Geodesy Study Questions PDF

GEODESY STUDY QUESTIONS: CHAPTER 7 1. Discuss four surfaces that we deal with in geodesy. Draw a figure to back up your answer There are 4 types of surfaces that we deal with in geodesy, a. the mathematical projection surface that is a flat surface that shows the Terrain of the e...

GEODESY STUDY QUESTIONS: CHAPTER 7 1. Discuss four surfaces that we deal with in geodesy. Draw a figure to back up your answer There are 4 types of surfaces that we deal with in geodesy, a. the mathematical projection surface that is a flat surface that shows the Terrain of the earth in a 2D surface. There is also a mathematical surface that is a spherical projection of the 2D surface. Next is the geoid model that considers the N height of the Mathematical surface. Finally, is Terrain which is modelled by the h=H+N formula A graph of a graph of a graph Description automatically generated with medium confidence 2\. Discuss the type of control networks we deal with in geodesy. Elaborate on the reason for this type there are three types of control networks that we deal with in geodesy there is the 2D horizontal control network which the Hz coordinates are accurately measured but the elevations are only approximately known, versus V 1d where the elevation is accurately measured, but hz are just approximate. 3D control network that all three components are known. 3.What does order and degree of a control network show? (elaborate on the meaning of absolute and relative accuracy and relate it to the concept of order and degree of the control network) For the degree and order of the control network the higher the order of the network the larger distance between stations but the relative accuracy of a control network in Canada should remain the same. 4\. Elaborate on the vertical network of Canada. (Add some reliable material to your answer by\ searching internet) There are multiple different height control systems in Canada first there was the Canadian vertical datum of 1928 (CGVD28). In 2013 they changed to the new Vertical Datum (CGVD2013) which corrects for the systematic errors in which the old datum did not. 5\. Elaborate on the horizontal network of Canada. (Add some reliable material to your answer by\ searching internet) the horizontal network of Canada provides precise positioning for mapping and navigation and based on the NAD83 control network it connects first order stations using triangulation and Modern GPS. This horizontal ensures high accuracy through the Canadian active control system (CACS). 6\. Elaborate on NAD27/NAD83/ITRF. NAD27 was developed for geodetic surveying in North America. It was the dominant reference system for the 20^th^ century. NAD27 uses a reference ellipsoid known as Clarke 1866 which was designed to fit the shape of the earths gravitational surface. The ITRF is a geodetic reference frame that is maintained by the IERS which is designed to provide a consistent reference frame for global positioning systems. 7\. Discuss in detail the current structure of Canadian Geodetic Network. (use NRCan website to answer this question) The Canadian Control network provides positioning data across Canada for multiple geodetic applications The CGN is the Canadian spatial reference system (CSRS) which uses datum NAD83 to ensure accuracy. The first order stations are the backbone of the system and the second degree stations are used for second order stations. The CORS network paired with the CACS enables real time high precision GNSS data. 8\. Discuss how tide gauge works and how MSL is measured. What is SST and how much is its magnitude? Tidal gauges are a pipe network in the ocean shores that connect to a station that fills up to the matching water level that now allows for accurate MSL measurements in a more controlled environment. SST which stands for Sea Surface Topography refers to the 3D surface of the oceans which varies due to the ocean currents tides and temperature variations and the magnitude of this is several decimeters. 9\. Discuss the conditions for a mathematical surface to approximate geoid. Based on these conditions, The mathematical approximation of a surface must meet several conditions a. it has to fit to earths gravitational field and the calculations should approximate the field values. It also must meet the symmetry values associated with the ellipsoidal model. Finally, it should accurately approximate the consistency with mean sea level. 10\. What are the parameters needed for defining sphere or biaxial/triaxial ellipsoids as the\ mathematical surface of the Earth? to define a sphere there is just one parameter needed the separation value between the geoid and the sphere which is about 11km. The biaxial is more difficult to use but the model is only about 80m away from the geoid. Finally, is the Spheroid is a higher order geometrical body but more difficult to use for positioning but very close to geoid 11\. Elaborate on the three methods used to determine the size and shape of the earth. there are three methods to determine size of the earth first is the Eratosthenes method which states that (f=0) R=5950km. Secondly is the French Academy of Sciences which uses two meridian arcs one high latitude and one near equator Finally there is the gravimetric method which uses Clairaut's Theorem, and used the method of measuring gravity at the equator and pole 12\. Discuss the geocentric and topocentric datum establishment parameters. Geocentric datums, like NAD83, use the Earth\'s center of mass as the origin, while topocentric datums use a specific point on the Earth\'s surface. Parameters include shift parameters (Δ𝑋,Δ𝑌,Δ𝑍), rotation elements (RX, RY, RZ), and a scale factor (1+Δ𝐿). 13\. Elaborate how a datum (like NAD27) is defined and evolved to a new one (like NAD83). NAD27 used the Clarke Ellipsoid of 1866 and fixed coordinates at Meade\'s Ranch, Kansas, relying on long-baseline surveys and triangulation. NAD83, based on the Geodetic Reference System of 1980 (GRS80), uses the Earth\'s center of mass as the origin and corrects distortions with data from terrestrial and Doppler satellite observations. 14\. What is the difference between a local and global datum? Local datums align their ellipsoids to fit the Earth\'s surface in a specific area, using a fixed point on the surface as the origin (e.g., NAD27). Global datums use the Earth\'s center of mass as the origin, providing a consistent reference worldwide (e.g., NAD83, WGS84). 15\. Define Tellluroid and quasigeoid. The telluroid is a theoretical surface of the Earth\'s gravity field used as a reference for measuring heights, while the quasigeoid is a surface that approximates mean sea level and is used for determining orthometric heights.