Just refreshing my memory on GPSGate...
When I looked at it some years ago, it was a very interesting and promising concept
. Maybe cheap AIS
did overtake it a bit on the water
, but it has been well worth some attention. However, I do not know the current
status of Franson software
and services offering.
Briefly, it works as follows:
Many targets can report their position via multiple channels to some organization, hosting a GPSGate Server. It can be over Internet
apps and - most notably - from a mobile phone
over SMS service
The server keeps a database of position reports.
The database can be interrogated by a client in two basic ways.
One type of request addresses a specific target. The response then takes form of a single
RMS sentence, without identification, because this is already well known from the query context.
Another type of request addresses a "Buddy Group" - a predefined set of targets. The response then takes form of a series of FRPOS statements, similar to RMS, but extended with target identification and other details, not present in NMEA
So, depending on whether one makes an individual or a group query, the stream of responses contains just RMS or just FRPOS sentences.
GPSGate Server and Client is not free, so I was not in a position to comfortably set up a test site. I just implemented the obvious: handling of FRPOS sentences, piggybacking on the existing AIS
subsystem. I left out the login/authentication and active interrogation part until having a real test bed
and gaining some experience. (That was in 2010...)
GPSGate targets differ from AIS targets, mainly because they do not age so easily. The position reports may come irregularly, and not so often - even once per day or so ... Some of the reports, I am not sure which, indicate only positions that had changed since the last interrogation. So directly translating FRPOS into AIVDM is not always right.
Tracking GPSGate Buddies has been fully implemented in some chartplotters. One example is SOBvMAX from Digiboat.
I do not think now that there is a need to put more effort into this. However, there would be 3 ways to move forward:
1. Implement full GPSGate Client into OCPN or a Plugin.
2. Write a small connector program to perform the login and interrogation, passing back the FRPOS responses to OCPN.
3. Find a way to use existing GPSGate software
to perform these tasks.
If I were an actual user, I would start from investigating choice #3.
Choice #2. is still a possibility.
I feel it is still too early for choice #1.
Notably, many users use GPSGate Client software just as a connectivity tool, not using the Server protocol at all, just routing NMEA
between various transports ...