Is the difference in English between height and length based solely on perspective?

In particular, I find it odd that a newborn baby is given a "length" whereas I as an adult am given a "height" even though the same dimension is being measured. The difference in use seems to be that a baby must be measured lying down whereas my height would be measured standing up. If I were measured lying down, would my height or length measured, most likely we would still say height.

The difference between is height and length is based on context rather than perspective. Basing it on perspective would imply that it would depend on a person’s view and could vary. A baby’s recorded measurement is its length due to the fact that it must be taken lying down. With length being the measurement from end to end, it applies here. This is not due to the perspective of the doctor or nurse, but due to a systematic approach that was decided for consistency as well as taking in other considerations (such as the baby’s safety in attempting to make it stand when it's not physically able to). A person, barring physical or mental impairments, can be reasonably expected to stand. With height being the measurement from base to top, a person would have their measurement taken down as height.

Perspective - Cambridge Dictionary

A particular way of viewing things that depends on one’s experience and personality

Source link: http://dictionary.cambridge.org/us/dictionary/english/perspective

Length - Wikipedia.com

In geometric measurements, length is the most extended dimension of an object.

Length may be distinguished from height, which is vertical extent, and width or breadth, which are the distance from side to side, measuring across the object at right angles to the length.

Source link: https://en.wikipedia.org/wiki/Length

Length - Merriam-Webster’s Dictionary

The distance from one end of something to the other end : a measurement of how long something is.

Source link: http://www.merriam-webster.com/dictionary/length —

Height - The Free Dictionary

The distance from the base of something to the top.

Source link: http://www.thefreedictionary.com/height