Basic Field Instruments Field Orientation, Basic Navigation ESRM 304

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1 Basic Field Instruments Field Orientation, Basic Navigation ESRM 304

2 Three Basic Navigation Measurements Direction Distance Elevation (or change in it) 2

Compass for Direction Looking from point to point, deviation from north is measured May include correction for magnetic declination (geographic north and magnetic

3 Compass for Direction Looking from point to point, deviation from north is measured May include correction for magnetic declination (geographic north and magnetic north may vary) Mirror allows the user to sight the target and adjust the dial simultaneously May need to step away from ferrous metallic objects to avoid magnetic effects 3

4 Compass Scale: Azimuths & Bearings Compass directions are circular Azimuths are shown here Azimuths run clockwise from N (0-360 o ) 4

5 Compass Scale: Azimuths & Bearings Compass directions are circular Bearings are shown here Bearings consist of a latitudinal hemisphere (N or S) followed by 0-90 o toward either longitudinal direction (E or W) 5

6 Compass Scale: Azimuths & Bearings As expected, can convert from azimuths to bearings and back again Bearings shown in red with azimuths in () 6

7 The Compass: Magnetic Declination Magnetic North (N m ) does NOT coincide w/ Geographic North (N g ) Declinations ( δ) are constantly changing 2015: Seattle / Kenmore decl. 16 o 7 E (moving 11 W each year) Declinations as of 2000 C.E. 7

8 Magnetic Declination Affects Your Compass Reading 8

9 Compass Parts Always read compass here: Fred Needle Red Base arrow Shed Screw to set declination: No further declination corrections needed! 9

10 A Compass Adjusted for E Declination 10

11 Following a given direction 1. Dial in given direction 2. Turn your body round until Red (needle) 3. is in the Shed (base arrow) 4. then follow Fred 11

12 Determining a direction (to an object, landmark, etc.) 1. Point Fred at object 2. Turn compass dial until 4. Read direction to Fred 3. Red is in the Shed 12

13 Measuring tape for Distance Simple device for measuring distance Various materials are used (for strength, lack of elasticity, etc.) Proper tension required to avoid sag Straight line required (sometimes vegetation needs to be cut) Air temperature should be recorded (due to shrink / expansion) 13

Your pace for Distance Even Simpler device for measuring distance A pace is a pair of left-right steps Count paces when the same foot hits the ground

14 Your pace for Distance Even Simpler device for measuring distance A pace is a pair of left-right steps Count paces when the same foot hits the ground Calibrate your pace by laying out a course of known distance and pace it several times take the average Standard land distance unit is the chain = 66 feet 14

15 Measuring slope distance w/tape Horizontal distances are assumed If stations are not at the same elevation, the tape should be held level. 15

16 Measuring slope distance Horizontal distances are assumed If holding tape level is not possible, measure the elevation angle and correct using trigonometric functions 16

17 Clinometer for change in Elevation Rotating dial indicates angle of elevation Align the cross hair with the target Read the angle of inclination through the viewfinder Percent scale is on the right; degree on the left Depending on your application, record in either degree or percent (use percent for this course) 17

18 Adjusting Slope Distance to Horizontal 18

19 T Height Measurement Tree Height = DT + BD. O D B 19

20 T Height Measurement Tree Height = DT + BD. O D DT/OD = tan(tod), therefore, DT = OD x tan(tod) DB/OD = tan(dob), therefore, DB = OD x tan(dob), B Tree Height = OD x tan(tod) + [ OD x tan(dob)], or, Tree Height = OD x [tan(tod) tan(dob)]. Horizontal distance OD is measured with a tape. Clino measures tangents of angles TOD, DOB in percent (100 x tan), so Tree Height = OD x [TOD% / 100 DOB% / 100], or Tree Height = OD / 100 x [TOD% DOB%]

21 Summary Navigation Tools Compass Parts: Mirror (cover), base, dial, needle, declination set screw (some models) Uses Determine a direction to travel Determine direction to known object Triangulating your position from or onto a scaled map 21

22 Summary Navigation Tools Surveyor tape Measuring HORIZONTAL distance Pacing Rough accuracy in horizontal distance Clinometer Measuring angular slopes / changes in elevation, heights of tall objects 22

Introduction to Land Measurement (Field Surveying and Navigation)

Introduction to Land Measurement (Field Surveying and Navigation) ESRM 304 Peter Schiess / Eric Turnblom 1 of 37 Overview Overview of surveying Survey mathematics Collecting and recording data Correcting