June 4, 2012 06:09
I have the Digital Yachts Class B Transponder AIT2000 with WLN10HS, and mainly use iNavX for AIS display on an iPad. All works brilliantly. However, there is merit in having the (free) iAIS app on my iPhone as a quick and simple way to assess collision risk when away from the iPad.
iAIS is a very nicely put together app however it has one major drawback: they say in the iAIS help file "iAIS display is Course up not North up, which is much better for AIS display". I strongly disagree with this.
The display is actually COG up. A small yacht approaching a shipping lane in fog may slow right down. With a tide running, the COG may be very different from Heading. If it stops and loses steerage way, its heading may swing and the resultant COG up display will be totally disorientating.
Having a radar in head up mode was, I believe, a contributing factor in the sinking of the yacht Wahkuna by the Nedlloyd Vespucci in 2003. The bearings appeared to be moving as ship's head swung when the true bearings were actually steady. Anti-collision is about avoiding situations where true bearings are steady, therefore a display that is referenced to a true bearing (e.g. North) is essential. I have suggested that DY either make the display North up, or have North/Heading/COG up as user selectable options, with North the default. This needs to be corrected with urgency. At present the display is of limited usefulness, and may even be dangerous.
iAIS is a very nicely put together app however it has one major drawback: they say in the iAIS help file "iAIS display is Course up not North up, which is much better for AIS display". I strongly disagree with this.
The display is actually COG up. A small yacht approaching a shipping lane in fog may slow right down. With a tide running, the COG may be very different from Heading. If it stops and loses steerage way, its heading may swing and the resultant COG up display will be totally disorientating.
Having a radar in head up mode was, I believe, a contributing factor in the sinking of the yacht Wahkuna by the Nedlloyd Vespucci in 2003. The bearings appeared to be moving as ship's head swung when the true bearings were actually steady. Anti-collision is about avoiding situations where true bearings are steady, therefore a display that is referenced to a true bearing (e.g. North) is essential. I have suggested that DY either make the display North up, or have North/Heading/COG up as user selectable options, with North the default. This needs to be corrected with urgency. At present the display is of limited usefulness, and may even be dangerous.