the imaginaryline from the North Pole to the South Pole that passes through Greenwich in England and marks 0° longitude , from which all other longitudes are measured 本初子午線（從北機(jī)到南極的一根假想線，它穿過英格蘭的格林尼治，標(biāo)示爲(wèi)經(jīng)線0°，其他經(jīng)線以此爲(wèi)測(cè)定標(biāo)準(zhǔn)） 返回 the prime meridian