pdsmc november 2008 planetary data system status report revisions to chapter 2. cartographic...

PDSMC November 2008 Planetary Data System

Status Report

Revisions to Chapter 2. Cartographic Standards

PDS Standards Referencev. 3.7, March 20, 2006

Lisa Gaddis

Planetary Data System Management Council

November 2008 22

• Participants and Reviewers– PDS: Lisa Gaddis, Mike A’Hearn, Dick Simpson, Mark Showalter, Mitch Gordon, Ed

Guinness– USGS/IAU: Brent Archinal, Jim Hilton (USNO), Peter Thomas (Cornell),– Experts: Randy Kirk (USGS), Bruce Campell (CEPS), Tom Duxbury (GMU), Frank

Lemoine (GSFC)

• Timeline– April, 2007: A’Hearn recognized the badly out-of-date discussion of coordinate

systems in the PDS Standards Reference, requested revision, circulated draft 1.0– May, 2007: Gaddis, Archinal edited, recirculated draft 1.1– June-Aug 2007: Comments from A’Hearn, Guinness, Gordon, Showalter, et al.– Feb-June, 2008: Gaddis iterated with Archinal on draft 1.2– July, 2008: Gaddis circulated draft 2.0– August, Sept 2008: Comments from Simpson, A’Hearn, Showalter, Archinal, Kirk– October, 2008: Gaddis circulated draft 3.0 to PDS and outside reviewers

• Comments rec’d from A’Hearn, Simpson, Campbell, Lemoine, Hilton, Thomas

– November, 2008: Draft 4.0• Not rec’d from Duxbury only

Chapter 2 Revisions


November 2008 33

• Quick Summary– Length expanded from 4.5 ss pages to 11 ss pages– Expanded content:

• Cites current national and international advisory groups and reports

• Defines reference frame and coordinate systems, notes international standard values as well as ‘customs’

• Expands explanation of time system definitions and values

• Recommends coordinate systems and frames for planets, small bodies, rings

• Explicit recommendations and examples for data products– Examples for Moon and Mars products cited, references to WGCCRE reports

for others– Recommendations on map projections, preferred uniform scales

– Updated references and citations• Reports from IAU WGCCRE

• PDS documents

Chapter 2: Changes


November 2008 44

• 2.1 Introduction– ‘All data providers for PDS products should follow accepted standards

and be aware of current NASA and international recommendations on cartographic coordinate systems and conventions relevant to their body of interest.’

– ‘An absolute requirement for all PDS products is that relevant coordinate systems and frames be clearly specified in product labels and supporting documents.’

– 2.1.1 International and NASA Advisory Groups for Cartographic Standards

• IAU/IAG Working Group on Cartographic Coordinates and Rotational Elements (WGCCRE)

– Archinal is Chair; A’Hearn, Thomas, Hilton are members• NASA Lunar Geodesy and Cartography Working Group

– Archinal is Chair; Gaddis, Campbell, Lemoine are members

• 2.2 Inertial Reference Frame and Time System– Defines reference frame, reference system, description of coordinates of

a planetary body in space in SI units, standard time reference, orientation of the inertial system, transformation between (old, new, preferred) frames and systems, etc.

Chapter 2 Current Content


November 2008 55

• 2.3 Spin Axes and Prime Meridians– International standards cited– Influx of new data often means that these values are being refined, so data

providers and WGCCRE must remain in close contact when this occurs

• 2.4 Body-Fixed Planetary Coordinate Systems– Common elements for planetary bodies

• Two body-fixed coordinate systems: Planetocentric and Planetographic– More complicated for some planets and satellites (2.4.1), small bodies (2.4.2),

rings (2.4.3); refer to WGCCRE reports for details

• 2.5 Surface Models– Digital terrain vs. digital image models as reference surface models for hard

bodies, recommendations for common usage

• 2.6 PDS Keywords

• 2.7 Map Resolution

• 2.8 References

Chapter 2 Current Content


November 2008 66

• ‘Change Log’ (for PDS SR v. 4.0?)– 2.1 Introduction:

• Recommendation to follow NASA and international standards• Explicit statement of duties of data providers to be aware and keep up with

standards and changes• 2.1.1 Advisory Groups: New section, with expanded reference information and

citations for IAU/IAG, LGCWG, MGCWG reports

– 2.2 Reference Frame, Time: Expanded section• Defines reference frame vs. reference system, describes coordinates of a

planetary body in space in SI units, provides info on standard time reference, orientation of the inertial system, transformation between (old, new, preferred) frames and systems

– 2.3 Spin Axes & Prime Meridians: Expanded, reorganized section• Describes spin axis orientation in the inertial reference frame, definition of ‘north

pole’, specification of prograde and retrograde rotation• For small bodies, describes the ‘positive pole,’ refers to WGCCRE reports for more

explicit discussion for complicated situations• Prime meridian reference to surface feature or mean direction of parent body; use

of arbitrary meridian for bodies w/out solid surfaces, refer to WGCCRE reports for details

Chapter 2: ‘Change Log’


November 2008 77

• ‘Change Log’ (cont.)– 2.4 Body-Fixed Planetary Coordinate Systems: Expanded, reorganized section

• Defines planetographic and –ocentric in single section, notes that either may be used

– Use of planetocentric for Mars products per MGCWG

• Keywords moved to later section

• 2.4.1 Planets and Satellites:

– Historical complications to current standard practices

– Examples: Moon data and products per LGCWG» Image mosaics and maps: Longitude range of 0° to 360° is recommended by LGCWG» Orientation: Use JPLDE403 or DE421 ephemeris per LGCWG

• 2.4.2 Small Bodies:

– Subsection added

– Simple case: Body with positive pole pointing to northern hemisphere of solar system has longitude (for both ocentric and ographic) increasing eastward and 0 to 360 degrees, and longitude decreases with time (as seen by outside observer)

– Complicated cases: Irregular shapes, other special cases discussed in WGCCRE reports

• 2.4.3 Rings:

– No longer separate section; grouped with other coordinate systems info

– Relevant keywords added to later section

– Statement added that international standards for ring coordinate systems were defined by Rings Node in consultation with broad cross-section of interested scientists

• Dropped Table 2.1 with rotation direction for planets and Moon, WGCCRE reports cited

Chapter 2: ‘Change Log’


November 2008 88

• ‘Change Log’ (cont.)– 2.5 Surface Models: Slightly expanded section– Expands on description of digital terrain vs. digital image models as reference surfaces– Added recommendations on map projections for DTMs and DIMs– Added possible use of elevation (height above potential surface) to as opposed to

radius for topographic models• Requires that method, constants and gravity field used to translate between elevation and

radius are described

– 2.6 Keywords: Slightly expanded, concatenated section• Combines keywords from planetary and rings sections

• Cites additional relevant existing keywords for planetary coordinate systems– A_AXIS_RADIUS, COORDINATE_SYSTEM_DESC, COORDINATE_SYSTEM_REF_EPOCH

• Cites PDS Data Dictionary, 2008 as reference for additional information

– 2.7 Map Resolution: Expanded section• Added recommendations on uniform spatial resolutions for global maps and other derived

products to account for differences in available image resolution and quality– Binary (2n pixels per degree of latitude) spatial resolution for global, regional, polar products

» Follows existing conventions for Mars data products– Meter scale resolution for high-resolution, landing-site scale products

– 2.8 References: Expanded section• Explicit citations for WGCCRE reports published to present time

Chapter 2: Change Log


November 2008 99

• ‘Change Log’ (cont.)– Implemented changes per outside reviewers

• See text in green on later slides for specifics

• Changes in red were not made (too much for this doc?)

– Mostly clarifications, small additions to text

– Major comments from Lemoine and Hilton

• Add references to ‘non-sanctioned’ coordinate systems for Mars– ‘Pathfinder’ system for Mars (used by GSFC)

• Tweaks to text– 2.2 Inertial Reference Frame and Time System

» Clarify Inertial Celestial Reference System vs. Frame» Add Barycentric Celestial Reference System» Add references for cited frame bias value

– 2.3 Spin Axes and Prime Meridians» Add clarification of ‘prograde’ vs. ‘direct’ rotation



November 2008 1010

• ‘Change Log’ (cont.)– One final clarification per Hilton comments:

• Capitalization of names of planets and satellites– Per IAU, ‘Spelling of Names’

» The IAU formally recommends that the initial letters of the names of individual astronomical objects should be printed as capitals (see the IAU Style Manual, Trans. Int. Astron. Union, volume 20B, 1989; Chapter 8, page S30)

» e.g., Earth, Sun, Moon: "The Earth's equator" and "Earth is a planet in the Solar System" are examples of correct spelling

» http://www.iau.org/public_press/themes/naming/#spelling

– Supported by Jenny Blue (USGS), Planetary Nomenclature expert for NASA and IAU, and Jan Zigler (USGS), Map editor for USGS Publication Services

– Planetary object names were capitalized

» Comments from Mike A’Hearn?



November 2008 1111

• Additional changes per outside reviews?• PDS Keywords: New Entries for Data Dictionary

– COORDINATE_FRAME_NAME• Purpose: to differentiate between coordinate systems and frames• Moon examples:

– System: mean Earth/polar axis– Frame: DE421 ephemeris rotated to the mean Earth/polar axis system

– Possible ‘Siblings’:• COORDINATE_FRAME_CENTER_NAME• COORDINATE_FRAME_DESC• COORDINATE_FRAME_ID• COORDINATE_FRAME_REF_EPOCH• COORDINATE_FRAME_TYPE

– Per Dick Simpson: Add for Rings?• AZIMUTH_RESOLUTION• MAXIMUM_OUT_OF_PLANE_DISTANCE

– Others?

• For all, definitions and acceptable values needed• Capitalizations for consistency with IAU recommendations?

Chapter 2: TBD List


November 2008 1212

• When are we done with reviews?– How many outside reviewers are necessary?– Which of their suggestions must be implemented?

• Who decides on the value of outside input for PDS?

• What comes next?– Approval by PDSMC– Gaddis to submit revisions (to whom?) for upload to online PDS

SR doc• When does v. 3.7 of SR become v. 4.0?

• When are new keywords added?– Before PDS4/PDS2010 implementation?

Chapter 2: Questions


November 2008 1313

• Campbell comments– Requested 10/28/08, received 10/29/08– ‘Draft looks very good’– ‘Provides a nice, clear explanation in particular of

the 2000 vs. 1950 and –ographic vs. –ocentric systems’

– ‘Maybe add a note that the pixel scale recommendations are most relevant to higher-level derived PDS products (since raw data will be archived at system resolution)’

Chapter 2: Outside Reviews of v. 3.1


November 2008 1414

• Thomas comments– Requested 11/06/08, received 11/10/08– ‘Nice, clear summary’– ‘Could only suggest the most tiny nit-picking on

words’• No suggestions made



November 2008 1515

• Hilton comments– Requested 11/06/08, received 11/12/08– Returned marked-up copy– ‘Takes approach of a nit picker’– ‘Places where the text is almost, but not quite correct’ – ‘Only a few minor changes, none of them show stoppers’

• Mostly tweaks to text in 2.2 Inertial Reference Frame and Time System, 2.3 Spin Axes and Prime Meridians, 2.4 Body-Fixed Planetary Coordinate Systems

• Possible addition to Rings portions of 2.6 Keywords• Clarification on 2.7 Map Resolution

– ‘Some unnecessary redundancy here and there’• E.g., prograde defined twice



November 2008 1616

• Lemoine comments– Requested 10/28/08, received 10/30/08– ‘Overall I think the manuscript is very complete’– ‘Section 2.3 (Spin Axes & Meridians), maybe cite a specific example, such as

the orientation of Mars from IAU 2004’– ‘For Mars, maybe cite the other ‘unsanctioned by IAU’ coordinate system (the

‘Pathfinder orientation’ model; Konopliv et al, 2006, Icarus)’• Konopliv MRO model will use this, MRO Nav Team at GSFC is using this• Don’t know if this is part of NAIF

– ‘For Moon, might clarify distinction between ME and PA system’• LLR natural (‘native’?) frame is PA

– ‘Maybe add section on how to convert from inertial to body-fixed coordinates’• Via application of a succession of rotation matrices• Include picture or figure?• Note that SPICE s/w of NAIF handles these rotations naturally

– ‘Maybe add note that some bodies undergo librations’• Expressed as periodic terns in the RA and DEC (e.g., ME model of Moon)

– ‘The approach to cite references for more information is a good one’


Did not makechanges in red.

Too much?

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