Glossary
Anemometer : An instrument meant for measuring wind speed. It comprises a system of cups and a speed indicator.
Aneroid Barometer : A portable instrument commonly used for measuring atmospheric pressure. It consists of a partially vacuumed metallic box, a flexible lid and a needle working on a lever. A change in atmospheric pressure is indicated by the motion of the elastic and sensitive top of the box.
Atlas : A collection of maps bound into a volume. Generally, these maps are drawn on small scales. The term atlas first appeared on the title page of the collection of Mercator’s charts in A.D. 1595. the origin of the word, however, goes back further into the past, as it relates to ‘Atlas’ supporting the heavens according to mythological beliefs.
Azimuthal Projections : A type of map projections in which a portion of the globe is projected upon a plane tangent to the globe at some specific point, e.g., the north or the south pole. These projections are also known as true Bearing Projections, because all points have their true compass direction from the centre of the map drawn of these projections. The word azimuth means bearing or direction.
Bar Graph: A series of columns or bars drawn proportional in length to the quantities they represent. They are drawn on a selected scale. They may be drawn either horizontally or vertically.
Barometer : An instrument for measuring atmospheric pressure which is the weight of the aircolumn at a given place and time. Fortin’s and aneroid barometers are examples of such an instrument.
Bench Mark: Exact height of specific points on prominent and durable material objects like rocks or buildings in the field, recorded for the sake of permanent reference. On a map, a bench mark is indicated by B.M., followed by the number giving the actual height of the mark above mean sea level.
Cadastral Maps : Maps drawn on a fairly large scale to show accurately the extent and measurement of every field and plot of land. The word cadastre means “a public register of the lands of a country for defining property and levying taxes.”
Cartogram : The representation of statistical data on a map in a diagrammatic way by purposefully distorting the original shape etc., of the area concerned. Usually, it is a highly abstracted and simplified map highlighting a single idea in a diagrammatic way. It is one of the important and popular tools of modern geography.
Cartography : The science of preparing all types of maps and charts and includes every operation from original surveys to the final printing of maps.
Central Meridian : When a meridian, whatever its value, stands at the centre of the projection, it is called the central meridian and has nothing to do with the prime meridian.
Central Tendency : The tendency of quantitative data to cluster around some value.
Chain : A length-measuring device used for the purpose of obtaining horizontal distances between two points. Chains are of various lengths, e.g., metric chains of 20 and 30 meters, Engineers’s chain of 100 feet, and Gunter’s chain of 66 feet.
Chain Survey : measuring of horizontal distances by the chain and the tape. This relatively simple method is used for surveying small areas along with their details with reasonable accuracy.
Chorophelth Maps : Maps drawn on a quantitative areal basis, calculated as average values per unit of area within specific administrative units, e.g., density of population and percentage of urban to total population.
Class Interval : Then difference between the lower and upper limits of any class of a frequency distribution is known as its class interval.
Climatic Map : A map of the world or a part of it, showing average conditions of temperature, pressure, wind, precipitation, and sky conditions over a period of time.
Composite Measurement : A measurement of the overall effect of several correlated variables.
Conical Projections : A type of map projections in which a map is projected on a paper cone imagined to be either resting on the globe or intersecting it in a particular manner. A conical projection may be with one standard parallel or with two standard parallels.
Contours : Imaginary lines joining all the points of equal elevation or altitude above means sea level. They are also called “level lines”.
Correlation Co-efficient : A measure of the degree and direction of relationship between two variables.
Cross-section : A side view of the ground cut vertically along a straight line : It is also known as a section or a profile.
Cumulative Frequency : The measurement of distribution of values in the different class intervals expressed as a percentage of the total frequencies either above or below specified value.
Cylindrical Equal-Area Projection : A kind of Cylindrical projection in which the area between two parallels is made equal to the corresponding surface on the globe by decreasing the distance between the parallels progressively towards the poles.
Diagonal Scale : An elaboration of the graphic scale by which one can measure up to a minute part of a centimeter or an inch. It gives divisions much smaller than the secondary divisions of a graphic scale.
Dispersion or Spread : The degree of internal variations in the different values of a variable.
Distribution Maps : Maps, which with the aid of certain symbols like dots and shading schemes, depict location of various geographic elements and their frequency or intensity or density as the case may be. For example, they may show distribution of crops, livestock, population, industrial output, etc., in a given area.
Drainage : A system of rivers or streams which drain all the rain water that falls in a region.
Flow Maps : Maps in which the ‘flow’ or movement of people or commidities is represented by ribands whose thickness is proportional to the quantity of goods or the number of people moving along different routes.
Frequency Distribution Table : The arrangement of the number of values of a variable falling in different ranges. These ranges of the values of the variable are known as classes and the number of values falling in each class is known as frequency.
Great Circle : A circle on the earth’s surface whose plane passes through the centre of the earth bisecting it into halves. The shortest distance between any two points on the earth’s surface is along the arc of a great circle.
Hachures : Small straight lines drawn on a map along the direction of maximum slope, running across the contours. They give an idea about the differences in the slope of the ground.
Hill-shading : A method of showing relief on a map by shading only those slopes that face south and east, presuming that the source of illumination is in the north-west.
Histogram : A graphical representation of frequency distribution, such as seasonal frequencies of rainfall.
Homolographic Projection : A projection in which the network of latitudes and longitudes is developed in such a way that every graticule on the map is equal in area to the corresponding graticule on the globe. It is, therefore, also known as equal area projection.
Index-Number : A measure which serves to depict the proportional changes of a characteristic independent of initial magnitude of the data and of the unit in which they are measured.
Isobars : Imaginary lines drawn on a map joining places with equal barometric pressure, reduced to sea level, in order to eliminate differences due to variying altitudes.
Isohyets : Imaginary lines drawn on a map joining places with equal amount of rainfall over a given period of time.
Isotherms : Imaginary lines drawn on a map joining places with equal temperature, reduced to sea level.
Land Use : The use which is made by man of the surface of the land. In sparsely populated areas, it includes occupation of land by natural and seminatural vegetation.
Layer Colouring : A method of showing relief with the help of contours, especially in atlas and wall maps. The contour scheme is followed universally, e.g., shades of blue for sea, green for lowlaying areas, brown for higher and pink for still higher lands.
Linear Scale : A method of expressing scale with the help of a line conveniently divided and subdivided, so that distances of the map can be directly measured and read off from a map.
Line Graph : A smooth line drawn through a series of points, which are determined by means of two co-ordinates along the X-axis and the Y-axis. Change in one variable is shown with reference to another. Usually, it is used for presenting data regrading rainfall, temperature, growth of population, production etc.
Location Quotient : The ratio of the percentage of some characteristic of an area to the same percentage in the region.
Lorenz Curve : A graphical method of showing the concentration of some characteristics.
Macro, Meso, Micro : Terms often used in regional geography to differentiate regions according to their size and level in an interdependent system of regions. Macro refers to large size, micro to the smallest, and meso to an intermediate level.
Magnetic North : The direction pointed to by the needle of the magnetic compass. It is determined with reference to the magnetic north pole, which is different from the geographic north pole and also moves slowly from time to time.
Map : A conventional representation of any area of the earth’s surface, small or large, drawn to scale of a flat surface.
Map Projection : A method of transferring the network of parallels and meridians, i.e., earth’s grid, from the spherical surface of the earth to a plane surface.
Mean Deviation : A measure of dispersion derived from the average of deviations from some central value, Such deviations are taken absolutely i.e. their signs are ignored. The central value is generally mean or median.
Median : It is the value which divides the number of observations in such a way that half the values are less than this and half of them are more. If the values of a variable are arranged in either ascending or descending order, the median is the middle value.
Mode : The mode is that value of a variable which occurs maximum number of times.
Meridian Scale : the distance along a meridian of longitude which is measured between two parallels of latitude.
Optical Square : The distance along a meridian of longitude which is measured between two parallels of latitude.
Optical Square : An instrument used in chain survey for setting out right angles for measuring short distances from the chain to the objects nearby.
Orthomorphic Projection : A type of projection in which every care is taken to preserve the correct shape of a given area of the earth’s surface. It is, therefore, also known as a correct shape projection.
Pantogaraph : An instrument used for enlargement and reduction of maps with accuracy.
Parallel Scale : The distance along a parallel of latitude which is measured between two meridians. The parallel scale is always correct along the standard parallel.
Plane Table : A surveying instrument by means of which a map of a small area may be drawn and completed in the field with a fair amount of accuracy. It is also useful for filling the details into a network of triangles.
Quartile : Quartiles are the values of the variable which divide the number of observations in four equal parts.
Rain Gauge : An instrument of measuring accurately the amount of rainfall at a given place over a fixed duration, say, 24 hours.
Ranging Rod : A wooden straight rod, coloured red and white, with a metal shod at one end to fix it securely in ground. Ranging rods are used in chain survey plane tabling and other methods of surveying.
Relief Map : A map showing relief of an area on a flat surface by means of any of the methods such as contours, form-lines, layer colouring, has chures, hill-shading or a combination of these.
Rhumb Line : A straight line of constant bearing intersecting all intermediate meridians at the same angle in a given projection.
Scale : The ratio which a distance between any two points on a map bears to the actual distance between the corresponding points on the ground.
Scatter Diagram : A diagram showing the joint variations of two characteristics on a graph paper.
Spot Height : The exact height of a given spot found out with the help of surveying instruments. It is shown on a map by a dot followed by a number expressing the height in meters or feet.
Standard Deviation : The most commonly used measure of dispersion. The standard deviation is the positive square root of the mean of the squares of deviations from the mean.
Standard Parallel : The parallel of latitude of any projection along which the scale is true.
Surveying : An art of making observations and measurements, both linear and angular, in order to determine the relative position of points on the earth’s surface. It helps to determine the boundaries, extent, position and relief of any part of the earth’s surface.
Tabulation : The process of putting raw data into a systematically arranged tabular form.
Topographic Map : A map of a small area drawn on a large scale depicting detailed surface features both natural and man-made. Relief in this map is shown by contours.
True North : The direction towards which the north pole of the earth points. It is also known as geographic north.
Variable : Any characteristic which varies. A quantitative variable is a characteristic which has different values the differences of which are quantitatively measurable. Rainfall, for example, is a quantitative variable, because the differences in its different values at different places or at different times are quantitatively measurable. A qualitative variable on the other hand, is the characteristic the different values of which cannot be measured quantitatively. Sex, for example, is a qualitative variable. It can be either male or female. A qualitative variable is also known as an attribute.
Watershed : A narrow elevated tract of ground separating water flowing in opposite directions.
Weather : The condition of the atmosphere at a given place and time with respect to atmospheric pressure, temperature, humidity, precipitation, coludiness and wind. These factors are known as weather elements.
Wheather Forecast : Prediction with a reasonable amount of certainly the conditions of weather that would prevail in the coming 12 to 48 hours in a certain area.
Wheel Diagram : A circular diagram in which a circle is divided into sectors for presenting data in percentage.
Wind Rose : A diagram showing the frequency and direction of wind blowing from each of the eight directions at a given place over a period of time.
Wind Vane : An instrument used for determining with direction.
