Published on February 18, 2014
Discussion on an HDF-GEO concept HDF Workshop X 30 November 2006
Abstract At the past several HDF & HDF-EOS Workshops, there has been some informal discussion of building on the success of HDF-EOS to design a new profile, tentatively called HDF-GEO. This profile would incorporate lessons learned from Earth science, Earth applications, and Earth model data systems. It would encompass all types of data, data descriptions, and other metadata. It might support 1-, 2-, and 3-D spatial data as well as time series; and it would include raw, calibrated, and analyzed data sets. It would support data exchange by building its needed complexity on top of minimal specialized features; and by providing clear mechanisms and requirements for all types of appropriate metadata. The organizers propose to host a discussion among the workshop participants on the need, scope, and direction for HDF-GEO.
Which buzzwords would fit? naming rules … profile data model best practices metadata content atomic & compound types HDF-GEO geo ref …ilities self docu -mentation data levels markup & schema platform support test suites tools
Questions for discussion by Earth science practitioners - Bottom-up analysis: What are the successful features of existing community data formats and conventions? (HDF5, HDF-EOS, netCDF, CDF, GRIB BUFR, COARDS, CF-1, NITF, FITS, FGDC RS extensions, ISO, geoTIFF, ...) Progress being made -- John Caron's Common Data Model Specific needs for geo- and time-referenced data conventions Specific needs to support observed (raw), calibrated, and analyzed data sets
Questions for discussion by Earth science practitioners - Top-down analysis: (1 of 2) What is a profile? Consider specifics of how a standard or group of standards are implemented for a related set of uses and applications. How does a profile relate to a format or other elements of a standard? What constitutes overkill? How much profile would be beneficial, and how much would be difficult to implement and of limited utility?
Questions for discussion by Earth science practitioners - Top-down analysis: (2 of 2) Why is it useful? Establishes specific meanings for complicated terms or relationships Establishes common preferred terms for attributes which can be described multiple ways. Establishes practices which are consistent with portability across operating systems, hardware, or archives Establishes common expectations and obligations for data stewardship Clarifies community (and sponsor) long-term expectations, beyond short-term necessity other ...
Wrap-up Send your list of provisional HDF-GEO requirements goals to be achieved How HDF-GEO would help to me at email@example.com
Motivation: In many instances, application-specific 'profiles' or 'conventions' or best practices have shown their utility for users. In particular, profiles have encouraged data exchange within communities of interest. HDF provides minimal guidance for applications. HDF-EOS was a mission-specific profile; resulted in successes and lessons learned. HDF5 for NPOESS is another approach. Is it time for another attempt, benefitng from all the lessons, and targeted at a broader audience?
HDF Lessons from NPOESS & Future Opportunities (excerpt) Alan M. Goldberg HDF Workshop IX, <firstname.lastname@example.org> December 2005 NOTICE This technical data was produced for the U.S. Government under Contract No. 50-SPNA-9-00010, and is subject to the Rights in Technical Data - General clause at FAR 52.227-14 (JUN 1987) Approved for public release, distribution unlimited © 2005 The MITRE Corporation. All rights reserved
Requirements for data products Deal with complexity – Large data granules Order of Gb – Complex intrinsic data complexity Advanced sensors produce new challenges – Multi-platform, multi-sensor, long duration data production – Many data processing levels and product types Satisfy operational, archival, and field terminal users – Multiple users with heritage traditions © 2005 The MITRE Corporation. All rights reserved
SENSORS CCSDS (mux, code, frame) & Encrypt Delivered Raw Packetization Compression Aux. Sensor Data Cal. Source ENVIRONMENTAL SOURCE COMPONENTS Filtration Comm Processing C3 S Comm Receiver RDR Production IDPS Comm Xmitter Data Store OTHER SUBSYSTEMS SPACE SEGMENT NPOESS products delivered at multiple levels RDR Level A/D Conversion Detection Flux Manipulation TDR Level SDR Production SDR Level EDR Level EDR Production © 2005 The MITRE Corporation. All rights reserved
Sensor product types Swath-oriented multispectral imagery – VIIRS – cross-track whiskbroom – CMIS – conical scan – Imagery EDRs – resampled on uniform grid Slit spectra – OMPS SDRs – cross-track spectra, limb spectra Image-array fourier spectra – CrIS SDR Directional spectra – SESS energetic particle sensor SDR Point lists – Active fires 3-d swath-oriented grid – Vertical profile EDRs 2-d map grid – Seasonal land products Abstract byte structures – RDRs Abstract bit structures – Encapsulated ancillary data Bit planes – Quality flage Associated arrays (w/ stride?) – geolocation © 2005 The MITRE Corporation. All rights reserved
NPOESS product design development Requirements - Multi-platform, multisensor, long duration data production - Many data processing levels and product types - Satisfy operational, archival, and field terminal users Constraints - Processing architecture and optimization - Heritage designs - Contractor style and practices - Budget and schedule Intentions - Use simple, robust standards - Use best practices and experience from previous operational and EOS missions - Provide robust metadata - Maximize commonality among products - Forward-looking, not backward-looking standardization Design Process - Experience - Trades& Analyses Result Resources - HDF5 - FGDC - C&F conventions - Expectation of tools by others © 2005 The MITRE Corporation. All rights reserved
Lessons & Way Forward © 2005 The MITRE Corporation. All rights reserved
Observations from development to date Avoid the temptation to use heritage approaches without reconsideration, but … Novel concepts need to be tested Data concepts, profiles, templates, or best practices should be defined before coding begins Use broad, basic standards to the greatest possible extent – FGDC has flexible definitions, if carefully thought through Define terms in context; clarity and precision as appropriate Attempt to predefine data organizations in the past (e.g., HDF-EOS ‘swath’ or HDF4 ‘palette’) have offered limited flexibility. Keep to simple standards which can be built upon and described well. Lesson: be humble It is a great service to future programs if we capture lessons and evolve the standards How do we get true estimates of the life-cycle savings for good design? © 2005 The MITRE Corporation. All rights reserved
Thoughts on future features for Earth remote sensing products Need to more fully integrate product components with HDF features Formalize the organization of metadata items which establish the data structure – Need mechanism to associate arrays by their independent variables Formalize the organization of metadata items which establish the data meaning – XML is a potential mechanism – can it be well integrated? – Work needed to understand the advantages and disadvantages – Climate and Forecast (CF) sets a benchmark Need a mechanism to encapsulate files in native format – Case in which HDF is only used to provide consistent access Need more investment in testing before committing to a design © 2005 The MITRE Corporation. All rights reserved
Primary and Associated Arrays Index Attribute n-Dimensional Dependant Variable (Entity) Array Primary Array e.g., Flux, Brightness, Counts, NDVI Associated Array(s) e.g., QC, Error bars dimension ≤ n
1-Dimensional Attribute Variables Index Attribute Primary e.g., UTC time or angle Additional e.g., IET time, angle, or presssure height Associated Independent Variable(s)
Multi-Dimensional Attribute Variables 2-Dimensional Independent Variable Array(s) e.g., lat/lon, XYZ, sun alt/az, sat alt/az, or land mask Key concept: Index Attributes organize the primary dependant variables, or entities. The same Index Attributes maybe used to organize associated independent variables. Associated independent variables may be used singly (almost always), in pairs (frequently), or in larger combinations.
Issues going forward - style Issues with assuring access understanding – How will applications know which metadata is present? – Need to define a core set with a default approach Issues with users – How to make providers and users comfortable with this or any standard – How to communicate the value of: best practices; careful & flexible design; consistency; beauty of simplicity – Ease of use as well as ease of creation Issues with policy – Helping to meet the letter and intent of the Information Quality Act Capturing data product design best practices – Flexibility vs. consistency vs. ease-of-use for a purpose © 2005 The MITRE Corporation. All rights reserved
Issues going forward - features Issues with tools – Tools are needed to create, validate, and exploit the data sets. Understand structure and semantics Issues with collections – How to implement file and collection metadata, with appropriate pointers forward and backward – How to implement quasi-static collection metadata Issues with HDF – Processing efficiency (I/O) of compression, of compaction – Repeated (fixed, not predetermined) metadata items with the same <tag> not handled – Archival format © 2005 The MITRE Corporation. All rights reserved
Possible routes: Should there be an HDF-GEO? Specify a profile for the use of HDF in Earth science applications: Generalized point (list), swath (sensor coordinates), grid (georeferenced), abstract (raw), and encapsulated (native) profiles. Generalized approach to associating georeferencing information with observed information. Generalized approach to incorporating associated variables with the mission data Generalized approach to ‘stride’ Preferred core metadata to assure human and machine readability Identification metadata in UserBlock Map appropriate metadata items from HDF native features (e.g., array rank and axis sizes) Preferred approach to data object associations: arrays-of-structs or structs-of-arrays? Design guidelines or strict standardization? © 2005 The MITRE Corporation. All rights reserved
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