1 11/26/2000 proposed revisions to the orm presentation given to wg8 meeting #5 orlando by paul a....

111/26/2000

Proposed Revisions to the ORM

Presentation given to WG8 Meeting #5 Orlando

by

Paul A. Birkel

November 28 - December 1, 2000

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Overview of Proposed Revisions

• Refine Object Reference Model to allow0 or more Object Reference Surfaces (ORS)

• Define ORS and characterize those which will appear in this International Standard

• Characterize dependency of “categories” of CS on ORS (e.g., projection-based CS on sphere or ellipsoid of revolution)

• Generalize from “geo” (and Earth) to “celestio”, as appropriate (e.g., ORM, CRM, ERM)

• Reorganize/rename “categories” of SRFs and incorporate choices of ORM, ORS(s), and CS

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Object Reference Model

• Current: An Object Reference Model is an n-dimensional surface.

• New: An Object Reference Model is a specification of at least N-1 (where N is the dimensionality of the object) distinguished orthogonal directions, and a distinguished point. It may optionally include the specification of one or more associated Object Reference Surfaces. The distinguished point and the distinguished orthogonal directions may together be used to form an object-centric coordinate system.

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Example ORM: Planetary Object

• N-1 = 2 distinguished orthogonal directions -- derived from an axis, and some plane containing a second axis.– The axis may relate to rotation, magnetics, or be fixed to an external

frame.– The plane may be rotational, perpendicular to a magnetic axis, or

ecliptic (among other choices).– The axis-in-the-plane may be defined by a unique point on an

associated ORS (e.g., a crater), an equinox, or some external point.

• The distinguished point may be a mass-center.

• The associated Object Reference Surface(s) may be:– Absent,– Based on a sphere, an ellipsoid of revolution, a tri-axial ellipsoid, a

surface of constant gravitational potential, a “well-known” surface such as “mean sea level”, a surface of constant pressure, or

– Some combination of these alternatives (e.g., an ellipsoid of revolution, and a surface of constant gravitational potential).

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Significant ORS (currently)

Object Reference Surface Scope

Sphere

Ellipsoid of Revolution Applies to most celestial objects in rotation.

Tri-axial Ellipsoid Applies to selected irregular celestial objects such asthe asteroids Ida and Gaspra.

Constant GravitationalForce

Applies to all celestial objects.

Mean Sea Level Applies only to the Earth.

Constant Pressure Applies to those celestial objects which have asignificant gaseous component.

Define and incorporate additional ORS’s as required.

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Generalization of ORM/ERM

• This International Standard should (also) apply to non-Earth objects, including:– Sun, planet, natural satellite, asteroid, and space-based

man-made objects.

• As currently drafted, it provides for only the most general case (which covers LSR/LSR2) and the Earth-specific case of ORMs (a specific planet).

• An intermediate case is required, perhaps termed the Celestial Body Reference Model (CBRM)– where “celestial body” is scoped to include suns,

planets, natural satellites, and asteroids -- of which the ERM is a special case.

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Characterization of Current ORMs (1)

ORM Definition Scope

Arbitrary-origin Provides distinguished directionsonly; the position of thedistinguished point is arbitrary; thereare no associated surfaces.

May not be used for surface-based SRFs (global, local, orprojection-based).(e.g., LSR/LSR2)

Artificial Body-centric

Provides distinguished directionsaligned with an artificial object with“inherent axes”; the position of thedistinguished point is internal to theconvex hull of the surface of theartificial object; there may be noassociated surfaces.

1. May only be used for localsurface-based SRFs if anassociated surface is present,and that surface uniquelydefines a local normal at allsurface locations.2. May only be used for globalsurface or projection-basedsurface SRFs if there is anassociated surface based oneither a sphere or an ellipsoidof revolution.

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Celestial Body,Arbitrary-basis(CBA)

Provides distinguished directionsaligned with several possible“inherent axes”; the position of thedistinguished point is typically themass-centre of the celestial body;there is usually at least oneassociated surface.

1. May only be used for localsurface-based SRFs if anassociated surface is present,and that surface uniquelydefines a local normal at allsurface locations.2. May only be used for globalsurface or projection-basedsurface SRFs if there is anassociated surface based oneither a sphere or an ellipsoidof revolution.

Celestial Body,Rotation-based,Mass-centred(CBRM)

Provides distinguished directionsbased on the rotational axis andequatorial plane; the position of thedistinguished point is the mass-centre of the celestial body; there isusually at least one associatedsurface.

Same as Celestial Body,Arbitrary-basis.(e.g., geocentric, geodetic,topocentric, all projection-basedSRFs)

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Celestial Body,Magnetic-based,Mass-centred(CBMM)

Provides distinguished directionsaligned with several possible“inherent axes”; the position of thedistinguished point is the mass-centre of the celestial body; there isusually at least one associatedsurface.

Same as Celestial Body,Arbitrary-basis.(e.g., some quasi-inertial SRFs)

Celestial Body,Revolution-based,Mass-centred(CBEM)

Provides distinguished directionsaligned with several possible“inherent axes”; the position of thedistinguished point is the mass-centre of the celestial body; there isusually at least one associatedsurface.

Same as Celestial Body,Arbitrary-basis.(e.g., some quasi-inertial SRFs)

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Removing Earth-centrism

• The following existing terms should be revised, wherever they appear in this International Standard excepting where the intended scope is exactly the Earth:

Current Revised

geocentric Celestial Body Centric, orCelestiocentric

geodetic Celestial Body Graphic, orCelestiographic

*As in “geographic”, “planetographic” (and “cartographic”)

*

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SRF Re-characterization (1)

ORM/ORS Basis SRF Name Acronym

Dimensionality

ORM or ORSLimitations

Local Space Rectangular 2D LSR2 2DArbitrary Origin, No ORS

Local Space Rectangular 3D LSR 2D

CBA, ORS-independent Celestial Body Centric CBC 3D

Celestial Body Graphic (2D) CBG2 2D Sphere, or Ellipsoidof revolution

CBA, ORS-dependent,Global Surface

Celestial Body Graphic (3D) CBG 3D Sphere, or Ellipsoidof revolution; mayuse gravity-basedor pressure-basedsurface for verticalmeasurements

Local Tangent Plane (2D) LTP2 2D

Local Tangent Plane(3D) LTP 3D

CBA, ORS-dependent,Local Surface

Global Coordinate System GCS 3D Earth-specific,WGS 84 Ellipsoid ofRevolution

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Dimensionality


Mercator M 2D Sphere, or Ellipsoidof revolution

Augmented Mercator AM 3D Sphere, or Ellipsoidof revolution; mayuse gravity-basedor pressure-basedsurface for verticalmeasurements

Oblique Mercator OM 2D Sphere

Augmented Oblique Mercator AOM 3D Sphere; may usegravity-based orpressure-basedsurface for verticalmeasurements

Transverse Mercator TM 2D Sphere, or Ellipsoidof revolution

CBA, ORS-dependent,Projection-Based

Augmented TransverseMercator

ATM 3D Sphere, or Ellipsoidof revolution; mayuse gravity-basedor pressure-basedsurface for verticalmeasurements

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Dimensionality


Universal Transverse Mercator UTM 2D Earth Ellipsoid ofRevolution

Augmented UniversalTransverse Mercator

AUTM 3D Earth Ellipsoid ofRevolution; mayuse gravity-basedor pressure-basedsurface for verticalmeasurements

Lambert Conformal Conic LCC 2D Sphere, or Ellipsoidof revolution

Augmented LambertConformal Conic

ALCC 3D Sphere, or Ellipsoidof revolution; mayuse gravity-basedor pressure-basedsurface for verticalmeasurements

Polar Stereographic PS 2D Sphere, or Ellipsoidof revolution

Augmented PolarStereographic

APS 3D Sphere, or Ellipsoidof revolution; mayuse gravity-basedor pressure-basedsurface for verticalmeasurements

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Dimensionality


Universal Polar Stereographic UPS 2D Earth Ellipsoid ofRevolution

Augmented Universal PolarStereographic

AUPS 3D Earth Ellipsoid ofRevolution; mayuse gravity-basedor pressure-basedsurface for verticalmeasurements

Equidistant Cylindrical EC 2D Sphere, or Ellipsoidof revolution

Augmented EquidistantCylindrical

AEC 3D Sphere, or Ellipsoidof revolution; mayuse gravity-basedor pressure-basedsurface for verticalmeasurements

Geomagnetic GM 3D

Geocentric Equatorial Inertial GEI 3D

Geocentric Solar Ecliptic GSE 3D

Geocentric Solar Magnetic GSM 3D

CBA, ORS-independent,Inertial & Quasi-Inertial

Solar Magnetic SM 3D

1 11/26/2000 proposed revisions to the orm presentation given to wg8 meeting #5 orlando by paul a....

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