MAPS ,COORDINATE SYSTEM AND MAP PROJECTION Day 1 –GIS Training IOE, Pulchowk

Presented By:Uttam PudasainiGeomatics Engineer

NAXA Pvt. Ltd.

Presentation Outline

Basic Concepts:

Maps

Types of Maps: Analog and Digital

Earth and its Shape: Geoids and Ellipsoids

Coordinate System: Geographical and Rectangular

Map Projection

Coordinate System in Nepal

Installation of Arc GIS Version 10.0

MAPS

A graphical representation of ground reality

Objects on the ground are reduced to a certain scale and represented

on map

Maps: Not a reality in itself

Analog Vs Digital MAPS

Analog Maps

Rigid form of map where message is conveyed by virtue of symbology.

Measurable but not interactive.

They are always projected.

Difficult to integrate with other data.

Digital Maps

Maps in a digital media.

Interactive options according to map’ objective.

Maps can be in both 2D and 3D format.

Easy integration with other data.

EARTH And its Shape (Misconceptions)

Earth surface is a plane surface.

If we are going to sail further, we are going to fall down one day.

Rectangular Earth

Earth is in fact flattened slightly at the poles and bulges somewhat at the equator.

Mathematical Shape of the earth : An Ellipsoid, A geometrical figure which would be obtained by rotating an ellipse about its shorter axis.

Coordinate System

Geographical Coordinate System

Uses latitude and longitude to represent the x,y position in space.

Useful for locating positions on the curved surface of the earth.

Rectangular Coordinate System

Uses x,y coordinates to represent positions on a plane.

The location of any point in this system is defined by a set of two values, p (x, y).

Contd…

Earth surface in reality is a curved surface with no perfect geometrical shape.

Mapping in a globe is an easy way to map the earth.

Measurement as well as sharing of data and details is always difficult if a map is represented on globe.

Projection: A method by which the curved surface of the earth is represented on a flat surface.

Map Projection

Includes two operations:

Alteration of Scale.

Transformation to Plane surface.

Contd..

Numerous projections have been invented, and arguments continue about which is best for which

purposes.

World Geodetic System - 1984 (WGS 84)

A three dimensional Right handed Cartesian coordinate system followed around the globe.

Origin = Earth’s centre of mass

Z-Axis = Direction of the Conventional Terrestrial Pole

X-Axis = Intersection of the WGS 84 reference meridian plane and the plane of the CTP’s equator.

Y-Axis = Measured in the plane of the CTP equator, 90° East of the x-axis.

Coordinate System in Nepal

Everest Ellipsoid:Reference Ellipsoid being adopted by Nepal

Semi major Axis ,a = 6377276.345 m

Semi minor Axis ,b= 6356075.413

Flattening 8017.300/1

a

baf

Universal Transverse Mercator (UTM) Projection

Introduced by US Army Map Service in the 1957.

Most common system of projection used for large scale mapping around the world.

Based on a Transverse Cylindrical projection.

Cylinder touches the reference globe along a chosen meridian.

Consists of 60 zones. Each zone has a width of 60 of longitude.

Zones are numbered sequentially from west to east, starting with 1. Zone 1= 1800W to 1740 W, with CM 177 W.

MUTM Projection System

Consists of 120 zones ,each of width 30 longitude

Unit of measurement is meter.

Scale factor at the central meridian = 0.9999.

False Easting at Central Meridian =500000 m.

False northing at the Equator is 0 m.

False Easting and False Northing:

Arbitrary large values are assigned to Y-axis origin and X-axis origin so called false easting and false northing respectively.

Overcomes the inconveniences caused by the negative numbers in Rectangular Coordinate System.

Conclusion

Reading Materials

Latitudes and Longitudes: https://www.youtube.com/watch?v=y6aPerEPbvw

Coordinate System and Projections: https://www.youtube.com/watch?v=HifUBn4APZA