The Local Hub must provide three services:
publication of ISO19115-3 metadata through a catalogue service - nominally GeoNetwork
publication of Web Mapping Service and Web Coverage Service according to AusSeabed protocols
direct download of Local Hub products through HTTP protocol
The Local Hub must also provide a description of their holdings in an Excel format that can be read by the Exploring For The Future Portal.
Publication of ISO19115-3 metadata
Most large organisations that distribute spatial data catalogue the existence of that data using a metadata catalogue system such as GeoNetwork. AusSeabed Local Hubs must provide a catalogue that can be harvested by AODN (and others) using GeoNetwork. AusSeabed requires that metadata entries be systematised to support downstream search and filter.
General Background
There are several metadata standards for describing spatial data, but ISO19115 continues to grow in popularity. The standard itself provides a wide range of flexibility in the forms of XML that it accepts. It is rarely possible for a system to understand the semantics of every component of XML that meets the standard. Likewise, the standard permits different ways of representing the same information. What has emerged are profiles of the ISO19115 that have agreed meaning among subsets of the spatial community. These can also include variations such as additional mandatory fields. In AusSeabed’s case the most notable is the marine community profile (ISO19115-3) that is designed for marine purposes (most notably documenting marine specimen samples). Worthy of similar mention is GA’s Community Profile that forces some metadata tags to be mandatory.
Technical Details
Geonetwork provides at least three method of editing metadata: a) a simple interface; b) the full interface; and c) an XML editor. Most metadata can be entered in the simple interface; however, a number of fields require the full editing interface or XML editor (or import) including:
Attribute | Location in XML | Interface |
|---|---|---|
Abstract | IdentificationInfo/Abstract | Simple |
Title | IdentificationInfo/Citation/Title | Simple |
Start Date | IdentificationInfo/Extent/TemporalExtent/TimePeriod/BeginPosition | Simple |
End Date | IdentificationInfo/Extent/TemporalExtent/TimePeriod/EndPosition | Simple |
Vessel | Acquisition Information/Platform/Identifier | Full/XML |
Instrument | Acquisition Information/Platform/Instrument/Identifier | Full/XML |
Vessel and instrument should also link to a valid vocabulary entry in a vocabulary server. E.g.
<mcc:code> <gcx:Anchor xlink:href="http://vocab.nerc.ac.uk/collection/C17/current/09SS">Southern Surveyor</gcx:Anchor> </mcc:code>
AusSeabed protocols for publishing Web Mapping Service and Web Coverage Services
For consistency, L3 products need to be presented through web services in the same way. Each L3 product served through a Web Mapping Service(WMS) must be presented as a group layer:
Presentation Order | Product | Type | Style |
|---|---|---|---|
Bottom | Extent Polygon | Polygon | |
Middle | Hillshade | Raster | |
Top | Bathymetry | Raster |
The extent polygon must contain metadata attributes of the layer:
Field | Example | |
|---|---|---|
AREA_KM2 | Area covered by the survey in square kilometres | 6654 |
BATHY_TYPE | Type of product (e.g. Multibeam, Backscatter) | Multibeam |
NAME | Title of product | Mentelle Basin Survey (GA-0293/SS08/2005) - Bathymetry grids |
START_DATE | Date that acquisition commenced | 28/09/2005 |
END_DATE | Date that acquisition completed | 19/10/2005 |
VESSEL | Name of Vessel | Southern Surveyor |
INSTRUMENT | Name of Instrument | Kongsberg EM300 |
BATHY_URL | Web resolvable link to bathymetry data | |
META_URL | Web resolvable link to metadata (persistent identifier preferred) |
The hillshade must be produced with azimuth 30 degrees, altitude 45 degrees and z scaling factor of 2. For geographic projection images, a scaling factor of 111120 must be applied.
All GeoTIFF images must be provided in Cloud Optimised form. For large images we have image overlays at 2 4 8 16 32 scales.