In this case, a leading possibility is that the signal originates from an unusual modulation between a GPS satellite and an unidentified Earth-based source.

在这种情况下，最主要的可能性是这道信号来源于一个一颗GPS卫星和未确认的地球发射源之间的不寻常的调制信号。

youdao

The difficulty is the viewing geometry that puts any Trojan, from the perspective of an Earth-based telescope, in bright skies.

观测特洛伊小行星的难点在于，在通过地面望远镜观测时，几何角度总是使其位于明亮的天空中。

youdao

Earth-based measurements suggest there is a large unaccounted-for surface “sink” of atmospheric carbon dioxide, but its location is fiercely debated.

地面测量数据表明，地表存在一个未被考虑到的大型二氧化碳“吸收槽”，但是关于它的位置还存在很多争论。

youdao

One of its official organizers in the United States is a Washington based nonprofit group called Earth Day Network.

VOA: special.2010.04.21

It is based on the story of a fairy from heaven who comes to Earth and marries a cowhand on a farm.

VOA: special.2010.02.08

Scientists say extensive observations from earth-based telescopes are needed to confirm the existence of the planets.

VOA: special.2011.02.09

According to a report released by the Wood Mackenzie firm in early January, Eagle Ford is now the largest oil and gas development on the face of the earth based on total capital expenditures.

FORBES: The Blessing That is the Eagle Ford Shale

Earth-based observations might not be sufficient to rule out an impact in 2036.

BBC: Foresight mission spacecraft Image

Astrobiological researchers have discovered significant regions below the surface of Mars that could be habitable for Earth-based life.

FORBES: Parts Of Mars May Be Habitable For Earth-Based Life