Complex sentence: In the early 19th century, the flattening of the earth ellipsoid was determined to be of the order of 1/300 (Delambre, Everest), the modern value as determined by the US DoD World Geodetic System since the 1960s is close to 1/298.25.
Split into simpler sentences: In the early 19th century, the flattening of the earth ellipsoid was determined to be of the order of 1/300 (Delambre, Everest). The modern value as determined by the US DoD World Geodetic System since the 1960s is close to 1/298.25.