CONS127_Assignment2_2023_Term1

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Dec 6, 2023

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1 Cons 127 Observing the Earth from Space Assignment 2: Where Are You? Google Earth and Geodesy Instructor: Chris Colton (chris.colton@mail.ubc.ca) Office: FSC 2223 TA: Tristan Douglas (tjdoug@mail.ubc.ca) Office hours: Please see the zoom page on the CONS 127 canvas site for office hour details. Objectives • Learn how to use geographic coordinate systems to find and describe locations on the globe. • Apply your knowledge of datums and how they can affect geospatial location mapping. • Apply your knowledge of projection systems. Deliverables • Answers to questions 1 through 16 • Submit your answers to the Assignment 2 Quiz before Oct 5 th at 11.59 pm Websites used • Google Earth Web • Compare Map Projections • Convert Geographic Units • What UTM Zone am I in? • Movable Type Scripts Notes • Please ask assignment questions via the Assignment 2 discussion board, this way your peers can also benefit from your question. Feel free to email Tristan ( tjdoug@mail.ubc.ca ) if you do not want to share your question or require an extension for this assignment. • Some websites, including Google Earth Web and Compare Map Projections , are only fully accessible through a small number of internet browsers. The website are fully accessible via Google Chrome, Mozilla Firefox and Microsoft Edge . • If the YouTube videos are not available in your country than you should use UBC’s VPN server . Note that the videos are not essential for making this assignment. • The internet is at your disposal, feel free to use it to help answer the questions. You are not expected to memorise every property of each projection, use the internet to investigate the properties of the projections mentioned in the assignment.

2 Open Google Earth Web and change settings following to the introduction video . This includes turning off fly animations, switching measurement units to ‘ meters and kilometers ’ , and changing geographic units to ‘degree s, minutes, s econds’ . 1. Look up the coordinate 0, 0 and move your cursor around the marker that appears. Watch how the coordinates at the bottom of the screen are changing in the different directions. 2. Now make sure gridlines are shown on the map. A latitude and longitude graticule will appear on the map. Q1. What are the names of the line of latitude and longitude crossing the 0, 0 coordinate? 3. Zoom out so that you can see the whole Earth. You should be able to see several yellow lines now highlighting the Tropics of Cancer and Capricorn and even the Arctic and Antarctic Circles. If you rotate the Earth, east or west, you should also be able to see the Anti-meridian Q2. State whether the following statements about the prime meridian, tropics and circles are True or False. o The prime meridian is adopted as the zero of latitude. o The prime meridian passes through Greenwich, England. o The prime meridian was established by delegates of 25 nations at the international meridian conferenc e in 1884, which was held in London on behalf of the United Kingdom’s prime minister. o An international standard prime meridian was mainly established to make navigation over long distance easier. o The tropic of Cancer is the most northern latitude, 23.43658° north of the Equator, where the sun can be directly overhead. This happens yearly around 21 December (+/- 1 day). o The position of the Antarctic Circle is fixed at 66°33′49.3″ south of the Equat or. 4. From this distance, i.e. zoomed out, it is easy to see the spherical shape of the Earth. A datum, which is a reference surface used to generate coordinates (latitude and longitude), is used to approximately represent the Earth in 3D. This would include more of the irregularities of the Earth’s surface, such as the bulge at the equator. However, datums are not detailed enough to represent topographic features like mountains and valleys. Q3. Which datum, i.e. reference ellipsoid, is used by Google Earth? 5. It is also helpful to represent the Earth in two dimensions (2D). A projection is the result of taking 3D points from a datum (or the Earth’s surface itself) and doing some geometrical transformations to display them on a 2D flat surface, like a map. A simple introduction of map projections is given in this

3 video , including why we need map projections, types and properties (what is distorted and what preserved). Q4. What projection system is typically used by online map providers such as OpenStreetMap and Bing Maps? Q5. What is the name of map projections that preserve angles locally? 6. Visit the website Compare Map Projections by Tobias Jung. Select and compare a few different map projections and look at how the grid of graticules changes. Specifically, look at how the boxes change shape and size vertically and horizontally across the maps. Also, note the comparison of map silhouettes and the Tissot indicatrix. A Tissot’s Indicatrix uses circles to show the distortion of a projection at a particular point on the map. 7. Compare the ‘Mercator’ , ‘Lambert Cylindrical’ and ‘Gall - Peters’ map projections. All are cylindrical map projections which have straight graticules that cross at 90° angles. The Mercator projection is one of the most well-known cylindrical map projections. They were developed for different purposes and preserve metric properties (area, shape, direction and distance) differently. Q6. Indicate for each map projection whether the metric properties area, shape, direction and distance are preserved or distorted Map Projection Mercator Lambert Cylindrical Gall-Peters Area Shape Direction Distance 8. On the same website ( Compare Map Projections) select the ‘Mollweide’ and ‘ Winkel Tripel ’ projection and inspect the Tissot’s Indicatri ces to answer Question 7. You may find it helpful to use the ArcGIS map projections descriptions to help answer. Q7. Indicate whether the following statements are TRUE or FALSE • The Mollweide projection preserves scale along the equator • The Mollweide projection preserves shapes at two points on the central meridian • The Winkel Tripel projection preserves scale along the equator • The Winkel Tripel projection preserves area better than the Mollweide projection 9. Now we have a feel for what different projections do, lets apply this knowledge to a hypothetical example.

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