Space-time location data model

[ktoddbrown]

We need to develop a time aware geolocation data model. This is very much a common problem so we should aggregate references here and refine the initial data model.

This should cover

• surface geolocation: inclusive of point reference with implied or explicit uncertainty and region
• depth below ground: inclusive of zero reference, orientation (down is positive), and interval
• time: when an observation (either measurement or land practice or treatment description) was made or applies to

[ktoddbrown]

We should add in depth partitioning method which would either be distance or horizon driven. Each of those should further have a method noting the motivation for the distance or what system is used for horizon classification.

[ktoddbrown]

Time could more generically be treated as an event which can be extended to cover land class categorizations, management records, and treatments. with_entry adherence to https://en.wikipedia.org/wiki/ISO_8601 and of_variable following control vocabulary for things like 'observation_date'