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NATIONAL GEOSPATIAL-INTELLIGENCE AGENCY

UNCLASSIFIED

GEODETIC SURVEYS DIVISION

Publication 15_H055

Absolute and Relative Gravity Survey University of Hawai’i-Manoa and Pier 35 Honolulu, Hawai’i

February - March 2015

UNCLASSIFIED 2. 3. 4. 5. 6. 7. 8.

Publication 15-H055: Absolute and Relative Gravity Survey, University of Hawai’i-Manoa (UH) and

UH Marine Center, Pier 35, Honolulu, Hawai’i

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Absolute and Relative Gravity Survey

University of Hawai’i-Manoa (UH) & UH Marine Center-Pier 35

Honolulu, Hawai’i

February-March 2015

TABLE OF CONTENTS

1. Introduction.............................................2

a. Background..........................................2

b. Points of Contact...................................2

2. Requirements.............................................2

3. Procedure................................................2

a. Absolute Gravity....................................2

b. Relative Gravity....................................2

4. Computations and Analysis................................3

a. Absolute Gravity....................................3

b. Relative Gravity....................................3

5. Survey Results...........................................4

6. Station Descriptions.....................................5

Publication 15-H055: Absolute and Relative Gravity Survey, University of Hawai’i-Manoa (UH) and

UH Marine Center, Pier 35, Honolulu, Hawai’i

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1. Introduction

a. Background

This report presents the results of a gravity survey at

the University of Hawai’i-Manoa (UH), Institute of

Geophysics and UH Marine Center, Honolulu, Hawai’i. The

survey was conducted by Mr. R. David Wheeler (Team Lead:

575-679-2893), John Maurais and SFC Brad Favinger of the

National Geospatial-Intelligence Agency (NGA). Survey

dates were 27 February thru 9 March 2015.

b. Point of Contact:

Scott Ferguson

Director of Marine Technical Services UH Marine Center

# 1 Sand Island Access Road

Honolulu, Hawaii, 96819

Tel: (808) 832-3081

Email: jscottf@hawaii.edu

2. Requirements

Gravity values were requested at two locations, the

University of Hawai’i-Manoa, Institute of Geophysics,

Laboratory’s Isolation Table and UH Marine Center’s new

location, currently under construction at Pier 35. And if

time permitted a third location was requested at the UH

Marine Center’s current location at Pier 45, Sand Island.

The acceleration of gravity accuracy requirements for this

survey were: +/- 0.100 milligal (mGal)(1-sigma) absolute and

+/- 0.100 mGal (1-sigma) relative to the absolute station.

3. Procedures

a. Absolute Gravity: Two absolute stations were established, one at UH Institute of Geophysics (UH HIG

AA) and one at the 84th Engineering Battalion, Schofield

Barracks (84th AA) with a Micro G LaCoste A-10 (serial

number 009) gravity meter. Multiple day independent

measurements were made at both absolute stations.

Publication 15-H055: Absolute and Relative Gravity Survey, University of Hawai’i-Manoa (UH) and

UH Marine Center, Pier 35, Honolulu, Hawai’i

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b. Relative Gravity: Relative observations from the established absolute station (UH Institute of Geophysics)

were made using a 1-2-3-3-2-1 type loop structure with

three Scintrex CG-5 Autograv gravity meters (Serial

Numbers 40244, 40245 and 40248). The loop structure

included relative measurements at UH HIG Excenter, Pier

35 Alpha, Pier 35 Bravo, Pier 45 200, Pier 425, Pearl

Harbor BA (Origin of a 1999 gravity survey) and 84th AA

(used to validate the absolute gravity data).

4. Computations and Analysis

a. Gravity Absolute: The absolute gravity value for both stations were determined from data collected with a Micro

G LaCoste A-10 gravity meter. More than 4 days of

independent observations were taken at both stations. A

weighted mean of these observations was calculated at

both stations and these values were compared via relative

ties to each other. Absolute station comparisons

(absolute versus relative) were less than 0.030 mGal (1-

sigma). The absolute precision terms were less than

0.012 mGal for both stations. Using the Scintrex CG-5

relative meters a gradient value (microGal/centimeter) at

each absolute site was determined. This gradient was

applied to the absolute gravity value to relocate it from

the A-10’s measurement location (approximately 71

centimeters above) to the established gravity monument on

the ground.

b. Gravity Relative: A dynamic drift value is computed from the observations at the control station for each meter.

This is applied to the individual observations, linearly;

by time. The relative gravity value for each station was

determined from data collected with the CG-5 meters. The

output from these meters is automatically corrected for

static drift and earth-tide effects. The delta gravity

value of the observations from each meter is then

processed with NGA proprietary GravNet software. These

delta’s were then applied to the absolute station to

determine the gravity value at each measured relative

gravity station. The relative precision terms were less

than 0.010 mGal for all stations.

Publication 15-H055: Absolute and Relative Gravity Survey, University of Hawai’i-Manoa (UH) and

UH Marine Center, Pier 35, Honolulu, Hawai’i

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5. Gravity Results

Absolute Gravity Values

STATION

NAME City

ADJUSTED

GRAVITY mGal

PRECISION

TERM mGal

UH HIG AA Manoa

978944.611

0.012

84th AA Schofield

Barracks

978917.103

0.011

Relative Gravity Values

STATION

NAME City

ADJUSTED

GRAVITY mGal

PRECISION

TERM mGal

UH HIG

Excenter Manoa 978944.235 0.0024

Pier 35

Alpha Honolulu

978927.887

0.0024

Pier 35

Bravo Honolulu

978928.593

0.0035

Pier 45 200 Sand

Island 978923.609 0.0054

Pier 45 425 Sand

Island 978923.274 0.0054

Pearl

Harbor BA

Pearl

Harbor 978925.615 0.0054

84th AA

(Comparison

Value)

Schofield

Barracks 978917.074 0.0056

Publication 15-H055: Absolute and Relative Gravity Survey, University of Hawai’i-Manoa (UH) and

UH Marine Center, Pier 35, Honolulu, Hawai’i

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DESCRIPTION OF GRAVITY STATION

GRAVITY STATION

NAME

Approx. WGS 84 Position

UH HIG AA Lat: 21°17'52.1"N Long: 157°49'00.0"W

LOCATION DESCRIBED BY University of Hawai’i-Manoa, Institute of Geophysics

Wheeler

ESTABLISHED BY DATE

NGA/SNSH March 2015

The station is located in the basement of University of Hawai’i-

Manoa, Institute of Geophysics, Honolulu, Hawai’i. The station

is the center of the top of the 3’x 5’ concrete isolation table.

Entrance is through the south side of the building down a ground

level flight of stairs. First door on your left (Room B5).

N

Publication 15-H055: Absolute and Relative Gravity Survey, University of Hawai’i-Manoa (UH) and

UH Marine Center, Pier 35, Honolulu, Hawai’i

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DESCRIPTION OF GRAVITY STATION

GRAVITY STATION NAME Approx. WGS 84 Position

Honolulu G (UH HIG AA Excenter) Lat: 21°17'52.6"N Long: 157°49'00.3"W

LOCATION DESCRIBED BY University of Hawai’i-Manoa, Institute of Geophysics

Wheeler

ESTABLISHED BY DATE

NGA/SNSH March 2015

The station is located outside on the 1st floor near Room 108 on

the southwest side of University of Hawai’i-Manoa, Institute of

Geophysics Bldg. The station is the USAMSFE International

Gravity Base Station bronze disk stamped Honolulu G and is

locally referred to the as the Wollard Mark. It is set in a

sidewalk approximately 0.1 meters from the building wall.

N

Honolulu G

Publication 15-H055: Absolute and Relative Gravity Survey, University of Hawai’i-Manoa (UH) and

UH Marine Center, Pier 35, Honolulu, Hawai’i

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DESCRIPTION OF GRAVITY STATION

GRAVITY STATION

NAME

WGS 84 POSTION

Pier 35 Alpha Lat:21°18'55.937"N Long:157°52'37.556"W EH:18.31m

LOCATION DESCRIBED BY University of Hawai’i, New Marine Center, Pier 35,

Honolulu, Hawai’i

Wheeler

ESTABLISHED BY DATE

NGA/SNSH March 2015

The station is located at the University of Hawai’i, Marine

Center, Pier 35 at the 550 foot mark along the north-south Pier.

The station is a 3” Brass NGA Gravity Station disk stamped “Pier

35 Alpha 2015”.

N

Pier 35 Alpha

Publication 15-H055: Absolute and Relative Gravity Survey, University of Hawai’i-Manoa (UH) and

UH Marine Center, Pier 35, Honolulu, Hawai’i

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DESCRIPTION OF GRAVITY STATION

GRAVITY STATION

NAME

Approx. WGS 84 Position

Pier 35 Bravo Lat: 21°18'56.2"N Long: 157°52'34.5"W

LOCATION DESCRIBED BY University of Hawai’i-Manoa, New Marine Center, Pier

35, Honolulu, Hawai’i

Wheeler

ESTABLISHED BY DATE

NGA/SNSH March 2015

The station is located at the University of Hawai’i, new Marine

Center, Pier 35 on the first floor under a stairwell of the

‘still under construction’ Marine Center building. The station

is a 3” Brass Gravity Station disk stamped “Pier 35 Bravo 2015”.

N

Pier 35 Bravo

Publication 15-H055: Absolute and Relative Gravity Survey, University of Hawai’i-Manoa (UH) and

UH Marine Center, Pier 35, Honolulu, Hawai’i

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DESCRIPTION OF GRAVITY STATION

GRAVITY STATION

NAME

Approx. WGS 84 Position

84th AA Lat: 21°29'49.5"N Long: 158°03’57.9"W

LOCATION DESCRIBED BY 84th Engineering Battalion Building, Schofield

Barracks, Hawai’i

Wheeler

ESTABLISHED BY DATE

NGA/SNSH March 2015

The station is located on the first floor of 84th Engineering

Battalion Building on Schofield Barracks, Hawai’i in the

southwest corner of the surveyors’ equipment storage room. The

station is a 1” Brass Gravity Station disk stamped “84th AA”

N

84th AA