Navigate the Pacific Despite the Bad Charts

By Art on (with 2 comments)

Once you decide to visit Fiji with your sailing yacht you begin to understand that the navigation charts you have trusted in most places of the world are way less useful here. Whether you are using charts on your navstation plotter from Navionics or Jeppesen, chart programs on the iPad, MaxSea, OpenCPN, Admiralty paper charts or even the local charts you can buy here in Fiji… you soon realize they all are pretty terrible for anything outside the Nadi and Suva areas.

In fact, they are so bad you can barely go anywhere without fear of crashing into something hard. So, what do you do to find your way around with more confidence? Well, our captain, Andrea, came up with a system we are happy with and we will share it with you so you can you decide if it is something that can help you too.

Since the charts (whether printed or electronic) are of such low resolution and the depths so questionable, how do you safely get from ‘point A’ to ‘point B’? Some passages on the charts between islands show ‘green’ meaning they are exposed at low tide however they might really be 20 meters deep. How can this be?

See the following images. On the left is a Navionics chart showing a green area (exposed at low tide) yet the Google image on the right clearly shows deep blue water all the way into an anchorage (remember, we have a 4m draft!). As it turned out, we never saw less than 20m on this routing using the Google image.

Which would you rather use for navigation?

When we asked the local authorities why the charts are so terrible, the answer we got is that the only areas that are properly sounded and charted are the places the commercial vessels go. Meaning big ports, passes through the outer reef to ocean, etc. Smaller areas that only yachts frequent are not worth the expense to chart. So you are very much on your own here!

So Andrea decided the way to do it is to use as much data as we can to make a good decision. We have purchased local charts here in Nadi that are marginally better than the one you can buy from the UK Admiralty however the one thing that never lies is an overhead photo.

For this we are very lucky that Google and Bing have taken satellite photos however, they are not geo-synched to your GPS so despite now having images that show you where the underwater hazards lie, they do not show you where your boat is at a particular moment in relation to the hazard.

Luckily there is a wonderful program for the iPad, Android and Windows called OvitalMap that does this (free but a little financial support allows faster downloads and more features). Without this program we would not be so confident moving our sailing yacht around these reefs. Supporting a developer who helps keep our yacht safe is worth the $3.99 he requests if you like the program!

OvitalMap allows you to download high resolution images of an area and then shows your GPS location on it (assuming you have an iPad with GPS or a USB GPS for your Windows computer). It doesn’t just allow one resolution of the image but, just like Google Earth, you can zoom in many levels to get more and more details. Once downloaded the images stay cached within OvitalMap for use offline. We have an iPad at the helm at all times while on passage.

Note: in OvitalMap you can choose to get images from either Google or Bing and sometimes, when an area has clouds over it in the image from one supplier, you can switch to the other supplier and get a clear image so it’s worth it to take a preview of images from both sources. The image below shows the same area in Fiji with the one from Google on the left and the one from Bing on the right. Our path through a pass in the outer coral reef is much clearer from Bing.

Same area of Fiji, Google image on the left, Bing image on the right

Our routine now is to spend time before our passage looking at the best path through the reefs, downloading all the images we need while we have good internet (Fiji has great internet!) and plotting the longitude/latitude coordinates on our chart plotter for a safe route to follow through the outer reef and into our anchorage.

We end up looking at a passage visually from the Google/Bing images to decide where it is safe to pass and where to anchor. Sometimes, this route is in direct conflict with what our other charts show however we’ve grown to trust the visual more than the printed charts.

Caution: While the images from Google and Bing are marvelous, they are not always complete.

The areas of, what Google and Bing decide, are ’open water without obstacles’ are not imaged and are shown as blurred areas. Be cautious here and check your paper and electronic charts as there could be some reef or even a small island there that the Google and Bing people decided was too small to care about showing an image for!

The color of the water in the Tropics allows you to visually estimate depth as it’s very easy to see the lighter blue colored areas, the brown reefs and the deeper blue water. All are good indicators of what is beneath the surface. The bommies and rocks all show up pretty well however don't expect this to work very well in water with poor visibility as you have in most other places of the world.

Be aware, we do not blindly follow this path but also put a crew member on the spreader with polarized sun glasses and binoculars as well as another crew member on the bow. For us, trust only goes so far when it comes to the possibility of bashing the boat into something hard!

In addition, while in New Zealand last year, we took the opportunity to install a ForwardScan sonar system for our B&G equipment and it has really come in handy for being able to see ahead of the boat as we slowly ease our way into a shallow area to anchor. We can ‘look’ 100+ meters ahead of the boat and down to 30-40+ meters in depth. Being able to see what’s ahead has helped tremendously to avoid hitting something.

Plastimo EchoTest II In some cases, where we doubt all the information we have onboard, we’ll get in our tender with a portable depth finder (the Plastimo EchoTest II is a good one) and an iPad set on tracking mode in one of the chart programs (like iSailor or Navionics). We can then research a clear path through at the depth we need. Once we get back to the yacht, we simply follow the iPad track to a safe anchorage. This is the ultimate ‘fall-back plan’ that always works.

After almost three months of navigating around Fiji we’ve done very well so far and are encouraged that perhaps we’ve come up with a system that works. We'll continue to test this system as we move on to Vanuatu and New Caledonia over the coming months but we're encouraged that we have found a good set of tools to use in helping us safely navigate here in the Pacific.

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Comments so far

  • comment from Bob Mc Davitt Bob Mc Davitt on August 21, 2016

    Bob McDavitt here. I have linked to this post from My Blog

  • comment from Eve Eve on August 16, 2016

    Auntie and I thank you for sharing OvitalMap with me in Fiji, Art. It has made exploration the grand adventure it should be, not the apprehension-filled tense one it was! it has also worked well for me in Vanuatu, so download all points you expect to encounter prior to Vila which is the first internet access location in Vanuatu. See you In some beautiful anchorage somewhere down the island chain! Eve