Cartographic Standards Body-Fixed Rotating Co-ordinate Systems Software, and ‘cubes’... 26th September, 2002: Data Prep. Workshop Dave Heather (ESTEC)

Body-Fixed Rotating Co-ordinate Systems There are two fundamental co-ordinate systems in planetary mapping –Plantocentric (planet at centre, fixed rotator) –Planetographic (planet rotates beneath ‘fixed’ spacecraft or sub-Earth point) These are discrete from the final map projection

Planetocentric System Co-ordinates Origin: COM Long: increasing to east Lat: positive to north, from equatorial plane (spherical) Used for: Mars post-1992, but not exclusively Pros: Requested officially as a standard by the PDS Cons: not precise for locating places on planetary surface

Planetographic System Co-ordinates Origin: COM Long: increasing with planet rotation (to west for prograde) Lat: positive to north, local vertical from equatorial plane Used for: Mars pre-1992 Pros: Precise location of surface features, accounts for shape Cons: no longer standard for PDS

Is this in the label? GROUP = IMAGE_MAP_PROJECTION A_AXIS_RADIUS = B_AXIS_RADIUS = C_AXIS_RADIUS = POSITIVE_LONGITUDE_DIRECTION = EAST MAP_PROJECTION_TYPE = 'SINUSOIDAL_EQUAL-AREA' MAP_SCALE = MAP_RESOLUTION = EASTERNMOST_LONGITUDE = WESTERNMOST_LONGITUDE = MINIMUM_LATITUDE = MAXIMUM_LATITUDE = CENTER_LONGITUDE = REFERENCE_LATITUDE = REFERENCE_LONGITUDE = MAP_PROJECTION_ROTATION =

The Ongoing Mars Feud Planetocentric (’02 onwards) –Inconsistant with previous data –Assumes sphere for projections –Requires separate model of planet shape for actual planetary positions –As measured in space missions –Directly compatible with S/W –Standard accepted by PDS Planetographic (Pre ’02) –Consistent with previous data –Acknowledges non- spherical nature of planet –Same model for positioning can be used for map projection –Requires transformation from space mission measurements –Requires transformation for most S/W (simple) –Not ‘PDS standard’

MOC vs MOLA MOC planetocentric MOLA planetographic 0.3 degrees latitude difference max. Equates to 20 km difference max Transformation required! MOLA MOC

What Should We Use Then? For full PDS compliance, Mars data should be planetocentric Planetographic will still be acceptable though! Lander surveys, planetographic more accurate Conversion is easy and routinely available BOTTOM LINE: –Use whatever you’re comfortable with!!

Software, ISIS, cubes etc.

Some Basic Software Available Co-ordinate conversion simple and standard for most up to date processing packages Image and Data Processing Packages: –ISIS (Geom, Plansinu, etc.) tfiles –ENVI –IDL –VICAR –etc. etc. All of these can convert systems and reproject images

What is this ISIS thing? Integrated Software for Imaging Spectrometers Uses cubes MGS, MPF, Clementine, Viking etc. Geometric, photometric, radiometric etc. More than 45 geometric routines in ISIS. See website:

ISIS cubes 3-dimensional data format x and y plane containing data z plane contains stacked bands (for example) Sub-cube specifier allows processing of any part of a cube.

______________________. / / /|. ^ / backplane / / | } suffix. / /_ _ _ _ _ _ _ _ _/_ _/ | } region. / / / /| |. / d / / / |c |. / n / / / |o |. / a / core / / |r |. / B / / / |n |. / /_________________/___/ e |e |. / > | | | d e|r |. | Sample | | | i n | /| l. | s | | |s a |/ / a. | L p | | | l / / r. | i a | core | |p /|/ t. | n t | | | / / c. | e i | | | / / e. | a | | | / / p. | l |_________________|___|/ / s. v | bottomplane | | / } suffix. |_________________|___|/ } region. spatial ^^^. suffix region. Cube File Structure

The Clementine Example Raw data to cube clem2isis Radiometric correction and file merging: calmrg or expmrg Geometric correction: plansinu and geom Photometric correction: photom These are mission specific - generic routines are also available.

Here end-eth the lesson…. Happy data-producing!