North Atlantic Treaty Organisation

North Atlantic Treaty Organisation

NORTH ATLANTIC TREATY ORGANISATION

(NATO)

ANNEX D

to

ADDITIONAL MILITARY LAYERS

NETWORK MODEL BATHYMETRY

PRODUCT SPECIFICATION

Version 0.2, 31st July 2007


Produced and issued by the United Kingdom Hydrographic

Office under the direction of the Geospatial Maritime Working

Group of the NATO Geographic Conference.

© UKHO 2007

ALL RIGHTS RESERVED

The copyright in this document, which contains information of a proprietary nature, is vested in UKHO. The contents of this document may not be used for purposes other than that for which it has been supplied.

Additional Military LayersNetwork Model Bathymetry Annex D

ANNEX D

BATHYMETRIC ATTRIBUTED GRID (BAG) IMPLEMENTATION OF network model bathymetry PRODUCT SPECIFICATION

Document Control

ISSUE

Date / Author / Issue / Summary of Changes
31/07/07 / P. Burton / 0.2 / Annex issued with V2.0 of main specification

APPROVALS

Approver and Title / Signature / Date
Chairman GMWG

VERSION CONTROL

Version / Review Date / Reviewed By

FILE DETAILS

Component / Name & Location / Tool
Document text / J:\AML\Specification\Specifications\NMB\ annex D\NMB PS Annex D v0.2.doc / MS Word
Correspondence and hard copy / N/A

Contents

D.1AML NMB Bathymetric Attributed Grid Format and Structure

D.1.1 References

D.1.2 Document Structure

D.1.3 BAG Content

Figure 1

D.1.4 Metadata

D.1.5 Grid Arrays

D.1.5.1 Elevation Grid

D.1.5.2 Vertical Uncertainty Grid

D.1.6 Tracking List

D.1.7 Certification

D.1.8 Encapsulation

D.2File Naming

D.3Updating

D.4Acknowledgement

D.1AML NMB Bathymetric Attributed Grid Format and Structure

D.1.1References

This document requires reference to the following documents;

  1. STANAG 7170 Additional Military Layers
  2. Additional Military Layers, Network Model Bathymetry, Product Specification
  3. Format Specification Document - Description of Bathymetric Attributed Grid Object (BAG) Version 1.0.0
  4. The Open Navigation Surface Working Group have developed source-code libraries and documentation which is available for download at the following address;
  5. Whitepaper entitled “Digital Signature Scheme for the Bathymetric Attributed Grid(BAG)”. Available from

D.1.2Document Structure

This document defines the implementation of Additional Military Layer (AML), Network Model Bathymetry (NMB) in conformance with the Bathymetric Attributed Grid (BAG) standard.

Reference must be made to the “Format Specification Document - Description of Bathymetric Attributed Grid Object (BAG) Version 1.0.0” for a full description of the BAG format and encoding details. This Annex only gives a high level description of the content of a BAG dataset.

This document is structured to support NMB and the variable resolutions at which data may appropriately be delivered in support of a given task.

AML NMB data files may be accompanied by an optional ASCII file containing general information, this file will be called “readme.txt”.

D.1.3BAG Content

The BAG contains a number of mandatory elements. These are:

  • Metadata – dataset metadata conformant to ISO19115:2005
  • Elevation grid – two-dimensional grid containing estimate of elevation from the referenced vertical datum at the grid node
  • Vertical Uncertainty Grid - - two-dimensional grid containing estimate of the vertical uncertainty of the corresponding elevation value
  • Tracking List – List of originally computed values of elevation and uncertainty that have been manually overridden within the grids
  • Digital Signature – a mechanism to validate that the contents of the file has not changed since original signature.

These elements are shown conceptually in Figure 1.

Figure 1

BAG has adopted Hierarchical Data Format version 5(HDF-5) as the encapsulation format.

D.1.4Metadata

The BAG has adopted the ISO19115 standard for metadata and ISO19139 XML encoding of this metadata. A master copy of the XML schema can be accessed via the ONS website.

Metadata Attribute / ISO Short name / Data Type / Domain
Production Agency / rpOrgName / CharacterString / Free text
role / Class / CI_RoleCode
Value: 010 (Publisher)
Producing Country / country / CharacterString / ISO 3166-3, other parts may be used
Dataset Name / resTitle / CharacterString / Free text
Edition Number / resEd / CharacterString / Free text
Date of Release / resEdDate / Class / Date
Product Specification Description / formatName / CharacterString / “AML NMB – BAG V1.0 FORMAT”
Product Specification Version Number / formatVer / CharacterString / “1.0”
Product Scale Band / equScale / Class / MD_RepresentativeFraction
<DataType>
International Defence Organisation (IDO) status or
Caveat / handDesc / CharacterString / Valid values for IDO Status:
NATO - North Atlantic Treaty Organisation
NACC - North Atlantic Co-operation Council
PfP - Partnership for Peace
WEU - Western European Union
NOTE: IDO status and Caveat are mutually exclusive
NOTE: Caveat is only applicable if Protective Marking is Confidential or greater
Protective marking / class / Class / MD_ClassificationCode
<CodeList>
Owner Authority / rpOrgName / CharacterString / Free text
role / Class / CI_RoleCode
Value: 003 (Owner)
Horizontal Geodetic Datum / Datum / Class / Valid Datum:
WGS84 – World Geodetic System 1984
Vertical Datum / vertDatum / Association / SC_VerticalDatum
(See Para 3.5.1 of the main document for valid vertical datums)
Elevation Units (Depths) / vertUoM / Class / UomLength
Valid value: Metre
Capture Date / refDate / Class / Date
refDateType / Class / CI_DateTypeCode
Value: 001 (Creation)
Source Agency / rpOrgName / CharacterString / Free text
role / Class / CI_RoleCode
Value: 006 (Originator)
Source Country / country / CharacterString / ISO 3166-3, other parts may be used
Source Extent / Polygon / Class / GM_Object
-90 to 90 latitude
-180 to 180 longitude
Source Date / exTemp / Class / TM_Primitive
Source ID / resTitle / CharacterString / Free text
Source Type / srcDesc / CharacterString / Free text
Source Scale / srcScale / Class / MD_RepresentativeFraction
<DataType>
Copyright Statement / useConsts / Class / MD_RestrictionCode
<CodeList>
Value = 001 (Copyright)
Number of Grid Dimensions / numDims / Integer / Integer
X-Axis / dimName / Class / MD_DimensionNameType
<CodeList>
Value = 002
Y-Axis / dimName / Class / MD_DimensionNameType
<CodeList>
Value = 001
Grid Size (X & Y axis) / dimSize / Integer / Integer
Grid Resolution (X & Y axis) / dimResol / Class / Measure
Degrees and decimals of arc
Grid Corner Points / cornerPts / Sequence / GM_Point
West Bounding Limit / westBL / Class / Angle
-180.0 <= West Bounding
Longitude
Value <= 180.0
East Bounding Limit / eastBL / Class / Angle
-180.0 <= East Bounding
Longitude
Value <= 180.0
South Bounding Limit / southBL / Class / Angle
-90.0 <= Latitude
Value <= 90.0; South
Bounding Latitude Value <=
North bounding Latitude
Value
North Bounding Limit / NorthBL / Class / Angle
-90.0 <= Latitude
Value <= 90.0; North
Bounding Latitude Value >=
South bounding Latitude
Value
Vertical Uncertainty Type / verticalUncertaintyType (extension to ISO19115 for BAG) / CharacterString / Unknown - The uncertainty layer is an unknown type
Raw_Std_Dev - Raw standard deviation of soundings that contributed to the node
CUBE_Std_Dev - Standard deviation of soundings captured by a CUBE hypothesis (i.e., CUBE’s standard output of uncertainty)
Product_Uncert - NOAA standard product uncertainty V1.0 (a blend of CUBE uncertainty and other measures).
Historical_Std_Dev – Estimated standard deviation based on historical/archive data.
Tracking Identifier / trackingId
(extension to ISO19115 for BAG) / CharacterString

D.1.5Grid Arrays

The BAG contains two co-located two dimensional arrays. These are organised in row major order starting from the south-western most data point. The south-western data point, grid resolution (distance between each node) and size of grid (number of x,y nodes) are all specified in the data set metadata. Multiple grid resolutions within one instance of a BAG file is not supported.

BAG is a node-based as opposed to a cell oriented grid. This means that each value held at the grid node only applies to that exact position and not to the whole cell.

The Grid coordinate system should be geodetic as opposed projected and the grid origin (Latitude and Longitude) and grid resolution described in degrees and decimals.

D.1.5.1 Elevation Grid

The elevation units must be metres. The vertical datum must be referenced in the dataset Metadata. Elevation values are positive above the vertical datum (heights) and negative below the vertical datum (depths).

For any node where the elevation is unknown the value shall be defined as 1,000,000.0.

The minimum and maximum elevation values contained within the array are encoded at the completion of the Elevation array.

Attribute Table for Elevation Grid

Attribute / Unit / Data Type / Domain / Unknown Value
Elevation / Metres / Float 32 [][] / (FLT_MIN,FLT_MAX) / 1.0e6
Minimum Elevation Value / Metres / Float 32 / FLT_MIN / N/A
Maximum Elevation Value / Metres / Float 32 / FLT_MAX / N/A

D.1.5.2 Vertical Uncertainty Grid

The vertical uncertainty units must be metres. The values are expressed as positive values.

For any node where the vertical uncertainty is unknown the value shall be defined as 0.0.

The minimum and maximum uncertainty values contained within the array are encoded at the completion of the Uncertainty array.

Attribute Table for Vertical Uncertainty Grid

Attribute / Unit / Data Type / Domain / Unknown Value
Uncertainty / Metres / Float 32 [][] / (FLT_MIN,FLT_MAX) / 0.0
Minimum Uncertainty Value / Metres / Float 32 / FLT_MIN / N/A
Maximum Uncertainty Value / Metres / Float 32 / FLT_MAX / N/A

D.1.6Tracking List

The tracking list contains the original elevation and uncertainty values from any node of the surface that has been modified by manual over-rides i.e. values that have been changed from those originally computed by an algorithmic method.

Due to the requirement for AML NMB to accurately define the scientifically most accurate depiction of the elevation it would be normal for the tracking list to be empty.

Attribute Table for Tracking List

Attribute / Unit / Data Type / Domain / Description
Tracking List Item / N/A / BAG Tracking List Item / N/A / X-location of modified node
Tracking List Length / N/A / Unsigned Integer 32 / [0,2^32-1] / Y-location of modified node

Attribute Table for Tracking List Item

Attribute / Unit / Data Type / Domain / Description
Row / N/A / Unsigned Integer 32 / (0,SizeOf_X-Array) / X-location of modified node
Column / N/A / Unsigned Integer 32 / (0,SizeOf_Y-Array) / Y-location of modified node
Elevation / Metres / Float 32 / Original elevation before change
Uncertainty / Metres / Float 32 / Original uncertainty before change
Track_code / N/A / Char / Code identifying reason for modification
List_series / N/A / Unsigned Integer 16 / Index number linking to metadata modification description

D.1.7Certification

The Digital Signature Scheme(DSS) implemented by BAG is intended to ensure that any modifications made to the originally produced dataset are readily detectable. Any end user of AML NMB can therefore be confident that the dataset in use is as authorised by the competent authority.

The DSS is not part of the actual HDF-5 data structure but appended to the end of the file to ensure the integrity of the signature is maintained.

Full details of the implementation of DSS within the BAG are detailed in references [3] and [5].

D.1.8Encapsulation

BAG has adopted the Hierarchical Data Format version5 (HDF-5) to encapsulate the data.

The BAG file structure is shown in Figure 2.

Figure 2

The structure of this encapsulation is shown below.

Group “BAG_root” {

Attribute “BAG Version”

Dataset “metadata” {

DATATYPEString

DATASPACE1-dimension, 0-N

DATASET {“XML….”}

}

Dataset “elevation” {

DATATYPEFloating point 4bytes

DATASPACE 2-dimensions, 0-N,0-M

DATASET {{}}

Attribute “Minimum Elevation Value”

Attribute “Maximum Elevation Value”

}

Dataset “uncertainty” {

DATATYPEFloating point 4bytes

DATASPACE 2-dimensions, 0-N,0-M

DATASET {{}}

Attribute “Minimum Uncertainty Value”

Attribute “Maximum Uncertainty Value”

}

Dataset “tracking list” {

DATATYPEbagTrackingListItem

DATASPACE1-dimension, 0-N

DATASET {}

Attribute “Tracking List Length”

}

}

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Additional Military LayersNetwork Model Bathymetry Annex D

D.2File Naming

AML NMB will follow the file naming convention develop for AML vector specification Version3.0.

D.3Updating

There is no mechanism for incremental updates (thin updating) to BAG format files.

Data will be updated by a complete refresh of the file contents.

D.4Acknowledgement

The contents of much of this Annex has been derived from references [3] and [5] produced by the Open Navigation Surface Working Group.

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