Surveying, Mapping and GIS

Reuters is carrying a story about the preservation of the 1507 Martin Waldseemüller World map, the first known to refer to the New World as America.

Some of the individuals cited in the article express their puzzlement at how Waldseemüller was able to portray as much detail and accuracy as he did, given the extremely limited amound of knowledge that is generally believed to have been extant regarding the New World at this time - for example, Vasco Núñez De Balboa had not crossed the Isthmus of Panama to reach the Pacific until 1513, and likewise, Magellan had not rounded the southern tip of South America until 1520, yet these are shown.


Interestingly, many features in this map are reversed in subsequent maps by Waldseemüller.

The map is cited in the article as a 'keystone map', showing a fundamental shift in how Europe viewed the New World. It also raises many questions about how much we really understand geographic awareness and the availability of cartographic information in ancient times.

My own notion is that we sometimes do not give our predecessors enough credit for their knowledge of the world around them.

The Map Room blog has an interesting article discussing a reinterpretation of an old portolan chart found in a Los Angeles library vault, by author Peter Trickett. In his book Beyond Capricorn, Trickett argues the case for Portuguese discovery of Australia, long prior to the British or Dutch. According to Trickett, Portuguese explorer Christopher de Mendonca led a small fleet into Botany Bay in 1522, more than 200 years ahead of Captain Cook, and ahead of Dutch explorers as well.

Is it another Gavin Menzies adventure? The argument is rather compelling in some ways - obviously the chart describes a massive landmass, which does align well with parts of the Australian coast.

According to this MSNBC article, the map describes features one might expect in that region of Australia, however the coastline had some inconsistencies. It's argued that these inconsistencies may be either intentional and/or miscopied, including a 90° rotation along the coastline.

The Google Earth Hacks blog has a download, which overlays the map graphic (respliced with the 90° fix) atop the Australian landmass, so you can see this for yourself:

In examining Rwanda and Cameroon, I came across a number of articles discussing limnic eruptions - this is a natural event, where large amounts of dissolved and trapped gases in lakes suddenly and catastrophically become released, causing death to all living things within a substantial radius of the lake.

Typically this is due to volcanic vents, which release CO₂, which becomes trapped in stratified layers deep in the lake. The trapped gases may remain undisturbed and in solution for long periods of time, and may continue to accumulate until an external event triggers instability, such as earthquake, landslide, rapid thermal change, or the like.

One particularly catastrophic and more well-known instance of this phenomenon is Lake Nyos, in Cameroon, where in August of 1986, an estimated 1,800 people and large amounts of livestock died due to suffocation. It is estimated that 1.6 million metric tons of CO₂ were released in that instance. As CO₂ is heavier than air, the gas fills valleys, and finds its way to low-lying areas in great concentration.

Fortunately this is a relatively uncommon occurrence - few lakes are known to have this type of supersaturation of gases and potential for catastrophic overturn. Lake Nyos is a fairly small lake, of 1.2 km² - Lake Monoun is another small lake in Cameroon which has had similar catastropic incidents and loss of life in the past.

Another lake that is somewhat disconcerting is Lake Kivu, bordering Rwanda and the Democratic Republic of Congo - Lake Kivu is much larger - 2,700 km², with a much larger population along its shores than these other lakes. It is unknown if Kivu is susceptible to similar massive overturn events, and Kivu has considerably greater depth that the two Cameroonian lakes, however it similarly displays the unusual supersaturation of gases characteristic of the other two lakes - and situated over the Rift Zone, and in proximity to Mount Nyiragongo, which last erupted in 2002- it is entirely possible that the same circumstances exist for continued contribution of CO₂ and other gases.

In some instances, the lakes are being degassed, via pipes which seek to gradually release the concentrated gases, similar to slowly letting the fizz out of a soda can.
One such project is being conducted by the Lake Nyos and Monoun Degassing Project.

In the Amazon Mechanical Turk effort to analyze imagery for potential clues in the disappearance of Jim Gray, I thus far managed to log 185 units of 5 images each, the count was well over 4000 when I started, and the last one I completed said 1 remaining. It was plainly evident that I had a great deal of company throughout this effort.

Certainly there were several instances of images where boats, along with their associated wakes, could be seen in the images, however a great many were difficult to read, with a great deal of reflectance, cloud cover, and so on.

It will be interesting to see what the next steps are - whether more data or additional passes will be offered up through Mechanical Turk, and if any of what participants identified will ultimately be able to correlated to other activity in the vicinity, or indeed provide clues to Gray's location.

UPDATE: Some additional images from a NASA aircraft have been posted to Mechanical Turk - see the following link: http://www.mturk.com/mturk/preview?groupId=J0XZ58STDWJZ5QY4F9M0

I have also located a blog site operated by the folks who have been organizing this effort: http://openphi.net/tenacious/
- They have posted quite a few updates and insights into the nature of the imagery and ongoing effort