Update earth_observation.md

docs/earth_observation.md

@@ -6,9 +6,10 @@ title: Earth Observation
 
 ## 1 Definition
 
-A science domain dealing with technologies and methods of collecting and analyzing observations about the different spheres (Geosphere, Atmosphere, Hydrosphere, Cryosphere, Biosphere, Anthroposphere) of our planet. This includes remote-sensing, such as satellite imagery, as well as in-situ observations, e.g., with ground-based devices.
+science domain dealing with technologies and methods of collecting and analyzing [observations](../observation) about the different [Earth spheres](../Earth spheres)
 
 ### Notes 
+- Earth Observation (EO) includes [remote sensing](../remote sensing), such as satellite imagery, as well as [in-situ observations](../in-situ observation), e.g., with ground-based devices.
 - Earth [Observation](../observation) (EO) can be categorised by [Location](../location) of the [Sensor](../sensor) into space-borne, air-borne, sea-borne, ground-based, underwater and underground EO.
 
 ### Examples