The idea of cruisers contributing data isn't all that difficult to
imagine. Products like Nobeltec, that when equipped with a suitable
sounder can build you a "personal bathyscape" view, basically
recording data as you travel and updating the chart database with that
so if you return to an area, you have better and more detailed
sounding data. I suspect you could encode several million seconds of
cruising into a gigabyte of data... round numbers, maybe a few hundred
hours of cruising per gigabyte. A gigabyte is nothing for modern disk
drives to store, and increasingly, not all that hard for networks to
swallow.

In our case, if our Nav software would record actual depth every few
seconds (or perhaps just places where it differs significantly from
the chart database to reduce upload data!) along with the time/date
(which makes it possible to estimate tidal state) and GPS position, a
trivial task for any computer, and then allow a compressed packet of
data to be uploaded periodically when we are back at home, we could
all become part of the survey team. Imagine having thousands or even
tens of thousands of additional survey vessels out there, going the
places that commercial boats don't!!

And as far as uploading data from user experience, many programs
already do it, albeit after asking permission, all as part of
gathering data to improve the software. With some quality control
measures added to validate the data, and given the widespread use of
computer-based Nav software, this isn't far-fetched.

The key is allowing the Nav software to have access to the sounder,
which I suspect isn't as common. The hardware guys would have to make
it a standard feature for sounders to send out NMEA messages on the bus.

This is a 21st century type of solution, well within the range of
available technology, just begging for a marine industry electronics/
software standardization effort to make it real.

John Marshall

----- Original Message -----
From: "John Marshall"

REPLY
John the big issue to deal with is people and getting them  to all  follow
the same procedure.
Something as simple as  the depthsounder  can still be  muddled if the
offset is  alterred  by the user.  Some people prefer an offset that tells
them clearance under the keel or prop tip with a bit added for safety. Other
elike to change th eoffset to  water line  in the belief this now means  the
sounder  will then read same as the charted  information.  Only true  at one
stage of tide.

On our survey launch  part of our daily check was to verify  the sounder did
in fact read correctly.
Our sounder  had to be mounted  so the precise location of the sounder and
GPS antenna was coincident.  We had two  other alternative  antenna mounts
and  we had to make a note of which antenna location was used.  Otherwise
the sounder data would not match the location given by the GPS.
In field work it is typical to  make 10 or even 100 times as many readings
as what is finally shown in the database.
Given  the example of how few people bother to correctly  configure their
AIS  with vessel name  size and  antenna mount location I am not hopeful
that a depth survey program would  see any better  consistency  of
instrument calibration.

As you say, better quality control  measures would be required before such a
program  becomes a viable reality.  I wonder how many boat owners are
willing to accept such rregimentation.
You probably know of the program where volunteer  vessels  are fitted with
an scientific data collection  system.  Even though the system is almost
self contained the  owner and crew must be given a familiarization  session
in order to ensure the data is collected in a consistent and reliable way.

Arild

Arild,
I agree with you, it would take some effort, and probably some kind
of certification program, to make sure the sounder is setup properly.
Possibly even a way for the data collection software to know if
settings had been tampered with. But this isn't technically difficult,
although it does require cross-vendor coordination and some standards
to be developed.

But if such a program was available, I'd definitely participate, even  

if it cost me a little bit to get set up with the right stuff.

Like a number of other cruisers, I'm spending all this summer poking  

my nose into coves in Alaska and Northern BC, many of which have
marginal sounding data and charting, and gathering my own data. I'm
sure many others have done this as well. There are LOTS of uncharted
rocks in these waters once you get outside the normal cruising routes.

Folks who travel the ICW on the East Coast would probably also  

appreciate frequently updated sounding data in their Nav system from
people who had traveled the same route days or weeks earlier.

As another poster said, we can't wait for NOAA or CHS to do this,  

given they have different priorities. And there are literally
thousands of coves up here which can be explored, and the ICW shoaling
varies seasonally.

I think there is a huge opportunity here if the marine electronics  

industry could cooperate on some equipment, software and procedures
that everyone could use.

They might also be able to make a little money by enlisting the self- 

interest of owners who would like have better sounding data on our
boats. Maybe a deal where you can't get access to the data unless you
are also willing to equip your boat and share data from your travels.
Whatever.

John Marshall
N55-20 Serendipity
Currently lying Pillsburg Cove, northern BC

On Jul 30, 2009, at 9:27 AM, 2elnav@netbistro.com wrote:

----- Original Message -----

REPLY
The hardware is already there . We don't even need much in the way of
industry cooperation.
Most if not all chart display programs  have the ability to display depth in
a box  in the border of the display.
What is really needed  is some sort of liason and co-ordination with  NOAA
and CHS and any other Hydrographic Offices that develops  charts for use by
recreational boaters.  Or maybe C-MAP or Navionics  would be interested.

Perhaps more importantly, there is a need for some kind of  training manual
and list of procedures  that participating  boaters have to follow  in order
for the data they collect to be considered credible enough to be used for
published charts used by a lot of people.
It is not difficult to learn. But it is important that the same procedure is
followed by all participants and  calibration checks  are done to verify the
accuracy of equipment.  This requires  a measure of self discipline by
participants.

You mentioned  tides. Time of observation is a critical  part of the
process. How many people verify the accuracy of their computer clock?  My
obsrvation is most people simply take it for granted.  Latency of displayed
data is also critical when doing a running line of soundings.  This is a
function of the software.  All manufacturers  provide a means to  integrate
the displayed  position  as a rolling average. ( but can you adjust it and
by how much? )  This is necessary  to avoid jitter of the numbers. People
tend to view rapidly flickering numbers as less reliable than a rock steady
number.  Unfortunately  this latency  plays hob with accurate positioning og
the sounding unless  correct procedures and sometimes calibration is done.

HDOP is something  the user has no control over. It is  a function of the
geometry of the sattelites in view.  But  poor HDOP  affects the ultimate
accuracy of  the displayed position.  We often had to stop our surveys
until the HDOP value improved.  Data collected  when HDOP was poor was
considered useless  because it was possibly inaccurate.  Speed of advance of
the survey vessel  also has to be considered.  This also has to be covered
by the procedures.  Such factors become more critical  as the water depth
decreases. Given that recreational boaters are mostly interested in  water
depths  10 feet and under; you can appreciate why this factor  becomes
significant.

All of the above assumes the computer systems are functioning  perfectly.
<VBG>

Arild