Friday, May 29, 2009

Comments on electronic charting in the Bahamas

Chris here... Well, it's almost time to head back to the US for the cruise up the east coast, and then back down here next Fall and on to the DR (or perhaps Cuba if we can). If you're not interested in boating "technology", just skip to Kristen's latest post below on snorkeling.

Before we left for the Bahamas I was unsure as to what to use for electronic navigation. Now I know, and I figured I'd share it with y'all. Keep in mind that this information strictly pertains to the following areas: Bimini, The Banks, Northwest Passage, Nassau, Exumas, Georgetown area, Cat Island, Little San Salvador, and Southern and Northern Eleuthera. I can't comment on areas such as the Abacos, Grand Bahama, Andros or the outer outer islands, but based on my cursory examinations of these areas and comparison between the solutions we have on board, I would tend to think this information is relevant for all the areas of the Bahamas.

On board Pelican we have three different kinds of charts - our Raymarine C-Series chartplotter with Navionics Gold charts (latest version as of 12/08 - supposed to be the most updated version), our Garmin Oregon handheld GPS with Bluechart G2 built in charts, and on our laptop we have Rosepoint Navigator Coastal Exlorer 2009 with Navionics S-63 charts of the Bahamas from Chartworld (these ain't cheap!). We also have the paper based Explorer Chartbooks, which are considered the gold standard for the Bahamas.

Which chart is the best? Without a doubt, the Garmin charts blow away the Navionics charts - no question. Explorer licensed their charts to Garmin and C-Map and they have been integrated into the C-Map and Garmin charts.

I have found that depths on the Navionics charts are often inaccurate, and large areas are just unsurveyed. I was hopeful since when I spoke to Navionics at the Miami Boat Show they told me that their charts of the Bahamas were recently updated - that they did their own surveys of the Bahamas and have updated large portions. I can definitely say that some portions of the Bahamas are better than others (Bimini and Nassau for example), but crossing the banks, the Yellow Banks, the Exumas, Georgetown, Cat Island, and now Eleuthera are either missing a lot of information or have inaccurate information.

For example, right now we're right off of Harbor Island. On our way here we had to navigate the "Devil's Backbone". This is an area on the northern tip of Eleuthera that has densely packed coral heads, rocks and a very slim channel. In several places you have about 75 feet of width to navigate through in order to get through the reefs. Other places you have to run 20 feet off the beach. It is considered one of the most treachourous places in the Bahamas to navigate in order to reach a populated area. The recommended method of navigation through this area is to hire a pilot to bring you through. We did this (about $80 for one boat or $60 each for two boats) but I kept my Garmin in the cockpit for the run. I also had my Raymarine chartplotter on.

Most of the coral heads and reefs were not marked on the Raymarine chartplotter (Navionics charts). In a number of places the depth on the chartplotter would show 10 feet and we'd only have 7 feet under us - at high tide. This is just dangerous. The charts on my laptop were the same - just inacurrate.

The Garmin, however, was spot on - showing all the dangerous coral heads and the correct depths. I turned on the "track" mode on the Garmin so I could review our path later, and there's no question in my mind - we could have made it through the area using the Garmin (and visual navigation). Depths were correct as were the locations of the coral heads.

So what are my thoughts? I'm happy we bought the Navionics charts for our laptop. Even though the depths aren't always correct, I can do all my planning and "what-if" scenarios on the laptop and then transfer them to the chartplotter. I can then use the Garmin (and the paper charts) for close in navigation. The Navionics charts are accurate with regards to coastlines, cuts, etc. so they can be used for broad navigation.

If I was to pick a single solution to use and we were only looking to navigate the US and the Bahamas, I would definitely pick either Garmin or a C-Map solution (Furuno, Northstar, Simrad, Si-Tex, Standard Horizon and a few others). If you are looking to go around the world, I've heard (but can't confirm) that the Garmin charts are not as good or are unavailable, so I'd go with a C-Map solution or a Navionics solution. Navionics is better than C-Map in certain areas of the world, and C-Map is better than Navionics in other areas. If you already have a Raymarine system or other Navionics system on board, look at supplementing this with a handheld Garmin unit.


Maria Sheridan said...

Chris, thanks for the info. We used Coastal Explorer back in 2006 along with Explorer paper charts. We felt we were okay but if we do it again, it's nice to know there are better options.

Melissa said...

You are not the first or last person to say not so good things about the Raymarine charts. When I went to Bimini I also found the charts way off. So let me know if you head back to Miami area!