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Publication_Date: 19990701
Title: WA_State_Marine_Bathymetry_Mosaic_NAD83
Geospatial_Data_Presentation_Form: raster digital data
Bathymetry is the measurement of the depth of large bodies of water. Bathymetry data can be stored in a number of formats including point soundings, isobaths (contours), and grids. The bathymetry mosaic dataset is a grid coverage of water depth generated from point soundings. The grid structure is a regular array of cells referenced to the Universal Transverse Mercator (UTM) coordinate system. Each grid cell represents water depth for a discrete 20- x 20-meter area. The mosaic is a continuous grid covering Washington marine waters, Oregon waters as far south as Seaside, and the Columbia River upstream to Bonneville Dam. Canadian marine waters are included for southern Vancouver Island. The dataset was funded by the Puget Sound Ambient Monitoring Program (PSAMP). Primary bathymetry grid processing was performed under contract by Environmental Consultants (ECI), Portland, Oregon.
The bathymetry mosaic is best applied in medium scale applications (e.g., 1:100,000-scale). In regions of high depth sounding density, such as in some regions of Puget Sound, larger scale applications may be possible. The bathymetry mosaic can be readily combined with other spatial data in a Geographic Information Systems (GIS) for scientific study, environmental management, isobath generation, and cartographic display.
The bathymetry mosaic is composed of grid cells representing depth. Cell values are organized in a regular grid. Cell value indicates water depth, decimal meters.The bathymetry mosaic coastline is defined by highwater line. An additional boundary is defined by low slope areas exposed at low tide, such as mudflats; these areas were excluded from processing due to highly variable sounding availability and mapping consistency.
Maintenance_and_Update_Frequency: None planned
West_Bounding_Coordinate: -127.077243
East_Bounding_Coordinate: -121.380743
North_Bounding_Coordinate: 49.527169
South_Bounding_Coordinate: 45.437535
Theme_Keyword_Thesaurus: None
Theme_Keyword: bathymetry, soundings, marine water depth
Place_Keyword_Thesaurus: None
Washington, Oregon, British Columbia, Puget Sound, Pacific Ocean, Strait of Juan de Fuca, Columbia River
Although these data have been processed successfully on a computer system at the Washington Department of Fish & Wildlife, no warranty expressed or implied is made regarding the accuracy or utility of the data on any other system or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. This disclaimer applies both to individual use of the data and aggregate use with other data. It is strongly recommended that these data are directly acquired from a Washington Department of Fish & Wildlife server, and not indirectly through other sources which may have changed the data in some way. It is also strongly recommended that careful attention be paid to the contents of the metadata file associated with these data. The Washington Department of Fish & Wildlife shall not be held liable for improper or incorrect use of the data described and/or contained herein.
1. The bathymetry dataset not to be used for navigational purposes. 2. Shoreline detail has been generalized due to grid cell processing. For projects needing fine-scale shoreline detail, it may be necessary to use point soundings and a vector shoreline, as well as additional low/high tide information, for generation of a bathymetry surface. 3. The grid cell depth values in intertidal areas in the bathymetry mosaic may be misleading. The input point soundings are referenced to Mean Lower Low Water (MLLW), and the shoreline represents the high waterline. Thus, sounding interpolation extends from MLLW to the high water line. For larger scale applications the data user may prefer to reconcile low and high tide depths with ancillary intertidal information. 4. Creation of the wide-area mosaic requires a uniform grid cell size. As such, there is a tradeoff between maintaining shoreline detail and interpolation of irregularly spaced soundings. The 20-meter cell size is overly optimistic for some areas given the highly variable depth sounding density observed in the project area. This is especially true for the heavily interpolated offshore region west of a line defined by the coordinates: (46.0, -125) (47.5,-125) (47.5,-125.5) (48.0,-125.5) (48.0,-126)(49,-126). Note the companion feature class WA_State_Marine_Bathymetry_netcovz10_NAD83 indicating window processing size.
Contact_Organization: Washington Department of Fish and Wildlife
Contact_Person: Lori Guggenmos
Contact_Position: Cartographer
Address_Type: mailing
Address: 600 Capitol Way North
City: Olympia
State_or_Province: Washington
Postal_Code: 98501
Contact_Voice_Telephone: (360) 902-2543
Hours_of_Service: 8:00 a.m. to 4:00 p.m. Monday through Friday
Washington Department of Fish and Wildlife, Olympia, Washington.
Microsoft Windows 7 Version 6.1 (Build 7601) Service Pack 1; Esri ArcGIS

A formal comparison between the bathymetry mosaic depth and an independent source of depth data was not performed. A qualitative assessment was performed using digital and hardcopy isobaths obtained from 1:100,000-scale sources, such as the USGS/NOS Bathymetric- Topographic series and the NOAA bathymetric Fishing Map series. The point-to-surface interpolation algorithm provided similar results as found in the 1:100,000-scale map series. Also note the Hydrographic Manual compiled by the National Ocean Survey for information concerning sounding data standards and requirements.
Step 1: Shoreline preparation. Four sources of shoreline data were required for this project. The Washington DNR Aquatic Resources' "Water Level Line" provided the bulk of the shoreline. USGS 1:24,000- scale and 1:100,000-scale DLG data were incorporated for the Columbia River shoreline from Portland upriver to the Bonneville Dam. Canadian shoreline information was incorporated for Vancouver Island and the Strait of Georgia.
(1) A master shoreline coverage was generated by appending all shoreline coverages from state, federal, and Canadian sources into one coverage, referenced to UTM Zone 10. (2)A polygon coverage was generated from the master shoreline coverage through addition of new arcs. (3) The polygon coverage was projected to Geographic Decimal Degree (GDD). (4) The polygon shore coverage was exported to an ASCII format and provided to the contractor. (5) The contractor subsequently converted the polygon data into a grid.
Step 2: Mudlfats/Sand Coverage Preparation. Generation of a master mudflat/sand polygon coverage. This layer, combined with the master shoreline, formed the land/water position.
Step 3: Depth Soundings Preparation/Extraction. Preparation of Canadian soundings and extraction of USA soundings from the NOS CD-ROM. (1)Digital Canadian sounding point data were projected from UTM Zone 10, NAD83 to GDD NAD27. (2) The Canadian soundings were adjusted to USA vertical datum using linear regression on a per-area basis. Size of processing area for each regression run was 30- x 30- seconds. An ASCII output was generated of the adjusted soundings and provided to the contractor. (3) Soundings for USA waters were extracted by the contractor from the National Ocean Survey, Hydrographic Survey Data, CD-ROM Set, Version 3.3, 1997. (4) Canadian and USA soundings were combined prior to grid processing.
Step 4: Bathymetry Tile Generation. Fifty-five, 30- x 30-second tiles, generated from interpolated point sounding data, were delivered by the contractor. All interpolation was performed within the GDD reference system. (1) A combined gridded shoreline and mudflat/sand grid was generated. (2) Point soundings were extracted for each 30- x 30-second tile and interpolated to a regular grid structure. Adjacent tiles were edge matched. (3) The grid cell dimensions of nearshore tiles are .00021150592217 x .00021150592217 degrees. Offshore tiles (12 tiles) have grid cell dimensions of .00086805555556 x .00086805555556 degrees. (4) The contractor output each tile in bil image format. Pixel value output as two-byte integer, data scaled by x10.
Step 5: Bathymetry Mosaic Generation. Generation of mosaic from 55 input tiles. (1) Each tile was imported from bil format to UNIX ARC/INFO/GRID version 7.2 using IMAGEGRID. (2) Processing limitations required each individual tile to be projected/resampled from GDD to UTM Zone 10 prior to mosaic generation. (3) All 55 tiles were combined into one mosaic with grid cell size equal to 20- x 20-meters with non-water areas converted to NODATA.
The bathymetry mosaic created in 1999 was cast on UTM Zone 10 NAD27. The NAD27 mosaic was reprojected to UTM Zone 10 NAD83 using bilinear resampling. The original depth values, therefore, were changed as a result of the reprojection. The original NAD27 mosaic is stored at Washington Department of Fish and Wildlife.

Direct_Spatial_Reference_Method: Raster
Raster_Object_Type: Grid Cell

Map_Projection_Name: NAD 1983 UTM Zone 10N
Scale_Factor_at_Central_Meridian: 0.9996
Longitude_of_Central_Meridian: -123.0
Latitude_of_Projection_Origin: 0.0
False_Easting: 500000.0
False_Northing: 0.0
Planar_Coordinate_Encoding_Method: coordinate pair
Abscissa_Resolution: 0.000000002220024164500956
Ordinate_Resolution: 0.000000002220024164500956
Planar_Distance_Units: meter
Horizontal_Datum_Name: D North American 1983
Ellipsoid_Name: GRS 1980
Semi-major_Axis: 6378137.0
Denominator_of_Flattening_Ratio: 298.257222101

Entity_Type_Label: Value
Entity_Type_Definition: Water depth decimal meters