Every map user and maker should have a basic understanding of projection no matter how much computer seem to have automated process. Briefly comment the statement.

 QUESTIONS,

i)                    Every map user and maker should have a basic understanding of projection no matter how much computer seem to have automated process. Briefly comment the statement.

Map projection is a mathematically described technique of how to represent the earth’s curved surface on a flat map.  To represent parts of the surface of the earth on a flat paper map or on a computer screen the curved horizontal reference mapped surface Must be mapped onto the 2 Dimensions (2D) mapping plane, (Knippers, 1998).

Projection can be defined as the formal process which converts mathematically, speaking map features between a spherical or ellipsoidal surfaces and projection surface, often flat, (Knippers, 1998).

Map projection is classified into three classes which are cylindrical, conical and azimuthal as explained as follows;

Cylindrical is a type of map projection of the earth’s surface projected on map wrapped around the global as a cylinder, (Knippers, 1998).

Conical projection is the types of map projection which is formed into cone and gives a conical map of the earth’s surface,(ibid)

Azimuthal projection, this is the type of map projection in which the earth’s surface is projected directly onto the mapping plane, (ibid).

ii)                  Describe the following fundamental problems of using GIS.

Geographical dimension is the crucial theory in geographical dimension. According to the definition of Neef, he argued that geographical dimension is the scale range in which the same assertion are possible, the same methodological objectives can be influenced and determined by set of methods, (Neef, 1963).

QUESTION TWO

a)      Map projection refers to the mathematical procedures by which all or part of a three dimensional, roughly spherical surface is translated on two dimensional, flat surfaces with minimal distortions. Substantiate the statement by site the examples.

According to Bhatta, (2012) he stated that projection, Is the system of mathematics and geometry where by the information on the surface of the sphere that is the earth  able to be transferred onto a flat area or a piece of paper, the basic projection technique describe the way an imaginary piece of paper is laid on the earth to obtain the latitude and longitude for the map.

Map maker or user should understand in relation to projections, where the imaginary “piece of paper” touches to the earth, there is distortion on the map. Moving  away from however, distortion increases with the distance. Because of this, map maker usually choose for the piece of paper to touch the earth in the middle of the map-thereby minimizing the amount of distortion,.

b)      Give the difference between the following terms.

                                  i.            Mean Sea level and datum.

Sea level is an average level for the surface  of more of earth’s oceans from which height such as elevations may be measured.  Mean sea level is a type of vertical datum – a standardized geodetic reference point.  For example, as a chart datum in cartography and marine navigation, while datum refer to a model of the earth that is used in mapping.  The datum consists of a series of numbers that define the number and size of the ellipsoid and its orientation in space, (Solomon et al, and 2007).

                                ii.            Geographical coordinate system and polar coordinate system.

Geographical Coordinate system is a three dimensional reference system that locates points on earth’s surface. The unit of measure is usually decimal degrees.  A point has two coordinate values that is to say the latitude and the longitude which measure angles whereas polar coordinate system is a two dimensional coordinate system in which each point on plane is determined by a distance from a reference point and an angle from a reference direction, (Michael, 2006).

                              iii.            Geoid and Spheroid

Geoid is the shape that the surface of the oceans would take under the influence of earth’s gravitation and rotation alone, in the absence other influences such as wind and tides while spheroid is a quadric surface obtained by rotating an ellipse about one of its principle axes, in other word an ellipsoid with two equal semi-diameters. If the ellipse is rotated about its major axis the result is a prolate (elongated) spheroid as like a football or rugby ball, (Fowler, 2005).

QUESTION THREE

i.                    Briefly describe properties of map projection.

Map projection, is a systematic transformation of the latitudes and longitudes of locations on the surface of a sphere or an ellipsoid into locations on a plane, (Michael, 2006).

The following are the properties of map projection:-

a.       Shape is also called conformality, shape is preserved locally within small areas when the scale of a map at any point on the map is the same in any directions.  Projections with these properties are called conformal, (Fowler, 2005).

b.      Distance is also called equidistance.  A map projection can preserve distance from the centre of the projection to all other places on the map but from the centre only.  Such a map projection is called equidistant.  Maps are also described as equidistant when the separation between parallels is uniform, (ibid).

c.       Direction, a map projection preserves direction when azimuths that is angles from the central point or from a point on a line to another point.  Are portrayed correctly in all directions as many azimuthal projections have these properties, (Michael, 2006).

d.      Area sometimes is known as equivalence, a map can portray areas across it in proportional relationships to the area on the earth that they represent such a  map projection is called equal – area or equivalent.  

II.         Describe why do people study GIS?

GIS is a computer system for capturing, storing, checking, integrating, manipulating, analyzing and displaying data which are spatially referenced to the earth surface, this is normally considered to involve a spatial referenced computer data base and appropriate application soft ware, (Bhatta, 2012)

The following are the reasons to why people study GIS.

i.        With GIS technology, people can compare the locations of different things in order to discover how they relate to each other.  For example, using GIS, the same map could include sites that produce pollutions, such as gas station, and site that are sensitive to pollutions like wetlands.  In this case map helps people in determining which wetlands are the most at risk, (ibid).

ii.         The user can access and select information by area or by themes to emerge one data set with another, to analyze spatial characteristics of data, to search for a particular features, to update quick and cheaply and assess alternative, (ibid)

iii. GIS can use any information that includes location.  The location can be expressed in many different ways, such as, latitude and longitude, address, place name and zip

Code.  Various types of information can be compared and contrasted using GIS.  The system can include data about people such as population, income or education level.  It can also include information about the land, such as the location of streams, different kinds of vegetation, and various types of soil.  Sometimes it can include information about the sites of factories, farms, and schools as well as storm drains, roads and electric power lines, (Solomon et al, and 2007).

REFERENCE

Bhatta, B. (2012). Remote Sensing and GIS Second Edition. New Delhi: Oxford University Press.

Fowler, C. M. R. (2005).  The Solid Earth; An Introduction to Global Geophysics. United

                          Kingdom:  Cambridge University Press.

Knippers, R. A. (1998).  Coordinate System and Map Projection:  New    York, Macmillan

                           Publisher.

Michael, F. (2006).  History of Thematic Cartography, Statistics, Graphic and Data

                         Visualization: New York. Mc Graw-hill Press.

Solomon et al, 92007).  Technical Summary, Section 3.4 Consistency Among Observations:

                         United Kingdom:  Cambridge University Press.