1 AUTOMATIC POSITIONREPORTING SYSTEM APRS PROTOCOLREFERENCE Protocol Version APRS Working GroupDocument VersionApproved Version of Issue29 August 2000 Copyright 2000 APRS Working GroupAll rights reservedTechnical EditorIan Wade, G3 NRWAPRS Protocol ReferenceProtocol Version the APRS Working GroupEdited by Ian WadePublished byTucson Amateur Packet Radio Corp8987 309 East Tanque Verde Road, #337 TucsonAZ 85749-9399 United States of 0-9644707-6-4 TAPR Publication Number: 99-4 Copyright 2000 APRS Working GroupAll rights reservedAPRS is a registered trademark of Bob , MacAPRS , X-APRS , PalmAPRS and APRS/CE are trademarks using the APRS name, licensed from Bob document may be copied for non-commercial purposes only, and mustinclude the above copyright statement and trademark statements in APRS Protocol Reference document represents the coming-of-age of WB4 APR s with a simple concept a way to track the location of moving objects via packet radio programs using the APRS protocol have grown into perhaps the most popular packet radioapplication in use today.
2 It s also become one of the most complex; from the simple idea grew,and still grows, a tactical communications SYSTEM of tremendous capability. Like many hamprojects, the APRS protocol was designed as it was being implemented, and many of itsintricacies have never been now. This specification defines the APRS on-air protocol with a precision and clarity thatmake it a model for future efforts. The work done by members of the APRS Working Group, aswell as Technical Editor Ian Wade, G3 NRW, should be recognized as a tremendous contributionto the packet radio art. With this document available, there is now no excuse for any developer toimproperly implement the APRS an APRS Working Group member whose role was mainly that of observer, I was fascinatedwith the interplay among the APRS authors and the Technical Editor as the specification tookform.
3 Putting onto paper details that previously existed only in the minds of the authors exposedambiguities, unconsidered consequences, and even errors in what the authors thought they discussion that followed each draft, and the questions Ian posed as he tried to wring out theuncertainties, gave everyone a better understanding of the protocol. I am sure that this process hasalready contributed to better interoperability among existing APRS who has watched the specification develop, from the initial mention in April 1999 untilrelease of this Version document in August 2000, knows that the process took much longerthan was hoped. At the same time, they saw the draft transformed from a skeleton into a heftybook of over 110 pages.
4 With the specification now in hand, I think we can all say the wait wasworth it. Congratulations to the APRS Working Group and, in particular, to G3 NRW, for a majorcontribution to the literature of packet Ackermann, N8 URTAPR Vice President and APRS Working Group Administrative ChairAugust 2000 Table of Contentsi APRS Protocol Reference APRS Protocol Version Version : 29 August 2000 APRS PROTOCOL REFERENCETABLE OF Working Version STRUCTURE OF THIS INTRODUCTION TO is APRS?..7 APRS THE APRS DESIGN Cycle Map Views APRS AND APRS DATA IN THE DESTINATION AND SOURCE ADDRESS Destination Address APRS Destination APRS Address with Software Version Encoded Grid Locator in Destination APRS Digipeater Source Address SSID to specify APRS DATA IN THE INFORMATION Data Data Type Data and Data Data of ContentsDocument Version : 29 August 2000 APRS Protocol Reference APRS Protocol Version 6 TIME AND POSITION of Null Locator (Grid Square).
5 25 NMEA APRS DATA and Direction and Wind , Effective Antenna Height/Gain/ Circle Radio Signal and Number/Range/ Object POSITION AND DF REPORT DATA COMPRESSED POSITION REPORT DATA Advantages of Data Data , Pre-Calculated Radio Range and Compression Type (T) Report MIC-E DATA Data Data Destination Address Address field Address SSID Information field Degrees of Contentsiii APRS Protocol Reference APRS Protocol Version Version : 29 August 2000 Longitude Minutes Hundredths of Minutes and Course +28 +28 +28 of Mic-E Speed and Course the Speed and of Decoding the Information field POSITION Telemetry Status Locator in the Mic-E Status Text in the Mic-E Status Text Data in Non-APRS OBJECT AND ITEM and an Object / an Object / Report Report Object WEATHER Report Type Weather Weather Software Unit Weather of a Raw and Positionless Weather with Raw and Positionless Weather Weather Reports with Timestamp and Weather Service TELEMETRY Report Definition of Telemetry Name Coefficients Sense/ Project Name of ContentsDocument
6 Version : 29 August 2000 APRS Protocol Reference APRS Protocol Version 14 MESSAGES, BULLETINS AND Weather Service Bulletin and Announcement and Announcement Implementation STATION CAPABILITIES, QUERIES AND and Station STATUS Report with Beam Heading and Effective Radiated Report with Maidenhead Grid Status NETWORK TUNNELING AND THIRD-PARTY Path on Receiving a Third-Party Example of Sending a Message through the USER-DEFINED DATA OTHER Data or Test Data Other APRS Symbol in the Information with Symbols in the Information in the Destination with Symbols in the Destination in the Source Address of Contentsv APRS Protocol Reference APRS Protocol Version Version : 29 August 2000 APPENDICESAPPENDIX 1: APRS DATA 2: THE APRS SYMBOL 3: 7-BIT ASCII CODE 4: DECIMAL-TO-HEX CONVERSION 5.
7 Conversion / Celsius Temperature Conversion 6: 7: DOCUMENT RELEASE APRS Protocol Reference APRS Protocol Version Version : 29 August 2000 PREAMBLEAPRS WorkingGroupThe APRS Working Group is an unincorporated association whose membersundertake to further the use and enhance the value of the APRS protocols by(a) publishing and maintaining a formal APRS Protocol Specification; (b)publishing validation tests and other tools to enable compliance with theSpecification; (c) supporting an APRS Certification program; and (d) generallyworking to improve the capabilities of APRS within the amateur the Working Group may receive support from TAPR and otherorganizations, it is an independent body and is not affiliated with anyorganization.
8 The Group has no budget, collects no dues, and owns no current members of the APRS Working Group are:John Ackermann, N8 URAdministrative Chair & TAPR RepresentativeBob Bruninga, WB4 APRT echnical Chair, founder of APRSB rent Hildebrand, KH2 ZAuthor of APRS+SAStan Horzepa, WA1 LOUS ecretaryMike Musick, N0 QBFA uthor of pocketAPRSK eith Sproul, WU2Z Co-Author of WinAPRS/MacAPRS/X-APRSMark Sproul, KB2 ICICo-Author of WinAPRS/MacAPRS/X-APRSA cknowledgementsThis document is the result of contributions from many people. It includesmuch of the material produced by individual members of the addition, the paper on the Mic-E data format by Alan Crosswell, N2 YGK,and Ron Parsons, W5 RKN was a useful starting point for explaining thecomplications of this NumberExcept for the very first public draft release of the APRS Protocol Reference,the document version number is a 3-part number (for an approveddocument release) or a 4-part number (for a draft release):Document Version NumberAPRS Version : 29 August 2000 APRS Protocol Reference APRS Protocol Version Thus, for example.
9 Document version number refers to document release 3 coveringAPRS Protocol Version Document version number is draft c of that HistoryThe release history for this document is listed in Appendix 7. DocumentConventions This document uses the following conventions: Courier fontASCII characters in APRS data. VASCII space character.. (ellipsis) zero or more characters. /$Symbol from Primary Symbol Table. \$Symbol from Alternate Symbol Table. 0xhexadecimal ( 0x1d). All callsigns are assumed to have SSID 0 unless otherwise specified. Yellow marker (appears as light gray background in hard copy).Marks text of interest especially useful for highlighting singleliteral ASCII characters ( ") where they appear in APRS data.
10 Shaded areas in packet format diagrams are optional fields. FeedbackPlease address your feedback or other comments regarding this document tothe TAPR aprsspec mail join the list, start at and then follow the path SpecialInterest Groups APRS Specification Join APRS Spec Discussion List. Authors Foreword3 APRS Protocol Reference APRS Protocol Version Version : 29 August 2000 AUTHORS FOREWORD This reference document describes what is known as APRS Protocol , and is essentially a description of how APRS operates today. It is intended primarily for the programmer who wishes to develop APRS-compliant applications, but will also be of interest to the ordinary user whowants to know more about what goes on under the hood.