On 28 June, 05:10, Harald Hanche-Olsen wrote:
+ "Wilbur Hubbard" :

Tide charts usually display the depth at MLW but these amateur committee
readings will have no such reference standard. It just depends upon the
state of the tide when the reading was taken - dumb, really dumb.
Harald,
We get date/time data from the logged GPS data.
We start with predicted tide heights, but then modify these according
to actual observed sea levels at tide gauge locations.
As you say, once we get a high enough density of data in a given area,
then we can start applying statistical methods to make the overall
accuracy greater than that of the individual data points.
Tim

I don't know the details of this project, but in principle at least, it
wouldn't be hard for the logging software to include timestamps in the
log so the collected data could be corrected using tide tables. Or would
it? Of course tide tables don't predict the exact tide everywhere, but
this should get you closer. It should also be possible to get some more
reliability and accuracy by having many boaters collecting data for the
same area.

--
* Harald Hanche-Olsen * * URL:http://www.math.ntnu.no/~hanche/
- It is undesirable to believe a proposition
* when there is no ground whatsoever for supposing it is true.
* -- Bertrand Russell