HFLINK | ALE-GPR Geo Position Report automatic link establishment

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Open Standard ALE-GPR v1.1

Various ALE radio manufacturers use proprietary methods of sending GPS via AMD, and some are encoded or encrypted by proprietary signalling formats (non-plain text).

Open Standard ALE-GPR for GPS via ALE Automatic Link Establishment transmits GPS information in plain text. It is supported by HFLINK, the amateur radio ALE community, and various ALE controller systems. The open standard is called ALE Geo Position Report or ALE-GPR. To make the ALE-GPR "universal" for ALE transceivers and controllers, the coordinates and other information of the GPS position is transmitted as a human-readable AMD message.

Example of ALE-GPR transmitted AMD:
GPR*KQ6XA*37N654321*122W987654*000003M*20050821Z135235*EVERYTHING FINE

Format ALE-GPR:
GPR*OBJECT*LATITUDE*LONGITUDE*ALTITUDE*TIME*COMMENT

A feature in the ALE controller PCALE provides this GPS position output to Google Earth. PCALE also provides an NMEA compatible GPS interface feature which converts and transmits ALE-GPR.

Here is an example of a series of two ALE-GPRs sent as Netcall AMD (TWS) by KQ6XA in California and received by Jeff KB2M in New Jersey, using PCALE on both ends of the path:
ALE GPR KQ6XA KB2M

image courtesy of Jeff KB2M

Example audio file:
Standard Use of Geo Position Report with NETCALL and AMD TWS:
Net name: GPR
Sample *.wav file Netcall to the "GPR" Net address with the GPR in an AMD and TWS termination:
KQ6XA_GPR_TEST.wav

By using NETCALL for an open GPR, the receiving stations may "opt in" to a GPR Net. Individual stations can exchange GPRs using Individual Calls.

ALE-GPR Open Standard String Format For AMD

Manual keypad entry of ALE-GPR limits the characters that can be used. It is important for ALE-GPR that the operator of the ALE transceiver, having knowledge of their own position, be able to manually enter the GPR as an AMD on the keypad of the ALE transceiver and send it. This manual entry method would not require the electronic connection of a GPS receiver to the HF transceiver or ALE controller, or modification of the ALE controller software/firmware. Displays on the front panels of some ALE transceivers use simple LCD readouts with about 10 to 20 characters displaying on a line. The AMD text is read by scrolling left/right with an arrow key on the keypad.

There are limitations on what characters read out on ALE transceivers.
The following characters are common to all ALE displays and most transceiver keypads:

ABCDEFGHIJKLMNOPQRSTUVWXYZ

0123456789

SPACE

Any other character sent in the AMD has a risk that it might not show on the display.

The ALE-GPR uses only 7 fields; with the * character as de-limiter:

Example of transmitted AMD:
GPR*KQ6XA*37N654321*122W987654*000003M*20050821Z135235*EVERYTHING FINE

String field format ALE-GPR:
GPR*OBJECT*LAxTITUDE*LONyGITUDE*ALTITUDf*YYYYMMDDZhhmmss*COMMENT

HFLINK Standard ALE-GPR Fields

Field Position	Field Name	Characters	Description	Format Example
1	GPR	3	"GPR" preamble to signify Geo Position Report follows. Since it is only 3 characters, it becomes part of the [CMD AMD] command word in the ALE protocol.	GPR
2	OBJECT	3 to 15	Object being reported. Normally this is your Callsign or Own ALE Address. It could alternatively be the name or callsign of another object being reported (or relayed). Use of the # character in this field indicates the slant bar / commonly used in callsigns.	ABCDE0123456789 (reporting an object with the name ABCDE0123456789)
3	LATITUDE	up to 9	Degrees and decimal degrees; with decimal point replaced by N or S for North or South. If this field is stuffed, mimumum field characters are 2 digits of degrees followed by the separator. The presence of the # character in any part of the latitude field indicates a manual entry or a non-valid position in the GPS receiver.	37N654321 (Latitude 37.654321 degrees North)
4	LONGITUDE	up to 10	Degrees and decimal degrees; with decimal point replaced by E or W for East or West. If this field is stuffed, minimum field characters are 3 digits of degrees followed by the separator. The presence of the # character in any part of the longitude field indicates a manual entry or a non-valid position in the GPS receiver.	122W987654 (Longitude 122.987654 degrees West)
5	ALTITUDE	up to 7	Altitude; with suffix M for meters or F for feet. Minimum field character is 1 digit for altitude plus the suffix. The presence of the # character in any part of the altitude field indicates a manual entry or a non-valid position in the GPS receiver.	0000003M or 3M (Altitude 3 meters)
6	YYYYMMDDZhhmmss	15	DATE-TIME Stamp. Year,Month,Day,Hour,Minute, Second; With "A-Z" as the timezone separator between date and time. Z=UTC (zulu) J=Local Time, etc. Time Zone Separator Chart The presence of the # character in any part of the time field indicates a manual entry or a non-valid position in the GPS receiver.	20050821Z135235 (2005 August 21 at 13hours 52minutes 25seconds UTC zulu)
7	COMMENT	up to 25	Text comments up to 25 characters, spaces permitted; and/or Un-defined fields.	EVERYTHING FINE HERE NOW (25 characters of text with spaces between words if needed)
All fields are de-limited by a single * character between fields, with no de-limiter at the beginning or end. Any character except * in fields 2 through 7 may be replaced by the # character as a spacer or null entry, or for other purposes. The presence of the # character in any part of the latitude, longitude, altitude, or time fields indicates a manual entry or a non-valid position in the GPS receiver.

FCC Compliance:
In addition to the global standard ALE protocols, the ALE-GPR documentation here provides the public documented technical characteristics called for in FCC rules § 97.309(a)(4) :

"(4) An amateur station transmitting a RTTY or data emission using a digital code specified in this paragraph may use any technique whose technical characteristics have been documented publicly, such as CLOVER, G-TOR, or PacTOR, for the purpose of facilitating communications."

"Documentation should be adequate to (a) recognize the technique or protocol when observed on the air, (b) determine call signs of stations in communication and read the content of the transmissions."

Typical Embedded-ALE Transceiver Displays and Keypads targeted for ALE-GPR compatibility:
PRC138 Linked with KQ6XA

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