Google Earth Community: Bahamas small islands Landsat overlays

First stab at a combined overlay for various small islands in the Bahamas. All of these have no GE photography except Samana Cay, where the GE photo is very cloudy and off color; the photo here has the same resolution as the GE photo but is completely cloudless. So these represent new places to see in GE.

This package contains these islands, drawn from the listed Landsat images:

Bimini.........................L501404219940205
Samana Cay................p010r44_5t850115
Plana Cays..................p010r44_5t850115
Ragged Islands.............p011r45_5t850207
Cay Verde....................p011r45_5t850207
Mira Por Vos Cays........p011r45_5t850207
Hogsty Reef..................p010r45_5t850115
Jumentos Cays.............p012r44_7t20000420 (south & central)
Jumentos Cays.............p011r44_5t850207 (north)
Anguilla Cays...............p014r44_5t19850111
Cay Sal & Elbow...........p015r43_5t19870430
Mayaguana (central)......p010r4_5t850115
Cay Santo Domingo......p011r45_5t850207
Green Cay......................L70104320010207
Scrub Cays & Little San Salv...p012r43_7t19991128

All are correctly sized and positioned.

Most of these have "standard" 321 color, with Landsat channels 3, 2, and 1 assigned to RGB respectively. To me, this leaves nearly everything in the Bahamas looking distinctly gray, which if you've been there know isn't true. So for the Samana Cay and Plana Cay photos, I experimented with a new system: instead of assigning green to channel 2, I created a green channel by averaging channels 2 and 4. Channel 4 is a near-infrared channel that reflects chlorophyll strongly. After the usual tweaking with brightness and contrast, and bumping G up a bit and B down a bit, I found the new system works pretty well and is a reasonably good reflection of the islands' actual color from the air.

I will update this post in the future as more islands are added. Currently I'm planning islands on the Cay Sal Bank and the Jumentos Cays, and possibly others to come.
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Update 2007-3-17: Added Jumentos Cays in three overlays, using enhanced Green channel as described above in south & central, but with channels 2 & 4 added (instead of averaged) for the north. This is the best yet, I believe.

Added regions for LOD fading, with different ranges for overlays and placemarks.
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Update 2007-03-19: Added three overlays on the Cay Sal Bank: one for Anguilla Cays (east), and one each for Elbow Cay and Cay Sal (west).

Images processed with green channel being Landsat channels 2 & 4 added, which gives a good approximation of true ground color.
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Update 2007-03-19: Added toponym placemarks for Ragged & Jumentos, including corrected position of Raccoon Cay (which is wrong in GE).
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Update 2007-03-20:
Tired of seeing nothing but clouds in central Mayaguana, added cloudless overlay to area without hi-res photo in GE. Also tweaked position of Plana Cays.
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Update 2007-03-21:
Added Cay Santo Domingo, and tweaked position of Ragged Islands, Cay Verde, and Mira Por Vos.
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Update 2007-03-23:
Added Green Cay and adjacent Scrub Cays on the Great Bahama Bank. Added full overlay of Little San Salvador and adjacent cays from same Landsat image as GE uses, but without the fading east and west.
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Update 2007-04-25
Minor tweaking of position for Ragged, Jumentos (all) & Plana. Position for Plana slightly differs from new (2007-04-10) GE standard photo, but mine is better.

This will be my last update (as far as I know) to this package.

Edited by KeithPickering (04/25/07 05:28 PM)

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