2004-05-23 Open Navigation Surface Working GroupCHC2004 Uncertainty Workshop

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The Open Navigation Surface Model

Brian CalderCenter for Coastal and Ocean Mapping &NOAA-UNH Joint Hydrographic Center

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Open Navigation Surface

• Community response to concerns for inter-operability of data products

• Intent:– Define a concrete representation of the Navigation

Surface data model

– Identify software technologies to support and implement the data model

– Provide a free, open source code-base as a reference implementation

• Hosted by CCOM as a vendor-neutral third party

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Open Navigation Surface Working Group

• Started by e-mail solicitation of statements of interest– Technical: navsurf_dev@ccom.unh.edu– General: navsurf_general@ccom.unh.edu

• Core group formed by responses from:– CCOM, NOAA, NAVOCEANO– IVS, CARIS, SAIC, 7Cs

• First meeting held 21-23 January 2004

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Goals of the ONSWG

• Determine the requirements for an Open Navigation Surface data object, specifying all of the mandatory data elements.

• Determine suitable software technologies to implement these requirements

• Develop one or more source-code libraries that form a reference model for reading and writing data in this format, and provide support and guidance to potential users

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Format Requirements

• A new name– “Navigation Surface” means different things to different people

– Adopted “Bathymetric Attributed Grid” (BAG) for the data elements used to make navigational products

– Reserved “Navigation Surface” to mean a BAG which has actually been made for a specific navigational purpose

• Meta-Data– Meta-data to include everything of interest that has happened to

the data (e.g., processing, certification for navigational use, etc.)

– Meta-data to be in XML using ISO19139 encoding to ISO19115 content standards

– Meta-data to be kept in the same file as the data to avoid loss in transit

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Format Requirements

• Mandatory Data Components– Elevations on a regular grid at a single resolution (may be different in x,y)

– Associated uncertainty on a co-located grid

– Special exceptions (human over-rides)

• Extension Data Components– Arbitrary ‘other’ data (grid or non-grid) as required by particular users

– Must remain open (reviewed by ONS architecture board), non-proprietary

– Procedures documented in Format Specification Document (BAG-FSD)

[All grids are single-resolution node-based objects, but can be geographic or projected, and are reduced to one of a number of vertical datums; SI units are used throughout, with a right-handed coordinate system (z is positive up)]

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Format Requirements

• Certificates and Digital Signatures– Every BAG will be hashed to the Secure Hash Standard (FIPS

180-2)– Every BAG will be digitally signed by the Digital Signature

Standard (FIPS 186-2) to ensure taper-detection and authentication– Signing a BAG requires an entry in the XML meta-data indicating

who did the signing, and what the certification implies for the data.

• Documentation– Defined by Requirements, BAG-FSD and BAG-API– Intended to be living documents in CVS control

• Advisory Board– Intended to review new modifications and requests– Co-opted by invitation, defined in BAG-FSD

• Platform Independence

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BAG Format Outline

Overall Metadata

Depth

Certification data

Meta-data

UncertaintyMeta-data

Change-Tracking ListMeta-data

Extensions (Optional)Meta-data

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Progress and Current Status

• Technologies Identified:– HDF-5 (1.6.1), zlib 1.1.4, szip 1.1– libgcrypt-1.1.44, libgpg-error-0.6– Geotrans 2.2.3 (NGA)– XML parser TBD, possibly Apache Xerces

• CVS Code/Documentation Repository Established– Open, but not public, access– Hosted at CCOM/JHC (brc@ccom.unh.edu)

• Documentation at V1.0 for BAG-FSD, BAG-API• Test code built for sub-components and checked

in; operation confirmed on Linux and Win32

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Summary

• The Open Navigation Surface is a file format specification known as BAG– Provides method for transfer of data– Provides enough flexibility for processing too

• The project is supported by the community for the community– Provides for open-source code-base libraries– Based on ‘standards’ where possible

• A BAG consists of:– Depth, Uncertainty and Change-tracking List for a single

bathymetric entity– Meta-data describing the data, including processing– Certification for authentication, tamper-detection– Optional extension elements for specific purposes

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Taking Part!

• Membership is open to all interested parties– Consists of willingness to be involved

– Send e-mail to brc@ccom.unh.edu

• Interact via the mailing lists:– navsurf_dev@ccom.unh.edu for technical details of

development, API and format coding

– navsurf_general@ccom.unh.edu for administrivia, policy and higher-level discussion

– Send e-mail to brc@ccom.unh.edu to be added

• Contribute code, time, enthusiasm (as available)

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Thank You To:

CCOM/JHC: Brian Calder, Rick Brennan, Lee AlexanderCARIS: Bill LameyIVS: Mark PatonSAIC: Shannon Byrne, Jim CaseNAVO: Dave Fabre, Wade Ladner, Jan DepnerNOAA: Barry Gallagher, Jack Riley,

Shep Smith, Rick BrennanSevenCs: Friedhelm Moggert

… and the supporting institutions for time, travel & expenses.