EOS 102: Dynamic Oceans Exercise 1: Navigating Planet Earth YOU MUST READ THROUGH THIS CAREFULLY! This exercise is designed to familiarize yourself with Google Earth and some of its basic functions while also learning something about our Earth and Oceans. If you don t already have Google Earth installed on your computer, go to www.google.com/earth/ and follow the directions on how to download and install the appropriate version on your computer. Go with Google Earth, Google Earth Pro requires a subscription. Once you have the program, open it. Google Earth is an incredibly powerful yet simple tool that lets you explore the surface of the Earth and the bathymetry of the ocean. If you are savvy with the touchpad on your laptop you can probably make this work but I highly recommend that you use an actual mouse to navigate in Google Earth it is easier, especially for a beginner. There are lots of online tutorials on their website to get you started with the basics of navigation. Once you feel comfortable, see if you do the following exercises: Let s explore the latitude and longitude grid of our Earth. Before you start, be sure to turn on GRID to display longitude and latitude lines on your globe. To do so go to VIEW Tab and turn on GRID. Also make sure that lat/long format is set to degrees, minutes, and seconds. Open the Tools tab and then click on OPTIONS to change this formatting if necessary. Let s put a marker right where the prime meridian (the longitude that has arbitrarily been chosen to be the 0 th longitude) intersect the equator. Into the SEARCH box copy and paste the following coordinates: Latitude: 0 0'0.00"N this makes the point lie somewhere on the equator Longitude: 0 0'0.00"E this makes the point lie somewhere on the prime meridian Like so: Now press, search. Google Earth will think for a second (or a few depending on your connection) and take you to this location (Google Earth is set to zoom in automatically, to better see where you actually are, just zoom out BUT DO NOT MOVE YOUR LOCATION!) 1
Click on the Marker button to place a marker here. A marker menu pops up. The default marker in Google Earth is a Yellow Pin. Unfortunately this is a little misleading visually as the tip of the marker is NOT the actual location, rather it is the center of the icon as a whole. Let s pick a better marker. After you clicked to mark a location, click on the little icon in the marker menu (right upper side). A list of icons pops up. Pick the small black target instead. Click OK when you are ready to place the marker (if you have inadvertently pressed RETURN while naming or changing the lat/long data above, just right click the marker to re-open the PROPERTIES menu). As you know latitude and longitude let you precisely define ANY place on Earth. Let s place a second marker. Go back to the Search line and type in the following location (then repeat the steps above to place a marker here). Latitude: 45 0'0.00"N Longitude: 0 0'0.00"E Call this point HALFWAY POINT and click OK. This point is now exactly 45 North of the equator. Remember that the North Pole is at 90 latitude. Using what you learned above, place a MARKER directly on the North Pole, call it NORTH POLE. So far so good. Let s try some measurements. Click on the ADD PATH menu: at the top to open the menu. Click on the measurement tab. For now, leave the unit in miles. Ok, very carefully, place the crosshair pointer exactly over the markerpoint of the MARKER on the equator. Click ONCE. Now move the screen to the HALFWAY point and zoom in so that you can see the grass growing on the side of the road (sort of). Click the crosshair pointer on the markerpoint of the MARKER. DO NOT CLICK ON THE MAP SCREEN TO MOVE TO THE HALFWAY LOCATION - YOU MUST CLICK ONLY ON THE NAVIGATION TOOLS ON THE RIGHT OTHERWISE YOU PLACE A SECOND POINT AND YOU HAVE TO START OVER AGAIN. Now look at the measurement displayed in the menu box. How far (in miles) is it between these points as the crow flies. Record that number here: 2
Miles OK, now repeat this procedure to measure the distances from the HALFWAY point to the NORTH POLE and record the distance here: Miles Interesting, no? Before you rush to repeat this because you suspect you did it wrong, think about this for a minute. Why are the two distances NOT the same, despite being half-way to the North Pole in terms of degrees? Explain. Put your answer here: Ok, now open the accompanying powerpoint to learn about how latitudes were first measured and defined and how the fact that the Earth is not perfectly spherical has had a peculiar impact on the precision of latitudinal distance today. Let s explore longitude and latitude a bit more. Latitude is expressed as degrees (0-90) above (N) or below (S) of the equator. Longitude is expressed as degrees (0-180) WEST of the prime meridian or EAST of the prime meridian. The units between degrees are divided into minutes and seconds with 60 minutes = 1 degree, and 60 seconds = 1 minute. To simplify things, locations are often converted into decimal degrees. This is accomplished by dividing the minutes by 60 and the seconds by 3600 and then adding the two results to the degrees For Example: 36 00'09.89"N = 36.0027 78 56'15.63"W = 78+(56/60)+(15.63/3600)= 78+0.9333+0.0043=78.9377 Go ahead and place a MARKER in Google Earth using the above Lat and Long data (in degrees, minutes, and seconds). This location is incredibly important if you ever wish to see me during my office hours (third floor). Ok, give this marker a name and press OK. Converting from one unit format to another is quite tedious as you can see in the example above. Good thing Google Earth can do this for us. Click on the Tools Tab and then choose Options. A menu opens. See where it says Show Lat/Long? Choose Decimal Degrees from among the four choices and click APPLY in the lower right hand corner. Right click your last marker and chose Properties now the lat/long data is in Decimal Degrees. NOTICE something important here though. Unlike my conversion above, the longitude displayed by Google Earth is actually NEGATIVE. This is a simple convention. Negative longitudes means 3
you are measuring WEST of the prime meridian, negative latitudes means you are measuring SOUTH of the equator. Obviously, a positive longitude means you are measuring East of the prime meridian and a positive latitude means you are in the Northern Hemisphere. Ok, let s have some fun checking out who lives DIRECTLY on the opposite side of Earth from me in my office in Old Chemistry! How do you do that? Well, directly opposite on Earth simply means a location that lies +180 longitude and +180 latitude away from where you are. Remember that latitude is measured from 0-90 N or S and longitude from 0-180 W or E. Convert my office location above to the location directly opposite on the other side of Earth: Lat: Long: Well, this is not a place I will likely ever travel to. For kicks, use the measurement tool in Google Earth to measure how many KILOMETERS this location is located from the South-East Indian (Spreading) ridge (marked in red on map) to the South (measure perpendicular to the ridge) Km Ok, let s practice using lat and long in Google Earth. What major feature is found on the OPPOSITE side of the planet from the following coordinates: Lat: -48.858238 Convert: Feature: Long: -177.705307 Lat: -27.987425 Convert: Feature: Long: -93.075160 Lat: 15.871999 Convert: Feature: Long: 110.627811 Lat: 63 04'01.34"S Convert: Feature:* Long: 28 59'29.84"E *be sure to use the name used by First Nation Peoples Last but not least. Type in your home address with city and state/country in the SEARCH bar in the upper left of the screen, to view your home from space. OK, now go on SAKAI and click on the Tests and Quizzes menu. Answer the questions to successfully submit EXERCISE 1. 4
YOUR GOOGLE EARTH SKILLS SO FAR: -know how to navigate using the navigation tools -know how to zoom in and out of the map screen -know how to turn the long/lat grid on or off -know how to place a marker -know how to change between different units of latitude in the Options menu -know how to manually change the latitude and longitude of an existing marker -know how to take measurements between markers in different distance units -know how to use the search bar 5