- - AGRICULTURE CORE CURRICULUM - - (CLF2000) Advanced Core Cluster: AGRICULTURAL MECHANICS (CLF2700) Unit Title: SURVEYING ______________________________________________________________________________ (CLF2703) Topic: Land Area Measurements Time Year(s) 2 Hours 1 / 2 / 3 / 4 ______________________________________________________________________________ Topic Objectives: Upon completion of this lesson the student will will be able to: Learning Outcome #: (O-2) - Perform land measurements, including pacing and taping of linear distance. Special Materials and Equipment: Steel tape, chaining pins. References: Bowers, W., Jones, B. A., Jr., & Olver, E. F. (1973). Engineering Applications in Agriculture. Champaign, IL: Stipes Publishing Co. Kissam, Phillip. (1978). Surveying Practice (3rd ed.). New York: McGraw-Hill. Evaluation: Test/quizzes by instructor. Have each student determine his/her pace, then have each student determine the approximate length of a building using his/her pace. Do exercise to lay out a right angle line using the 3-4-5 method. Do exercise to have students determine the area of a field using the steel tape. TOPIC PRESENTATION: Land Area Measurements A. Pace 1. A pace is the distance (in feet) from the heel of one foot to the point where the heel of the other foot hits the ground. 2. Distances can be measured by pacing when no greater than 2% accuracy (2 feet in 100 feet) is required. 3. Pace can be determined by the following technique: a. Accurately measure off a 100-foot distance. b. At a normal walk, count the number of steps it takes to cover the 100 feet. 1) It is best to walk the 100 foot course three times and take average number of paces required to complete the course. c. To determine an indiviual's pace, divide the average number of steps into 100. For example, if it takes an average of 35 steps to cover the 100 foot distance, individual's pace is 100/35 = 2.9 feet. 4. When using pace to determine distances, it is best to determine pace under the same conditions that the distance is to be measured. a. For example, pace will vary if measurements are taken uphill or downhill, in wet or muddy conditions, in tall or short vegetation, or in loose or firm soil. B. Laying Out a Right Angle (90§ angle) with a Tape (3-4-5 method) 1. Lay out either a 3' or 30' measurement along the base line as depicted below. -----x----------------------------------x-------- A---------------30'----------------B 2. Measure a line (4' or 40') from one end of the first line (Point A below) and scribe an arc such that line AC is approximately perpendicular (at right angles) to the line AB. x | | 40' | | | -----x-------------------x-------- A-------30'---------B 3. Measure a line (5' or 50') from the other end of the base line (Point B) to where it intersects with the scribed arc from step 2 above. When the distance BC is 50', then a right angle has been formed. 4. Set a pin or stake where the two arcs intersect (Point C). C x | | 40' | | | -----x-----------------x-------- A-------30'-------B C. Using the tape to determine field area (in square feet and acres). 1. Measure the sides of the field (in feet) using one of the techniques described previously. 2. Calculate the area of the field in square feet. 3. Divide the area of the field in square feet by 43,560 square feet to determine the area of the field in acres. a. There are 43,560 square feet in one acre. For example: if a field is measured and determined to have 85,000 square feet, the number of acres in the field can be determined by the following computation: Area in acres = 85,000/43,560 = 1.95 acres. 4. Use the following formulas to determine the area of common geometric-shaped fields: a. Square or rectangular fields: 1) Area = (width)(length) Where, width = width of the field in feet length = length of the field in feet b. Triangular fields: 1) Area = (1/2)(b)(h) Where, b = length of the base of the trianglar field in feet h = perpendicular height to the base of the triangular field in feet c. Circular fields: 2 1) Area = (3.1417)(d )/4 Where, d = diameter of the field in feet d. Irregularly-shaped fields: 1) Make an accurate (scale) drawing of the field. 2) Break the field down into recognizable shapes and compute the area of each part. 3) Add all of the areas of the parts of the field to get the total area of the whole field. For example: you have measured off the field pictured below. Compute the area of the field in square feet and in acres. H G x--------------------------------------------------x | | | | | E | | x-------------x | | F | C | | x----x | | D x-------------------------------x A B Given: AB = 300' EF = 200' BC = 100' FG = 250' CD = 100' GH = 600' DE = 150' HA = 500' Solution: Break the field down into recognizable shapes and compute the area of each part: H G x--------------------------C'---E'-------------x | | | | | E | | x-------------x | | F | C | | x----x | | D x--------------------------x A B Compute: 1. Area of rectangular section defined by connecting points ABCC'HA = (AB)(HA) = (300)(500) = 150,000 square feet. 2. Area of rectangular section defined by connecting points CDEE'C'C = (CD)(DE + FG) = (100)(400) = 40,000 square feet. 3. Area of rectangular section defined by connecting points EFGE'E = (EF)(FG) = (200)(250) = 50,000 square feet. 4. Add all of the parts to get the total area of the field: Area = 150,000 + 40,000 + 50,000 = 240,000 square feet. 5. Convert the area in square feet to acres: Area = 240,000/43560 = 5.5 acres. D. Land Description 1. The rectangular system of land survey is used in 30 western states in the U.S. 2. This system is based upon the following subdivisions: a. Quadrangles are square tracts of land approximately 24 miles on each side. b. Quadrangles are subdivided into 16 townships, each approximately 6 miles on a side. 1) Townships are bounded on the north and south by township lines and on the east and west by range lines. c. Townships are subdivided into 36 sections, each approximately 1 mile on a side and containing 640 acres. 1) Sections are numbered by starting in the northeast corner and continuing west and east across the township as shown below: |-----------------------------------| | 6 | 5 | 4 | 3 | 2 | 1 | | | | | | | | |-----------------------------------| | 7 | 8 | 9 | 10 | 11 | 12 | | | | | | | | |-----------------------------------| | 18 | 17 | 16 | 15 | 14 | 13 | | | | | | | | |-----------------------------------| | 19 | 20 | 21 | 22 | 23 | 24 | | | | | | | | |-----------------------------------| | 30 | 29 | 28 | 27 | 26 | 25 | | | | | | | | |-----------------------------------| | 31 | 32 | 33 | 34 | 35 | 36 | | | | | | | | |-----------------------------------| d. Sections are subdivided into quarter-sections, each approximately 1/2 mile on a side and containing 160 acres. e. Quarter-sections may be divided into fractional areas, the individual tracts containing 80, 40, 20, 10, or 5 acres or combinations of these. 7/12/91 JR/tf #%&C