Thoughts - My Progress at Mapping the Tuamotus
Tuamotu EVS Precision Mapping Progress
It has been nine days since my last post. What have I been doing? Keeping up with my summer duties - "honey do's", watching and entertaining my grandchildren (9 and 6 years) and mapping the Tuamotus. My goal this summer was to complete all 4 layers of EVS precision mapping for each of the 76 islands within the group - island polygon, vegetation, shallow reef and deep lagoon. To date 59 islands are complete. What exactly does that mean?
76 islands is not quite accurate. The Tuamotus are made up primarily of atolls. Each atoll has a number of islands, motus, to be exact. Just how many? A preliminary count puts the number of motus at approximately 5,640. Those are above water land. If the motu contains vegetation, I create a vegetation polygon. That means another 1,100 polygons to create (about 20% of the motus contain significant vegetation). Each atoll is surround by a shallow reef and an interior deep lagoon. However many of these interior lagoons are peppered with coral heads. If they show up on my base imagery, I map them. Probably another 2,000 polygons. All in all, I have to digitize 8,740 polygons, at least, to complete my summer project.
I have finished 59 atolls leaving me only 17 atolls to map. That is the good news. Now for the challenging news. Those 17 atolls will contain about 60% of the remaining polygons. All I have left to do is digitize another 5,240 polygons and I'll be finished.
If that seems like alot, it is. However, when this island group is mapped to EVS precision I will have accomplished my summer goal. It might be December 2008 before I complete my summer goal, but complete it I will. Wish me luck and...
Enjoy!
Labels: atoll, EVS Precision, French Polynesia, Landsat ETM+, Tuamotus
Hi Mr. Minton,
This is Brad Balukjian, grad student at UC Berkeley studying the evolutionary biology of insects in French Polynesia. As an island fanatic, I want to thank you for this website and the mapping that you do. I'm interested in the figure of 5,640 motu that you came up with--is that your count from the maps you've made? Also, when you say you do a vegetation layer, does that mean that the map shows differences in vegetation? How detailed are you able to get this? Can you divide the island according to different vegetation zones? Thanks!
Posted by
Anonymous |
8/17/2008 09:24:00 PM
Brad,
1) The count of 5,640 polygons breaks down as follows for the 59 completed atolls: 2,722 island polygons (motus), 1,391 vegetation polygons, 2,113 reef shallow polygons, 139 reef deep polygons and 298 inland water polygons.
2) I have made attempts to differentiate vegetation layers. Using Landsat's 14.5-meters per pixel resolution, it is difficult to make reliable vegetation layers. However, using DigitalGlobe imagery from Google Earth one can make reasonable vegetation determinations.
3) #2 begs the question "Am I able to use the information for research or within the educational community?" One needs to secure permission from DigitalGlobe, which is quite often given, just so you aren't trying to earn big bucks from the imagery or maps derived from their imagery. You must secure their, DG's permission.
Posted by
Mr Minton |
8/19/2008 07:41:00 AM