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Network Working Group                                          T. Clarke
Internet-Draft                                                      BATC
Intended status: Informational                            March 22, 2019
Expires: September 23, 2019


Concise Binary Object Representation (CBOR) Tag for Coordinate Reference
                       System (CRS) Specification
                        draft-clarke-cbor-crs-00

Abstract

   The Concise Binary Object Representation (CBOR, RFC 7049) is a data
   format whose design goals include the possibility of extremely small
   code size, fairly small message size, and extensibility without the
   need for version negotiation.

   In CBOR, one point of extensibility is the definition of CBOR tags.
   An existing CBOR tag, 103, allows for the representation of
   geographic coordinates.  Proper exploitation of geographic
   coordinates requires an associated reference frame.  The present
   document defines a CBOR tag for referencing the coordinate reference
   system (CRS) for a geographic coordinate.  It is intended as the
   reference document for the IANA registration of the CBOR tag defined.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on September 23, 2019.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Objectives  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Applicability . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Semantics . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     4.1.  Well-known Text . . . . . . . . . . . . . . . . . . . . .   3
     4.2.  EPSG Spatial Reference Identifier . . . . . . . . . . . .   3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   3
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Appendix A.  Examples . . . . . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Specifying geographic coordinates for a location on Earth requires
   the definition of a coordinate reference system (CRS).  A CRS is made
   up of several components: [EDS1]

   o  Coordinate system: The X, Y grid upon which your data is overlayed
      and how you define where a point is located in space.

   o  Horizontal and vertical units: The units used to define the grid
      along the x, y (and z) axis.

   o  Datum: A modeled version of the shape of the Earth which defines
      the origin used to place the coordinate system in space.  You will
      learn this further below.

   o  Projection Information: The mathematical equation used to flatten
      objects that are on a round surface (e.g. the Earth) so you can
      view them on a flat surface (e.g. your computer screens or a paper
      map).





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2.  Objectives

   This document aims to address the specification of coordinate
   reference systems in CBOR [RFC7049] encoded data.  This is
   accomplished using complete CRS specification or through a well-known
   spatial reference identifier.

3.  Applicability

   This tag is designed for use with the Geographic Coordinates CBOR Tag
   103 [CBOR-GC].  A CRS may be attached to a Geographic Coordinate or
   it may specify a default CRS for an entire scope.  This is the
   expected application but this tag may be used in any relevant
   context.

4.  Semantics

   The CBOR CRS tag shall be associated with one of multiple CBOR data
   types.  Each allowed type is associated with a different method of
   specifying a CRS.

4.1.  Well-known Text

   OGC [OGC] Well-known Text (WKT) [WKT] is a standarized format for CRS
   specification.  When the CRS tag is associated with a Text String
   (CBOR Major type 3), the data shall be interpreted as OGC WKT.  This
   allows for complete CRS specifcation of and subtype of CRS.

4.2.  EPSG Spatial Reference Identifier

   A spatial reference identifier (SRID) is a unique value which
   unambiguously identifies a CRS.  Many vendors and registries provice
   SRIDs.  This association is not intended to allow specification of an
   arbitrary SRID, but provides a way to reference an SRID in the
   European Pertroleum Survey Group's (EPSG) SRID database.  EPSG
   numbers are a de-facto standard for CRS reference and are very
   commonly used.  EPSG numbers can be searched and referenced in a
   number of places including [EPSG.io] and [SpatialReference.org].
   When the CRS tag is associated with a basic numeric type (CBOR Major
   type 0), the data shall be interpreted as an EPSG SRID.

5.  IANA Considerations

   IANA is requested to allocate a tag from the Specification Required
   space, with the present document as the specification reference.






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   +-----+----------+--------------------------------------------------+
   | Tag | Data     | Semantics                                        |
   |     | Item     |                                                  |
   +-----+----------+--------------------------------------------------+
   | TBD | multiple | Geographic Coordinate Reference System WKT or    |
   |     |          | EPSG number                                      |
   +-----+----------+--------------------------------------------------+

   *RFC editor note*: Please replace TBD by the tag number allocated by
   IANA throughout the document and delete this note.

6.  Security Considerations

   The security considerations of [RFC7049] apply; the tag introduced
   here are not expected to raise security considerations beyond those.

7.  References

7.1.  Normative References

   [CBOR-GC]  "CBOR Geographic Coordinates", n.d.,
              <https://github.com/allthingstalk/cbor/blob/master/
              CBOR-Tag103-Geographic-Coordinates.md>.

   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <https://www.rfc-editor.org/info/rfc7049>.

   [WKT]      Open Geospatial Consortium, "Geographic information -
              Well-known text representation of coordinate reference
              systems", May 2015,
              <http://www.opengis.net/doc/IS/wkt-crs/1.0>.

7.2.  Informative References

   [EDS1]     Wasser, L., "Earthlab/Earth-Analytics-R-Course: Earth
              Analytics Course In The R Programming Language",
              Zenodo article, DOI 10.5281/zenodo.1326873, August 2018.

   [EPSG.io]  "MapTiler EPSG Reference Website", n.d.,
              <https://epsg.io>.

   [OGC]      "The Open Geospatial Consortium", n.d.,
              <http://www.opengeospatial.org/>.

   [SpatialReference.org]
              "Spatial Reference Website", n.d.,
              <http://spatialreference.org>.



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   [SR-ORG-7428]
              "SR-ORG:7428 WGS 84 (3D EGM96 geoid height)", n.d.,
              <http://spatialreference.org/ref/sr-org/7428/>.

Appendix A.  Examples

   CRS for EPSG:4326, the World Geodetic System 1984 horizontal
   coordinate system used by GPS satellites, specified using an EPSG
   SRID.

       D8 68      # Geographic Coordinate System - tag(104)
          19 10E6 # EPSG:4326                    - unsigned(4326)

       # Diagnostic notation: 104(4326)

   CRS for WGS 84 3D EGM96 geoid height [SR-ORG-7428] specified using
   WKT


































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       D8 68             # Geographic Coordinate System - tag(104)
          79 0191        # OGC WKT                      - text(401)
             47454F4743535B225747532038342028
             33442045474D39362067656F69642068
             656967687429222C444154554D5B2257
             6F726C642047656F6465746963205379
             7374656D2031393834222C5350484552
             4F49445B22574753203834222C363337
             383133372E302C3239382E3235373232
             333536332C415554484F524954595B22
             45505347222C2237303330225D5D2C41
             5554484F524954595B2245505347222C
             2236333236225D5D2C5052494D454D5B
             22477265656E77696368222C302E302C
             415554484F524954595B224550534722
             2C2238393031225D5D2C554E49545B22
             444D53222C302E303030303034383438
             31333638313130393533365D2C415849
             535B2247656F6465746963206C617469
             74756465222C4E4F5254485D2C415849
             535B2247656F6465746963206C6F6E67
             6974756465222C454153545D2C415849
             535B22477261766974792D72656C6174
             656420686569676874222C55502C4155
             54484F524954595B2245505347222C22
             35373733225D5D2C415554484F524954
             595B2245505347222C2234333239225D5D

       # Diagnostic notation:
           104("GEOGCS[\"WGS 84 (3D EGM96 geoid height)\",
                DATUM[\"World Geodetic System 1984\",
                SPHEROID[\"WGS 84\",6378137.0,298.257223563,
                AUTHORITY[\"EPSG\",\"7030\"]],
                AUTHORITY[\"EPSG\",\"6326\"]],
                PRIMEM[\"Greenwich\",0.0,AUTHORITY[\"EPSG\",\"8901\"]],
                UNIT[\"DMS\",0.00000484813681109536],
                AXIS[\"Geodetic latitude\",NORTH],
                AXIS[\"Geodetic longitude\",EAST],
                AXIS[\"Gravity-related height\",UP,
                AUTHORITY[\"EPSG\",\"5773\"]],
                AUTHORITY[\"EPSG\",\"4329\"]]")

Author's Address








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   Trevor R.H. Clarke
   Ball Aerospace and Technologies Corp.
   2862 Presidential Dr.
   Fairborn, OH  45324
   United States

   Phone: +1-937-320-4000
   Email: tclarke@ball.com











































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