USING UTM, MGRS

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USING UTM, MGRS USNG

• Monica Spicker
• Some slides adapted from Harry Frank
• 2008

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Objectives

• Understanding UTM system
• Finding coordinates of a point
• Plotting a point

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Universal Transverse Mercator (UTM)

• NATO system
• Metric units (meters)
• World is split into 60, 6º degree zones
• Spokane area is Zone 11N
• Distorted above North 84º, and South 80º, not
  applied above these latitudes.
• Smallest grid unit on USGS 124000 maps is 1 km.
  May be different on different scale maps!
• Coordinates get larger going east (easting) from
  the zone meridian and larger going north
  (northing) from the equator.

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Identifying the grid

• Some USGS sheets have the grid drawn
• Older Sheets show blue tick marks and numbers on
  the border.
• Other maps have various ways to show the grid.
• Usually written like exponents
• Margin numbers are whole kilometers north of
  equator and east of the zone meridian.

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Identifying the grid
466
467
(Easting)
5157
5157
Map
5156
5156
(Northing)
466
467
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Determining Coordinates Easting
Find the nearest smaller coordinate to the LEFT
(W) of your point
465
466
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Determining Coordinates Easting
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Determining Coordinates Easting
Divide the distance between the coordinate to
the left of your point and the coordinate to the
right of your point into tenths
3 tenths
This is hundreds of meters
465
466
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Determining Coordinates Easting
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Determining Coordinates Northing
Find the nearest coordinate below (S) of your
point
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Determining Coordinates Northing
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Determining Coordinates Northing
Count or estimate the number of tenths from the
coordinate BELOW your point TO the corner.
This is hundreds of meters
8 Tenths
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Determining Coordinates Northing
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Final Coordinates of

• 465300E 5165800N
• But we can go finer, if we use a template

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Using a Template

• Must match map scale!
• Can estimate how far into box on a scale of 1 to
  10 to find nearest ten meters.

5165820N
465360E
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Another Way to Use the Template

• Put the 0 corner of the template on the point.
• Read where the block margin hits the template
  scales.

465360E
5165820N
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Determining Coordinates
489520E
5315440N
Start here. 489000E, 5315000N
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Practice Exercises
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Plotting Points

• Underline the last 3 digits of each coordinate.
• Whats not underlined are the margin coordinates.
• Example 490150E 5315325N

Use template to determine position within the
kilometer box.
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Plotting 490120E 5315340N
490120E
5315340N
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Practice Exercises
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MGRS and USNG

• Military Grid Reference System
• US National Grid System
• USNG and MGRS are identical
• Based on UTM
• Default datum is NAD83
• Includes
• UTM zone (number and letter)
• A two letter grid designator that replaces the
  smaller written UTM number in the margin
• only the ending 5 numbers. More can be
  truncated, if you are not going down to single
  meters.
• Most GPS support MGRS.
• Most commercial maps do NOT.

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Example

• in UTM 11T 490150E 5315325N
• in MGRS
• 11T MP 90150E 15325N NAD83 1 meter
• 11T MP 9015E 1532N NAD83 nearest 10 meters
• 11T MP 901E 153N NAD83 nearest 100
  meters