To unify the magnetic field level of the whole area in Marine geomagnetism surveying, the base value of the secondary base station must be reduced to the main base value.

海洋磁力测量多站日变改正中，为了使整个测区磁场水平统一，必须以主站为基准对分站日变基值进行归算。

youdao

In later years Moscow became their secondary base, after Peter the Great founded his new capital St Petersburg.

BBC: Inside the Kremlin walls

Dual-shot adds a second layer of colored, transparent or translucent polycarbonate on top of a base layer to produce secondary color blends and depth effects.

ENGADGET: Nokia Lumia 620 announced: 3.8-inch WVGA display, 5MP camera, $249

Although the secondary market is still young, it is routine for companies to halt trading before an IPO to have time to account for its current shareholder base, said a person familiar with the secondary market.

WSJ: Facebook Targeting May IPO