Name: Tadele Dagne EwunetuDomain: Applied Remote Sensing (ARS)
Student number: s6039553
Summary
According to ADDIN CSL_CITATION {“citationItems”:{“id”:”ITEM-1″,”itemData”:{“author”:{“dropping-particle”:””,”family”:”Knippers”,”given”:”R.”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},{“dropping-particle”:””,”family”:”Tempfli”,”given”:”K.”,”non-dropping-particle”:””,”parse-names”:false,”suffix”:””},”chapter-number”:”3″,”container-title”:”The Core of GIScience: a systems-based approach”,”id”:”ITEM-1″,”issued”:{“date-parts”:”2013″},”note”:”fdbbd bfgb”,”page”:”93-114″,”title”:”Spatial referencing and satellite-based positioning”,”type”:”chapter”},”uris”:”http://www.mendeley.com/documents/?uuid=9549d4f6-f73d-4281-ba21-8179d00483ca”},”mendeley”:{“formattedCitation”:”(Knippers & Tempfli, 2013)”,”plainTextFormattedCitation”:”(Knippers & Tempfli, 2013)”,”previouslyFormattedCitation”:”(Knippers & Tempfli, 2013)”},”properties”:{“noteIndex”:0},”schema”:”https://github.com/citation-style-language/schema/raw/master/csl-citation.json”}(Knippers & Tempfli, 2013), two main reference surfaces (Geoid and Ellipsoid) are made available to approximate the shape of the earth and compromise its surface irregularities of continents and oceans. In the global level, Geoid and Ellipsoid reference surfaces are used to measure height (uses vertical datum) and location (uses horizontal datum) respectively. In Geoid reference, ocean’s water level is registered at coastal locations continuously to determine the mean sea level and also other local vertical datum are fixed to consider the effect of local activities like tides, ocean currents, coastal activities. Ellipsoid reference uses mathematical descriptions like flattening (f=a-b/a) and eccentricity (e2=a2-b2/a2) in order to project horizontal coordinates onto a mapping plane. Local ellipsoids (horizontal datums, like Amersfoort) and global ellipsoid (horizontal datums, like ITRF) are established throughout the world. The former is to provide the best fit of local Geoid (local mean sea level) in the different regions and the latter is to make geodetic results mutually compatible and coherent. As spatial data need to be spatially referenced, we use two coordinates systems which are, spatial coordinate system and planar coordinate system. The first is to locate data in 3D space (ellipsoid) and the second is to locate data in 2D space (flat surface like maps). All the aforementioned aspects will help our understanding of how the different reference systems are systematically implemented on earth to be able to acquire spatial data.

Reference
ADDIN Mendeley Bibliography CSL_BIBLIOGRAPHY Knippers, R., ; Tempfli, K. (2013). Spatial referencing and satellite-based positioning. In The Core of GIScience: a systems-based approach (pp. 93–114).