Abel Tasman's mystery New Zealand coastline

Everyone has heard of Abel Janszoon Tasman.

He was the first European explorer to see New Zealand.

But Isaac Gilsemans?

Tasman, Gilsemans and Francoijs Visscher were together in Japan in 1640.

It was there that they conceived, planned and promoted an expedition in search of the fabled Great South Land in the South Pacific.

Their zest for exploration led to the voyage which brought them all to New Zealand in December 1642.

Tasman was in charge and Visscher was chief navigator of the little two-ship fleet - the Heemskerck and the Zeehaen.

Gilsemans took part in the 1642-43 voyage as merchant on the Zeehaen - the officer in charge of trade goods - and as a skilled "drawer of lands."

Writing about Gilsemans in his new book The Merchant of the Zeehaen, Grahame Anderson calls the Dutchman "virtually unknown, and certainly unsung."

"He plays no part in the conventional history of the discovery of New Zealand as it has been told in the history books," Anderson says.

But he declares that Gilsemans made a major contribution to the 1642 voyage and others by Tasman.

Anderson says he has shown him to have been the author of many previously anonymous or otherwise attributed documents among the records of Dutch oceanic exploration.

But more important, Anderson also puts Gilsemans into context in New Zealand cartographic history as the first European artist to draw views of the New Zealand landscape.

Anderson, an architect and writer, lives in Nelson.

His interest in draughtsmanship, history, sailing and the New Zealand seashore sparked an initial discovery.

This lead to more research and, eventually, the book.

He writes in his preface that the book grew out of an attempt to discover the answer to what seemed a simple question about one of the coastal illustrations in Tasman's 1642 journal - who was the artist?

It turned out to be Gilsemans, who drew the other illustrations of New Zealand in the journal.

He was also responsible for other drawings done during the voyage, including those of the Tasmanian coast.

The perplexing illustration that concerned Anderson showed a "strangely curved perspective of an unidentified stretch of coast" - long thought to be a rough sketch of some part of the east coast of d'Urville Island - the western limit of the Marlborough Sounds - or perhaps part of Admiralty Bay, lying to the north of French Pass.

Tasman had anchored thereabouts and ridden out a five-day northwest gale over Christmas 1642, after his deadly encounter with Maori in Murderers' Bay, now Golden Bay.

His given plots, recorded with the aid of inaccurate and inadequate instruments, did not quite tally.

But by carefully following Tasman's tracks and working from the explorer's journal, Anderson determined that the anchorage had to be on a line south-southeast from Stephens Island in Cook Strait, in 33 fathoms (66m) of water.

In February 1985, Anderson motored on a friend's yacht westward along latitude 40 degrees 56 minutes until Stephens Island lay north-northwest and the depth sounder confirmed 33 fathoms.

"And that was all the searching we had to do.

"As we stopped, the whole scene simply fell into place. Not vaguely or partially ... but with clarity and precision."

Gilsemans' drawing was all-embracing rather than local in its depiction of the scene.

The drawing represented an accurate, panoramic coastal landscape from Cape Jackson in the southeast to Cape Stephens in the northwest - almost the entire northern end of the Marlborough Sounds.

The islands, rocks, headlands and peaks stretching around the horizon from the yacht exactly matched Gilsemans' drawing.

Anderson said the illustration was a precise record.

"There can no longer be any dispute or doubt.

"On December 21 1642, the Heemskerck and Zeehaen anchored ... three nautical miles from the east coast of d'Urville Island and five miles south of Stephens Island.

"The journal illustration was drawn, with considerable accuracy and attention to details, from that position."

Anderson says that by pinning down the anchorage (he gives the exact latitude and longitude) he had found the key to the New Zealand section of Tasman's journey by knowing how much error there had been in the Dutchmen's daily calculation of their positions.

Anderson's book shows a redrawn and precise plot of the Dutch ships' course along New Zealand's west coast from arrival to departure.

* The Merchant of the Zeehaen: Isaac Gilsemans and the Voyages of Abel Tasman, published by the Museum of NZ, was launched by Te Papa Press in Wellington on Friday.

- NZPA