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sphere at a single point. Meridians of normal azimuthal projections are
straight radial lines, and parallels are circles that are centered in the
point of the meridian’s intersection.
2) - by distortions or projection properties. The values of

distortions in lengths, areas and angles are used as a main criterion for
classifying and choosing map projections for specific regions. An easy
way of visualizing the distortion of a map at a given point (P) is

Tissot's indicatrix, which is an ellipse centered at a point. If the
indicatrix is a circle, then the map is conformal (angle preserving) at a
point, otherwise the main axes of the ellipse give the directions of
maximal a and minimal b length distortions. All indicatrices, though

they are of a different shape, have the same area.
In order to preserve shape, area and/or distance (length), key map
properties, projections can be classified as:

- Equal-area or equivalent projections – relative areas are
preserved.
- Conformal projections – directions and relative shapes are

preserved.
- Equal-distance projections – relative distances (lengths) are
preserved along particular lines.

- Compromise projections - attempts to minimize distortions in
areas and directions.
3) -by aspects of developable surface. Such maps assume distinct
orientations of projection developable surfaces. Map projections can

be oriented to the following aspects:
- Normal - central axis of the developable surface is oriented
north-south.

- Transverse - central axis of the developable surface is oriented
east-west (perpendicular to the earth's axis).
- Oblique - assumes a variety of oblique aspects.

Selected Map Projections

The Mercator projection is a conformal projection where the

equator is the single standard parallel.
The Transverse Mercator (TM) projection, in its various
forms, is the most widely used projected coordinate system for world

topographic and navigational chart mapping. The Transverse Mercator
is similar to a Mercator projection except it is turned 90° so that it is

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