We sailed south to a new island anchorage yesterday - four long tacks into a light south west wind. It took more than two hours to accomplish what had taken 45 minutes a few days before when the winds were stronger and from the north. There were virtually no waves and the wind was so light that we chose to hand steer to make the most distance on each tack.
We have on board now a new set of charts for Tonga, created from surveys carried out by the New Zealand navy. Mike on 'Kokoamo', a Scot who spends his time between here and New Zealand, had watched as the navy ship cruised through the islands taking soundings a few years ago. New Zealand has made the charts available for free and when I visited Mike on his boat, he copied the charts onto our hard drive. These are raster charts that come as a series of '.kap' files. I believe these are simply image files with some extra meta-data (such as their location and scale) to make them usable with charting software.
We use excellent free charting software named 'OpenCPN'. To add the new charts, you simply specify the directory in which they are located and the software displays these charts along with others you previously loaded. This makes comparison between charts easy and it is clear that the older surveys of Tonga are not perfectly accurate. We are often shown as being anchored on the land or as passing over reefs when in fact we are in deeper water. You can see this by toggling between the CM93 vector charts of Tonga and the new ones. In the area we are in now, the old charts are transposed by a couple of hundred meters to the northwest on average.
When I snorkeled the anchor, the wind had vanished and the water was so still that I could lie with half my mask in one world and half in the other. I cannot recall another time on this trip when I have swum in still water. Later we sat on deck watching the sun dip into the clouds and a full moon rise. Beams of moonlight filtered through the high scudding clouds and the anchorage was lit by the reflections dancing lightly on the lapping water. As night descended, the bird songs quieted and a gentle chorus of insects took their place reaching across the bay from the nearby jungle. We feel so lucky at times like this.
Today we must find water, for our tanks are running low. We know of a cistern on an island a few miles from here, so will sail there when the wind returns.