This information is not intended for navigational purposes.
Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Please recognize the U.S. Geological Survey (USGS) and the Southwest Washington Coastal Erosion Study (SWWCES) as the source of this information.
Water depth relative to NAVD88 was calculated by first determining the primary tidal station used for a particular survey. This information was obtained from original smooth sheets and/or descriptive reports where possible, or assumed where such information didn't exist. Relative offsets between MLLW and NAVD88 at each tidal station was determined based on geodetic information provided for NOS benchmarks, determined by independent geodetic surveys conducted by the Department of Ecology, or estimated where no other information was available. The NAVD88 values were thus calucalated by adding the relative differences between datums to the MLLW depth values. In some cases, a larger datum correction was applied to offset obvious bias in the original data set. An in-depth description of the methodolgy employed for these conversions, along with a discussion of specific corrections, are available in Buijsman, et al., 2002.
DATA SET SPECIFIC INFORMATION: For the data set: h4634_1927 The primary tidal station used is: Ft. Stevens, assumed The source used to determine the tidal station: no data available The vertical datum relative to NAVD88 is: -0.16 meters The conversion applied to charted depths: -0.16 meters
2706 points were given a cartographic code of 888 where soundings overlapped with other surveys (H4634, H4635, H4618, H4619, H4620, and H4621) or points appeared erroneous. Some points closer to shore showed better agreement with overlapping surveys so points were left unchanged. This survey is more irregular than survey H4635 and is typically from 3-7 m deeper than H4635. H4635 seems to agree with H4611 better.
Only soundings with a cartographic code of 711 should be used for analysis.