OCNMS Raster Digital Terrain Models (DTMs)

Survey HMPR-110-2002-04


A zipped extent shapefile may be obtained here (if you have difficulty, try right click and ‘save target as…’)

Projection: NAD_1983_HARN_StatePlane_Washington_South_FIPS_4602, Units Foot_US


These data consist of three tiles. Data is directly downloadable at the following locations.


digital terrain model a



digital terrain model b



digital terrain model c




Physical Description


These data are ASCII Grid (*.asc) format.  Resolution is 1 Meter. 


Projection: WGS_1984_UTM_Zone_10N, Units Meters

Vertical Datum: MLLW, Units Meters


In 2002 and 2003, hydrographic survey data were collected using Reson 8101 multibeam echosounders outfit to 9.8m survey launches.  Bathymetry data were cleaned of anomalies using Caris HIPS software, creating BASE (Bathymetry Associated with Statistical Error) surfaces for each of three survey blocks with the CUBE (Combined Uncertainty Bathymetric Estimator) method (Calder and Mayer 2003). Accepted XYZ values from the CUBE surface were ultimately converted to ESRI Arc ascii grid format.


Horizontal Accuracy:

 The 2003 survey data were intended to meet NOAA NOS hydrographic specifications, which can be found at http://chartmaker.ncd.noaa.gov/hsd/specs/specs.htm.  NOS specification for hydrographic positioning is that the total error in position of soundings, dangers, and all other significant features, at the 95 percent confidence level, will not exceed 5 meters +5 percent of the depth.  This accuracy requirement is independent of survey scale.  The 2002 survey data may not meet these specifications.


Vertical Accuracy:

See NOS hydrographic stanards http://chartmaker.ncd.noaa.gov/hsd/specs/CHAPTER5.htm.  The 2002 survey data may not meet NOAA NOS hydrographic standards due to sound velocity errors and/or timing or latency problems which were evident in the processed data.

Related Data Products

Survey specific habitat polygons are provided on the OCNMS Data Catalog under 110-2002-04.  Also, see OCNMS SoNAR Mosaic HMPR-110-2002-04.


Other Useful Information

Import of ASCII Grid (*.asc) using your particular GIS software’s import utilities will be required.


This page contains content copied from OCNMS’s Data Catalog.  Please see their webpage for comprehensive information on OCNMS SoNAR data and data products


Also, see their Benthic Mapping webpage.  Overviews of side scan sonar and multibeam sonar are available as well as a comprehensive overview of their benthic mapping program.


A comprehensive citable report pertaining to this specific survey is can be downloaded here in *.pdf format.



Questions? Comments?

Contact Keven Bennett kbenet@u.washington.edu


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