To measure the difference in elevation between poles, surveyors used an optical level—a telescope on a level base—placed halfway between the poles.

为了测量两极之间的高程差，测量员在两极中间的一个水平基座上使用了光学水准望远镜。

youdao

Why It's Unique: Despite the mountainous topography of the region, trains traveling through the Gotthard Base Tunnel willremain at nearly the same elevation for the entire trip.

独特之处： 尽管该地区属于山地地形，但通过圣哥达基地隧道的火车在整个行程中几乎处于同一海拔高度。

youdao

The Federal Emergency Management Agency (FEMA) publishes maps that designate Special Flood Hazard Areas delineated by a Base Flood Elevation (BFE).

美国联邦应急管理署（FEMA）发布了一张用“洪峰基线海拔”（BFE）描绘洪涝频发重灾区轮廓的地图。

youdao

The climbers spent six weeks at base camp, elevation 17, 500 feet.

WSJ: Mayo Clinic Researchers on Everest Study High Altitude's Effects on the Body

So, of the 17.34 foot record elevation of the station base sea level caused by Sandy, yes, a maximum of about six inches might be related to human activity.

FORBES: It's the Holiday Season, and Global Warming Hype Is Filling the Air

Mr Mulcair's elevation to the leadership shores up the NDP's novel base in Quebec.

ECONOMIST: Canada��s opposition