Estimated Depth Maps of the Northwestern Hawaiian Islands Derived from High Resolution IKONOS Satellite Imagery

Estimated shallow-water, depth maps were produced using rule-based, semi-automated image analysis of high-resolution satellite imagery for nine locations in the Northwestern Hawaiian Islands. This project is a cooperative effort among the National Oceanic and Atmospheric Administration, State of Hawaii Department of Land and Natural Resources, and the U.S. Fish and Wildlife Service to produce benthic habitat maps and georeferenced imagery for the Northwestern Hawaiian Islands. This project was conducted in support of the U.S. Coral Reef Task Force.

This project was conducted in support of the U.S. Coral Reef Task Force http://www.coris.noaa.gov

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Estimated depth (estimated water depths in feet) were assigned either a range of numeric values or a single numeric value representative of (but not equal to) depth. These individual numeric values or ranges of numeric values were used to apply a ramped RGB color palette. Because the environment in the NWHI is very complex, two profiles of estimated depth were generated. Deep-water locations (Lisianski Island, Laysan Island, Maro Reef, Necker Island, and Nihoa Island). RESULTS = min_depth,max_depth,red_color_value,green_color_value,blue_color_value_,0,255,255,2551,2,243,251,2553,4,227,244,2555,6,211,238,2557,8,195,231,2559,10,179,225,25511,12,162,219,25513,14,146,212,25515,16,130,206,25517,18,118,201,255_,19,102,195,25520,21,85,188,25522,23,69,182,25524,25,53,175,25526,27,37,169,25528,29,21,162,25530,31,5,156,25532,33,0,151,25534,35,0,145,25236,37,0,138,246_,38,0,132,24139,40,0,126,23641,42,0,119,23043,44,0,113,22545,46,0,106,21947,48,0,102,21549,50,0,95,21051,52,0,89,20453,54,0,82,199_,55,0,76,19356,57,0,69,18858,59,0,63,18360,61,0,57,17762,63,0,50,17264,65,0,45,16866,67,0,39,16268,69,0,33,15770,71,0,26,15172,73,0,20,146_,74,0,13,14175,76,0,7,13577,78,0,0,13079,80,0,0,12681,82,0,0,12083,84,0,0,11585,92,0,0,10993,99,0,0,100100,109,0,0,100110,111,0,0,95112,116,0,0,95117,127,0,0,90128,138,0,0,90139,143,0,0,90144,200,0,0,90201,240,0,0,0241,241,40,0,100242,249,0,0,0_,250,167,133,119251,255,0,0,0. Shallow-water locations (Kure Atoll, Midway Atoll, Pearl and Hermes Atoll, and French Frigate Shoals). RESULTS = min_depth,max_depth,red_color_value,green_color_value,blue_color_value,_,0,255,255,255,_,1,243,251,255,_,2,227,244,255,_,3,211,238,255,_,4,195,231,255,_,5,179,225,255,_,6,162,219,255,_,7,146,212,255,_,8,130,206,255,_,9,118,201,255,_,10,102,195,255,_,11,85,188,255,_,12,69,182,255,_,13,53,175,255,_,14,37,169,255,_,15,21,162,255,_,16,5,156,255,_,17,0,151,255,_,18,0,145,252,_,19,0,138,246,_,20,0,132,241,_,21,0,126,236,_,22,0,119,230,_,23,0,113,225,_,24,0,106,219,_,25,0,102,215,_,26,0,95,210,_,27,0,89,204,_,28,0,82,199,_,29,0,76,193,_,30,0,69,188,_,31,0,63,183,_,32,0,57,177,_,33,0,50,172,_,34,0,45,168,_,35,0,39,162,_,36,0,33,157,_,37,0,26,151,_,38,0,20,146,_,39,0,13,141,_,40,0,7,135,_,41,0,0,130,_,42,0,0,126,_,43,0,0,120,_,44,0,0,115,45,48,0,0,109,49,52,0,0,100,53,57,0,0,92,58,62,0,0,85,63,68,0,0,80,69,75,0,0,72,76,80,0,0,65,81,85,0,0,60,86,92,0,0,55,93,200,0,0,50,201,240,0,0,0,241,241,40,0,100,242,249,0,0,0,250,167,133,119,251,255,0,0,0

Not to be used for navigation.

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These maps are NOT to be used for navigation. These estimated depth maps of the Northwestern Hawaiian Islands have been reviewed by numerous decision makers and scientists familiar with the Northwestern Hawaiian Islands region.

Once maps were positioned, validation was performed by comparison to independently-acquired, trackline LIDAR data from Kure Atoll, Midway Atoll, and Pearl and Hermes Atoll. Validation also was performed by comparison to NOS nautical charts. The draft estimated depth maps were reviewed by scientists in Hawaii who have first-hand local knowledge of the Northwestern Hawaiian Islands. Comments were received and incorporated into draft maps.The absolute accuracy of estimated depth varies with water depth. The error is generally 0.3 meters for water less than 1 meter deep, + or - 15 percent in water up to 15 meters deep, and + or - 30 percent in water greater than 15 meters deep.

Spatial data meets or exceeds national map accuracy standards for fixed features. Kure Atoll, Midway Atoll, Pearl and Hermes Atoll, Lisianski Island, Laysan Island, French Frigate Shoals, and Nihoa Island are positioned to within five (5) meters at sea level. Necker Island is positioned to within 15 meters at sea level. Maro Reef is positioned to within eight (8) meters at sea level.

none reported

High-resolution satellite imagery was analyzed to produce estimated depth maps of the North Western Hawaiian Islands. Estimated depth can be determined from imagery for clear water to between 20 m and 35 m, depending on the bottom type and absolute water clarity. Because the water surrounding Gardner Pinnacles is too deep, no estimated depth was generated there. No satellite imagery was available for Gambia Shoal.

Multispectral satellite imagery was positioned using National Geodetic Survey ground control data for Kure Atoll, Midway Atoll, Pearl and Hermes Atoll, Lisianski Island, Laysan Island, French Frigate Shoals, and Nihoa Island. Satellite imagery of Necker Island was positioned using satellite ephemeris data. Satellite imagery of Maro Reef was positioned using a combination of satellite ephemeris data and supplemental depth transect data.