplane /- House 6 - house /y House (yagi) 7 - Apartment /x Diamond 8 - Bell /w Water 9 - soda can \< Advisry Flag A - golf green with flag /' Airplane B - bird /s Boat C - fish \P Parking D - Parking sign \R Food E - Restaurant icon