# Maps, Charts and Coordinate Systems

## Presentation on theme: "Maps, Charts and Coordinate Systems"— Presentation transcript:

Maps, Charts and Coordinate Systems

Maps A map is a two-dimensional representation of the Earth.
Maps incorporate projections and datums for accuracy. All maps distort the earth to some extent. When using a map with a GPS receiver, the datum and coordinate system must match.

Map and Chart Scales DeLorme Gazetteer - 1:65,000 to 1:400, ” = 1.0 miles to 6.3 miles (Scale varies by state) CBSAR uses this

Projecting a Sphere Onto a Plane

Types of Projections Cylindrical Projection Conical Projection
Plane Projection

Types of Projections Accurate Shapes Accurate Sizes Exaggerated Sizes
Distorted Shapes

Types of Projections

Projections and Datums

Coordinate Systems All coordinate systems reference some particular set of numbers for the size and shape of the earth (the datum). Coordinates designate locations within a spatial reference system (datum). There are two types of global coordinate systems: Angular Coordinates Rectangular (Cartesian) Coordinates Latitude and longitude, and Universal Transverse Mercator are two global coordinate systems used by GPS. Many other coordinate systems exist worldwide.

Latitude & Longitude A spherical coordinate system that is unprojected. Angular coordinates are perfectly suited to the spherical surface of the earth. Coordinates are expressed in degrees, minutes and seconds (and variations of that). Position coordinates are based on an angular distance from a known reference point. The intersection of the Prime Meridian and Equator. Lat/long is the predominant coordinate system used for nautical and aeronautical navigation.

Latitude & Longitude

Latitude & Longitude Prime Meridian (Longitude) Equator (Latitude)
10º S Equator (Latitude) Point of Origin

Latitude Latitude is comprised of parallels, which are circles around the earth paralleling the Equator. Parallels are designated by their angle north or south of the Equator. The Equator is 0º latitude, and the North and South Poles are at 90º angles from the Equator. The linear distance between parallel lines never changes, regardless of their position on earth. 1 minute of latitude = 1 nautical mile = 6076 feet 1 degree of latitude = 60 nautical miles = 69 statute miles

Parallels of Latitude 10º

Crested Butte is 38oN of the Equator
Parallels of Latitude 20º N 10º N 10º 690 statute miles 0º N 690 statute miles 10º 10º S 10º 690 statute miles Crested Butte is 38oN of the Equator

Longitude Longitude is comprised of meridians that form one-half of a circle. Meridians are designated by their angle west or east of the Prime Meridian. The Prime Meridian is designated 0º and extends from the North Pole to the South Pole through Greenwich, England. Meridians are angled, and do not parallel each other. The linear distance between one degree of longitude at the Equator is approximately 69 statute miles. The linear distance between one degree of longitude at the Arctic Circle is about 26 statute miles.

Meridians of Longitude
10º

Meridians of Longitude
10º 240 mi 10º 460 miles Equator 10º 690 miles 120º W 110º W

Determining Latitude & Longitude
Prime Meridian (0º) 30ºN, 50ºW 50º W 30º N Equator (0º)

Lat/Lon Coordinates Different coordinates representing the same location: hddd0 mm’ ss.s”: N ’ 55.8” X W ’ 14.1” (55.8” / 60 = .93’) Degrees Minutes Seconds Coordinate Systems Think of coordinate systems as just another way of expressing a geographic location. For example, the intersection of Fifth Avenue and Main Street can also be described as “the corner where Floyd’s Barber Shop is located.” These are merely two different ways of describing the same location. Similarly, that same geographic location can be identified using a variety of geographic coordinates, such as the UTM coordinates 17S E N. Or, using latitude and longitude Floyd’s Barber Shop might be: N 40° 23’ 45” W 98° 12’ 06” (expressed in degrees, minutes and seconds). As for latitude and longitude, there are three to describe coordinates: degrees, minutes and seconds: N 40° 23’ 45” W 98° 12’ 06” degrees and decimal minutes: N 40° 23.75’ W 98° 12.1’ decimal degrees: N ° W ° Each of the above sets of coordinates represent the same location. To convert seconds to decimal minutes, divide the seconds by 60 to get decimal minutes. To convert decimal minutes to decimal degrees, divide the decimal minutes only by 60 to get decimal degrees. Universal Transverse Mercator (UTM) is different than latitude and longitude, so it looks and behaves differently. But it is still just another way of expressing the location of a point on a map or on the ground. The “UPS” included with UTM stands for “Universal Polar Stereographic”, a coordinate system that is a variation of UTM that is used in the north and south polar regions in place of UTM. hddd0 mm.mmm’: N ’ X W ’ (40.93’ / 60 = ) Degrees Decimal Minutes hddd.ddddd0 : N X W Decimal Degrees

Exercise Please do this quick exercise and then go to the next slide to see the answer.

The answer is on the next slide.
Here is an actual map. Write the latitude point for the top of Round Mountain in both decimal and second format on a piece of paper. The answer is on the next slide.

N 38o 46.8’ N 38o 46’48”

Team Computer The previous exercise was made on the team computer.
We added grids to make it easier for you. The normal 2.5 grid map is more difficult to use to estimate positions. Following is a map similar to those found in the cache.

Latitude and Longitude

Latitude and Longitude
With computer & software we can add grids to make it easier We can plot exact locations or eyeball it Let’s practice Go to next slide

Latitude and Longitude
With computer & software we can add grids to make it easier We can plot exact locations or eyeball it Let’s practice Write down the Lat. & Long. of the intersection of the two roads. Only do it to 1/10 of a minute accuracy. e.g. N 38o 53.1’

Latitude and Longitude
With computer & software we can add grids to make it easier We can plot exact locations or eyeball it Let’s practice Answer N 38o 53.4’ W 106o 58.4’ If you were within .1’ of the above answer, you did great!

Reporting Lat/Lon Coordinates
Do not read off just the numbers – use the words degrees, minutes and seconds as appropriate Read 104º 54.9’ as one hundred four degrees fifty four point (or decimal) nine minutes Read 104º 54’ 55” as one hundred four degrees fifty four minutes fifty five seconds

Latitude and Longitude

Determining Latitude 17’ 30” Latitude of red square = 2.5 min
LONGITUDE 7.5 min. scale 1:24,000 17’ 30” Latitude of red square = 44º 16’ 48” 2.5 min 44º 15’ 00” Latitude Lines (Parallels)

Determining Longitude
A T I U D E LONGITUDE 7.5 min. scale 1:24,000 Longitude of red square = 115º 19’ 00” Longitude Lines (Meridians) 2.5 min 20’ 115º 17’ 30”

End of Lat. & Long. Section
Next section will be UTM Universal Transverse Mercator