# Siam Physics Congress 2015

20-22 May 2015
Asia/Bangkok timezone
The Centennial Celebration of General Relativity Theory and 80 Years of Thai Physics Graduate

## Using relative gravimeter to determine vertical gravity gradients at NIMT

20 May 2015, 14:30
15m
Phokeethra 2 ()

### Phokeethra 2

Oral presentation Instrumentation, Metrology and Standards

### Speaker

Dr Tasanee PRIRUENROM (Pressure Laboratory, Mechanical Department, National Institute of Metrology (Thailand), Pathumthani, THAILAND 12120)

### Description

This work presents the method used to determine the vertical gravity gradients at National Institute of Metrology (Thailand), NIMT, using the relative gravimeter Scintrex Autograv CG-5. This value will be used to transfer the absolute gravity from the reference height of an instrument to a new specific position because the reference height of each absolute gravimeter is different depending on its construction that can be found between about 80 and 130 cm. Thus, in the comparison between absolute gravimeters, the measurement results must be corrected from the reference height of their gravimeters to the same reference level. That is why, it is necessary to determine the vertical gravity gradients as high accuracy as it is possible. In this work, three locations were selected to perform measurements that are two points at NIMT-Klong 5 (Pathumthani) and one point at NIMT-Rama 6 (Bangkok). The vertical gradient at each location was determined from linear fitting using the relative gravity values measured by CG-5 at five vertical levels above the ground benchmark. The results of gravity gradients found in this work range from 300.4 $\mu$Gal m$^{-1}$ to 320.4 $\mu$Gal m$^{-1}$ (1 $\mu$Gal = 10$^{-8}$ m s$^{-2}$) that the normal value of vertical gradient is 308.6 $\mu$Gal m$^{-1}$.

### Primary author

Dr Tasanee PRIRUENROM (Pressure Laboratory, Mechanical Department, National Institute of Metrology (Thailand), Pathumthani, THAILAND 12120)

### Co-author

Mrs Nattanan WORADET (Pressure Laboratory, Mechanical Department, National Institute of Metrology (Thailand), Pathumthani, THAILAND 12120)

 Slides