coordinate systems map projections and graphical and atoms ppt group (B).pptx
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The document provides an overview of coordinate systems, geodetic datum, and map projections, explaining the importance of geographic coordinate systems (GCS) like WGS 84 and projected coordinate systems (PCS) for accurate spatial analysis. It also describes datum as reference systems for defining geographic feature locations, highlighting their variations and the need for datum transformations to ensure mapping accuracy. Additionally, the document details different map projection methods, including conic, cylindrical, and planar projections, and their specific uses and characteristics.
coordinate systems map projections and graphical and atoms ppt group (B).pptx
- 1. Coordinate systems ,Geodetic Datum and map Projections BAKHAT ALI Institute of Geoinformatics and Earth Observation, Pir Mehr Ali Shah Arid Agriculture University Rawalpindi , Punjab, Pakistan [email protected]
- 2. Outline: Coordinate systems Geodetic Datum Map projections
- 3. Coordinate systems: "Coordinate system is a reference system used to represent the locations of geographic features, imagery and observation within a common geographic framework". Two types of coordinate systems : 1. Geographic Coordinate Systems (GCS) 2. Projected Coordinate Systems (PCS)
- 4. 1. Geographic Coordinate Systems (GCS) A geographic coordinate system (GCS) uses a three-dimensional spherical surface to define location on the earth. A point referenced by its latitude and longitude values A global address is given as two numbers called coordinates. The two numbers are a location's latitude number and its longitude number The most commonly used geographic coordinate system is the World Geodetic System 1984 (WGS 84). It is used by GPS receivers and is the standard for most GIS applications.
- 5. Latitude and Longitude line Latitude: It measures the north-south position on the Earth's surface and is represented in degrees north (N) or south (S) of the equator. The equator is at 0° latitude, and the North Pole is at 90° N, while the South Pole is at 90° S Lines of latitude are called parallels knows as equator . Longitude: It measures the east-west position on the Earth's surface and is represented in degrees east (E) or west (W) of the Prime Meridian, which is typically located at 0° longitude. Longitudes range from -180° to 180°. Lines of longitude are called meridians.
- 6. Graticule • The parallels and meridians of latitude and longitude form a Graticule. • The GCS uses a network of imaginary lines (longitude and latitude) to define locations. This network is called a graticule. • Graticule on a globe, a grid of orthogonal lines
- 7. 2. Projected Coordinate Systems (PCS) • Projected coordinate systems use a flat, two-dimensional SURFACE to represent earth’s curved surface. PCS is used to represent locations on a map and is useful for measuring distances, calculating areas, and performing other spatial analysis. For examples, Projected coordinate systems include the Universal Transverse Mercator (UTM) and Stale Plane Coordinate System (SPCSJ.
- 9. Datum's A datum in geography refers to a reference system used to define the location of geographic features on the Earth's surface. It serves as a reference point from which measurements of latitude and longitude are made. Datum's often have horizontal and vertical components. The horizontal component deals with latitude and longitude, while the vertical component involves elevation or depth. Datum's can change over time due to advancements in measurement technologies and a better understanding of the Earth's shape. Upgrades and adjustments may occur to improve accuracy. When working with maps or spatial data in different datum's, datum transformations are necessary to convert coordinates from one datum to another. This ensures consistency and accuracy in spatial analysis. The choice of datum can significantly affect the accuracy of maps and geographic information systems (GIS) data. Different datum's may lead to variations in the representation of geographic features. Some datum's are designed for specific regions or countries (local datum's), while others are global in scope and widely used for international mapping and navigation.
- 10. Geodetic Datum A geodetic datum in geography is a reference framework used to precisely define the position of points on the Earth's surface in terms of latitude, longitude, and elevation. It provides a coordinate system for locating geographic features, serving as the basis for mapping and navigation. Examples of widely used geodetic datum's include WGS84 (World Geodetic System 1984) and NAD83 (North American Datum 1983). Modern technologies, such as GPS, are integrated into geodetic datum's to enhance precision and keep them up-to-date. Geodetic datum's take into account the Earth's shape and size, providing a model that best fits the actual dimensions of the planet.
- 12. Map projections: Map projection is any method of representing the surface of earth or other three-dimensional body on a plane. 3D Surface into 2D Plane Surface Three kinds of developable projection surfaces: Cone Cylinder Plane • The name of the projections made from these surface are: 1. Conic Projection 2. Cylindrical Projection 3. Planar Projection
- 13. 1. Conic Projection: • Conic projection is fan shaped, characterized by an upside down cone over the sphere • Conic projection are at an true scale along a standard parallel/s between the equator and a pole • Conic projections are used for midlatitude zones that have an east– west orientation • If equally space, distance preserve • If distance between parallels increase near border, shape preserve • If distance towards north and south • pole decreases, area preserve
- 14. 2. Cylindrical Projection: Cylindrical projection is a rectangular grid representation, characterized by a cylinder over a sphere Cylindrical projections are at an true scale along a central meridian/s and standard parallel/s near a equator Cylindrical projection mostly use for tropical zones All cylindrical projections are equidistant along central meridian/s and standard parallel/s
- 15. 3. Planar Projection: Planar projection is a circular representation with a focus, characterized by plane over a sphere Planar projection is also called Azimuthal projection or Zenithal projection Planar projections are true only at their focus Planar projections mostly use for polar zones rectangular regions
- 16. 4. Azimuthal or Polar Projection: This projection use to map polar regions and preserves direction but distort distance and shape. 5. Equal Area Projection: This projection preserves the relative areas of land masses but distort shapes and distances. 6. Stereographic Projection: This projection is commonly used for mapping polar regions and preserves the shapes of small areas, but distorts the overall shape of larger land masses.