Compass Use

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Compass Use Land Measuring
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Terms to know

• MAGNETIC DECLINATION the angular variation of
  magnetic north from true north declination may
  be either east or west
• AGRONIC LINE the line of zero declination (no
  correction needed)
• ISOGONS lines having equal declination

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• BEARINGS horizontal angles that are referenced
  to one of the quadrants of the compass (NE, SE,
  SW, NW)
• AZIMUTHS comparable angles measured clockwise
  from due north, thus reading 0o to 360o
• SURVEYING the art of making field measurements
  that are used to determine the lengths and
  directions of lines on the earths surface

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• PLANE SURVEYING the measurement of distances
  angles, the location of boundaries and the
  estimation of area this is what a forester is
  concerned with

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Measurement lengths to know

• One chain 66 feet
• One chain 100 links
• One link 7.92 inches
• One acre 10 square chains
• One acre 43, 560 square feet
• One mile 5,280 feet

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How to use the compass

• Make sure
• The compass is perfectly level
• The sights are properly aligned
• The needle swings freely
• All readings are taken from the North End of the
  needle.

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Area formulas to know

• Area of a square
• Formula (S)2
• Area of a rectangle
• Formula L x W
• Area of a triangle
• Formula 1/2BH

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• The main formula that we will use is
• Heros formula. This is used to calculate the
  area of a triangle when you know the three sides.
• Formula
• Areasquare root of s(s-a)(s-b)(s-c)
• s a b c
• 2

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Legal Land Descriptions

• History
• Ordinance of 1785 established the rectangular
  surveying system as developed by Thomas Jefferson
• 13 original colonies, Ohio, Tennessee Kentucky
  were surveyed with metes bounds

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• Metes bounds system was not accurate since it
  followed natural land features such as ridges,
  streams, etc.
• States west of Ohio were surveyed using the
  rectangular surveying system

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Rectangular surveying system

• Subdivided land into square areas by using
  Principal meridians and base lines
• Meridians run north south
• Base lines run east west

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Ranges

• A six mile strip of land which runs north south
  parallel to the principal meridian
• Labeled with consecutive numbers east or west of
  the principal meridian

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Townships (also called tiers)

• A six mile strip of land that runs east west,
  parallel to the base line
• Labeled with consecutive numbers using the south
  baseline as the starting point

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• Subdivided into a rectangular grid of 36
  sections. Each section is one square mile.
• Contains 36 square miles and is six miles square
• Each section is divided into quarters for
  reference purposes

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• Quarter sections are 160 acres each are
  abbreviated as SE ¼, SW ¼, NE ¼, or NW ¼
• Quarter sections can be divided into quarters or
  halves which can be further divided into
  quarters.
• Description of land within a section must be read
  backwards

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• Legal land descriptions for every piece of
  property can be found in the county plat books.
• One township is displayed per page with all the
  land tracts separated by property owner/s
• Each land tract list owners acreage
• Smaller acreages, especially subdivision lots,
  are not individually shown
• Plat books are not accurate enough to locate
  exact property boundaries