space is the first and most restricted space that refers to the area that a person's body covers without any movement, including objects that can be easily reached. Vista space is the second subspace that refers to the space beyond the body but that is still close enough to be completely visualized without moving, for example, a room. Environmental space is the third subspace which is said to "contain" the body because of its large size and can only be fully explored through movement since all objects and space are not directly visible, like in a city. Environmental space is the most relevant subspace to humans for navigation because they best allow for movement throughout space in order to understand our environment. Geographical space is the last level because it is so large that it can not be explored through movement alone and can only be fully understood through cartographic representations which can illustrate an entire continent on a map. Reference frames In order to build spatial knowledge, people construct a cognitive reality in which they compute their environment based on a reference point. This framing of the environment is a reference frame. Usually there is a distinction made between egocentric (Latin ego: "I") and allocentric (ancient Greek allos: "another, external") reference frames; Egocentric frame of reference refers to placing yourself in the environment and viewing it in the first person, which means that objects' locations are understood relative to yourself. The egocentric frame of reference is centered around the body. Allocentric frame of reference on the other hand, refers to objects' location based on other objects or landmarks around it. Allocentric frame of reference is centered around the world around you, not around yourself. However, a third distinction can also be made, namely the geocentric reference frame. It is similar to the allocentric reference frame in the way that it has the capacity to encode a location independent from the position of the observer. It achieves this by encoding the space relative to axes that are distributed over an extended space, not by referring to salient landmarks. The geocentric space is most commonly coordinated in terms of longitude and latitude. The difference between an allocentric reference frame and a geocentric reference frame is that an allocentric reference frame is used for smaller-scale environments, whereas a geocentric reference frame is used for large-scale environments, like earth. Whilst spatial information can