Wednesday 06 Oct 2021 | 14:25 | SYDNEY
Wednesday 06 Oct 2021 | 14:25 | SYDNEY

Sinking Sandy Island: A data-sharing parable

29 November 2012 14:41

Olivia Wilson is a geoscientist and mapping specialist.

Sandy Island has brought ocean mapping to the forefront of news, reminding the world that exploration on this planet is still possible.

This small Pacific island can be found on numerous maps, including one dated 1908. Sandy Island, however, was shown not to exist when the Australian research vessel Southern Surveyor (pictured) sailed through where it was meant to be located. Not only did Sandy Island not actually exist, but water depths where it was supposed to be were in the region of 1400m.

Maps that displayed this island included those used by Google Earth. Nautical charts made by charting authorities, however, did not show the island. This blog has a great comparison of charts and maps that do and do not show Sandy Island.

Scientists on board Southern Surveyor (and several journalists) were quick to mock Google Earth, focusing on just how it was possible that such a large and prominent company got it so wrong. What I'd like to convince you of is that it is not those who got it wrong who we should be criticising, but those who got it right.

Producing global maps of the sea floor is difficult. It involves lots and lots of data, what the tech industry likes to call Big Data. Today, depth data is collected by ships, planes and satellites. Each technique has different advantages. Research ships, for example, can only map lines up to a few kilometres across, planes only to certain depths, satellites only to limited accuracy. Given the scale of the world's oceans, each voyage is still like shining a very small torch inside a very large cave. This data collection is expensive and it is paid for by numerous organisations, a large chunk of it by the taxpayer.

There is a lot of data out there but it is not all freely available, and there are areas where there is no data at all. But Google Earth wouldn't look nearly as good if there were holes in areas where data was not available, so scientists create models to effectively guess the depths in these areas; it's called 'interpolation'. If you look closely at the oceans on Google Earth, you can see the tracklines (highlighted by white lines I've drawn on the map to the left) of ship collected data used to make the map.

So with the combination of an incorrect coastline, low accuracy satellite data and only some surrounding high resolution data, the models may well have perpetuated the existence of Sandy Island. It was an unfortunate outcome.

Wherever the original mistakes came from, the point is that those who produced the nautical charts had access to data showing there wasn't an island there at all. The people who made the maps that fed into Google Earth did not have this data.

Data sharing is not only nice, it is also powerful. The power of data is in its use and visibility; Google Earth carries weight because it produces a great looking, easy to use, product that it distributes for free.

The US leads the way with public domain data and Australia has some default licensing along the same lines. That is a good first step but everyone needs to be on board to create the best products we can. That means legislating for data sharing, enabling simple access and facilitating a culture for it. There are too many situations where, despite legislation, sharing is effectively discretionary.

Seabed maps aren't just used for interesting imagery. There are scientists out there who use them to further our knowledge and for the public good. Seabed maps are used for climate change science and predicting sea level rise which help us to learn about what will happen to real Pacific islands in real danger of being lost. They are used for tsunami wave modeling and habitat mapping for conservation.

But the science is only as good as the data that goes into it.

Governments and research institutes need to do more than just correct this now well publicised mapping error. Sandy Island should be seen as a wake-up call. This incident is symptomatic of patchy and inconsistent international data sharing.  If the data custodians are not already opening up their databases, they need to get on board and become part of a global effort to share this data online and ensure that Sandy Island is sunk for good.

Photo by Flickr user ARM Climate Research Facility.