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STC-S – A Readable Metadata Serialization

STC-S – A Readable Metadata Serialization. Arnold Rots SAO/ CXC. STC-S: Introduction. A linear string serialization of STC Inspired by Jim Gray Originally focused on spatial regions; expanded to: Time, Space, Spectral, Redshift/Doppler velocity

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STC-S – A Readable Metadata Serialization

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  1. STC-S – A Readable Metadata Serialization Arnold Rots SAO/ CXC IVOA Interop Waikoloa/DAL: STC-S - Arnold Rots

  2. STC-S: Introduction • A linear string serialization of STC • Inspired by Jim Gray • Originally focused on spatial regions; expanded to: • Time, Space, Spectral, Redshift/Doppler velocity • Some restrictions apply, some defaults are allowed • One-to-one mapping between STC-S and STC-X We have a demo tool that does conversions • Compact and human-readable • Unambiguous and complete metadata description IVOA Interop Waikoloa/DAL: STC-S - Arnold Rots

  3. Basics • For each of the four astronomical coordinate types it allows stringing the STC elements together, with their values, in a specific order with embedded coordinate system information: • Coordinate space volume • Coordinate value • Error • Resolution • Size • Pixel size IVOA Interop Waikoloa/DAL: STC-S - Arnold Rots

  4. Restrictions (excluding the arcane) Only Time, Space, Spectral, Redshift axes No custom coordinate frames No spatial offsets Only simple errors No relocatable frames No planetary reference frames No Sectors or Convex Hulls Ellipse position angles: in degrees, limited reference Only IAU 1976 geodetic reference spheroids IVOA Interop Waikoloa/DAL: STC-S - Arnold Rots

  5. Example 1: Regions Common usage: footprints Simple region: Circle ICRS BARYCENTER 148.9 69.1 2.0 shape ref frame reference position parameter values Compound regions: Union ICRS TOPOCENTER (Polygon 147.8 69.2 147.4 69.2 147.3 69.4 147.9 69.4 Polygon 147.9 69.7 147.6 69.7 147.5 69.9 148.0 69.9) IVOA Interop Waikoloa/DAL: STC-S - Arnold Rots

  6. Example 2: Complex Compound Regions Union ICRS TOPOCENTER (Circle 180 10 20 Circle 190 20 20 Intersection (Circle 120 -10 20 Difference (Circle 130 -10 20 Circle 125 -10 2 ) Not (Circle 118 -8 3) ) ) IVOA Interop Waikoloa/DAL: STC-S - Arnold Rots

  7. Example 3: Locations • Simple position: Position ICRS GEOCENTER 147.6 69.3 • Simple position with its uncertainty: Position ICRS GEOCENTER 147.6 69.3 Error 0.01 0.01 IVOA Interop Waikoloa/DAL: STC-S - Arnold Rots

  8. Example 4: Cut-out Specification TimeInterval TT GEOCENTER 1996-01-01T00:00:00 2013-09-26T20:00:00 Box ICRS BARYCENTER 147.6 69.3 1.0 1.5 Spectral BARYCENTER 1420.4 unit MHz RedshiftInterval BARYCENTER VELOCITY OPTICAL-400 400 IVOA Interop Waikoloa/DAL: STC-S - Arnold Rots

  9. Example 5: Add Resolution, Pixel Size TimeIntervalTT GEOCENTER 1996-01-01T00:00:00 2013-09-26T20:00:00 Box ICRS BARYCENTER 147.6 69.3 1.0 1.5Resolution 0.001778 0.001778PixSize 0.000889 0.000889 Spectral BARYCENTER 1420.4 unit MHz RedshiftInterval BARYCENTER VELOCITY OPTICAL -400 400Resolution 0.7PixSize 0.3 IVOA Interop Waikoloa/DAL: STC-S - Arnold Rots

  10. To Conclude • The strings are very readable and flexible in what they can express • While still rigorously conforming with the standard • Tools may still restrict what they are prepared to accept • E.g., what elements, which coordinate systems • Still to be added: Polarization IVOA Interop Waikoloa/DAL: STC-S - Arnold Rots

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