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use the Mercator projection with true scale at the 
latitude x27.476?. Each map covers an area of 22.5? 
(longitude) by 15? (latitude) on the Martian surface. 
the other 76 maps including 56 of the medium 
latitudes (x30? - 165°) use Lambert conformal 
projection and 20 of the two polar regions (+65d -+ 
90°) use polar stereographic project. Maps with 
Lambert projection have true scales at latitudes of 
35.83° and 59.17°. Stereomodels on the analytical 
plotters range from 2 to 16 for the compilation of each 
quad with an average of 8 stereomodels each. A total 
of more than 1,100 stereomodels were compiled for 
the 1:2,000,000-scale series of maps. Maps have a 
contour interval of 1 km. Map elevations are referred 
to the Mars topographic datum. 
Factors that limited the accuracy of compilation 
include low-resolution (800 to 1,000 m/pixel) of high- 
altitude photography, the very narrow field-of-view of 
the Viking camera , weak model geometry (i.e., small 
base-to-height ratios) and the presence of dust and 
haze in the Martian atmosphere. However, at an 
altitude of 1,500 km, the ground resolution is about 
37.5 m. with low-sun-angle images, standard errors or 
repeatability in the elevation measurements are small, 
ranging from 12.7 to 22.2 m. The maximum S.E. from 
images of the same condition is 34 m. In general, 
maps of the equatorial belt have a precision of £1 km, 
and maps of the two polar regions have +1.5 km due 
to the lack of stereocoverages. 
6.2 Mars 1:5,000,000-scale Series of Topographic 
Maps: 
The 1:5,000,000-scale topographic maps cover the 
entire Martian surface with 30 maps. There are 16 
maps (MC-8 - MC-23) covering the equatorial belt 
from +30° to -30° of latitudes with each having a 
coverage of 45° lat by 30° lon using the Mercator 
projection. There are 12 maps (MC-2 - MC-24 & MC- 
24 -MC-29) covering from +30° to +65° of latitudes with 
each map having a coverage of 35° lat and 60° lon 
using Lambert conformal projection. The two polar 
regions from +65° to +90° are covered by two maps 
with polar stereographic projection (MC-1 & MC-30). 
The current version of this series of maps was 
compiled with topographic data extracted from all of 
the 140 quads of 1:2,000,000-scale contour maps 
and with additional remote sensed data including 
ground-based data. 
6.3 Mars Global Topographic Maps 
There are two global maps of Mars, 1:15,000,000 and 
1:25,000,000 scales. Both cover the entire Martian 
surface. The 1:15,000,000-scale maps consists of 
three sheets: the Western hemisphere from lon 0° to 
180°w, the Eastern hemisphere from lon 180° to 
360°W, and the two polar regions above lat 55°. Both 
the Western and the Eastern sheets have the Mercator 
projection and cover latitudes from 57° to -57°, 
whereas the two polar regions have a polar 
stereographic projection. 
The 1:25,000,000-scale global topographic map 
covers the entire Martian surface by one sheet with the 
Mercator projection from lat +65° to -65° and the polar 
stereographic projection covering lat above +65°. Both 
scales of global maps were compiled from 
topographic data extracted from the stereoscopically 
compiled 140 quads of 1:2,000,000-scale contour 
maps. In addition, occultation data and Earth-based 
radar data were included. Maps have a contour 
interval of 1 km.  Elevations refer to the Mars 
topographic datum. Elevation precision is about t1 
km in the equatorial band and +1.5 km in the two 
polar regions. 
6.4 Special Topographic Maps of Mars 
Using the developed special photogrammetric 
techniques with available high-resolution Viking 
Orbiter images of Mars, topographic maps of features 
of geologic interest and of areas that are the subject of 
future mission planning are compiled at larger scales, 
1:1,000,000 or 1:500,000. Completed special maps 
include those of Olympus Mons (Wu et al., 1981), 
Arsia Mons, Mars Canyonlad and others. For the 
compilation of larger-scale maps, a separate control 
network is established for each compilation. For 
example, a control net with 316 control points of 
Olumpus Mons was established from a block of 103 
Viking Orbiter images. It took just about 100 
stereomodels to compile the topographic map at a 
scale of 1:1,000,000 with a contour interval of 200 m. 
Contour maps of the two Viking Lander areas were 
compiled by applying special techniques for the use of 
Mars surface images taken by the two fixed-base 
facsimile cameras on each of the two Viking landers. 
Pictures reconstructed from data of the facsimile 
cameras represent a portion of a spherical surface. in 
order to use them for stereocompilation, the 
panoramic images were converted to the equivalent of 
a frame pictures using a gnomonic projection (wu, 
1984). Contour maps were then compiled on analytical 
plotters for the use of guidelines of the surface 
activities of the Viking landers during the Viking 
missions. Maps were compiled at a scale of 1:10 with 
a contour interval of 1 cm. : 
Using 64 high-resolution and 15 low-resolution images 
of Phobos, one of the two Martian moons, a geodetic 
control net with 536 control points was established. 
From these control points, Phobos has radii ranging 
from 8.523 to 13.950 km. Also a triaxial ellipsoid figure 
of Phobos has ben modeled with semi-major axes A = 
12.747 km and B = 12.321 km, and the semi-minor 
969 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996