| GLOSSARY OF TERMS | |
| ACTINIC LIGHT RAYS | The invisible, chemically active light rays which act on photographic emulsions. |
| AERIAL PHOTOGRAPH | A photograph of a portion of the earth's surface, taken from an aircraft. There are two principal types of photographs; vertical (the camera lens is parallel to the ground below) and oblique (lens is purposely titled from the vertical, generally 30–60 degrees). |
| AERONAUTICAL CHART | A map of the earth's surface, designed for aviation use. Depicts necessary topographic information, aids to navigation and obstructions. |
| ALGORITHM | A set of well-defined rules for the solution of a problem in a finite number of steps. |
| ALPHANUMERIC CHARACTERS | Computer coded characters which represent numerals or letters of the alphabet. |
| ARTWORK | Drawings, overlays, etc., prepared for reproduction of maps or graphics. |
| AUTOPOSITIVE | A class of photographic material which yields a positive image from a positive original without an intermediate negative stage. |
| AZIMUTH | The angular distance in a horizontal plane measured clockwise from true north to a given course or celestial object. |
| BACKLIGHT | Light passed through a clear or translucent copy from behind the image in photographic reproduction. |
| BAND | A selected range of wavelengths of the electro-magnetic spectrum. |
| BAR SCALE | A line or parallel lines divided at specific intervals indicating map distances in relation to earth distances. |
| BASE MAP | A map containing geographic information for purposes of referencing study data and displaying its distribution and inter-relationships. |
| BATHYMETRIC CHART | A map showing water depths and underwater topography, often in various shades or colours. |
| BEARING | Direction of a line with reference to the cardinal points of the compass. |
| BENCH MARK | An accurately established elevation point in relation to chart datum. |
| BUOY | A floating object, moored or anchored to the sea bottom, used as an aid to navigation or as a floatation device. |
| CADASTRAL MAP | Large-scale maps indicating subdivisions, townships, and exact positions and dimensions of properties. |
| CARTOGRAPHY | The art, science and technology of making maps and charts and their study as scientific documents and works of art. |
| CHANNEL | (1) The part of a body of water deep enough for navigation; (2) The deepest part of a stream, bay or strait through which the main current flows; (3) A band of radio frequencies within which a radio station must remain to prevent interference. |
| CHROMA | The range from neutral grey to full saturation of a single colour hue. |
| COLOUR SEPARATION | (1) The mechanical and hand process of separating artwork destined to be coloured into negative overlays or components for each of the printing colours; (2) The optical process of separating coloured artwork by means of colour filters into separate single-colour negatives for each of the subtractive primary colours. |
| COMPILATION | The assembly of source material such as aerial photographs, photogrammetric information, surveys and data taken from existing maps. |
| COMPOSITE PRINT | Reproduction of two or more images on a single base. |
| CONJUGATE PRINCIPAL POINT | The photographic position on an aerial photograph of the principal point of the adjoining photograph. |
| CONTACT PRINT | A photographic reproduction made from a negative or positive in contact with sensitized paper, film or printing plates in a vacuum frame and therefore produced at an identical size. |
| CONTINUOUS-TONE | A photographic image which contains a smooth and continuous transition of tones from black to white. |
| CONTOUR | An imaginary line connecting points on the land surface or sea floor of the same elevation or depth respectively. |
| CONTOUR INTERVAL | The difference in elevation between adjacent contours. |
| CONTRAST (Photography) | The difference in value or tone between highlight and shadow (background) on an image. |
| CONTROL | System of accurate measurement used to obtain distances and directions. The specific controls are classified as follows: (1) Horizontal, relating to parallels and meridians; (2) Vertical, relating to elevations; (3)Astronomic, relating to the solar system; (4) Ground, relating to photogrammetry; (5) Recovered, identified from other sources. |
| COORDINATES (Grid) | System for locating points on the earth's surface by means of a rectangular grid super-imposed and keyed to a map projection. |
| COPY | Term used in the printing industry to refer to any material such as photographs or artwork which will be reproduced. |
| CRT | Cathode Ray Tube - a video display. |
| CULTURAL FEATURES | Map features that have been built or established by man. These include: roads, dams, canals, bridges, boundaries, etc. |
| CYAN | One of the subtractive primary colours which is used in the four colour printing process. It reflects blue and green light and absorbs red light. |
| DATA BASE | A store of information, usually in digital form, organized so that retrieval can be done on a selective basis. |
| DATUM | A reference, such as a line, or plane, in relation to which the position of other elements is determined. |
| DENSITOMETER | An instrument for measuring the amount of transmitted or reflected light. |
| DENSITY | The degree of darkness (light absorption or opacity) of a photographic image. |
| DEVELOPER | The chemical agent and process used to render photographic images visible after exposure to light. |
| DIAPOSITIVE | A transparent positive on a stable base. |
| DIAZO | A process normally used for reproduction in contact printing techniques or to provide a light sensitive coating for proofs and plates. |
| DIFFUSION TRANSFER | A system which consists of a photographic emulsion on which a temporary negative is produced. A chemical or activator softens the unexposed image parts and a positive image is transferred to a receiver sheet during processing. |
| DIMENSIONAL STABILITY | The ability to maintain size; the resistance of paper or film to dimensional change due to variations in temperature or humidity. |
| DISPLACEMENT | A shift in the position of an image on an aerial photograph due to tilt, local variations in relief or scale changes. |
| DRYING HEIGHTS | The height above the sounding datum of rocks and banks that cover and uncover with tidal fluctuations. |
| DUPLICATING FILM | A film for making positives from positives, and negatives from negatives. |
| ECHO SOUNDER | A device which measures the time it takes a sound signal to travel from a ship to the ocean floor and back. This is converted into a depth reading. |
| EDITING | Checking a map in its various stages of production to insure correct interpretation of the data sources used and final appearance before reproduction. |
| ELECTROMAGNETIC SPECTRUM | The range of electromagnetic radiation from the shortest cosmic rays, through gamma rays, x rays, ultraviolet radiation, visible light, infrared radiation, microwaves and all longer radio wavelengths. |
| ELECTROPHOTOGRAPHY | Image transfer systems used in copiers to produce images using electrostatic forces. |
| ELEVATION | Vertical distance above sea level. |
| ELEVATION TINT | The layer of colour between selected and general contours, according to altitude. |
| ELEVATION TONES | A method of accentuating the elevation expressed by the contours through the use of different tones of the same colour. |
| ELLIPTICAL DOT | In halftone reproduction, elongated dots which give improved gradation of tones, particularly in middle tones and vignettes. |
| EM | A square measurement in type composition which equals the width and height of the point size being set. So named because the letter “M” in early fonts was usually cast on a square body. |
| EMULSION | A suspension of light sensitive materials such as silver halides, in a colloidal substance (usually gelatin), which is used to coat photographic films, plates and papers. |
| EN | One half the width of “em”. |
| EQUAL AREA | Applied to maps showing areas correctly throughout the map. |
| EQUIDISTANT | Applied to maps which have selected lines along which distances, or scale, can be measured correctly. |
| EXPOSURE | The step in photographic processing during which light produces the image on the light-sensitive emulsion. “ |
| “F” STOPS | In photography, fixed stops for setting lens apertures and controlling the light entering a lens and shutter system. |
| FALSE COLOUR FILM | Film that does not record the blue light reflected from a subject but instead registers the green, red and infrared radiation it reflects. This produces an abnormal coloured image. |
| FEATURE SEPARATION | The process of preparing a separate piece of artwork or negative for only selected portions of the data on a complex map. |
| FILTER | A transparent medium that absorbs specific regions of the spectrum and transmits other portions. |
| FIXING | Chemical action following development to remove unexposed light sensitive materials from a film. This makes the image stable and insensitive to further exposure. |
| FLASH EXPOSURE | In halftone photography, the supplementary exposure given to strengthen dots in the shadow areas of negatives. |
| FLAT | In printing, the assembled composite of negatives or positives ready for platemaking. |
| FLATBED PLOTTER | A digital plotter in which the output material is mounted on a flat surface. |
| FLIGHT LINE | The path that an aircraft or other airborne sensor follows when collecting data. |
| FOCAL LENGTH | In photography, the distance measured along the optical axis from the optical centre of the lens to the film plane, measured when the lens is focused at infinity. |
| FONT | In type composition, a complete assortment of letters, numbers, punctuation marks, etc., of a given size and design. |
| FORESHORE | The intertidal zone of a beach. |
| FORM LINES | Lines that represent contours that are sketched to show the shape of the terrain rather than elevation. |
| GEODESY | The science which considers the size and shape of the earth on a mathematical basis. |
| GEODETIC | Basic relationship of the earth to the curvature of its sea level surface. |
| GRADIENT | The rate of change of a variable quantity. |
| GREY SCALE | A strip of standard grey tones, ranging from white to black, placed at the side of original artwork during photography to measure tonal range and contrast obtained on the copy. |
| GRID | Network of lines on a plane surface upon which coordinates are based and to which the map features are referenced. |
| GUIDE IMAGE | Image obtained on scribing film by a photo-chemical method. The image is used as a guide for scribing. |
| GUTTER | The blank space or inner margin, from printing area to binding on a page. |
| HACHURE | Line symbol used to indicate land formations on maps. |
| HALATION | The spreading of light beyond its proper boundaries in a developed photographic image. |
| HALFTONE | A continuous-tone image such as a photograph, reproduced through a crossline or contact screen, which converts the image into dots of various sizes. |
| HICKEYS | In printing (offset), spots or imperfections caused by dirt or other particles on the printing plate. |
| HISTOGRAM | A graphic display of information which shows the frequency of occurrence along the vertical axis and the individual values along the horizontal axis. |
| HOMOLOGRAPHIC | Applied to maps showing the same graphic representation. |
| HUE | The characteristic of a colour associated with a wavelength of light which distinguishes it from other colours. |
| HYDROGRAPHIC CHART | A chart showing water features such as depths, channels, islands and other aids to navigation. |
| HYDROGRAPHY | Science which deals with the measurement and description of physical features of the oceans, lakes and rivers and their adjoining coastal areas. |
| HYPO | An abbreviation for sodium thiosulfate or sodium hyposulphite, a chemical used to fix the image on a photographic film after it has been developed. |
| HYPSOMETRY | Vertical control in map making with reference to elevation relative to an established datum. |
| INFRARED RADIATION | Energy in the 0.7–100 micrometres (microns) area of the electromagnetic spectrum. “Invisible light”, longer than visible light, is known as the near infrared. This can be recorded on photosensitive materials. Far infrared radiation is often termed “thermal infrared” and must be recorded by electronic means. |
| INTENSITY | The richness or brilliance of a colour. |
| ISOTHERM | A line connecting points of equal temperature. |
| ITALIC | The style of letters that slant, in contrast to the normal upright or Roman form. Used for emphasis in text and commonly to refer to water features on maps. |
| JUSTIFY | In type composition, to space out lines uniformly to a predetermined length. |
| KERNING | In type composition, the subtraction of space between letters or characters so that they appear closer together and form a visual unit. |
| KEYLINE | An outline drawing of finished artwork to indicate the exact shape, position and size for each of the basic elements in the design. |
| LANDMARK | A conspicuous man-made or natural feature that may be of assistance to a mariner for determining position. |
| LARGE-SCALE | Scale of 1:25,000 or larger (1:10,000, 1:5,000, etc.). The smaller the number, the larger the scale. |
| LASER | Acronym for Light Amplification by Stimulated Emission of Radiation. An intense light beam with very narrow band widths. |
| LAYOUT | The drawing or sketch of a proposed piece of artwork. |
| LEADING | In type composition, the distance between lines of type, measured in points. |
| LETTERSPACING | The placing of additional space between each letter of a word. |
| LINE MAP | Map composed of point, line and area symbols as contrasted to continuous-tone images. |
| LITH FILM | A high contrast, orthochromatic film used traditionally for photomechanical work. |
| LORAN | Acronym for Long Range Navigation. A system using pulsed, low frequency radio waves. |
| LOWER CASE | The small letters in type, as distinguished from capital letters. |
| MAGENTA | One of the subtractive primary colours which is used in four colour process printing. |
| MAGENTA SCREEN | A dyed contact screen, used for making half-tones. |
| MANUSCRIPT | Original drawing of a map as compiled from various data sources. |
| MAP | A graphic representation of the earth's surface drawn to an established scale on a plane surface. |
| MARGIN | That area of a map or chart lying outside the border, also known as “surround”. |
| MARGINAL INFORMATION | The explanatory notes, diagrams and scales shown in the map margin. |
| MASKING | In photomechanical processing, the blocking out of an area by means of actinically opaque material to prevent exposure in the blocked out area. |
| MEAN | A statistical term meaning the average value of a data set. |
| MERIDIAN | A north-south line connecting the poles. |
| MOIRE | The undesirable screen pattern of light and dark patches caused by overlapping screens printed at incorrect angles. |
| MOSAIC | Two or more overlapping aerial photographs assembled together. |
| NADIR | In aerial photography, the point vertically beneath the perspective centre of the camera lens. |
| NANOMETER | A unit of length, one billionth of a metre or 1 x 10-9 m. Also known as a millimicron. |
| NAUTICAL CHART | Hydrographic or marine map. |
| NAVSTAR-GPS | Acronym for Navigational Satellite Timing And Ranging - Global Positioning System; a system of 18 satellites offering precision navigation. |
| NEATLINE | The inner border of a map. |
| NEGATIVE | An image formed of lines and symbols which allow the passage of light on a background which is opaque to light. |
| OPAQUE | Impervious to the rays of light. Opaque also refers to a variety of substances that prevent transmission of light. |
| OPEN WINDOW NEGATIVE | A negative having open areas in which solids, screens, rulings and tints of a colour may be printed. |
| ORTHOCHROMATIC | Photographic materials insensitive to red light but recording ultraviolet, blue, green and yellow light. |
| ORTHOPHOTO | Image derived from aerial photographs by differential rectification so that all scale errors have been removed. |
| OVERLAY | A transparent or translucent material which is fitted or registered over the base map in use for the purpose of adding information. |
| OVERPRINT | New information printed on an existing map or chart to show data of importance or additions to those originally printed. |
| PANCHROMATIC FILM | Photographic film sensitive to all visible colours of light. |
| PARALLAX | The apparent change in the position of one object relative to another when seen from a different location. |
| PASS POINTS | Points determined from photographs by photo-grammetric methods for use in orientation of other aerial photographs. |
| PHOTO ENGRAVING | Photomechanical process for converting any object that can be photographed into a relief plate for letterpress printing. |
| PHOTO MAP | An unrectified reproduction of an aerial photograph or a mosaic made from several aerial photographs for the purpose of depicting geographic and/or thematic information. |
| PHOTOGRAMMETRY | Method of obtaining accurate measurements from aerial photographs. |
| PHOTOGRAPH | General term for a positive or negative print on various support materials produced by several reproductive methods. |
| PHOTOMECHANICAL TRANSFER (PMT) | A diffusion transfer copying process which produces high contrast images on film or paper in line or halftone. |
| PICA | A unit of type measurement used in type-setting. One pica is approximately 1/6 inch. |
| PIN REGISTRATION | The use of accurately positioned holes and special pins on artwork, films and plates to ensure proper registration and fit of components and overlays. |
| PLANIMETRIC MAP | Map indicating only the horizontal positions of features without regard to elevation. |
| POINT | A unit of type measurement. There are 12 points to a pica and approximately 72 points to one inch. |
| POSITIVE | An image formed of lines and symbols which are opaque to light on a background which either allows all light to pass through (transparency) or reflects all light (a white background). |
| PRESS PROOF | A map proved on a printing press or taken from the first printed copies for editing purposes. |
| PROCESS COLOURS | The subtractive primaries, yellow, magenta and cyan plus black used in four colour process printing. |
| PROGRESSIVE PROOFS (Progs) | Proofs made from the separate plates in colour process printing, showing the sequence of printing and the result after each additional colour has been applied. |
| PROJECTION | A system of lines on a map representing a series of imaginary lines on the earth's surface. |
| PROOF | A preliminary single or multi-colour copy of a map, chart or graphic produced by photo-mechanical processes for the purpose of editing and correction, and to show final appearance before printing. |
| PROVISIONAL MAP | A rapidly produced map that sacrifices accuracy for speed of production. |
| RADAR | Acronym for Radio Detection and Ranging; an instrument using beamed and timed electro-magnetic radiation to detect or track objects, measure height or obtain an image of the surface. |
| RAGGED LEFT | In typesetting, text that is aligned on the right and ragged on the left edge. |
| RAGGED RIGHT | In typesetting, text that is aligned on the left and ragged on the right edge. |
| REFLECTION COPY | A copy of artwork produced on opaque materials which must be photographed by light reflected from its surface. |
| REGISTER | The correct position of one component of a composite image in relation to the other components. |
| REPROGRAPHY | Copying and duplicating. |
| REVERSE LETTERING | Light lettering on a dark background. |
| REVERSE READING OR WRONG READING | An image readable in a normal way (left to right) when viewed from the non-emulsion side of a film copy. |
| RIGHT READING | An image readable in a normal way (left to right) when viewed from the emulsion side of a film copy, plate or paper print. |
| SAFELIGHT | A special darkroom lamp used for illumination without fogging sensitized materials. |
| SANS SERIF | A typeface without serifs. |
| SCALE | The ratio of distance measured on a map to the corresponding distance on the ground. |
| SCREEN | Sheet of transparent film or glass carrying a regularly repeated pattern which may be used in conjunction with an area negative to photo-mechanically reproduce areas of the pattern. |
| SCREEN ANGLE | Angle at which halftone screens or screen tints for each colour are printed in relation to one another to avoid moire patterns. Angles normally used are black 45°, magenta 75°, yellow 90°, cyan 105°. |
| SCREEN, HALFTONE | A variable opacity screen used to convert continuous-tone to varying size dots. |
| SCREEN RULING | The number of lines or dots per inch on a halftone screen or screen tint. |
| SCREEN TINT | A screen of closely and evenly spaced dots or lines used on open window negatives to produce tones. |
| SCRIBING FILM | A transparent base which carries an actinically opaque coating that can be removed by scribing to produce open images. The finished scribe-sheet can be used as a photographic negative in the photomechanical processes. |
| SEISMOMETER | A device for recording data on the structure of the earth's crust by recording small sounds, obtained from distant earthquakes or man-made sources. An Ocean Bottom Seismometer (OBS) records data from the ocean bottom. |
| SENSOR | A generic name for a device that senses either the absolute value or a change in a physical quantity such as temperature or salinity and converts that change into an input signal for an information gathering system. |
| SERIF | The short cross-lines at the ends of the main strokes of many letters in some type faces. |
| SHORELINE | On charts this represents the line of contact between the land and a selected water elevation. |
| SIDELOOKING RADAR | An all-weather, day or night remote sensor. It is defined as an active sensor; it generates its own energy, which is transmitted and reflected from the ground target area in the form of a photo-like picture. Also known as Side-Looking Airborne Radar or SLAR. |
| SIDE-SCAN SONAR | An acoustic device which sends out a beam of sound waves laterally from a ship's course to map the seabed topography in broad swaths. |
| SPECTRAL SIGNATURE | Quantitative measurement of the detected properties of an object at several wavelengths. |
| SPECTRUM (Light) | The complete range of colours in the rainbow, from short wavelengths (blue) to long wavelengths (red). |
| SPECTRUM (Radiation) | A series of radiation wavelengths sequentially arranged. |
| STABILIZATION PROCESS | A rapid-access photographic process which uses special paper in which a developing agent is incorporated into the emulsion layer, allowing fast development. |
| STANDARD DEVIATION | The square root of the arithmetic mean of the squares of the deviations from the mean. A measure of the dispersion from the mean in a frequency distribution. |
| STEREOGRAPHIC | Having a visual three-dimensional appearance. |
| STEREOSCOPIC FUSION | The mental process which combines the two perspective images on the retinas of the eyes in such a manner as to give a mental impression of a three-dimensional model. |
| STEREOSCOPIC MODEL | An optical three-dimensional reconstitution of an object by means of superimposed projected images of a stereoscopic pair, or the viewing of the pair of photographs with the aid of a stereoscope. |
| STEREOSCOPIC PAIR | Two aerial photographs of the same area taken from different camera stations. A portion of the same area appears on both photographs. |
| STRIPPING FILM | Thin photographic film which, after exposure, may be removed from its base support and transferred to any suitable medium, using a thin layer of wax as an adhesive. |
| TELEMETRY | The science involved with measuring a quantity, and transmitting this value to a station for interpretation or recording of the quantity. |
| THEMATIC MAPPER | A multispectral scanning system with seven channels of operation. |
| TILT | The angle between the optical axis of a camera and a plumb line. |
| TINTS | Even-toned area of a colour. |
| TOOTH | The slightly rough finish of paper or plastics which permits ink to adhere to the surface. |
| TOPOGRAPHY | The features of the surface of the earth, including relief, vegetation and water. |
| TRANSPARENT COPY | A copy such as a colour transparency or positive film which allows the passage of light, permitting a clear view of objects beyond. |
| ULTRAVIOLET RADIATION | Electromagnetic radiation of shorter wavelengths than visible radiation but longer than x-rays; in the wavelength interval between 10 and 4000 Angstroms (one Angstrom equals 10-10 of a metre). |
| VACUUM FRAME | A contact frame, the upper surface consisting of glass, from which air is extracted to ensure close contact between photographic materials during exposure. |
| VALUE (Colour) | The sensation of relative darkness (low) or lightness (high) of a colour or tone compared to another or as measured in relation to a grey scale. |
| VIGNETTING | The gradual fading of a colour. |
| XEROGRAPHY | A copying process that utilizes a selenium surface and electrostatic focus to form an image. |
| ZENITH | The “point” in the sky directly above a given place. |
