Lab two 2012 fall

Earth and Sun Relationships and Topographic Maps Lab Two

The first days of the seasons are solstices and equinoxes. These are key periods within Earth-Sun Relationships.

Subsolar Point

• This is the place on Earth where the suns’ angle is 90° and solar radiation strikes the surface most directly.– Earth’s axial tilt and it’s orbit cause the

subsolar point to move between 23.5° north and 23.5° south over the course of a year.

Equinox and Solstice Conditions

• Equinox-when the subsolar point is at the equator and all locations on the earth experience equal hours of daylight and darkness

• Solstice-when the sun angle is at 90° at either end of the tropic boundaries.– Topic of Cancer 23.5° N– Tropic of Capricorn 23.5° S

Analemma

WHAT IS AN ANALEMMA?

An analemma is a natural pattern traced out annually in the sky by the Sun.

Analema• The analema is

the geographers tool used to locate the subsolar point, or the point on Earth’s surface where the sun is directly overhead at noon.

• The analema can be used for any place on earth, and any day of the year.

• Due to the earth's tilt on its axis (23.5°) and its elliptical orbit around the sun, the relative location of the sun above the horizon is not constant from day to day when observed at the same time on each day.

http://en.wikipedia.org/wiki/Analema

Using the Analemma

• The analemma can be used to determine the sun’s subsolar point for any given date.– For example: find October

10th on the analemma, follow that point on the analemma out to the right edge of the grid and notice that it is at 6° south.

• This means that on October 10th, the subsolar point is 6° south, in other words 6° south is the place on the Earth where the sun’s rays are striking at a 90° angle.

Using the Analemma

• The analemma is also uses to determine what time the sun reaches its zenith, or what time noon is.

• Again, look at October 10th. Follow that point to the top of the grid.

• Notice that for October 10th, the sun’s zenith is 12 minutes fast.

• This means that noon will be 12 minutes early on October 10th, so the sun will reach its zenith at 11:48 AM.

Using the Analemma

• The analemma can also be used to determine the angle that the sun is hitting ANY location on earth for any given date.

Using the Analemma to Calculate the Sun’s Declination or Angle of Incidence1. Where are you calculating from? What is your

location?2. Second you must determine the subsolar point for that

date.3. If your two locations (your location and the subsolar

point) are in the same hemisphere, you will minus those two latitudes.

4. If your two locations are in opposite hemispheres, then you will add those two latitudes together.

5. The end result is your arc distance.6. Once you have determined your arc distance, you

simply minus it by 90° in order to calculate the solar altitude at your location.

Example

• Use the analemma to find the sun’s declination (angle) for Los Angeles (34°N) on July 16.– 1. Where: 34°N– 2. Subsolar point July 16 = 21°N– 3. Hemisphere: SAME!– 4. 34° - 21° = 13°– 5. 13° is your arc distance– 6. 90 – 13 = 77°

• SO THAT MEANS THE SUN’S DECLINATION (ANGLE) IN LOS ANGELES ON JULY 16TH IS 77°

Example

• Use the analemma to find the sun’s declination (angle) for Los Angeles (34°N) on November 20.– 1. Where: 34°N– 2. Subsolar point Nov. 20 = 20°S– 3. Hemisphere: OPPOSITE– 4. 34° + 20° = 54°– 5. 54° is your arc distance– 6. 90 – 54 = 36°

• SO THAT MEANS THE SUN’S DECLINATION (ANGLE) IN LOS ANGELES ON November 20TH IS 36°

Done at 8:30 AM Eastern Time

http://vrum.chat.ru/Photo/Astro/analema.htmIt shows position of the Sun on the sky in the same time of a day during one year. Analemma - a trace of the annual movement of the Sun on the sky - is well known among experts of sun-dials and old Earth's globes as a diagram of change of seasons and an equation of time. Between August 30th 1998 and August 19th 1999 I have photographed the Sun 36 times on a single frame of 60-mm film. The pictures were taken exactly at 5:45 UT (Universal time) of every tenth day.

Topographic Maps• Topographic maps are large-

scale maps that use contour lines to portray the elevation and shape of the topography.

• Topographic maps show and name both natural and human-made features.

• The US Geological Survey (USGS) is the principle government agency that provides topographic maps for the United States.– USGS topographic maps

cover the entire United States at several different scales.

Computing Distances with Fractional Scales

• To determine distances represented on a map by using the fractional scale:

1. Use a ruler to measure the distance on the map in inches (or centimeters). This is the measured distance.

2. Multiply the measured distance by the map’s fractional scale denominator. This will give you the actual distance in inches (or centimeters).

3. To convert your actual distance in inches (or centimeters) to other units, use the following formulas:

Measuring Road Distance

• Look at the map scale. – In the lower left or right

corner there will be a small graph that shows a unit that corresponds to the distance on the map.

– For example, if the scale is one inch long and is labeled five miles, then one inch on the map is equal to five miles on the ground.

– Hold a ruler next to it and measure it.

• Lay one end of string on one end of the road so that it follows every curve as accurately as possible. If you don’t have a string, tear a strip of paper and bend it along the curves of the road.

• Hold the string or paper so that you pinch it where the road begins and ends.

• Measure it with a ruler.

• Multiply the length of the string by the scale.

• For example, if the string was 7 inches long and each inch represents 5 miles, the road is approximately 35 miles long.

• Look for small sequential numbers next to the road on the map.

• These numbers indicate miles.

• On detailed maps, there may be a marker every mile, but on less detailed maps it could be every 10 miles, or some other scale.

• Find the number at the beginning of the section of the road you’re driving and the number at the end.

• If the numbers only show every several miles, estimate the location.

• For example, if the road ends between 50 and 60 miles, call it 55.

• Subtract the lower number from the higher number to get the total distance.

• For example, if the road starts a the 25 mile marker and ends at the 55 mile marker, the total is 55 – 25 = 30 miles.

How to Use a Compass

• A compass can help you navigate a forest, a sea, or even a city. If you have a compass and a map, read on for instructions on how to figure out where you’re currently heading, where you need to head, or where you already are.

http://www.wikihow.com/Use-a-Compass

Understand the basic layout of compass.

• We’ll use a baseplate compass as an example, but the same principles apply with other models.

Figure Out Where You’re Headed

1. Place the compass flat on your palm and your palm in front of your chest. This is the proper compass stance.

2. Move the compass until the direction of travel arrow is pointing in the direction you wish to head. Unless you’re heading north, the magnetic needle will spin off to one side.

3. Twist the degree dial until the orienting arrow lines up with the north end of the magnetic needle. Once they are aligned, this will tell you where your direction of travel arrow is pointing.

4. Take off local magnetic variation by twisting the degree dial. This magnetic variation (i.e. the difference between magnetic and true north) is known as declination and is due to the fact that Earth’s magnetic field lines are constantly moving relative to the actual North Pole. Since our maps are all based off of true north, you must adjust the compass to compensate. There are many web resources you can use to determine this for your area.

5. See where the direction of travel arrow lines up with the degree dial. This will tell you which direction you’re heading. For example, if the arrow is between the S and the W, you’re heading southwest.

6. Transpose the direction of travel onto your map. Place your map on a horizontal surface, then place the compass on the map so that the orienting arrow points to true north on the map. Then, slide your compass around so that its edge passes through your current position (but its orienting arrow continues to point north).

7. Draw a line along the compass' edge and through your current position. If you maintain this bearing, your path from your current position will be along the line you just drew on your map.

Figure Out Where You’re Headed

8. Continue moving in this direction. To do so, simply hold the compass in the proper stance, turn your body until the north end of the magnetic needle once again aligns with the orienting needle, and follow the direction of travel arrow. Check your compass as often as you need to, but be sure not to accidentally twist the degree dial from its current position.– To accurately follow the direction of travel arrow, look down at the

arrow, then focus on a distant object to which it points (ex. tree, telephone pole, etc.) and use this as a guide; however, don’t focus on anything too distant (ex. mountain), as huge objects aren’t precise enough to navigate by accurately. Once you reach each guide point, use your compass to find another.

– If visibility is limited and you cannot see any distant objects, use another member of your walking party (if applicable). Stand still, then ask them to walk away from you in the direction indicated by the direction of travel arrow. Call out to them to correct their direction as they walk. When they approach the edge of visibility, ask them to wait until you catch up. Repeat as necessary.

Figure Out Where You’re Headed

• Place the map on a horizontal surface and place your compass on the map. The magnetic needle won’t work properly if held at an angle.

• Using the edge of the compass as a ruler, place it so that it creates a line between your current position and where you intend to go. You may also want to draw this line on your map for future reference.

• Rotate the degree dial until the orienting arrow points to true north on the map. This will also align the compass’s orienting lines with the map’s north-south lines. Once the degree dial is in place, put the map away.

• Take off local magnetic variation by twisting the degree dial.

Figure Out Which Way You Need to Head

Figure Out Which Way You Need to Head

• Hold the compass horizontally in front of you with the direction of travel arrow pointing away from you. Eventually, you’ll use the direction of travel arrow to guide you to your destination.

• Turn your body until the north end of the magnetic needle aligns with the orienting needle. You are now properly oriented toward your mapped destination.

• Follow the direction of travel arrow. Look down at the arrow, then focus on a distant object to which it points (ex. tree, telephone pole, etc.) and use this as a guide; however, don’t focus on anything too distant (ex. mountain), as huge objects aren’t precise enough to navigate by accurately. Once you reach each guide point, use your compass to find another.

– If visibility is limited and you cannot see any distant objects, use another member of your walking party (if applicable). Stand still, then ask them to walk away from you in the direction indicated by the direction of travel arrow. Call out to them to correct their direction as they walk. When they approach the edge of visibility, ask them to wait until you catch up. Repeat as necessary.

Figure Out Your Current Position Via Landmarks

• Choose 3 prominent landmarks that you can both see and find on your map. These should be as widely spread around your field of view as possible.

• Aim the compass' direction of travel arrow at the first landmark. Unless the landmark is north of you, the magnetic needle will spin off to one side.

• Twist the degree dial until the orienting arrow lines up with the north end of the magnetic needle. Once they are aligned, this will tell you where your direction of travel arrow is pointing.

• Take off local magnetic variation] by twisting the degree dial.

Figure Out Your Current Position Via Landmarks

• See where the direction of travel arrow lines up with the degree dial. This will tell you which direction you’re heading. For example, if the arrow is between the S and the W, you’re heading southwest.

• Transpose the direction of the landmark onto your map. Place your map on a horizontal surface and then place the compass on the map so that the orienting arrow points to true north on the map. Then, slide your compass around so that its edge passes through the landmark on the map (but its orienting arrow continues to point north).

• Draw a line along the compass' edge and through your approximate position. This is the first of three lines you will draw to triangulate your position.

• Repeat steps 2 through 7 for the other two landmarks. When you’re done, you will have three lines that form a triangle on your map. Your position is inside this triangle, the size of which depends on the accuracy of your bearings. (More accurate bearings reduce the size of the triangle and, with lots of practice, you may get the lines to intersect at one point.)

Compass Tips• The compass's tips are usually marked with either red or black tips. The northern tip is usually

marked with an N, but if for some reason it isn’t, try to figure out which one is north by orienting your compass to the north or south in relation to the sun.

• For maximum accuracy, hold the compass up to your eye and look down the direction of travel arrow to find landmarks, guide points, etc.

• You can also hold the compass square to your body by holding the sides of the baseplate between both hands (making L shapes with your thumbs) and keeping your elbows against your sides. Stand facing your objective, look straight ahead, and square yourself with the object by which you are taking your bearing. The imaginary line extending out from your body will travel through your compass along the direction of travel arrow. You can even rest your thumbs (against which the end of the compass is resting) against your stomach to steady your hold. Just be sure you aren't wearing a big steel belt buckle or some other magnetic material close to the compass when doing this.

• Magnetic (as opposed to true) north is currently around northern Canada, which means that magnetic deviation changes depending on where you are in the world. Many compasses have a means by which you can adjust for magnetic declination: either on the fly (by using a declination scale inscribed on the baseplate) or semi-permanently (by adjusting the compass housing within the baseplate. Read your instruction manual for instructions geared toward your compass.

• It's often easier to use features in your immediate vicinity to locate your precise position. Triangulation is more useful if you're really lost or you are in a barren, featureless area.

• Trust your compass: 99.9% of the time it is giving you the correct direction. Many landscapes look similar, so again, TRUST YOUR COMPASS.

GPS Technology

By Tomarr Sanders

What is GPS Technology?

The Global Positioning System (GPS) is a satellite-based navigation system made up of a

network of 24 satellites placed into orbit by the U.S. Department of Defense. GPS was

originally intended for military applications, but in the 1980s, the government made the

system available for civilian use. GPS works in any weather conditions, anywhere in the

world, 24 hours a day. There are no subscription fees or setup charges to use GPS.

GPS Development   GPS or the Global Positioning System was invented by the U.S. Department of Defense (D.O.D) and Ivan Getting, at the cost of twelve billion taxpayer dollars. The Global Positioning System is a satellite navigational system, predominantly designed for navigation. GPS is now gaining prominence as a timing tool.

GPS Locations

GPS Devices/Receiver.

A GPS receiver's job is to locate four or more of these satellites, figure out the distanc e to each, and use this information to deduce its own location. This operation is based on a simple mathematical principle called trilateration.

GPS Devices/Receiver.The use of Global Position System (GPS) has become quite diverse from automobiles, mobile phones, tourist facilities, city maps, and even pet collars. GPS works through a network (often called constellation) of 27 satellites that move around the Earth in geo synchronous orbit. These satellites exchange relative data to fix the position of one particular object on the surface. Similar to the Internet, the technology was original implemented for military use in order to help precise control of troops as well as getting accurate information about enemy troops and armament placement and movement. And like the Internet it was soon the commercial use that would dominate global reliance on GPS.

GPS Devices/Receiver.WHAT DOES A GPS RECEIVER DO? A GPS receiver (GPSR) is a RECEIVER of radio signals and it does not transmit anything to anywhere. The GPSR provides, as its primary function, the ability to locate your CURRENT POSITION anywhere on the planet. Normally, it can do this to an accuracy of perhaps 6 to 8 meters with 95% certainty depending on obstructions to the sky. Some models also have built in (or up loadable) maps to allow you to view on the GPSr's screen your current position. Also selected models will receive WAAS corrections, resulting in accuracies of 3 to 4m 95% of the time as shown PROVIDED your are in the clear. WAAS is more susceptible to tree cover than non-WAAS. 

What can GPS do?ESSENTIAL MAP READING SKILLSCreating GPS technology that is readily available; our younger generation is losing the essential ability to read maps. With any computer devise, all can have problems that may cause the devise to malfunction or break. If you are someone who relies heavily on a devise that tells you which route to take and it happens to malfunction, you may not a map available as an alternative.

Advantages / Disadvantages Advantages:-fast speed-leads u in right direction-helps improve mapping skills-makes navigation easier-has panic buttons built in-you can be found easier if in danger or in accident-plugs into your car cigarette lighter

Disadvantages:-cellular devices can track other cellular device users- not very cheap-people focus on GPS more than road = accidents-should be used as backup map but used as 1st resource-needs good care and handling-external power-needs batteries (handheld ones)If anyone has found more information please add on!!!!!!

Sources Cited.www.Goolgle.comwww.Garmin.com

www.gpsinformation.net