KenMankoff

Pine Island Glacier Publication TimeMap

In which I present a rough geo-spatial-temporal map of Pine Island Glacier (PIG) publications.

Geo-spatial-temporal time-map of Pine Island Glacier (PIG) publications

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Geo-Tagging Photos

I have ~2700 photos from my recent trip to Antarctica. All but a few dozen were taken while on the ship, and the GPS track of the ship is known. The few that were taken off ship were within a three mile radius while deploying the ITP. If you don’t have a ship recording your GPS for you, you can get simple GPS systems for less than $100, or even a few $10s of dollars on eBay. The TrackStick is good for this type of project as it does not have a screen or realtime outputs.

I wanted to geotag all my photos by adding the latitude and longitude to the JPEG EXIF data. I was going to code it as the algorithm is quite simple (for each image, get the creation time, find the GPS location nearest that time in the GPS list, and add the (lat,lon) coordinates to the image), but not surprisingly this problem has already been solved. Repeatedly.

Three steps are required.

1. Convert your GPS data into GPX format. If you are comfortable on the command line then use gpsbabel. If not, then go here for a web interface to gpsbabel. If you need help post in the comments. If you were on NBP09-01 a GPX file of our cruise is here.
2. Add the GPS coordinates to the image EXIF tags. There are many tools that will take a GPX or NMEA file and add latitude and longitude coordinates to your photos. I use gpicsync and photoGPSEditor looks nice too.
3. Output KML files. gpicsync does this for you, and has a list of other software that might help here. You can also upload your photos to Picasa and get a KML file that way (instructions).

The end result might look like this.

NBP09-01 Press Release

I tried to give some details about the cruise while it was happening, but if you want a PR overview the first big NBP09-01 press release has been issued by the NSF.

Photos from Antarctica

If you’ve been following this blog you’ve seen a dozen or so low-quality photos posted during my trip. Now you can see full resolution pictures. In total, I took 2718 photos during the 54 days between when the Nathaniel B. Palmer (NBP) left Punta Arenas, Chile and returned. I’ve selected 350 of the best ones and uploaded them. There are 31 from the sea ice science projects, 54 of the NBP itself, 66 of animals (added to the animal photos from last year), 101 of the Pine Island Glacier, and 98 miscellaneous photos of the Amundsen and Bellingshausen seas, sea ice, sunsets, and sunrises.

You can view all of the photos listed above in the various Antarctica photo albums, or you can view them all geospatially (KMZ) in Google Earth. The ship recorded GPS a few times a second, and I have a one-minute (temporal) resolution data file that I used to geotag the photos.

Notes: If you are viewing the photos on the website, you ought to have the Cooliris plugin installed. Load times might be a bit slow, this computer is hosted at home. If you don’t see any photos in Google Earth you’ll need to drag the time slider to the right. They’ll pop up as you pass the time they were taken.

NBP Photos Geotagged in Google Earth

Updating the Map

Just a short note to update the map. We are currently zig-zagging to the west along the continental shelf, Amundsen Sea, Antarctica.
 
Location: lat:-71.6992, lon:-114.6032
 
http://kenmankoff.com/maps/NBP09-01/

More on Sextants

Current Location: lat:-73.1986, lon:-114.9596
 
Sailing south toward the Getz Ice Shelf
 
Weather: Gray skies, gray sea, -0.5C (Air), -0.01C (Water)
 
Moods: Excited to finally leave Pine Island Bay and do something new (although new really just means more CTDs and more mooring deployments).
 
Note about last image: Photo of me taking sextant reading by Katie Leonard (I hear multiple of her friends and family might be reading this).
 
I was asked to provide more info about the sextant reading. We took 18 samples across the front of the ice shelf. By “we” I mean Katie Leonard and Chris Little (author of the other NBP09-01 blog). I helped with the first few and then went to bed, most of the transect happened on their shift. An example one went something like this:
 
 * Date: …
 * Time: …
 * Lat: …
 * Lon: …
 * Radar dist: 0.18 nautical miles
 * Sextant: 8 deg 8.6 min
 * Note: Caves just north of ship, elephant seals spotted nearby.
 
After we were done, we began the analysis. The math is pretty basic trigonometry:
 
1) Convert the distance from nautical miles to meters (333)
2) Convert the angle to degrees (8.1)
3) Convert degrees to radians (0.14)
 
Draw a triangle, knowing one angle and side:
 
 
  __—-|
  __– |
  __— |
  __— | h = ?
 o) theta = 0.14 |
-|- ——————-|
 ^ d = 333
 
I’m not sure how that looks to you readers but as I write it I have drawn a person on the left, and a vertical line on the right.
 
In general, tangent = opposite/adjacent
 
So tan(theta) = h/d
 
we want to solve for h so multiply both sides by d and you get
 
h = d * tan(theta)
 
  = 320 * tan( 0.14 )
 
  = 45.1 m high
 
We took a additional steps to make sure things were more accurate. For example, the radar measured 333m but we corrected for the distance between where the radar took its measurement and where we took our measurement, which was not directly under the radar, and about 10 meters closer to the ice shelf.
 
As you can see by plugging in 310 instead of 320, we were close enough that a 10 m error makes a significant difference in the height of the ice shelf.
 
310 * tan( 0.14 ) = 43.7 m
 
Further analysis will refine the equation to take into account the height of the radar and the height of the average observer eye above sea level. We could even take into account the difference in eye height between Chris, Katie, and I, but I do not think that will make much of a difference.

Me Using Sextant

Me using sextant to measure angle Pine Island Glacier fills vertically in field of view. Distance provided by ship radar. Geometry provides height.

View from Bridge

Current location is lat:-72.981, lon:-111.356
 
Photo location is somewhere NW of Pine Island Bay.

PIG Micro

Image is approximately 5 mm across. See recent post “PIG Macro” to compare and contrast scales.

Sextants

Yesterday we did a transect along the face of the glacier. Every 15 minutes we fired an XBT down to measure temperature, pinged the bottom of the ice shelf with our multibeam bathymetric mapper, used the radar to get the distance from the ice shelf, and used a sextant (old school!) to measure the angle the ice shelf fills in our field of view. With a bit of geometry we now have a rough estimate of the height and draft of the ice shelf. The temperature data crosses the boundary below the ice shelf draft, and we can see how the open bay interacts with the water under the shelf.
 
In other news, I think tomorrow is the half-way point of the cruise. For those of you out there anxious to see those of us down here once again, you are beyond half-way. We left you four or five days before the cruise began and will see you much sooner after it has ended.