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Uluru from the air

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Written by netkingcol

February 12, 2014 at 5:41 pm

Joshua Slocum in Google Earth: Mauritius to Port Natal

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Follow Joshua Slocum’s Sailing Alone Around the World at: http://www.hazelhurst.net/Slocum

Fully provisioned and rested, Slocum sails from Port Louis, Mauritius on 26Oct1897. At first the winds are light and he draws away from the island slowly. By the next day he is passing the island of Réunion. The sea is too rough to consider landing, but a pilot comes out of Galets on the north-west corner of the island when Slocum hands over a Mauritius paper.

A course is set to Cape St. Mary, the southernmost point of the island of Madagascar. The trade winds are weakening now and by 30Oct1897 Slocum finds himself becalmed:

The sloop was now drawing near the limits of the trade-wind, and the strong breeze that had carried her with free sheets the many thousands of miles from Sandy Cape, Australia, fell lighter each day until October 30, when it was altogether calm, and a motionless sea held her in a hushed world. I furled the sails at evening, sat down on deck, and enjoyed the vast stillness of the night.

On the following day, a light breeze carries the Spray past Cape St. Mary. About one week later and for the rest of the voyage to Port Natal (Durban) strong gales batter the yacht and heavy thunderstorms were prevalent¹.

Here the Spray suffered as much as she did anywhere, except off Cape Horn. The thunder and lightning preceding this gale were very heavy.

It takes the Spray 18 days to cover the 800 miles between Madagascar and Durban, an average of 45 miles per day made good. This is less than half the distance per day that she is capable of. In reality, the course is not a straight line because the “succession of gales of wind…drove her about in many directions.” So, the Spray is sailing as fast as ever, but on some crazy zig-zag course dictated by the winds².

Slocum stays in Port Natal for four weeks; he meets all the members of both yacht clubs and sails on the crack yacht Florence; he meets Henry Morton Stanley, the Welsh-born naturalised American who is a renowned explorer of Africa; and he encounters a trio of men who believe that the world is flat. They visit Slocum actually expecting to find information that will support their hypothesis. He must disappoint them:

With the advice [to them] to call up some ghost of the dark ages for research, I went ashore, and left these three wise men poring over the Spray‘s track on a chart of the world, which, however, proved nothing to them, for it was on Mercator’s projection, and behold, it was “flat”.

The Spray sails from Port Natal on 14Dec1897 and is once more: “off on her alone,” as they say in Australia.


The section of Joshua Slocum’s journey reported here concludes Chapter XVII of Sailing Alone Around the World, and this post is a trailer for the adventure that I am retelling in Google Earth at:  http://www.hazelhurst.net/Slocum

Notes

1. Thunder and lightning or rather lightning followed by thunder was a fresh challenge to my animation skills. Again, I used models created in Google SketchUp to represent the effect of lightning; I added to this a couple of thunder tracks from the WavePad sound effect library. Normally I would try to enhance TourMaker by adding a directive that would generate the thunder and lightning automatically. This time I hand-coded it. Each lightning model flashes on and off twice (by setting visibility=1 then visibility=0 ) with each period of visibility lasting about 100ms. A few seconds later the thunder-clap audio is output.

2. I realised that a better animation of a rolling yacht would result from oscillating the angle of roll about the current ‘Roll’ setting, rather than about the vertical. This would create the effect of the yacht being heeled over in the wind while  waves introduce an additional periodic rolling motion. I have amended TourMaker accordingly

Copyright © Colin Hazlehurst, 2012

Joshua Slocum in Google Earth: Thursday Island to Christmas Island

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Follow Joshua Slocum’s Sailing Alone Around the World at: http://www.hazelhurst.net/Slocum

A few days after the celebrations on Thursday Island to mark Queen Victoria’s diamond jubilee, Slocum sets sail. He heads westward, out into the Arafura Sea, passing Booby Island on the way. He has seen the island before, about 30 years back, but then he was in a fever (possibly contracted in Batavia for his ship, the Soushay, was Sydney-bound from that port), and it was only through an act of will that he dragged himself on deck to see it.

While the sea is relatively shallow he sees many sea snakes writhing and tumbling in the waves and, because the waning Moon leaves the nights dark, he is treated to a fiery display of phosphorescence¹:

It was my good fortune to enter the [Arafura] sea on the last quarter of the moon, the advantage being that in the dark nights I witnessed the phosphorescent light effect at night in its greatest splendour. The sea, where the sloop disturbed it, seemed all ablaze, so that by its light I could see the smallest articles on deck, and her wake was a path of fire.

The weather is serene and the trade winds favourable. Slocum takes this northerly route in order to enjoy these conditions; he has no desire to go around the Cape of Good Hope before the middle of the southern summer and he finds that this plan gives him the time to loiter among the islands along the way.

Even so, as an inveterate sailing ship master he wants to get the best speed out of his vessel. For whatever reason he is dissatisfied with the Spray‘s pace and to remedy this he sets his flying-jib as a spinnaker², using as a pole “the stoutest bamboo that Mrs. Stevenson had given me at Samoa.”

As in the Pacific, the Spray holds her course with remarkable accuracy and for days on end he finds the latitude at noon to be 10° 25’S.

By 02Jul1897 Slocum sees the island of Timor to the north; the next day he passes close by Dana Island off the western end of Timor and smells the fragrances wafted offshore by a breeze. He has crossed the Timor Sea and he enters the Indian Ocean heading for Christmas Island about 1,000 miles distant, arriving eight days later on 11Jul1897.


The section of Joshua Slocum’s journey reported here concludes Chapter XV of Sailing Alone Around the World, and this post is a trailer for the adventure that I am retelling in Google Earth at:  http://www.hazelhurst.net/Slocum

Notes

1. Using  TourMaker I simulated the phosphorescence that Slocum saw by stretching out a white strip to keep pace with the Spray.

2. I needed to create another model to show the flying-jib set as a spinnaker. While I was about it I swung out the mainsail boom to give a goose-wing effect.

Copyright © Colin Hazlehurst, 2012

Joshua Slocum in Google Earth: Cooktown to Thursday Island

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Follow Joshua Slocum’s Sailing Alone Around the World at: http://www.hazelhurst.net/Slocum

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Slocum sails from Cooktown on 06Jun1897 and by the evening of the 7th the Spray is at anchor near the Claremont Islands. Apart from in harbour at Port Denison and Cooktown, this is the only time Slocum anchors in the Barrier Reef Channel. By the next evening he wishes it isn’t. The Spray is sailing into the night at full speed ahead and passes the light-ship at the southern end of ‘m’ reef.¹ He expects there to be a beacon light at the north point; if there is one he doesn’t see it and the Spray strikes the reef. The next swell carrier her safely over but not before Slocum sees the ugly sharp coral rocks and realises just how lucky he is.

Keeping further out to sea now, heeding the advice to keep clear of the residents of Cape Grenville,  Slocum passes outside all of the islands including Home Island off the tip of the cape itself. He squares away westward in the direction of Sunday Island and shortens sail as he passes it; he doesn’t want to reach Bird Island before daylight — that island group is low-lying and surrounded by navigational hazards. On the morning of the 9th Bird Island is only 2.5 miles ahead, so he was lucky again that the current carrying him along was not stronger.

He spends the rest of the day sailing from Bird Island to Cape York, navigating Albany Pass, between mainland Australia and York Island, “as the sun drew low in the west over the hills of Australia.”

He anchors in a cove near the Tawara, an American built and skippered pear-fisher. Next day, he spends a pleasant few hours with the crew of Tawara and with the Jardine family from nearby Somerset. It turns out that Mrs. Jardine is cousin to Faamu-Sami, princess of Samoa and daughter of King Malietoa, who had visited the Spray at Apia.

From this cove, Slocum makes the short trip into the Torres Strait across to Thursday Island. He finds that celebrations are planned for Queen Victoria’s diamond jubilee on 22Jun1897, and doesn’t need much persuading to extend his visit here.


The section of Joshua Slocum’s journey reported here continues Chapter XV of Sailing Alone Around the World, and this post is a trailer for the adventure that I am retelling in Google Earth at:  http://www.hazelhurst.net/Slocum

Notes

1. On the evening of 08Jun1897, the Spray struck a reef and luckily there was enough water for the next swell to carry her over it. Slocum identifies this as ‘M Reef’; however, a search of the web delivers no information about the location of this hazard. I didn’t want to use a random reef in the animation so I had to dig further until I found an online version of a chart compiled from mid-19th century surveys by the Great Britain Hydrographic Department. The chart is made available by the National Library of Australia.

British Hydrographic Department chart showing the reefs of the Barrier Reef Channel

By close examination of the chart, I was able to find the identification letters of the significant reefs that skirt the Barrier Reef Channel. I couldn’t find all of them but at least it was clear which is ‘m’ reef.

To help anybody else who is looking for reefs in the Barrier Reef Channel using their identification letter, I have plotted them in Google Earth and kept their labels visible throughout the animation.

2. This chapter of Slocum’s book is one in which a lot of ground is covered with relatively few words. I like the animation of the model Spray to coincide with the narrative so, at times, it is necessary to move the model to a new location without accompanying voice-over. This can seem like an awkward silence and to overcome it I use two techniques:

  • The background sound effect of water lapping against the hull; if nothing else this helps to distract sufferers of tinnitus from their condition, and it does seem to work.
  • Using the ‘Show’ directive of TourMaker, I pop up labels that identify significant landmarks like capes, islands, and bays.

3. I am using an unabridged version of Sailing Alone Around the World. There are a few places where I have chosen not to speak the words that Slocum wrote as they are offensive to the modern ear. This chapter includes one such passage in which he describes the appearance of the men and women who travelled over to Thursday Island for the jubilee celebrations.

Copyright © Colin Hazlehurst, 2012

Joshua Slocum in Google Earth: Whitsunday Passage to Cooktown

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Follow Joshua Slocum’s Sailing Alone Around the World at: http://www.hazelhurst.net/Slocum

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Captain Cook, taking Endeavour through Whitsunday Passage (named by him because 03Jun1770 was Whit Sunday), sailed through the night and arrived the following morning at: “a lofty promontory that I named Cape Gloucester”.

Joshua Slocum, a few days short of 127 years later, passes here on 26May1897. His charts show more accurately than Cook’s survey that the promontory is actually detached from the mainland and is now called Gloucester Island. The Spray hauls into the bay to the west of the island and anchors at Port Denison, close to the small town of Bowen.

Bowen at that time has a population of around 1,000; large enough to support a keen audience for Slocum’s story.

By 31May1897, the Spray, has carried Slocum safely through 350 miles of the Great Barrier Reef. Without anchoring anywhere, Slocum sails past many of the other capes, bays, and islands named by Cook:

  • Cape Upstart
  • Cape Cleveland
  • Cleveland Bay
  • Cape Richards
  • Rockingham Bay
  • Cape Grafton
  • Fitzroy Island
  • Cape Tribulation (“for here all my troubles began”)

Cook also named the Endeavour River, for it was here that H.M.Bark Endeavour was beached for repairs after she had struck a reef just north of Cape Tribulation (the reef was named unsurprisingly Endeavour Reef).

Cooktown was certainly in existence before the gold rush of the 1870s, when the settlement grew rapidly as a supply port, because Slocum reports visiting on the steamship Soushay in 1866; he didn’t see much of it at that time because he was ill with a fever.

The “lecture tour” continues when a meeting is arranged in the Presbyterian church and Slocum delivers his “story of the sea.”


The section of Joshua Slocum’s journey reported here opens Chapter XV of Sailing Alone Around the World, and this post is a trailer for the adventure that I am retelling in Google Earth at:  http://www.hazelhurst.net/Slocum

Copyright © Colin Hazlehurst, 2012

Joshua Slocum in Google Earth: South Solitary Island to Whitsunday Passage

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Follow Joshua Slocum’s Sailing Alone Around the World at: http://www.hazelhurst.net/Slocum

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After exchanging signals at South Solitary Island, Slocum continues north and on 19May1897 sails past Point Danger, named by Captain Cook after his encounter with shoals and strong currents there.

On the 20th, the Spray rounds Sandy Cape, a significant point that marks the beginning of the Great Barrier Reef. The light on Sandy Cape is visible for 27 miles and his next way point is the Lady Elliot Island light. This is important to find because Slocum is heading into a dangerous region shoals and reefs and all the charts in the world are of little use if you don’t know where you are. Lady Elliot Island is about 45 miles from Sandy Cape but it seems to take an endless time to cover that distance. Slocum concludes he is pushing against a strong current.

The Spray had sailed for hours in suspense, evidently stemming a current. Almost mad with doubt, I grasped the helm to throw her head off shore, when blazing out of the sea was the light ahead. “Excalibur” cried “all hands,” and rejoiced, and sailed on.

So he finds the light on Lady Elliot Island¹ and passes into the serene, but still risky, waters inside the Great Barrier Reef and is protected from the worst of the Pacific Ocean’s waves. Progress is good and the Spray averages 4.6knots over the next four days:

On the 24th of May, the sloop, having made one hundred and ten miles a day from Danger Point, now entered Whitsunday Pass, and that night sailed through among the islands. When the sun rose next morning I looked back and regretted having gone by while it was dark, for the scenery far astern was varied and charming.


The section of Joshua Slocum’s journey reported here concludes Chapter XIV of Sailing Alone Around the World, and this post is a trailer for the adventure that I am retelling in Google Earth at:  http://www.hazelhurst.net/Slocum

Notes

1. The  technical challenge in this part of the presentation was to simulate the light from the Lady Elliot Island lighthouse. I wanted to create a beam of white light that rotates about the location of the lighthouse; furthermore, I wanted it to have the same characteristic as the current light, which is described on charts as: Fl.W. 7.5s. This code means that the light is white and flashes every 7.5 seconds.

To achieve this I needed two things:

  • A model to animate.
  • A TourMaker directive to generate the animation.

I created the beam of light by drawing a cone in Google Sketchup and colouring it white. The cone was about a mile long, oriented along the green axis, which is north when the model is exported to Google Earth, and its apex was placed about 100 feet above the origin.

In the KML file for this leg of Slocum’s journey, I added the model as a Placemark, positioning it at the latitude and longitude of the Lady Elliot Island lighthouse (at the south end of the island). I set the visibility of the Placemark initially to zero (invisible), because I wanted to ‘turn on’ the light at the instant in the narrative that Slocum sees it.

To simulate a rotating beam I would need to animate the model by changing its orientation. By placing the origin of the model at the position of the lighthouse, a change in its orientation would have the desired effect of a light sweeping round.

I measured the angle subtended by the model and found that the edges of the cone were 15° apart. To achieve a smooth rotation, I would want each new orientation of the model to be no more than 15° away from the last one. I also knew that the beam should sweep through 360° in 7.5 seconds, in other words its angular velocity should be 360/7.5 degrees per second, which  comes out at 48° per second.

I used this information to determine how many orientation changes per second would be required to generate a smooth animation at the required rotation rate. Quite simply, if each animation step rotates the model by 15° and we need to rotate the model at 48° per second, then we need 48/15 animation steps per second (3.2), so the duration of each animation step should be 1/3.2 seconds (0.312s).

All of this is easy to code, taking only a few hours of development and testing. To control this behaviour, I added a ‘Rotate’ directive to TourMaker, and its parameters identify which model to animate, the duration of the animation, the angular velocity required, and the delay until the animation should start. This last parameter allowed me to switch on the beam as the narration reads:

Almost mad with doubt, I grasped the helm to throw her head off shore, when blazing out of the sea was the light ahead

The animation starts at the word ‘blazing’; the Placemark is made visible, the light sweeps around for 30 seconds and the Placemark is then made invisible.

Copyright © Colin Hazlehurst, 2012

Joshua Slocum in Google Earth: Devonport to South Solitary Island

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Follow Joshua Slocum’s Sailing Alone Around the World at: http://www.hazelhurst.net/Slocum

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By 18Apr1897, Joshua Slocum judges that the southern summer is over and it is time to head north away from the winter which is “rolling up from the south”. He sails from Devonport in bracing winds that carry him quickly around Cape Howe at the south-east corner of mainland Australia. He exchanges signals again with the residents of Cape Bundooro and then has a fine sail with clear skies to Port Jackson, Sydney, where he anchors in Watson’s Bay, close to the entrance to Sydney Harbour. He is impressed by the number of boats of all shapes and sizes working and having fun in the harbour:

The harbor from the heads to Parramatta, up the river, was more than ever alive with boats and yachts of every class. It was, indeed, a scene of animation hardly equalled in any other part of the world.

A few days later the weather is much rougher and a steamship, struggling into harbour from the heads, while Slocum is ashore, collides with the Spray and rips away her anchor and chain. The captain of the steamship takes the Spray in tow to pull her out of further danger and she is returned later by some of his crew¹:

But what yawing about she made of it when she came with a stranger at the helm! Her old friend the pilot of the Pinta would not have been guilty of such lubberly work. But to my great delight they got her into a berth…

Slocum sails from Sydney on 09May1897 in fair weather and with strong winds from the south-west. He falls into an easy routine, reading day and night, and occasionally trimming the sails. He remembers the struggle, several months earlier, when he had to fight southwards past these headlands, to Newcastle; he compares his life now with that of the old circumnavigators. He feels that he’s having rather an easy time of it².

Ten miles short of Port Macquarie, Slocum comes upon a yacht in distress. She is manned by the three most incompetent crew he has ever encountered; their appreciation of the perilous situation they are in is scant and their ineptitude has resulted in the loss of their sounding lead and their dinghy. They refuse his offers of help; he wants to tow them to Port Macquarie but they are not interested. He reads later, in a Cooktown newspaper, that the yacht was lost off Crescent Head but the crew was saved.

Pressing on, Slocum comes up to South Solitary Island, a “dreary stone heap in the ocean just off the coast of New South Wales”, and exchanges signals with the people on it. By way of identification, he raises the Stars and Stripes and assumes that the people ashore know all about his voyage for their next message is simply: “Wishing you a pleasant voyage”, and Slocum writes: “…which at that moment I was having.”


The section of Joshua Slocum’s journey reported here continues Chapter XIV of Sailing Alone Around the World, and this post is a trailer for the adventure that I am retelling in Google Earth at:  http://www.hazelhurst.net/Slocum

Notes

  1. To get the Spray to yaw as she was sailed back to Watson’s Bay by her lubberly crew, I needed to implement an ‘AnimatedYaw’ directive in TourMaker. This function oscillates the heading of the model, by the number of degrees in the ‘angle’ parameter, to either side of the calculated bearing between the two Placemarks that define the model’s movement over the ground.
  2. Slocum had on board “a full set of admiralty sheet-charts of the coast and Barrier Reef”. It’s worth taking a look at the journal of the man who first surveyed the eastern coastline of Australia and created the first version of the charts that enabled Slocum to have a relatively carefree voyage in these waters: Captain Cook’s Journal During the First Voyage Round the World.

Copyright © Colin Hazlehurst, 2012

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