One Mile Level Line

YouTube Video – “One Mile Level Line”

 

1_mile_151109Observations made in November of 2015 between Mile Posts 27 and 28 on NJ Route 206.

first_vidMy first video, “Geodetic Surveyor Straightens Out The Flat Earth”.                                                             ….. Hooray !   Geodesy to the rescue !   Nope.

1_mile_151109_2Six sets of near real-time reciprocal zenith angles were measured and recorded. The tabulated reduced data is shown below.

151109_observations

1_mile_151109_3The raw measurements uncorrected for deflection of the vertical are referenced to the geoid. These measurements reveal the tilt that exists between the vertical plumb directions at the ends of the line. At this latitude, the tilt is found to be approximately 1 arc minute in one mile rounding off. If need be, for various specific applications that require very precise determinations of the curvature and the tilt, high precision measurement procedures can be applied to account for these differences at very exacting positional tolerances. One such example among numerous that can be examined is the case of the construction of the LIGO facilities.

ligoThe closest LIGO will ever come to detecting gravity was during the construction when the tubes were being built STRAIGHT rather than following the natural curved level path linear structures such as pipelines, highways, and railroads normally follow. In the case of LIGO, the long tubes had to be constructed straight to within very exacting tolerances.

……. back to New Jersey Route 206 –

img_3665High precision GNSS receivers were used to record repeated static sessions in November 2015 and again in November 2016. Carrier phase multi-constellation, multi-frequency GNSS data was logged to produce high precision 3D vectors between Mile Posts 27 & 28. Geodetic latitude, longitude and ellipsoid heights were produced by adjusting the repeated vectors from NGS CORS (Continuously Operating Reference Stations) “NJTW” and “NJGC” .

gnss_observationsTabulation of post-processed vectors

gnss_adjustmentAdjusted  Latitude, Longitude,  Ellipsoid Height, State Plane Coordinates and Elevations.

Returning One Year Later To Repeat The Test ….

By setting the target and the theodolite up at these calculated heights, a level line of sight was established at elevation 59.30 feet NAVD88.

level_line

img_3775Target at Mile Post 27 over the point at elevation 53.79 at a measured height of 5.51 feet places the target at elevation 59.30 feet.

img_3791Theodolite set at Mile Post 28

img_3788Setting the theodolite at a measured height of 4.78 feet over Point 28 at elevation 54.52 places the telescope at elevation 59.30 feet.

img_3800_closeupView of horizontal cross hair through the telescope set level at elevation 59.30 feet on Point 28 looking at the target set up at elevation 59.30 feet on Point 27. Note the distance the cross hair is over top of the target. Six independent sets of 4 zenith angle repetitions in F1 & F2 positions were observed and recorded for a total of 24 near real-time reciprocal zenith angles over a 4 hour period from both ends of this level line. The results are tabulated down below.

img_3806Setting the theodolite at a measured height of 5.51 feet over Point 27 at elevation 53.79 places the telescope at elevation 59.30 feet.

img_3777Target at Mile Post 28 over the point at elevation 54.52 at a measured height of 4.78 feet places the target at elevation 59.30 feet.

img_3818View of horizontal cross hair through the telescope set level at elevation 59.30 feet on Point 27 looking at the target set up at elevation 59.30 feet on Point 28. Note the distance the cross hair is over top of the target. Six independent sets of 4 zenith angle repetitions in F1 & F2 positions were observed and recorded for a total of 24 near real-time reciprocal zenith angles over a 4 hour period from both ends of this level line. The results are tabulated down below.

Time and weather were recorded at the start and the end of each independent set of zenith angle repetitions.

time_weather

 

img_3547No thank you …..

161117_set_a

161117_set_b

161117_set_c

161117_set_d

161117_set_e

161117_set_f

161117_reciprocal_sets_

final_results

 

 

 

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