Unit 2 Chapter 3

R. Schroeder Geo 20G - Unit 2 - Chapter 3 1 Unit 3 – Objectives

 Learn various methods of locating places on maps.

R. Schroeder Geo 20G - Unit 2 - Chapter 3 2 Unit 3 – The Words

 Compass Point  Latitude  Compass Rose   Compass Bearing  Prime  Alphanumeric Grid  Global Positioning  Map Grid System (GPS)  Easting  Zone  Northing  Standard Time  International line  Daylight-saving Time

R. Schroeder Geo 20G - Unit 2 - Chapter 3 3 Unit 3 – Locating Places on a Map

 Compass Points – Usually refers to the 16 different points on a compass e.g. N, S, SW, etc.  Four main compass points are the “cardinal” points  The next (secondary) points are the “ordinals”  All other compass points are sub-divisions of the ordinals

R. Schroeder Geo 20G - Unit 2 - Chapter 3 4 Compass Points and Bearings

 Compass Rose – Features the compass points in diagram form  Note: Atlases usually avoid using a compass rose due to their grid design  Compass Bearing – Using “degrees” with values of 0° to 360°, to more accurately determine position  Note: 0° & 360° are the same position

R. Schroeder Geo 20G - Unit 2 - Chapter 3 5 Compass Points and Bearings

 www.gisnet.com/notebook/comprose.html

R. Schroeder Geo 20G - Unit 2 - Chapter 3 6 Compass Points revisited

Principal Points aka “Cardinal” Points =  North, South, East and West

Secondary Points aka “Ordinal” Points =  Northeast, Southeast, Southwest and Northwest

R. Schroeder Geo 20G - Unit 2 - Chapter 3 7 Compass Rose vs. Compass Bearings

R. Schroeder Geo 20G - Unit 2 - Chapter 3 8 Compass Points revisited

More subdivisions (8):  North Northeast, East Northeast, East Southeast, South Southeast, South Southwest, West Southwest, West Northwest and North Northwest

Even more subdivisions (16):  North by East, Northeast by North, Northeast by East, East by North, East by South, Southeast by East, Southeast by South, South by East, South by West, Southwest by South, Southwest by West, West by South, West by North, Northwest by West, Northwest by North, North by West

R. Schroeder Geo 20G - Unit 2 - Chapter 3 9 The 32 Compass Points

Point Direction Azimuth Point Direction Azimuth  0 North 0° - 0‘  16 South 180° - 0‘  1 N by E 11° - 15‘  17 S by W 191° - 15‘  2 NNE 22° - 30‘  18 SSW 202° - 30‘  3 NE by N 33° - 45‘  19 SW by S 213° - 45‘  4 NE 45° - 0‘  20 SW 225° - 0‘  5 NE by E 56° - 15‘  21 SW by W 236° - 15‘  6 ENE 67° - 30‘  22 WSW 247° - 30‘  7 E by N 78° - 45‘  23 W by S 258° - 45‘  8 East 90° - 0‘  24 West 270° - 0‘  9 E by S 101° - 15‘  25 W by N 281° - 15‘  10 ESE 112° - 30‘  26 WNW 292° - 30‘  11 SE by E 123° - 45‘  27 NW by W 303° - 45‘  12 SE 135° - 0‘  28 NW 315° - 0‘  13 SE by S 146° - 15‘  29 NW by N 326° - 15‘  14 SSE 157° - 30‘  30 NNW 337° - 30‘  15 S by E 168° -45‘  31 N by W 348° - 45'  16 South 180° - 0'

R. Schroeder Geo 20G - Unit 2 - Chapter 3 10 Grid Systems

 Three Types: Alphanumeric, Map (Military) Grid, and Latitude and Longitude  Alphanumeric Grid  Uses Letters and Numbers to identify location/s  Letters are on one side of the map (and often on the side just opposite) while numbers run along the other (one or two) sides  Road maps usually use this design

R. Schroeder Geo 20G - Unit 2 - Chapter 3 11 R. Schroeder Geo 20G - Unit 2 - Chapter 3 12 R. Schroeder Geo 20G - Unit 2 - Chapter 3 13 Application – Alphanumeric Practice

 Use Winkler Map and plot all the businesses  Do all questions on page 30

R. Schroeder Geo 20G - Unit 2 - Chapter 3 14 Grid Systems

 Map Grid (aka Military Grid)  Uses blue grid lines  Used on topographic maps

 Four-Digit Grid Reference  “Read Right Up” (RRU) aka “Through the Door and up the Stairs”

 Vertical Lines are the “easting” (two-digits) – read the grid from left to right of the easting, until the next column begins

 Horizontal Lines are the “northing” (two digits) – read grid from bottom to top of the northing, until the next row above

R. Schroeder Geo 20G - Unit 2 - Chapter 3 15 R. Schroeder Geo 20G - Unit 2 - Chapter 3 16 Application – Four-digit Grids

 Do Question 1 near the top of page 31

R. Schroeder Geo 20G - Unit 2 - Chapter 3 17 Grid Systems

 Six-Digit Grid Reference  RRU  Divide individual four-digit grid squares into 10 even spaces to further specify location within a square  These “10ths” of a grid, provide an additional digit for both the easting and the northing – e.g. If the original grid was 8710, then 875102 would mean that the location is ½ way between columns 87 and 88, and the 102 would indicate that the location is at northing 10 and 2/10ths closer to northing 11

R. Schroeder Geo 20G - Unit 2 - Chapter 3 18 R. Schroeder Geo 20G - Unit 2 - Chapter 3 19 R. Schroeder Geo 20G - Unit 2 - Chapter 3 20 Application – Six-digit Grids and Putting it all together

 Do Question 1 in the middle of Page 31

R. Schroeder Geo 20G - Unit 2 - Chapter 3 21 Application – Six-digit Grids and Putting it all together

 Complete the Brandon Topographic Map Study with your “study buddy”– Pages 33-34

R. Schroeder Geo 20G - Unit 2 - Chapter 3 22 R. Schroeder Geo 20G - Unit 2 - Chapter 3 23 R. Schroeder Geo 20G - Unit 2 - Chapter 3 24 R. Schroeder Geo 20G - Unit 2 - Chapter 3 25 Grid Systems

 Latitude and Longitude – Divides the entire Earth into squares to provide a type of location “address”  0° Latitude and 0° Longitude are in the Gulf of Guinea – Geographic center of the world  Recorded as angles and are based on the center of the Earth

R. Schroeder Geo 20G - Unit 2 - Chapter 3 26 Grid Systems

 Latitude  runs north and south from the  0° to 90° north and 0° to 90° south  Therefore, 180° in total  111km apart  Latitude is always stated first

R. Schroeder Geo 20G - Unit 2 - Chapter 3 27 Grid Systems

 Longitude  Aka “Meridians” of longitude  East and west of the “”  Lines meet at both poles  Are 0° to 180° east and 0° to 180° west of the Prime Meridian

R. Schroeder Geo 20G - Unit 2 - Chapter 3 28 R. Schroeder Geo 20G - Unit 2 - Chapter 3 29 Grid Systems  (66° 33' 38" N)  (23° 26' 22" N)  Equator (0° N a/o 0° S)  (23° 26' 22" S)  (66° 33' 38" S)

R. Schroeder Geo 20G - Unit 2 - Chapter 3 30 Northern By Tauʻolunga - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=927625

https://www.youtube.com/watch?v=enlih8M5DN0 https://www.youtube.com/watch?v=MVDCsXUygEw https://www.youtube.com/watch?v=To-oFiyd6Dc https://www.youtube.com/watch?v=0jHsq36_NTU

R. Schroeder Geo 20G - Unit 2 - Chapter 3 31

By I, Dennis Nilsson, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=3262268 Northern Solstice By Tauʻolunga - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=927625

R. Schroeder Geo 20G - Unit 2 - Chapter 3 32 Northern Solstice By Tauʻolunga - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=927625

R. Schroeder Geo 20G - Unit 2 - Chapter 3 33 Southern Solstice By Tauʻolunga - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=927625

R. Schroeder Geo 20G - Unit 2 - Chapter 3 34 Southern Solstice By Tauʻolunga - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=927625

R. Schroeder Geo 20G - Unit 2 - Chapter 3 35 Application – Latitude and Longitude

 Take a trip around Canada – Pages 35-36

R. Schroeder Geo 20G - Unit 2 - Chapter 3 36 Global Positioning System (GPS)  GPS  Identifies location according to the longitude and latitude grid  Works and night  Uses satellite tracking to determine location  Can be applied to numerous devices to trace activity  Works via “triangulation” in which three satellites are required to measure the output signal of the GPS Unit R. Schroeder Geo 20G - Unit 2 - Chapter 3 37 GPS

 www.howstuffworks.com/gps.htm

R. Schroeder Geo 20G - Unit 2 - Chapter 3 38 GPS

 Trilateration Basics  When people talk about "a GPS," they usually mean a GPS receiver. The Global Positioning System (GPS) is actually a constellation of 27 Earth- orbiting satellites (24 in operation and three extras in case one fails). The U.S. military developed and implemented this satellite network as a military system, but soon opened it up to everybody else.

R. Schroeder Geo 20G - Unit 2 - Chapter 3 39 GPS Each 3-4,000 pound solar powered satellites circles the globe at about 12,000 miles (19,300 km), making two complete rotations every day. The orbits are arranged so that at any time, anywhere on Earth, there are at least four satellites "visible" in the sky.

R. Schroeder Geo 20G - Unit 2 - Chapter 3 40 GPS A GPS receiver's job is to locate four or more satellites, figure out the distance to each, and use this information to deduce its own location. This operation is based on a simple mathematical principle called trilateration. Trilateration in three-dimensional space can be a little tricky, so we'll start with an explanation of simple two-dimensional trilateration.

R. Schroeder Geo 20G - Unit 2 - Chapter 3 41 GPS – 2D Trilateration

 Imagine you are somewhere in the US and you are TOTALLY lost – for whatever reason, you have absolutely no clue where you are.  You ask a friendly local, "Where am I?“  He says, "You are 625 miles from Boise, Idaho."  This is a nice, hard fact, but it is not particularly useful by itself.  You could be anywhere on a circle around Boise that has a radius of 625 miles, like this:

R. Schroeder Geo 20G - Unit 2 - Chapter 3 42 GPS – 2D Trilateration • You ask somebody else where you are, and she says, "You are 690 miles from Minneapolis, Minnesota.“ • Now you're getting somewhere. • If you combine this with the Boise information, you have two circles that intersect. • You now know that you must be at one of these two intersection points, if you are 625 miles from Boise and 690 miles from Minneapolis.

R. Schroeder Geo 20G - Unit 2 - Chapter 3 43 GPS – 2D Trilateration • If a third person tells you that you are 615 miles from Tucson, Arizona, you can eliminate one of the possibilities, because the third circle will only intersect with one of these points. • You now know exactly where you are – Denver, Colorado. • This same concept works in three-dimensional space, as well, but you're dealing with spheres instead of circles.

R. Schroeder Geo 20G - Unit 2 - Chapter 3 44 Dimensions Explained

 4D - https://www.youtube.com/watch?v=MGv8MMi8QO0

 How Earth Moves - https://www.youtube.com/watch?v=IJhgZBn-LHg

R. Schroeder Geo 20G - Unit 2 - Chapter 3 45 Longitude & Time Zones

 Time Zones  There are 24 different time zones  Time Zones exist because the Earth rotates once in 24  360° divided by 24 (separate time Zones) equals time zones that are 15° in width  “Standard Time” is the time that is shared by all locations within the same

R. Schroeder Geo 20G - Unit 2 - Chapter 3 46 Longitude & Time Zones

 Canadian - Sir Sandford Fleming proposed the establishment of time zones  Time zones were adopted in 1884 in Washington D.C.  The “Prime Meridian” runs through the “Royal Observatory” in Greenwich, England  The Prime Meridian bisects its time zone  Prime Meridian, or zero meridian, mean the same thing

R. Schroeder Geo 20G - Unit 2 - Chapter 3 47 CANADIAN TIME ZONES CANADIAN CREATOR

• In 1858, as the chief engineer of the Northern Railway, he proposed the idea of a great rail project stretching to the western coast of Canada. • In order to help the transcontinental train run on time, he devised the concept of Standard Time and splitting the world into 24 time zones. His concept was adopted in 1884. YOU DO THE MATH! • WORLD IS ROUND 360 degrees (longitude)

• There are how many hours in a day? 24

• So how many degrees wide is each time zone? 360 / 24 = ? Degrees 15 degrees Time Zones- A Time Zones-B Time Zones-C Do you see a difference?

Why does Saskatchewan not change their time from summer to winter? The time zone boundary cuts their province in half. Why would northeastern BC not change their time from summer to winter? They do business on both sides of the border, so they stay with one time. SIX – CANADIAN TIME ZONES How do you remember them? • From west to east… Poor Men Can’t Eat Any Nachos P M C E A N A O E A T E W C U N S L F N I T T A O F T R E N U I A A R T N D C I L N I L N C A N D SIX - TIME ZONES

55 What does it look like?

Pacific Mountain Central Eastern Atlantic Newfound - land 12:00pm 1:00pm 2:00 pm 3:00 pm 4:00 pm 4:30 pm Sample 1 Pacific Mountain Central Eastern Atlantic Newfound - land 12:00pm 1:00pm 2:00 pm 3:00 pm 4:00 pm 4:30 pm

If it is 12:00 pm in Vancouver, what time is it in Ottawa? ANSWER: 3:00 pm Sample 2 Pacific Mountain Central Eastern Atlantic Newfound - land 11:00 am 12:00 1:00 2:00 2:30 pm pm pm pm

If it is 11:00 am in Calgary AB, what time is it in St. John’s NFLD?

ANSWER: 2:30 pm Question #1

P M C E A N 2:30 4:30 pm pm Question #2

P M C E A N 11:30 2:30 am pm Question #3-4

P M C E A N 3:00 5:00 am am

Calculate the time in Ottawa. Then add 3 hours.

Answer: 8:00 am Question #5

P M C E A N 8:00 12:00 pm am

Calculate the time in Halifax. Then add 7 hours. Answer: 7:00 am No, they will just go straight to the 8:00 am meeting. Question #6 P M C E A N Ralph Sally Bob

3:00 am 4:00 am 6:00 am

Sun rises on what side of the country? East or West Answer:

Why? Question #7 P M C E A N 3:00 am 5:00 am 10:00 pm 12:00 pm

Convert either the wake up or go to bed time into the other timezone. Do the math! Answer: 19 hours R. Schroeder Geo 20G - Unit 2 - Chapter 3 65 Longitude & Time Zones

 UT stands for  15° on either side of the prime meridian is the center of the neighboring time zone  Earth turns from east to west so… west zones are behind the prime meridian  Time zones have irregular shapes to account for political or awkward boundaries e.g. China or “Newfie” time

R. Schroeder Geo 20G - Unit 2 - Chapter 3 66 R. Schroeder Geo 20G - Unit 2 - Chapter 3 67 R. Schroeder Geo 20G - Unit 2 - Chapter 3 68

 International Date Line  Exactly opposite the prime meridian  Has an irregular shape – not a straight line  At 180° Longitude – in  If crossing to the west, add 1 day  If crossing to the east, lose 1 day

R. Schroeder Geo 20G - Unit 2 - Chapter 3 69 Daylight-Saving Time

 Daylight-saving time is used in the summer season to extend evening hours  In NA, “Spring-forward” on the Sunday in March  In NA, “Fall-back” on the first Sunday in November  Dates may differ elsewhere

R. Schroeder Geo 20G - Unit 2 - Chapter 3 70 Longitude and Time

 Longitude required accurate  John Harrison (Br.) develops the “” – 1735

R. Schroeder Geo 20G - Unit 2 - Chapter 3 71 Longitude and Time & Location

 E.g. #1 Exact local time = 7:00 am, Greenwich time = 12:00 noon (pm)

 Where in the World are you?

R. Schroeder Geo 20G - Unit 2 - Chapter 3 72 Longitude and Time & Location

 E.g. #1 Exact local time = 7:00 am, Greenwich time = 12:00 noon (pm)  Therefore, 5 hours behind = west of the PM  So,… 5 hours X 15° = 75 degrees west of PM  Possible locations:  Arctic, Canada, USA, Cuba, Colombia, Peru, Chile,

R. Schroeder Geo 20G - Unit 2 - Chapter 3 73 180° 165° 150° 135° 120° 105° 90° 75° 60° 45° 30° 15° 0° 15° 30° 45° 60° 75° 90° 105° 120° 135° 150° 165° 180°

172.5° 172.5° 172.5° 172.5°

EAST WEST EAST WEST

R. Schroeder Geo 20G - Unit 2 - Chapter 3 74 Longitude and Time and Location  E.g. #2 Exact local time = 7:00 pm, Greenwich time = 12:00 noon (pm)

 Where in the World are you?

R. Schroeder Geo 20G - Unit 2 - Chapter 3 75 Longitude and Time and Location  E.g. #2 Exact local time = 7:00 pm, Greenwich time = 12:00 noon (pm)  Therefore, 17 hours behind (west of the PM)  But a difference greater than 12 hours means we are west of the International Date Line  Therefore, we are actually 7 hours ahead of GMT (UT)  So,… 7 X 15° = 105 degrees east of PM

R. Schroeder Geo 20G - Unit 2 - Chapter 3 76 180° 165° 150° 135° 120° 105° 90° 75° 60° 45° 30° 15° 0° 15° 30° 45° 60° 75° 90° 105° 120° 135° 150° 165° 180°

172.5° 172.5° 172.5° 172.5° WEST EAST EAST WEST

R. Schroeder Geo 20G - Unit 2 - Chapter 3 77 180° 165° 150° 135° 120° 105° 90° 75° 60° 45° 30° 15° 0° 15° 30° 45° 60° 75° 90° 105° 120° 135° 150° 165° 180°

172.5° 172.5° 172.5° 172.5°

WEST EAST EAST WEST

R. Schroeder Geo 20G - Unit 2 - Chapter 3 78 Longitude and Time

 Possible Locations:  Arctic, , Qazaqstan (former Kazakhstan), Kyrgyzstan, Tajikistan, (Kashmir), Pakistan, India, Antarctica

R. Schroeder Geo 20G - Unit 2 - Chapter 3 79 Application – Chapter Questions

 Do Questions: 1-3, 5-18 – Pages 40-42

R. Schroeder Geo 20G - Unit 2 - Chapter 3 80 R. Schroeder Geo 20G - Unit 2 - Chapter 3 81 R. Schroeder Geo 20G - Unit 2 - Chapter 3 82 R. Schroeder Geo 20G - Unit 2 - Chapter 3 83 Latitude, Longitude and Time  “Coordinates” = described by two numbers – latitude and longitude  They are two angles, measured in degrees, " of arc" and " of arc“  They are denoted by the symbols ( °, ', " )  e.g. 35° 43' 9" means an angle of 35 degrees, 43 minutes and 9 seconds  A degree contains 60 minutes of arc and one contains 60 seconds of arc

R. Schroeder Geo 20G - Unit 2 - Chapter 3 84 Latitude, Longitude, and Time

 Latitude  If the Earth was a transparent sphere  Through the Earth we coulda see its equatorial plane  At the center of the Earth is point O  To determine latitude at surface point P, draw the radius line OP to that point  The elevation angle of that point above the equator is its latitude  Northern latitude if north of the equator  Southern latitude if south of the equator

R. Schroeder Geo 20G - Unit 2 - Chapter 3 85 Latitude, Longitude and Time  Longitude  Lines of constant longitude ("meridians") that extend from pole to pole  All meridians cross the equator  Since the equator is a circle, it can be divided into 360 degrees  The longitude of a point is the marked value of that division where its meridian meets the equator.  The value of longitude lines or "meridians“ depends on where we begin to count – zero longitude

R. Schroeder Geo 20G - Unit 2 - Chapter 3 86 Latitude, Longitude and Time  Meridian is Latin for meri, a variant of “medius” (middle) and diem (day)  The word once meant “noon”  Times before noon were “ante meridian”, while times after were “post meridian”  The terms a.m. and p.m. Are used today  At noon, the Sun was “passing meridian”  All points on the same line of longitude experience noon (and any other ) at the same time, and are on the same “meridian line”

R. Schroeder Geo 20G - Unit 2 - Chapter 3 87 Latitude, Longitude and Time

 For historical reasons, the meridian passes through the old Royal Astronomical Observatory in Greenwich, England  It is called “zero longitude”  Greenwich is located at the eastern edge of London

R. Schroeder Geo 20G - Unit 2 - Chapter 3 88 Latitude, Longitude and Time

 The public museum has a band made of brass that stretches across its yard to mark the “prime meridian”  Here, you can straddle it – with one foot in the eastern and the other in the western hemispheres

R. Schroeder Geo 20G - Unit 2 - Chapter 3 89 It’s about Time! – Local and Universal  Two important concepts re: latitude and longitude are Local time (LT) and Universal time (UT)  Local time is a measure of the position of the Sun relative to a location  At 12 noon local time the Sun passes to our south and is furthest from the horizon ()  It rises about 6 am and sets around 6 pm  Local time is what we use to regulate ourselves locally including: school times, work times, meals and sleep

R. Schroeder Geo 20G - Unit 2 - Chapter 3 90 It’s about Time! – Local and Universal  However, to time an astronomical event – e.g. the time when the 1987 supernova was first detected – we needed a single, agreed upon , that marks time world-wide and is not tied to our local times  Universal time (UT) is the local time in Greenwich at the zero meridian

R. Schroeder Geo 20G - Unit 2 - Chapter 3 91 Local Time and Time Zones  are measured from zero to 180° east and zero to 180° west (or -180°)  The 180-degree longitudes, are the same line - in the middle of the Pacific Ocean  As the Earth rotates around its axis, at any one line of longitude – "the noon meridian“ – faces the Sun  At that moment, it will be noon everywhere on it  After 24 hours the Earth will have fully rotated with respect to the Sun  The same meridian faces noon again  So,… each hour the Earth rotates by 360/24 = 15 degrees

R. Schroeder Geo 20G - Unit 2 - Chapter 3 92 Local Time ! – Local and Universal  When it is 12 noon (LT) – 15° to the east it is 1 p.m. because that is where the sun was one hour ago  On the other hand, 15° to the west the time is 11 a.m. because in one hour that meridian will face the Sun and experience noon  When it is 12 noon where you are, 15° to the east the time is 1 p.m., because that is the meridian that faced the Sun an hour ago. On the other hand, 15° to the west the time is 11 a.m., because in one hour, that meridian will face the Sun and experience noon.

R. Schroeder Geo 20G - Unit 2 - Chapter 3 93 Local Time ! – Local and Universal  In the middle of the 19th communities across the US defined its own local time, by determining when the Sun (on average), reached the farthest point from the horizon (for that day) at 12 o’clock.  However, travelers crossing the US by train had to re- adjust their at every city, and long distance telegraph operators had to coordinate their times.  The confusion led railroad companies to adopt time zones, broad strips (about 15° wide) which observed the same local time, differing by 1 hour from neighboring zones, and the system was adopted by the nation as a whole.

R. Schroeder Geo 20G - Unit 2 - Chapter 3 94 Local Time ! – Local and Universal  The continental US has 4 main time zones-- eastern, central, mountain and western, plus several more for , the Aleut islands and Hawaii. Canadian provinces east of Maine observe Atlantic time; you may find those zones outlined in your telephone book, on the map giving area codes. Other countries of the world have their own time zones; only Saudi Arabia uses local times, because of religious considerations.

R. Schroeder Geo 20G - Unit 2 - Chapter 3 95 Local Time ! – Local and Universal  In addition, the clock is generally shifted one hour forward between April and October. This "" allows people to take advantage of earlier sunrises, without shifting their working hours. By rising earlier and retiring sooner, you make better use of the sunlight of the early morning, and you can enjoy sunlight one hour longer in late afternoon.

R. Schroeder Geo 20G - Unit 2 - Chapter 3 96 The International Date Line and Universal Time (UT)  Suppose it is noon where you are and you proceed west at an instant rate of travel  Fifteen degrees to the west the time is 11 a.m., 30 degrees to the west, 10 a.m., 45 degrees - 9 a.m. and so on  Keeping this up, 180 degrees away one should reach midnight, and still further west, it is the previous day. This way, by the time we have covered 360 degrees and have come back to where we are, the time should be noon again - yesterday noon  Hey! - wait just one minute! You cannot travel from today to the same time yesterday!

R. Schroeder Geo 20G - Unit 2 - Chapter 3 97 The International Date Line and Universal Time (UT)  The trouble is that longitude only determines the hour of the day - not the date, which is determined separately.  To avoid this problem, the International Date Line has been established – mostly following the 180th meridian  Common agreement states that whenever we cross it the date advances one day (going west) or goes back one day (going east)  The IDL passes the Bering Strait between Alaska and Siberia, which means they have different dates - but for most of its course it runs in mid-ocean and does not inconvenience local time keeping

R. Schroeder Geo 20G - Unit 2 - Chapter 3 98 The International Date Line and Universal Time (UT)  Note: Astronomers, astronauts and those working with satellite data may need a time schedule which is the same everywhere, not tied to a locality or time zone.  The , the astronomical time at Greenwich (averaged over the ) is generally used here. It is now called Universal Time (UT).

R. Schroeder Geo 20G - Unit 2 - Chapter 3 99 Celestial Globe

R. Schroeder Geo 20G - Unit 2 - Chapter 3 100 Right Ascension and Declination

 The globe of the heavens resembles the globe of the Earth, and positions on it are marked in a similar way, by a network of meridians stretching from pole to pole and of lines of latitude perpendicular to them, circling the sky.  To study some particular galaxy, an astronomer directs the telescope to its coordinates.

R. Schroeder Geo 20G - Unit 2 - Chapter 3 101 Right Ascension and Declination  On Earth, the equator is divided into 360 degrees, with the zero meridian passing Greenwich and with the longitude angle φ measured east or west of Greenwich, depending on where the corresponding meridian meets the equator.  In the sky, the equator is also divided into 360 degrees, but the count begins at one of the two points where the equator cuts the ecliptic - the one which the Sun reaches around March 21.  It is called the vernal ("vernal" means related to spring) or sometimes the first point in Aries, because in ancient times, when first observed by the Greeks, it was in the zodiac constellation of Aries, the ram - It has since moved.

R. Schroeder Geo 20G - Unit 2 - Chapter 3 102 Right Ascension and Declination  The celestial globe uses terms and notations that differ from those of the globe of the Earth. Meridians are marked by the angle α (alpha, Greek A), called right ascension, not longitude.  It is measured from the vernal equinox, but only eastward, and instead of going from 0 to 360 degrees, it is specified in hours and other divisions of time, each hour equal to 15 degrees.  Similarly, where on Earth latitude goes from 90° north to 90° south (or -90°), astronomers prefer the co-latitude, the angle from the polar axis, equal to 0° at the , 90° on the equator, and 180° at the .  It is called declination and is denoted by the letter δ (delta, Greek small D).  The two angles (α, δ), used in specifying the position of a star are jointly called its celestial coordinates.

R. Schroeder Geo 20G - Unit 2 - Chapter 3 103