English

A PROJECTION in which all angles around any point are correctly represented. In such a PROJECTION the SCALE is the same in all DIRECTIONS about any point. Very small shapes are correctly represented, resulting in an orthomorphic projection. Hence, the terms of 'confor­mal' and 'orthomorphic' are used synonymously since neither characteristic can exist independently of the other.

A PROJECTION produced by projecting the GEOGRAPHIC MERIDIANS and PARALLELS onto a cone which is tangent to (or intersects) the surface of a sphere, and then developing the cone into a plane.

A PROJECTION produced by pro­jecting the GEOGRAPHICAL MERIDIANS and PARALLELS onto a cylinder which is tangent to (or intersects) the sur­face of a sphere, and then developing the cylinder into a plane.

A PROJECTION having a constant area scale. Such a PROJECTION is not conformal and is not used for NAVIGATION. Also called equivalent pro­jection.

A PERSPECTIVE PROJECTION on a plane tangent to the surface of a sphere having the point of projection at the centre of the sphere. The PROJEC­TION is neither CONFORMAL nor EQUAL AREA. It is the only PROJECTION on which GREAT CIRCLES on the sphere are represented as straight lines. For this reason this PROJECTION is used principal­ly for CHARTS for GREAT CIRCLE SAILING.

The name given to the TRANSVERSE MERCATOR PROJEC­TION when the latter is extended right over both POLES. It is used for air charts of polar areas.

A CONFORMAL PRO­JEC­TION of the conical type, on which all GEOGRAPHIC MERI­DIANS are represented by straight lines which meet in a common point outside the limits of the MAP, and the GEOGRAPHIC PARALLELS are represented by a series of arcs of circles having this common point for a centre. MERIDIANS and PARALLELS intersect at right angles, and angles on the EARTH are correctly repre­sented on the PROJECTION. This PROJECTION may have one or two STAN­DARD PARALLELS along which the SCALE is held exact.

A CONFORMAL PROJECTION of the cylindrical type. The EQUATOR is represented by a straight line true to SCALE; the GEOGRAPHIC MERIDIANS are represented by parallel straight lines perpendicu­lar to the line representing the EQUATOR; they are spaced according to their distance apart at the EQUA­TOR. The GEOGRAPHIC PARALLELS are represented by a second system of straight lines perpendicular to the family of lines representing the MERIDIANS, and there­fore parallel with the EQUATOR. CONFORMALITY is achie­ved by mathematical analysis, the spacing of the PARAL­LELS being increased with the increasing distance from the EQUATOR to conform with the expanding SCALE along the PARALLELS resulting from the MERIDIANS being repre­sented by parallel lines. Since RHUMB LINES appear as straight lines and DIRECTIONS can be measured directly, this PROJECTION is widely used in NAVIGATI­ON.

An OR­THOGRAPHIC PROJECTION having the plane of the projection parallel to the plane of some selected MERIDIAN; in this PRO­JECTION, the GEOGRAPHIC PARALLELS and the CENTRAL MERIDIAN are straight lines, the outer MERIDIAN is a full circle, and the other MERIDIANS are arcs of ellip­ses.

A perspective azimuthal PRO­JECTION in which the projecting lines, emanating from a point at infinity, are perpendicular to a tangent plane. This PROJECTION is used chiefly in NAUTICAL ASTRONOMY for interconverting COORDINATES of the CELE­STIAL EQUATOR and HORIZON systems.

The representation of a figure on a surface, either plane or curved, by means of project­ing lines emanating from a single point, which may be infinity. Also called geometric projection.

An ORTHOGRAPHIC PROJEC­TION having the plane of the projection perpendicular to the AXIS of ROTATION of the EARTH (parallel with the plane of the EQUATOR); in this PROJECTION, the GEOGRA­PHIC MERIDIANS are straight lines.

A PROJECTION having the central GEOGRAPHIC MERIDIAN repre­sented by a straight line, along which the spacing for lines representing the GEOGRAPHIC PARALLELS is proportional to the distances apart of the PARALLELS; the PARALLELS are represented by arcs of circles which are not concentric, but whose centres lie on the line representing the CENTRAL MERI­DIAN, and whose radii are determined by the lengths of the elements of cones which are tangent along the PARALLELS. All MERIDIANS except the central one are curved. This PROJECTION is neither CONFORMAL nor EQUAL AREA but it has been widely used for MAPS of small areas because of the ease with which it can be con­structed.

Any standard PROJECTION used in MAP or CHART construction, which does not conform to a general north-south format with relation to the NEAT LINES of the MAP or CHART.

A PERSPECTIVE PROJECTION having the point of PROJECTION at the opposite end of the diameter of the sphere from the point of tangency of the plane of projection. It is conformal and is the only AZIMUTHAL PROJECTION having that quality. When the centre of the PROJECTION is located at a POLE of the sphere, it is called a stereographic polar projection; when on the EQUATOR, a stereographic meridional projection; and when on some other selected PARALLEL of LATITUDE, a stereographic horizon projection. Also called azimuthal orthomorphic projection.