EM300 Multibeam Sonar Data collected from January 26 to April 22 from NOAA Ship Hi'ialakai cruise HA-15-01 to the Pacific Remote Island Areas and American Samoa in 2015

Multibeam data were collected using a Simrad EM300 30-kHz sonar aboard NOAA Ship Hi'ialakai, a 68-m (218') NOAA research vessel, from January 26 to April 22, 2015 during cruise HA-15-01. Multibeam data were acquired at Johnston, Howland, Baker, Jarvis, and Palmyra in the Pacific Remote Island Areas, and Swains and Tutuila in American Samoa. The multibeam data were collected using Kongsberg SIS software in the *.all format and processed using SABER and QPS Qimera editing software. Surface sound velocity values were supplied by Seabird SBE-45 MicroTSG and a SBE-38, and motion corrections from a TSS/Applanix POS MV (Model 320 Version 4) vertical reference were applied to the data in real time. WGS84 datum. The vessel is equipped with a sound velocity profiler; however, no casts were acquired during mapping operations. Attempts were made to improve vertical fit of the EM300 data by using sound velocity profile data from other sources (data from previous cruises, and synthetic data derived from World Ocean Atlas using velocipy); however, these alternatives were not effective. Resulting vertical discrepancies with pre-existing surfaces are ±10m; however, the EM300 data cover deep depths (up to 4800m) and therefore these errors were considered acceptable. The EM300 data only covered new terrain around Howland and Baker islands, and therefore only the data for these areas have been processed. Depths mapped range from ~50 m to 4800 m. These data are not to be used for navigation.