Navionics chart updating

[Fr J Hackett]

I watched the latest UMA video yesterday and having been out of the game for a few years was very impressed with the concept that people can supply updated "survey" data from their own boat that Navionics will then use to update their charts.
It did raise the question of relying on people to calibrate their boats transducer depth properly though.

 

[dunedin]

I watched the latest UMA video yesterday and having been out of the game for a few years was very impressed with the concept that people can supply updated "survey" data from their own boat that Navionics will then use to update their charts.
It did raise the question of relying on people to calibrate their boats transducer depth properly though.

AFAIK there are two forms of “crowd sourced“ updates to Navionics et al.
- firstly comments and notes ( “user edits”) submitted by chart users - these are generally comments on hazards or facilities, associated with a specific location ; and
- sonar data of depths - which only works for areas with a lot of boat traffic (which isn’t a huge help, as the busy places are generally well charted anyway)

I have always been suspicious of Navionics crowd sourced data - not least after the fictitious “deep water channel” through the Shingles that was once shown and much discussed on here - as it didn’t exist in practice.
However, I think that the use of sonar data is a bit more scientific now. They can’t know the keel offset calibration etc, and probably don’t attempt to guess the tide height. My suspicion is that if they have enough data, they can process it such that they calibrate based upon known depths that are passed over. To do so will need a lot of data and data processing. So of no practical interest for remote anchorages, IMHO.

User edits also need to be used with caution. But there can be value in considering them. There was an example of a CA member this year hitting a rock in the Mediterranean that was not shown on the official Hydrographic Office chart data - but when looking at the online Navionics web viewer, a user edit was shown which did warn about the rocks.
Interestingly, a look at Google Earth also showed the rocks - so always worth a look at other sources such as Google Earth in shallow waters.

 

[Solent sailer]

The crowd sourced depth only works on the "non-drying" areas, the bits we are generally interested in are the green bits, working out the deep channel at half tide etc. if you display "sonar charts" you loose all that data.
As said in the last reply you get a lot of data for busy areas where good data is already available and no data to try and enter any tidal ports.