BajaNomad - Marine GPS and Garmin Blue charts

Marine GPS and Garmin Blue charts

Alan - 6-11-2013 at 07:43 AM

I have an older Garmin 182C with a Bluechart chip. The plotting is right on the money when on the water in SoCal. It is so accurate I have often joked that I could pull into a slip just using the plotter, just never had the courage to actually try it. :lol:

However when fishing in Baja the plotter is practically useless. For example when motoring around BoLA the plotter shows the boat traveling right across the various islands.

Does anyone know if this can be corrected by changing the datum in the setup menu and if so which datum I should use?

I know it doesn't impact the waypoints I set and I can return to them easily enough. My concern is being able to identify those shallow rocks and reefs when in unfamiliar waters. They are indicated on the charts but when in Baja they are not where they should be in relation to my boat according to my plotter.

Udo - 6-11-2013 at 07:48 AM

The Lowrance HDS-5 has been highly accurate for myself, Alan.

Alan - 6-11-2013 at 07:53 AM

Quote:

Originally posted by Udo
The Lowrance HDS-5 has been highly accurate for myself, Alan.

Yes I have considered an upgrade but I've been pretty happy with what I have, Furuno 600L and this 182C. Just hoping I could learn about an easy fix.

bill erhardt - 6-11-2013 at 09:06 AM

Alan......I had a Garmin 182 and found the same thing. Called Garmin and spoke to various techs and supervisors and all said there is no way to correctly orient the map on the chart plotter. In some places in the SOC the map is off by half a mile, or so. If it makes you feel any better, on my newer generation, touch screen 740s the problem is the same. I've become accustomed to sometimes running my boat over dry land, per my charter, and don't even notice it any more. I've long since learned to ignore the rocks and shoals marked on my Garmin chart, mark them myself with the GPS, and observe those marks although they be inland a quarter of a mile or in the center of an island.

Hook - 6-11-2013 at 09:18 AM

Quote:

Originally posted by Udo
The Lowrance HDS-5 has been highly accurate for myself, Alan.

Have you used it in the Sea of Cortez, around any islands?

Alan - 6-11-2013 at 09:24 AM

Quote:

Originally posted by bill erhardt
Alan......I had a Garmin 182 and found the same thing. Called Garmin and spoke to various techs and supervisors and all said there is no way to correctly orient the map on the chart plotter. In some places in the SOC the map is off by half a mile, or so. If it makes you feel any better, on my newer generation, touch screen 740s the problem is the same. I've become accustomed to sometimes running my boat over dry land, per my charter, and don't even notice it any more. I've long since learned to ignore the rocks and shoals marked on my Garmin chart, mark them myself with the GPS, and observe those marks although they be inland a quarter of a mile or in the center of an island.

That's what I was afraid the answer was going to be. Planning to take the boat to La Paz around the first of July. I guess I'll just have to go slow until I get the major hazards marked :lol:

gallesram - 6-11-2013 at 10:57 AM

I have a Garmin 430s and it's actually pretty accurate; I use it in the Bay of Concepcion and the plotter typically shows me right where I'm supposed to be. I wonder if it's something to do with the chip that has your maps? Maybe try reloading it or get a new one?

Pescador - 6-11-2013 at 02:06 PM

The cartography that the Garmin Blue Chip is based on for the Sea of Cortez is a 1954 survey. It is up to 4 miles off in the Santa Rosalia Area. Since Garmin does not take Navionics chips, you are pretty much stuck with the map that you have. The old Furuno would allow you to reposition the map but Garmin has never had that capability. Navionics is a little more accurate but that would mean changing out your Chartplotter. Motion X App for I-Pad is very accurate and uses Google maps for their base, but again you would need an I-pad that has GPS built in to use that.
It does allow you to see the general configuration of things and when zoomed out a long way, the map is a little less off of position, but do not try to use it for navigation.
On our boat that we use for cruising the sea of Cortez, we used the old maps and Blue charts which gave us some relative idea, but it was always a problem. The new Navionics is a little better but is still not as good as things are in the US. Until such time as we get a new cartography survey (which I understand they are working on) we just have to adapt as much as possible.

DaliDali - 6-11-2013 at 03:57 PM

A C-Map chart was/is not much better running in a Furuno chart plotter.

As Bill experienced, I found myself motoring down the island mountain ridge many times.

[Edited on 6-11-2013 by DaliDali]

Udo - 6-11-2013 at 05:50 PM

I have used it around the Ensenada area, and worked great. I'll try it in BA later this year.

Quote:

Originally posted by Hook

Quote:

Originally posted by Udo
The Lowrance HDS-5 has been highly accurate for myself, Alan.

Have you used it in the Sea of Cortez, around any islands?

chuckie - 6-11-2013 at 06:02 PM

Reminds me of a story about Irish fishermen....An englishman asked "How do you find your way in these fogs" "Well I drive the boat ya see, and Mick is in the bow with a sack of potatoes" How does that work" says the Englishman...."Well, he throws a potatoe every now and then. and if it dont splash, he says STOP ya f*****ker".....just sayin....

ncampion - 6-12-2013 at 07:46 AM

I think you'll find the same problem as the rest of us. It's not the plotter, it's the e-charts. They are all based on old surveys.

Quote:

Originally posted by Udo
I have used it around the Ensenada area, and worked great. I'll try it in BA later this year.

Quote:

Originally posted by Hook

Quote:

Originally posted by Udo
The Lowrance HDS-5 has been highly accurate for myself, Alan.

Have you used it in the Sea of Cortez, around any islands?

jgletne - 6-12-2013 at 07:09 PM

I have the Garmin 740s and had the same problem. I got in touch with a cartography tech with Garmin and he sent me a new card. He said they finally got updated charts for Mexico. I'm headed to BOLA in 10 days to try the new maps.

Alan - 6-13-2013 at 07:01 AM

Quote:

Originally posted by jgletne
I have the Garmin 740s and had the same problem. I got in touch with a cartography tech with Garmin and he sent me a new card. He said they finally got updated charts for Mexico. I'm headed to BOLA in 10 days to try the new maps.

Thats where it seemed to be the worst so it will be interesting to see if they have improved. Please keep us posted. Of course I doubt if they would work with my unit since mine uses the older card that I am sure they no longer support.

jgletne - 6-14-2013 at 06:09 PM

Will do. If I forget remind me after July 1.

msteve1014 - 6-14-2013 at 06:14 PM

Quote:

That will be good info. for a lot of people if it works out. I have a good friend with a pistachio ranch in Terra Bella, small world.

BajaBruno - 6-14-2013 at 09:47 PM

Alan, I leave the tracking on and set some waypoints. After a couple of trips out I have a pretty good idea how to avoid obstacles, like islands and beaches, so if I have to navigate at night I just follow the track and ignore the cartography.

Alan - 6-14-2013 at 10:40 PM

Quote:

Originally posted by BajaBruno
Alan, I leave the tracking on and set some waypoints. After a couple of trips out I have a pretty good idea how to avoid obstacles, like islands and beaches, so if I have to navigate at night I just follow the track and ignore the cartography.

That's exactly what I do as well and we have several barely submerged rocks in the La Paz area that are marked on the chart but not where they are "supposed" to be in relation to the boat position. Just hoping there was a simple way to slew the chart such as if the Mexican base charts used a different datum. It would also be nice to get some idea of the hazards when in unfamiliar waters for the first time out.

I am currently set to WGS84 and was wondering if someone knew that the old Mexican charts were based on a different datum such as NAD 27 or if there was a way to determine what datum was used on the specific chart that had been inputted. I know there is a way (don't remember at the moment) to determine the chart number of the input chart for bluechip for that area. Just wondering if someone figured out how to retrieve the appropriate datum.

[Edited on 6-15-2013 by Alan]

Garmin Blue Charts in BOLA

jgletne - 7-19-2013 at 11:59 AM

My new charts are still not accurate in BOLA. They seem to be better close to town, but up or down the coast, or near the big island, they are still off quite a bit.

Pescador - 7-19-2013 at 07:57 PM

Check what I just wrote on Navionics charts for BOLA to Santa Rosalia.