This is oldest original cartographic artifact in the Library of Congress. Map showing Mediterranean Sea from the Balearic Islands to the Levantine coast; also covers western part of Black Sea. Author is anonymous, probably Genoan
John Hessler, mathematical wizard and the senior cartographic librarian at the Library of Congress, slipped into the locked underground vaults of the library one morning earlier this week. Hessler, 49, is one of the world's leading experts in trying to decode the mysteries of the early world maps.
Slim, handsome, intense, bespectacled, Hessler approached a priceless 1559 portolan chart on the table before him, sketched in the hand of Mateo Prunes, the Majorcan mapmaker. The nautical map of the Mediterranean and Black seas is inked onto the skin of a single sheep.
It is a rare representative of one of the world's greatest and most enduring mysteries: where and how did medieval mapmakers, apparently armed with no more than a compass, an hourglass and sets of sailing directions, develop stunningly accurate maps of southern Europe, the Black Sea and North African coastlines, as if they were looking down from a satellite, when no one had been higher than a treetop?
The earliest known portolan (PORT-oh-lawn) chart, the Carta Pisana, just appears in about 1275 -- with no known predecessors. It is perhaps the first modern scientific map and contrasted sharply to the "mappamundi" of the era, the colorful maps with unrecognizable geography and fantastic creatures and legends. It bears no resemblance to the methods of the mathematician Ptolemy and does not use measurements of longitude and latitude.
And yet, despite it's stunning accuracy, the map "seems to have emerged full-blown from the seas it describes," one reference journal notes. No one today knows who made the first maps, or how they calculated distance so accurately, or even how all the information came to be compiled.
"The real mystery is that if you took all the notebooks from the sailors used in making these charts, along with the coordinates and descriptions," Hessler says, tapping the glass that covers the ancient vellum, "you still couldn't make this map."
Sponsored by the Philip Lee Phillips Society, the fundraising arm of the library's Geography and Map Division, it drew about 200 academics, donors and collectors to a day-long session that presented the ancient mystery of the portolans (from the Italian word for "ports"). It was one of those moments in which Washington, invariably portrayed as a dry city of faceless bureaucrats, revealed itself as a place filled with people who could, with a little fictional help, just as easily be the basis for a ripping good thriller.
"People think maybe the Romans made the first ones and they've been lost, or the Phoenicians, or even aliens," says Evelyn Edson, author of "The World Map: 1300-1492" and one of the conference's speakers. "It certainly seems related to the introduction of the compass, in the 11th century. But there's nothing at all to explain how they were made. . . . It's been very tempting for people over the years to try to make up the answer."
"The ancient Greeks and Romans had traditions of map-making, there's Ptolemy, and there's a line of progression," Hessler says. "But here, it just explodes out of nowhere. It appears to be a true invention of the Middle Ages."
Hessler's means of research isn't cultural or nautical -- it is entirely mathematical. He has taken 22 of the few hundred portolan maps known to be in existence and measured them against modern maps of the same area. He uses, say, 100 points of comparison on each map and then applies complicated algorithms to calculate the differences between each point on each map. (We could go into your basic Euclidean transformation method of calculating scales of error, and of course the Helmert transformation, but since these calculations take three or four months for each map, let's just move along.)
Hessler compares these two maps on a computer-modeled overlay, with the scale of error then plotted onto a "deformation grid." He is then able to see where the charts were more accurate and where they were less accurate, from which he infers where sailing and close observation took place, and which areas were more loosely charted. This, in turn, reveals more about the birthplace and methodology of the map. For example, the maps were good in the various seas of the Mediterranean, but terrible once out in the Atlantic, rounding up to the British Isles.
"That tells me different sources were used to make the same map," he says. "So now you start to discover where those different charts came from, and how they got to the mapmaker."
The maps usage began to come to an end during trans-Atlantic exploration. For all their regional accuracy, the mapmakers did not know how to calculate for the curvature of the earth on a flat map. Across the Mediterranean, they could take you from port to port because the distances were comparably small. Over the distance of the Atlantic, if you set out for modern-day Miami, you'd wind up on Long Island.
Still, they were reliable guides to the known world for 400 years, and they have concealed the secrets of their origins and methods for another four centuries, leaving the answers to the realm of novelists and storytellers.
"Even with all the research that has been done on them the world over," Hessler says, looking up from the Prunes masterpiece, "there's not a single question about them that we can definitively answer." Links :
MapHist, discussion group on the history of cartography
The submarine polar expedition "Deepsea Under The Pole" is an innovative human adventure, focusing on the underwater side of the icefloe, this hidden side being still quite unknown due to its difficult access.
Its objectives consist in :
realizing an audiovisual testimony (pictures, video and sound) about the underwater side of the icefloe in order to constitute its « memory » and to reveal it before it disappears victim of global warming
carrying out two scientific programs related to sea ice melting (ice and snow thickness measurement along the progression) and to human physiology under extreme conditions (particularly adaptation of divers’ decompression subjected to efforts and intense cold).
In order to reach these various objectives, 8 professional crew members have proceed on skis pulling pulkas during 45 days (from March 25th to May 11th 2010) through 1200 km of icefloe and have realized 51 dives (one as deep as 35 meters) between geographical north pole and Ellesmere Island in the extreme north of Canada (89°25'N/76°08'W, close to Ward Hunt Island), exploring the magical and surreal world underneath the Arctic ice. “The images that we are bringing back show a good testimony of the reality of the world that surrounded us here – they are magical and surreal.” reported Ghislain Bardout, leader of the expedition.
Note :Marine GeoGarage viewer based on Google Maps uses Mercator projection for maps display. Because the Mercator projects the poles at infinity, Google Maps cannot show the poles. Instead it cuts off coverage at 85° north and south. This is not considered a limitation, given the purpose of the service : there are not a lot of navigations at those latitudes, except this type of scientific expeditions...
Download this Marine GeoGarage kmz file (60.4 Mb) to display the following NOAA specific raster charts (oil spill projections -updated NOAA 5/25/10 11:33 AM CDT-) in Google Earth application :
The following widget is provided by PBS.org to calculate the extent of the oil spill resulting in the Gulf of Mexico due to the explosion and subsequent sinking of the Deep Horizon oil drilling rig. The flow rate can be adjusted to take into account the various figures being bounced around by various groups.
BP's estimate that only 5,000 barrels of oil are leaking daily from a well in the Gulf of Mexico, which the Obama administration hasn't disputed, could save the company millions of dollars in damages when the financial impact of the spill is resolved in court, legal experts say. But BP could be facing a crippling liability of up to $10bn unless its latest effort to contain the oil leak in the Gulf of Mexico meets with success. (CNBC) A preliminary internal investigation by BP has found that there were “several new warning signs of problems” in the hours before the Deepwater Horizon explosion, according to US lawmakers who were briefed by the company on Tuesday. (CNN)
Regardless of which figures are used, this is clearly an unprecedented disaster. see : underwater video of oil slick (OceanFuturesSociety) Experts at NOAA announce that they have extended the area where fishing is currently forbidden in the Gulf of Mexico. The closed area now represents 54,096 square miles, which is slightly more than 22 percent of Gulf of Mexico federal waters.
However, that didn’t stop BP Chief Executive Tony Hayward from claiming that the ongoing and largely uncontained spill is “relatively tiny” when compared to the volume of the Gulf of Mexico. (Daily Telegraph) BP attempts to plug Gulf of Mexico oil leak with mud in 'top kill' technique : company awaits test results before trying to choke off Deepwater Horizon leak by force-feeding it mud and cement. (The Guardian)
By the way, more than 650,000 gallons of chemical dispersant have gone into the Gulf of Mexico to try to break up the oil. But after giving BP the go-ahead to use the chemical, and to inject it undersea, the Environmental Protection Agency changed course yesterday and demanded that BP switch to a less toxic dispersant. (The Guardian)
Meanwhile, as BP’s solutions to stopping the leak and cleaning up the spill continue to struggle, a new savior has stepped up: Kevin Costner who is in real life, an avid environmentalist, fisherman, and greentech entrepreneur. While making Waterworld in 1995, Costner was troubled by oil spills like the Exxon Valdez and started developing a system to cruise the surface of the sea and clean oily water. “The machines are essentially like big vacuum cleaners, which sit on barges and suck up oily water and spin it around at high speed,” his business partner said in the Los Angeles Times. “On one side, it spits out pure oil, which can be recovered. The other side spits out 99% pure water”. BP and the U.S. Coast Guard plan to test six of the massive devices this week.
How high is the sky? Scientists have a pretty good handle on that one, what with their knowledge of the troposphere, stratosphere an the other "o-spheres." Now, thanks to new work headed by the Woods Hole Oceanographic Institution (WHOI), they are closing in on the other half of that age-old query: How deep is the ocean?
They're also tackling an even more intriguing -- if less romantic -- question: What is the volume of the Earth's oceans? It's hard to imagine Irving Berlin putting those words into the mouth of a serenading lover -- as he did in his classic song, "How Deep is the Ocean?" -- let alone the answer: 1.332 billion cubic kilometers.
But that figure is pure music to the ears of Matthew Charette, an associate scientist in WHOI's Department of Marine Chemistry and Geochemistry who is part of a research effort to audit all the water on the planet. "A lot of water values are taken for granted," he says. "If you want to know the water volume on the planet, you Google it and you get five different numbers, most of them 30- or 40-year-old values."
The researchers report that the world's total ocean volume is less than the most recent estimates by a volume equivalent to about five times the Gulf of Mexico, or 500 times the Great Lakes. While that might seem a lot at first glance, it is only about 0.3% lower than the estimates of 30 years ago.
What may be more interesting, he says, is how accurate scientists were in the past, using cruder techniques to measure ocean depth. As long ago as 1888, for example, John Murray dangled lead weights from a rope off a ship to calculate an ocean volume -- the product of ocean area and mean ocean depth -- just 1.2% greater than the figure Charette and Smith now report.
Starting in the 1920s, researchers using echosounders improved depth estimates significantly, according to the researchers. Most recently, Smith and others have pioneered the use of satellites to calculate ocean volume.
The trend toward a progressive lowering of volume estimates is not because the world's oceans are losing water. Rather, it reflects a greater ability to locate undersea mountain ranges and other formations, which take up space that would otherwise be occupied by water.
Satellite measurements reveal that ocean bottoms "are bumpier and more mountainous than had been imagined," said Smith. As measurements improve, ocean-volume values are lowering, he notes, emphasizing that this does not reflect an actual lessening of water but a more accurate accounting of undersea formations.
Satellite-based radar cannot "see" the ocean bottom, he explains. Rather, it measures the ocean surface, which reflects what lies beneath. For instance, if a mountain range lurks under a certain part of the ocean, the surface above it will bulge outward. "I take the data set and estimate the location and height of the mountains," Smith says.
The satellite project has covered virtually all the world's oceans, except for some areas of the Arctic that are covered with ice, he says. The result is a "new world map" of the oceans, Smith adds. "Matt and I are seeing a better picture of the shape and volume of oceans."
But satellite measurements have their shortcomings. "There is a problem of spatial resolution, like an out-of-focus camera," says Smith. "We're measuring the sea surface that is affected by mountains," he says, "but we're seeing only really big mountains, and in a blurry way. The resolution is 15 times worse than our maps of Mars and the moon."
Consequently, the researchers say, more ship-based measurements are needed to augment and "fine tune" the satellite data. And so far, ship-based sonar and other instrumentation have mapped only 10% of the Earth's seafloor. "We have gaps in echosounding measurements as wide as New Jersey," says Smith.
It would take a single ship 200 years (or 10 ships 20 years) to measure all the ocean-floor depths with an echsounder, according to published U.S. Navy estimates. "That would come to about $2 billion," Smith says. "NASA is spending more than that on a probe to [the Jupiter moon] Europa."
Charette and Smith are not sure why so little ship-based ocean mapping has been done throughout history. It may be because ocean depth and volume seem to have few direct, practical implications.
However, Charette notes, accurate estimates of ocean depth and volume could tie in with the growing field of ocean observation and exploration as well as, perhaps, climate change models and estimates of salt in the oceans.
And for those of you wondering -- as Berlin put it so eloquently in his music -- if you ever lost your love, how much would you cry? Apparently not as much as you might have 30 years ago. The study's calculation of the ocean's mean depth is 3,682.2 meters -- that's 21-to-51 meters less than previous estimates.
Portolan nautical chart of Mediterranean Sea around 1320-1350. 
