Determination of the Ovality of Crude Oil Storage Tanks Using Least Squares

Abstract

In the processing of field measurements, the observations are adjusted using the least squares principle which gives unbiased estimate of the parameter sought together with their accuracies. In this paper, the use of the Least Squares model in the determination of the tank radius, centre point coordinates and ovality are discussed. The circular cross section of the crude oil storage tanks was divided into sixteen monitoring stations at equal intervals around the tank and at an elevation of 2m from the tank base. Total station instrument was then used to carry out angular and linear measurements by method of multiple intersection to reflectors held on the studs. The field measurements were post processed and adjustment of observation carried out by Least Squares adjustment method. The adjusted coordinates together with the computed radius were then used to determine tanks ovality. All data processing and adjustment were carried out with the aid of MATLAB Software for the 2003, 2004 and 2008 measurement epochs.The results of the study revealed an expansion of the tank shell between 2004 and 2008 measurement epoch. The radius of the tank was computed to be 38.187m in 2003 and 2004 and 38.205m in 2008 respectively.