Imagery of the Island of Yap

Data Processing
Images were obtained through the The image used for this study came from the University of Maryland’s Global Land Cover Facility using the Landsat 7 satellites Enhanced Thematic Mapper (ETM+). The pixel resolution for all of the satellite images came in 30x30 pixel resolution.The image itself was taken back in February 2001. No images were available through the University of Maryland website that had an image of Yap on a cloudless day. Cloud cover did prove to be a problem later on once the image was processed as clouds obscured the vegetation on the ground. This problem is present in the image that was used and shows up as dark-grey or just grey. Processing of the original Landsat image was done using the ENVI image processing program.

Historical aerial photographs
Analysis of the impact of bombings on the southern part of Yap during the Second World War was done by using photographs by those pilots that undertook the bombing runs on Yap. Technological limitations on camera technology of the time meant that all of the images are in black and white and not in the visible spectrum. The limited number of photographs that are available have allowed given a limited picture of the destruction that bombing caused to the island. What we do have available shows concentrated around the area where one would find the airport today. Yet, none of these images are able to encompass a wide swath of the island making their use limited.

Image 5.
Source: http://www.missingaircrew.com/images/micr/NA02010.jpg

Landsat ImageThe Landsat image for Yap was obtained by using an Iso Data classification with bands  (2,3) in order to clearly mark where the original forest on the island could be located.  The few areas of red on the image mark where the last remaining patches of dense tropical forest remain on the island. This is followed by areas of orange that represent lesser dense vegetation cover such as mangroves. All of this ends with yellow areas that mark areas of the shortest and least dense vegetation on the island. It is these areas where one finds the open grasslands of Yap. This image shows that the majority of Yap’s remaining forest  is located on the northern two areas of Maap and Gagil-Tomil.  Interference as a result of cloud cover are present in the Landsat image used and can be seen best as dark-grey patches in the north center of the island. Fog was also present on the southern part of the island. This might explain why the southern tip of the island is almost completely missing any of its original forest or vegetation cover. More detailed images using the (2,3) bands still show sparse vegetation on the southern part of the island. (Image 6).

Image 6.
ETM+ image