Santiam Pass Ski Patrol

Lat and Long

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Longitude – meridian – great circle – +/-180° E/W. Size changes depending on latitude.

Latitude – parallel – slices – 0-90° N or S. One minute is one nautical mile or 6,076′.

Determine your position using latitude and longitude.

Datum

Format

On the printed map – use a ruler to determine coordinates on a printed map with decimal degree markings.

  1. Construct pencil lines surrounding the target location
  2. Measure this into 10ths.
  3. Write the coordinates

Using your gps

How to share a coordinate on paper, by text/email, and by radio

Reference

https://fws.gov/r7/nwr/Realty/data/LandMappers/Public/Help/HTML/R7-Public-Land-Mapper-Help.html?Datumsprojectionsandcoordinatesy.html

https://www.maptools.com/tutorials/lat_lon/formats

Lat/Long “trivia”

  • At the equator One degree of latitude equals approximately 364,000 feet (~69.17 miles), one minute equals 6,068 feet (1.15 miles), and one-second equals 101 feet.
  • At 45° (N) latitude One degree of latitude is still about 69 miles, but a degree of longitude is only about 49 miles.
  • How close am I with decimal degrees? How many decimal places do I need to find you?
    • A degree of latitude is about 69 miles or 364,320 feet.
      • A 10th of a degree is 36,432 feet – 6.9 miles. 45.1°
      • A 100th of a degree is 3,642 ‘. 45.12°
      • A 1,000th of a degree is 364′. 45.123°
      • A 10,000th of a degree is 36′. 45.1234°
      • A 100,000th of a degree is 4′. 45.12345°
    • At 45° N a degree of longitude is about 49 miles or 258,720 feet.
      • A 10th of a degree is 25,872 feet – 4.9 miles. -121.1°
      • A 100th of a degree is 2,587 feet. -121.12°
      • A 1,000th of a degree is 259 feet. -121.123°
      • A 10,000th of a degree is 26′. -121.1234°
      • A 100,000th of a degree is 3′. -121.12345°

  • https://www.usgs.gov/faqs/how-much-distance-does-a-degree-minute-and-second-cover-your-maps
  • https://www.johndcook.com/how_big_is_a_degree.html
  • https://www.nwcg.gov/course/ffm/location/610-latitude-longitude
  • https://oceanservice.noaa.gov/facts/longitude.html#:~:text=At%20the%20equator%2C%20longitude%20lines,poles)%2C%20it%20reaches%20zero.
  • https://www.redrockcanyonlv.org/wp-content/uploads/topographic-map-activity-6-miles-for-a-degree-of-longitude-072820.pdf
  • https://www.nhc.noaa.gov/gccalc.shtml

I forgot where I got this image

How many digits do you use?

https://www.xkcd.com/2170/

Datum

MapTools article

MapTools Tutorials on Coordinate Systems

MGRS – military gird reference system

USNG – United States National Grid – On MapTools