Friday, May 2, 2014

BRINGING DATA TO LIFE

Some researchers took 351 years of
weather observations collected from the logs and reports of ships sailing the world's oceans and data from research buoys and animated it using Google maps. Collecting surface observation weather information was one of the things that warships did for centuries. As with anything that gathers dust, researchers started mining the data once they found the central records repositories and realized what was there.

I remember the first time I saw the power of detailed routine maritime observations when a retired Navy captain showed up on one of my ships with an early laptop computer and a program he called GFMPL. The Navy's Geophysics Fleet Mission Program Library had the data from many, if not all, of the hundreds of thousands of expendable bathy-thermograph (XBT) buoys used by the US Navy as its warships characterized the ocean's sound velocity profile.  Each of them recorded temperature vs depth over their recording range (about 1000-2000 feet). The primary purpose of the information was to find the deep sound channel and acoustic layer below which submarines could not be detected from the surface.

The GFMPL model merely contained the Sound Velocity Profile information that historically prevailed at a given coordinate at a given time of year over the course of decades. It let you plug values into the Sonar Equation even when you had no first hand observational data. You would not believe how helpful/critical this can be. The study of sound in water matters deeply to navy officers. There are ways to find submarines but the worst approach, bar none, is shown below. It is better if you use sound looking up their kilts or from aircraft they cannot reach. 1 vs 1 in ASW these days is not for the timid.

The picture represents the active ray path of a destroyer type ship hunting a submarine using active SONAR. Where it became personal though was using active SONAR against mines floating in the volume. When the ray path was pretty much straight down it was a good day to go back to bed. There wasn't much point in hunting mines with SONAR if physics suggested that it was taking the day off.

A few years after I left off all that, I ran across an article about a Lieutenant of the Navy who had suffered a crippling injury that prevented him from ever serving at sea again. We don't have a word for that anymore although for a long time we thought we did. Some people like to think that we keep people on in the Navy because they're pretty smart not because of how good they look in Ray Bans. Like the sound velocity profile though, that changes every day.

This was also the origin of the navy's entire geophysical data project. A naval officer named Matthew F. Maury, banished from life at sea due to a debilitating accident, found himself at the Naval Observatory and by location, custodian of the central repository of all logbooks from the Navy's ships. He found that he could transform his exile from the sea into a wonderment by taking the composite of all the weather and marine observations of generations that was slowly moldering away and turning  it into useful guides known as Sailing Directions.


Long before RADAR we had a means to guide mariners in their closest approaches to shore. I was looking for the old Charlie's Charts which used pen and ink drawings of approaches throughout Baja which I remembered from sailing there as a young Lieutenant on a 40 footer but this will do in lieu of that:


You would have to sail a thousand miles at sea to appreciate how much a geography of your desired landfall means if you want to establish your whereabouts in the pre-GPS/RADAR era. Yes, all landfalls look the same in the dark but we don't make landfall in the dark do we? No. No we most assuredly don't. We head back out to sea and live to enjoy landfalls with Mimosas in the morning and a light heart. Finding Cabo Falso unexpectedly at 0200 when the Fathometer stops working all of a sudden....not the place for sudden demonstrations of sang froid. We can do it, but no. Just saying.

4 comments:

  1. Most interesting and enlightening. I'm confused, however, about this in the video:

    Ships and vessels are colored red-yellow, and other observing platforms (buoys, etc.) are colored blue-cyan.

    How or why do those blue buoy tracks travel great distances, often in a circular pattern? Are those buoys dropped by ships and then tracked for as long as they remain viable? Enquiring Minds™ wanna know.

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    1. The buoys are pretty interesting. This article talks about the set and drift of buoys in an ocean area of specific interest these days:http://www.bees.unsw.edu.au/why-locating-mh370-southern-ocean-so-difficult

      They buoys communicate up to 18 times a day via satellite channels and each update includes a posit. Two meters/second is actually pretty darned fast if you do it 24/7 forever. Ocean surface currents follow a pattern. They are circular upwellings from the equator that move west to the coastline, up latitude to the pole and then back down the western seaboard of the east side of the ocean basin. In the roaring 40s they follow the same pattern but there is no real obstruction to the east so they may follow eddy currents. When people talk about the absence of wreckage at the locations of MH370, we have to consider that it was crashed more than a month before it was reported in that ocean. 6 feet/second x 3600 seconds/hour x 24 hours/day x 30 days = a lot of ocean for debris to float in.
      In the case of Ocean research, the buoys will be tracked until the comm channel goes down. With NASA and its deep space probes, that means consciously turning off the receivers. I don't know of any buoys that we have done that with. With the caveat: those buoys whose positions have been established are ignored after they run aground, lose their instrument package or get picked up/run over.

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    2. Thanks for that, Curt.

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  2. This is fascinating. Going now to read more.

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