Error analysis of the NGS’ surface gravity database

• Published in: Journal of geodesy Vol. 87; no. 3; pp. 203 - 221
• Main Authors: Saleh, Jarir, Li, Xiaopeng, Wang, Yan Ming, Roman, Daniel R., Smith, Dru A.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.03.2013; Springer Nature B.V
• Subjects: Earth and Environmental Science; Earth Sciences; Error analysis; Fourier transforms; Geodetics; Geophysics/Geodesy; Gravity; Mountains; Original Article; Polls & surveys; Errors; Biases; Surface gravity anomaly residuals; Crossover analysis; Geoid
• ISSN: 0949-7714; 1432-1394
• DOI: 10.1007/s00190-012-0589-9

Are the National Geodetic Survey’s surface gravity data sufficient for supporting the computation of a 1 cm-accurate geoid? This paper attempts to answer this question by deriving a few measures of accuracy for this data and estimating their effects on the US geoid. We use a data set which comprises million gravity observations collected in 1,489 surveys. Comparisons to GRACE-derived gravity and geoid are made to estimate the long-wavelength errors. Crossover analysis and -nearest neighbor predictions are used for estimating local gravity biases and high-frequency gravity errors, and the corresponding geoid biases and high-frequency geoid errors are evaluated. Results indicate that 244 of all 1,489 surface gravity surveys have significant biases  mGal, with geoid implications that reach 20 cm. Some of the biased surveys are large enough in horizontal extent to be reliably corrected by satellite-derived gravity models, but many others are not. In addition, the results suggest that the data are contaminated by high-frequency errors with an RMS of  mGal. This causes high-frequency geoid errors of a few centimeters in and to the west of the Rocky Mountains and in the Appalachians and a few millimeters or less everywhere else. Finally, long-wavelength ( ) surface gravity errors on the sub-mGal level but with large horizontal extent are found. All of the south and southeast of the USA is biased by +0.3 to +0.8 mGal and the Rocky Mountains by to  mGal. These small but extensive gravity errors lead to long-wavelength geoid errors that reach 60 cm in the interior of the USA.