CONS127_Assignment2_S1_2024
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Geography
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May 24, 2024
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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 May 23 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.
3 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 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 ‘
Nell-Hammer
’
projection and inspect the Tissot’s Indicatri
ces to answer Question 7. You may find it helpful to use other online resources such as the ArcGIS map projections descriptions to help answer (hint: use https://www.mapthematics.com/ProjectionsList.php?Projection=122 for Nell-Hammer).
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4 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 Nell-Hammer projection preserves scale along the equator •
The Nell-Hammer 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. Q8. Imagine you are a researcher who wants to know how the area of a country relates to its population size. What projected coordinate system listed below would be most appropriate to use when calculating the area of each country in the world. - Mercator projection - Cassini projection - Gall stereographic projection - Nell-Hammer projection 10.
Go back to Google Earth Web and search for the coordinate 49.260044
°
, -123.248875
°
, which is given in decimal degrees. Convert the coordinate from decimal degrees to degrees, minutes, seconds
and standard Universal Transverse Mercator (UTM)
using the following website
, maintain the Datum as WGS 84. Q9. Provide the coordinate in degrees, minutes seconds. Include unit symbols, such as ° for degrees, ' for minutes, and " for seconds to get full points. Don't use spaces like in "49° 12' 20.3". Q10. Provide the coordinate in Standard UTM. Write the coordinate concisely, e.g. not “Zone: 10 Hemisphere: S Easting: 334456 Northing: 5393331” but just “10S 334456 5393331”. You should use white spaces. A great circle
is the largest circle you can draw on a sphere. Hint: the equator and all meridians are great circles but the Tropics of Cancer and Capricorn are not. Great circles are used to calculate the shortest distance between two points on the surface of a sphere and are used as travel routes by planes. Visit http://www.movable-type.co.uk/scripts/latlong.html and enter the coordinates of ‘YVR Vancouver Airport’ and ‘Cape Spear’
, “
49.1938, -123.1794
” and “
47.5167, -52.6333
” respectively, as ‘Point 1’ and ‘Point 2’ under the ‘
Great-circle distance between two points
’ box. The corresponding coordinates are Click on the text “see it on a map” to show the path on a map using the Mercator projection.
5 Q11
. What is the distance between ‘YVR Vancouver Airport’ and ‘Cape Spear, NFL’ using the Great Circle Distance (to the nearest km)? 11.
Scroll down and go to the box for calculating ‘Rhumb line’ distance.
Q12
. What is the distance between ‘YVR Vancouv
er Airport’ and ‘Cape Spear, NFL’,
using the Rhumb Line Distance (to the nearest km)? Q13. What is true about Great Circles and Rhumb lines? Select the correct answers.
12.
For UTM zones in the northern hemisphere the Northings are always measured from 0 meters (at the equator) to approximately 9,300,000 meters at the pole (84 degrees North). Within UTM zones in the southern hemisphere the northings are measured from 1,100,100 meters at the pole (80 degrees south) to 10,000,000 meters at the equator. The central meridian of each zone is defined as 500,000 meters. Q14. What are the minimum and maximum Eastings of each UTM zone in meters? Enter the numbers without any commas, points, or units. Hint: At the equator, each UTM zone is 666000 m wide (6 degrees of longitude), and the meridian of each zone is always defined as 500000 m. 13.
Visit https://mangomap.com/robertyoung/maps/69585/what-utm-zone-am-i-in-#
. The UTM coordinate system uses a 2D Cartesian coordinate system to assign coordinates to locations on the surface of the Earth. Zoom in and click on the different zones to see the UTM zones of the locations we have focused on throughout this assignment. 14.
6 Q15. What are the UTM zones of the cities Vancouver, Calgary, Halifax, and Cape Town (South Africa)? 15.
In the maps we have been investigating in this assignment the meridian lines have always corresponded to the rotational axis of the Earth. The point where all meridian lines cross in the northern hemisphere is called ‘
True North
’
or the ‘geographic
North Pole
’
. True North is very useful for making maps because it provides a common point of reference for every projection. However, True North is not the only type of north we use for navigation. Magnetic North is the location where the Earth’s magnetic field lines converge and point directly down. If you use a compass it will point to Magnetic North, not True North. This information is not needed when interpreting map projections or describing a location on Earth using coordinates, but it is very important to understand when using maps to navigate in the real world. Briefly research the differences between True North and Magnetic North to understand the following situation and answer the corresponding questions. Q16. Imagine you and a friend are competing to reach the North Pole. Your friend is only using the stars and a paper map (designed using an azimuthal equidistant projection) to navigate. You are only using a magnetic compass and are simply following where the needle points north. i)
Would you and your friend arrive at the same place at the end of your journey? ii)
50 years later you decide to repeat the challenge with the same navigational tactics. Would you and your friend reach the same location(s) as you did 50 years ago? --------- END OF ASSIGNMENT -------
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