International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B4. Istanbul 2004
existing range of Martian small- and mid-scale series (cf.
Greeley & Batson, 1990) with a large-scale frame, as it is
appropriate for high-resolution HRSC imagery and future
mapping purposes.
A sophisticated cartographic software system, the Planetary
Image Mapper (PIMap), has been developed at the Technical
University of Berlin. Based on a detailed set of initialization
parameters, this software generates and compiles the entire map
content automatically. However, some interactive finalization is
still necessary. Compared to common map generation proce-
dures — including the preparation of all components on its own
followed by intricate merging processes —, this comprehensive
approach is a substantial step towards future planetary carto-
graphy.
Recently, the first map sheets based on HRSC image data have
been generated.
2. CARTOGRAPHIC CONCEPTS
2.1 Martian Reference Bodies and Coordinate Systems
The common Martian reference body for planimetry is a
rotational ellipsoid with an equatorial axis of 3396.19 + 0.10
km and a polar axis of 3376.20 + 0.10 km. This parameter set is
defined by the International Astronomical Union (IAU) as the
Mars IAU 2000 ellipsoid (Seidelmann et al., 2002).
According to IAU conventions in principle two different types
of planetary coordinate systems are in use. One consists of
positive western longitudes in combination with planetographic
latitudes (west/planetographic), the other one of positive eastern
longitudes and planetocentric latitudes (east/planetocentric).
Latter is recommended by the Mars Geodesy/Cartography Wor-
king Group (MGCWSG) to be employed in future map products
(Duxbury et al., 2002). Therefore, the east/planetocentric sys-
tem is defined also as the standard for Mars Express mapping
(Gehrke et al., 2003). The prime meridian — i.e. zero longitude
going through the Airy-0 crater — is determined by an angle Wy
of 176.630° with respect to the inertial coordinate system
(Seidelmann et al., 2002).
An areoid (Martian geoid) is defined as the topographic refe-
rence surface for heights (Seidelmann et al., 2004).
2.2 Map Projections
Equal-area map projections are used for compiling the Topo-
graphic Image Map Mars 1:200,000. Because of its useful
mathematical and graphical properties, the Sinusoidal pro-
jection (cf. equations 30-8 and 3-27a/30-9 in Snyder, 1987) is
applied to map sheets between 85° north and 85° south. How-
ever, the polar regions can not be mapped appropriately by this
projection. Therefore the Lambert Azimuthal projection (cf.
equations 21-17 and 24-18 in Snyder, 1987) was selected for
mapping those regions between 85° and 90° north or respec-
tively south (Lehmann et al, 1997). The same scheme is
applied for the generation of special target maps.
It should be pointed out, that in this context, i.e. for Mars
Express mapping purposes, the Sinusoidal map projection
yields truly equal-area results, even though it is carried out with
an ellipsoidal reference body as defined for Mars. In planetary
sciences approximations based on the spherical formulae (cf.
equations 30-1 and 30-2 in Snyder, 1987) — using both either
planetocentric or planetographic latitudes — have been widely
used, mainly for data storing purposes but less for mapping.
The occurring differences between those projections and the
true ellipsoidal form have been further investigated by the
authors; see also Deuchler et al. (2004).
2.3 The Topographic Image Map Mars 1:200 000 Series
Fundamentally the Topographic Image Map Mars 1:200,000
series was introduced by Lehmann et al. (1997) for HRSC
mapping purposes during the preparations for the failed Mars96
mission.
N zn
| North Polar Region, 85° to 90° Latitude @
i V
| Lambert Azimuthal Projection
|
Western Hemisphere, -85° to 85° Latitude
(Eastern Hemispehre equivalent)
Sinusoidal Projection
NN.
Remark:
Due to the common
central meridian in this overwiew
the Sinusoidal Map sheets are distorted.
South Polar Region, 85° to 90° Latitude >
Lambert Azimuthal Projection
Figure 1. Sheet Lines System of the Topographic Image Map
Mars 1:200,000
The map series completes the existing bandwidth with the
required large-scale frame. Hence, the following scales and/or
series are in use for Mars:
Global maps (mainly 25M and 15M)
e Mars Charts MC 5M and MC 2M
e Mid-scale maps (1M)
e Mars Transverse Mercator series MTM 500k
e Topographic Image Map Mars 1:200,000 (200k)
While most of these listed maps are conformal (ie. Mercator,
Lambert Conic and Polar Stereographic projection), the Topo-
graphic Image Map Mars 1 :200.000 is based on equal-aret
projections (Figure 1). For the Sinusoidal sheets, i.e. those
between -85° and +85°, the central meridian (which is shown in
true scale) corresponds with the particular center longitudes
Therefore, each sheet features its individual projection par
meters. The latest IAU reference body definitions and coor
dinate systems have been adopted. Hence, the sheet lines ae
based on the planetocentric/east system. Each quadrangle
covers two degrees of latitude. Longitude dimensions increase
from the equator towards the poles. Altogether the Martian sui
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