docvandijk - 10-3-2012 at 03:57 PM
Hi folks,
I'm trying to find a bathymetric chart for the Sea of Cortez. I'm specifically interested in the East Cape region.
A bathymetric chart is a topographic map of the bottom.
My search has been nearly futile.
Thanks.
windgrrl - 10-3-2012 at 04:27 PM
Probably not the detail you want, but
Mexfish East Cape map
bigmike58 - 10-3-2012 at 05:03 PM
I'll be watching this for info...
btw, I bought the "badass" so. cal and baja platnium navionics card for my raymarine displays...you know, "The multi-dimensional marine charts that
take the navigational experience to a whole new level with 3D view, integrated aerial imagery layer, and port photos". 
my 2 yr old
with crayons does a better job of mapping the sea of cortez.
[Edited on 10-4-2012 by bigmike58]
Osprey - 10-3-2012 at 05:47 PM
Baja Judy on this forum has the very best sub marine topo map of East Cape. I bought one and loved it so much I had to give it to a friend who knows
how to use it.
bajajudy - 10-3-2012 at 06:34 PM
Here you go
http://bajabooksandmaps.com/books/EAST_CAPE.html
OOPS
If you look on the left hand side of the page you will see Fishing Guides & Charts. Click on that for the entire collection
[Edited on 10-4-2012 by bajajudy]
BajaBruno - 10-3-2012 at 09:00 PM
BloodyDecks was recently advertising a very nice Baja fishing chart book with excellent bathymetric detail. I'm not sure what the source of those
data was, however. I heard a rumor that a new survey has been done of the penninsula area, but not who did the survey.
You probably already know this, but I'll note it for those who may not. The existing charts are based on surveys up to 100 years old and are not only
very thin on bottom detail, but the land masses (and points in the water) are up to about one mile off from their actual Lat/Lon location. That makes
it very hard to find a specific point by plugging it into your GPS. I usually go to the location on the chart and then do a grid search using the
fathometer to locate a chart feature.
My chartplotter chip has the same problems. It seems to have detailed information, but little of it matches to actual observations. I compared notes
with Bill Erhardt, who has a different chip than I do, and he has the same problem with chart features not aligning with his GPS coordinates. If
someone has a chart that is accurate to a GPS, I’d love to see it.
Pescador - 10-4-2012 at 08:56 AM
The charts on the Eastern side of the Peninsula can be very accurate, but the maps are newer there. I find most of the charts to be off by up to 5
miles in the Santa Rosalia area of the SOC. Furuno used to have an adjustment procedure, but all of the others with Garmin, Lowrance, Humminbird, and
Raymarine are mostly from maps that were done 1945-1954. The Cartographers are not quick to disclose this information and continue to try to sell
their products, but they are of very limited use in the Sea of Cortez.
The Mexican Government is doing a new mapping of the area with helicopter and claims that everything will be GPS matched, but who knows how long that
will take to be available and then what kind of time lag before it is available to the cartographers.
I probably have 300 or more waypoints with information on each that I have gathered over the years about spots and depths so I can be pretty accurate
with fish locations on certain currents and tides, but it took years to develop. I also spent a lot of time with local fishermen who knew a small
area and could challenge the best GPS locations with triangulation.
In addition, I am always running with the Depthfinder at full power and will temp mark any interesting looking spots to come back to and fully explore
if they look good. That way I am not fishing on top of the locals who are trying to make a living with their fish, and the challenge is greater to
find my own spots anyway. (Course, a few seem to be following me lately)
docvandijk - 10-4-2012 at 12:54 PM
I figured this would be the right crowd to ask. I knew the existing nautical chart relies on a few soundings made by a Liberty ship before Steinbeck
wrote the Log.
I too have found differences, measured in miles, between the few charts I have seen.
Really disappointed in hearing the 3d doesn't cut it.
Thanks to everybody who chimed in to help me out. I'm on my way to Judy's.