Blank maps. Introductory text.

Outline maps given in this part present a general idea about distribution of the main relief features on Mercury, Venus and Mars, and on the Moon and Phobos as well. These maps were developed first of all as the basic maps for all the series of maps included in the Atlas. Usage of the outline maps as a basis for the thematic maps and the sketch maps allowed to control special content of maps to the real relief. As for the set of the surface maps for the celestial bodies listed above (section III), they can serve at the same time to define more exactly the location and configuration of certain relief features shown by shading. That is illustrated by Figs. 1-4 of sections III and IV.
The following main scales has been accepted for the outline maps:
Phobos    1:200,000,
Moon    1:25,000,000,
Mercury    1:35,000,000,
Mars    1:50,000,000,
Venus    1:75,000,000,
Earth    1:75,000,000.
The outline map of the Earth is not given as an independent one, since it doesn't possess supplementary information. It is only used as a basic map in the other parts.

Since scales are multiple, the terrestrial planets and their moons can be shown within the single size of the adopted page of the Atlas (29 cm x 36 cm) which is not larger than the size of a table-book. Actually, though the radius of the Moon is half as less the radius of Mercury, half the radius of Mars, three and a half times shorter than the radius of Venus, the radii of hemispheres of Mercury, the Moon, Mars and Venus on the given scales turn to be equal to 10.65 cm; 10.67 cm; 10.39 cm; 12.36 cm, correspondingly, in the Lambert projection, and to 12.15 cm; 12.13 cm; 11.83 cm - in the Poster projection. An exception has been made for Phobos since it has a size too small for this row of scales. The scale adopted for the map of Phobos is twenty times larger and corresponds to the size of a page of the Atlas.

Two ways of mapping have been chosen for the outline maps: hemispheres with an overlap equal to 20° and separate representation of the latitudinal zone within ±60° and the polar zones with an overlap of 10° by latitude and 20° by longitude. Overlaps ensure better joining of images within the marginal zones. It's also more handy to pass from one
hemisphere to the other in case of hemispheres. More perfect representation of the polar zones intensifies the effect of sphericity for the hemispheres. Representation of the polar zones in the form of segments simplifies turning of the latitudinal zone into the polar one for the second case. Phobos is an exception in case of constructing a map, since the second variant is the only admissible way for its mapping [47]. It is connected with a significant deviation of its figure from the sphere of a mean radius.

Outline maps of Mercury, Mars and the Moon are given in the three classic projections:
•    transversal equivalent azimuthal Lambert projection;
•    transversal equidistant azimuthal Postel projection; and
•    normal conformal cylindrical Mercator projection (equatorial zone) and normal conformal stereographic perspective projection (polar zones).
Venus is presented in the Lambert and Mercator projections only, and Phobos - in the normal conformal cylindrical projection of triaxial ellipsoid (equatorial zone) and equidistant along the meridians azimuthal projection of the triaxial ellipsoid (polar zones). An outline map of Deimos has not been plotted. The sketch map presented in the section XII gives the main idea of the Deimos's relief. It was taken into account that the Lambert projection ensures preservation of proportions for the sizes of the regions. So the outline maps done in this projection were used to map area features of the relief. The distances from the central point to any point are not distorted in the Postel projection. That's why basic maps in this projection were used to plot pointed phenomena on sketch maps. Angles are not distorted in the Mercator projection, and similarity of the smallest features is also preserved. That's why, the content of the relief features is maximum for the maps in this projection. Maps in Lambert and Postel projections are similar as for their contents of relief features which have to be reference points for thematic mapping. In addition, outline maps in the Postel projection have been used to illustrate planetary toponymy.

The outline maps have been plotted in the common system of map symbols which arc tabled at the beginning of the Atlas. But specific features of the relief are taken into account by these signatures for each planet and moon. Some relief features such as, for example, tcrrae and regions of Venus and others, are marked by signatures only.

The content of the outline maps includes the following elements: cartographic grid given by black color, the main relief features (in brown), place names of the main relief features (in black). All the craters with the diameter about 3 mm and larger (on the scale of the map) are marked for highlands. Craters of a smaller size were shown only with the necessity to represent peculiarities of either region. It was done on planitiae more often since small-scale craters serve as reference points for these zones.

Names are placed on the outline maps as far as possible evenly within the whole area. Their placement is done proceeding from 1-2 names for the ground of 20° x 20°. Nomenclature of the craters has two gradations: nomenclature of large-scale craters is placed inside them or with partial superposition on a crater; nomenclature for small-scale craters is given near them or also with partial superposition, The nomenclature of the outline maps corresponds to the nomenclature approved by IAU. All names are given in transcriptions adopted by the Commission on space toponymy of the Russian Academy of Sciences.
At the beginning of the section there is a list of the main cartographic and supplementary materials used to plot outline maps.
Signatures tabled on p. 11' are repeated with taking into account peculiarities of the celestial bodies to be represented. That is done to comfort usage of the map symbols.