Projection maps in information systems

Shape of the earth which we see so far is a model who made the earth by man, sometimes there is a round sometimes elliptical. Tp is not really like that shape the earth, its shape is irregular. And though more easily ngegambarnya, eventually become more common round. And this round by making a flat map. His name is also a map, picture of the earth's surface in the plane

Because the earth's surface is not flat, curved arch alias irregular, but the maps need a picture of the plane, it would require the conversion of the actual field curvature of the earth onto a flat surface to prevent distortion of the earth's surface.

This nieh size of the earth in number

Ellipticity: 0003 352 9
Mean radius: 6,372.797 km
Equatorial radius: 6,378.137 km
Polar radius: 6,356.752 km
Aspect Ratio: 0996 647 1

equatornya radius is longer than the polar radius

Ever peel an orange? Bangat definitely hard to put the orange peel into a flat surface, but the orange peel all connected. who was also experienced by cartographers when mapping the earth's surface, they must move the geographical certain way, pull back and combine the parts together in order to connect a flat map. the map is no exception globe is distorted from the real world. For smaller areas, the distortion is not significant due to small areas in the globe looks like a flat surface. For larger areas or for purposes that require high accuracy, however the distortion is very important. Therefore we need a map projection. In the preparation of maps required a projection map which gives the relationship between the points on the earth with the maps, well-chosen projections which are required to have a small distortion.

In principle, the meaning of the projection map is an attempt to change the shape of curved to form a flat surface, with the requirements of a modified form that must be fixed, changed surface area should be fixed and the distance between one point to another point on the surface is modified to be fixed.

Map projections are the techniques used to describe partial or complete three-dimensional surface that is spherical kasaran into a flat two-dimensional surface with as little distortion as possible. In a map projection system that delivers pursued the relationship between the position of the points on the earth and on the map

to meet all three requirements change from curved to flat field bangat it was not possible, then there kompromi2 in using these terms, so came the various types of projections. Some common types of projection is a cylinder / tube (cylindrical), cone (conical), plane (zenithal) and composition (arbitrarry)

Type of projection that we often encounter everyday are spin projection, the projection is obtained through calculation. Type of projection is often used in Indonesia is the WGS-84 (World Geodetic System) and UTM (Universal Transverse Mercator)

WGS-84 (World Geodetic System) is the best for the overall geoid ellipsoid. Largest deviation between the geoid to WGS-84 ellipsoid is 60 m above and 100 m below it. When the size of the long axis of WGS-84 ellipsoid is 6,378,137 m with kegepengan 1/298.257, the largest deviation of this ratio is 1/100 000. Indonesia, like other countries, using the size of this ellipsoid for the measurement and mapping in Indonesia. WGS-84 "set, diimpitkan" obtained such that the smallest deviation in the archipelago of Indonesia. Impit point WGS-84 geoid in Indonesia with a datum known as Padang (relative geodetic datum) is used as a reference point in the national mapping. Genuk datum previously known in the area around Semarang to the Dutch created the mapping. Using the same ER - WGS 84, since 1995 Indonesia's national mapping using absolute geodetic datum. DGN-95. In this absolute datum system, ER center coincides with the center of the earth.

UTM projection is a projection map that many of the choosing and in use in mapping activities in Indonesia because of the ideal value syarat2 meet in accordance with the shape, location and extent of Indonesia. UTM specifications include (1) using a cutting cylinder area of ​​the globe on two standard meridian which has a scale factor k = 1, (2) The width of the zone of 6 ° was calculated from 180 ° West by zone numbers 1 through to 180 ° east by numbers zone 60. Each zone has its own central meridian, (3) each zone has its own central meridian with a magnification factor = 0.9996, (4) Boundary parallel top edge and bottom edge is 84 ° N and 80 ° S and (5) projected to be in conformity. According to Frans ( UTM using a cylinder which wraps ellipsoid with axes standing perpendicular to the cylinder axis ellipsoid (axis of rotation of the earth), so that the ellipsoid and the tangent cylinder is a line which coincides with the longitude on the ellipsoid. As a result, titik2 on the line lies in both fields, so that although his position is moved (projected), from ellipsoid to cylindrical, it will not change (distortion).

World UTM map