On Sun, 16 Jan 2005 11:04:38 -0500, "Glenn Ashmore"
wrote:

http://www.goupstate.com/apps/pbcs.d...60/1051/NEWS01

Not that any of us will be cruising at 30 knots 500 feet below the surface
but navigating soly by GPS you are just as blind. Many of the charts we use
are from surveys over 100 years old.

Indeed. I was looking at some Softcharts of SW Carribean last night.
I loaded up some GPS tracks captured in the area and was unsurprised
to see a track pass through the middle of a sizable island.

It's an interesting situation. The government cartographic agencies
trust a century old report from a vessel that may not have gotten a
celestial fix in days, but not a solid GPS fix from a yachtsman.

I've often wondered whether it would be feasible to implement a public
or private program for vessels to have their instrument suites
validated and a way for them to upload the data to a central
authority.

With enough reports from a given area, said authority would then apply
statistical techniques to validate the data. For instance, my
cpRepeater program captures water depth, temp, and position (among
other things) and logs them. I could easily add something like an MD5
algorithm to digitally sign the log, proving that it has not been
altered. That would suffice for soundings. A snapshot of a radar
display would locate shorelines precisely.

The analysis would be tricky: apply celestial tide state, smooth the
results, look for outliers in the data, decide whether the resultant
confidence level in the data is sufficient for navigational use.
__________________________________________________ __________
Glen "Wiley" Wilson usenet1 SPAMNIX at world wide wiley dot com
To reply, lose the capitals and do the obvious.

Take a look at cpRepeater, my NMEA data integrator, repeater, and
logger at http://www.worldwidewiley.com/