Ignore potential ARPA targets close to existing AIS/ARPA/MARPA targets

[keesverruijt]

Do not recognise ARPA target closer than a certain distance from an existing target, especially an AIS target. This is to prevent ARPA picking up targets already seen as AIS targets.

[marcus-aa]

Even better would be if a real target fusion code could be developed. In ECDIS systems, ARPA positions updates AIS target positions. Especially for fast boats with Class B AIS with 30 second update intervals, this can be really useful since they travel quite far between updates. /Marcus

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On 2017-08-15, at 16:23, Kees Verruijt wrote: Do not recognise ARPA target closer than a certain distance from an existing target, especially an AIS target. This is to prevent ARPA picking up targets already seen as AIS targets. — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub, or mute the thread.

[Hakansv]

I'm not sure if I misunderstand this issue but we're actually trying to not view (M)ARPA targets covered by a nearby AIS target. See RadarMarpa.ccp at around row 910:
`// Check for AIS target at (M)ARPA position
double posOffset = (double)m_pi->m_settings.AISatARPAoffset;
// Default 18 >> look 36 meters around + 3% of distance to target

double dist2target = (3.0 / 100) * (double)pol.r / (double)RETURNS_PER_LINE * m_ri->m_range_meters;
posOffset += dist2target;
if (m_pi->FindAIS_at_arpaPos(m_position.lat, m_position.lon, posOffset)) s = L;
PassARPAtoOCPN(&pol, s);
}`

It may possible to streamline this function using the facilities of API 1.14 instead of JSON messages and the updated array table?

[keesverruijt]

hhmm, I hadn't actually looked at that code. I just logged the issue because I had a number of AIS targets show up with a ARPA target right besides it. I did have a slight heading misalignment -- maybe that caused it. The track and "COG/SOG" of the ARPA target matched perfectly, so the Kalman filter is working beautifully.