扇形速度点相对于给定中心的速度

sector velocity

绿色走廊沿河或在两个城市中心区之间的由未开发土地形成的走廊，为市民休闲娱乐或环境保护而保留

A corridor of undeveloped land, as along a river or between urban centers, that is reserved for recreational use or environmental preservation.