Survey monument A is at Latitude 40E 25\' 40\" N Longitude 85E 50\' 35\" W Your

Question

Survey monument A is at Latitude 40E 25' 40" N Longitude 85E 50' 35" W Your are searching for a second survey monument B that is shown on a survey dated March 15, 1885 to be 500 feet from A and at a magnetic bearing of S 65E 35' E. a. Use the NGDC (now NCEI) magnetic declination calculator to determine the 1885 survey declination value at monument A. Use the IGRF model. Include a printout of the declination calculator result with your solution. b. Use the NGDC (now NCEI) magnetic declination calculator to determine the 2015 survey declination value at monument A. Use the IGRF model. Include a printout of the declination calculator result with your solution. c. If you are at monument A and using a compass, what magnetic bearing would you use to survey the line to monument B and commence your search for the monument? Include station sketch at A and compute bearings to the nearest minute. d. NGDC (now NCEI) magnetic declination calculator states that “Declination results are typically accurate to 30 minutes of arc”. How big is your search are for monument B?

Explanation / Answer

momument A (year 1885)

latitude = 40E 25' 40'' N

longitude 85E 50' 35'' W

momument B

distance = 500ft

magnetic bearing = S 65E 35' E

a. by the NGDC magnetic declination calculator

the the survey of monument A on date 15 march 1885

IGRF12 = model taken

has the declination = 2.65o E changing by 0.06o W

b. declination of monument A for the date 15/3/2015

latitude = 40E 25' 40''

longitude = 85E 50' 35W

declination we got from the NGDC (NCEI) magnetic declination calculator

with model IGRF12

declination = 4.91o W changing by 0.06o W

c. we have the magnetic bearing S 65E 35'E and distance stated as 500ft from monument A

true bearing is the angle in clockwise direction from north point measured in degrees

fr ex. 65o degrees is a true bearing from north point

so the magnetic bearing which we use to survey the line to monument B

true bearing + magnetic bearing

therefore,

65o + 65o35'

magnetic bearing we use = S 130E 35' E

d. from the distance of 500ft(152.4) (from bearing 130E 35' and 65E 35' we get 65o)

our search for monument B is = 65oby the distance of 152.4m from monument A

i.e 9906m

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