UC Position Arbitrary features along a borehole

This use case describes the need to provide various communities, possibly outside geoscience, with a consistent way to present their data in the context of a borehole. This might mean a pattern over existing model (such as O&M) or by proposing new features. It might also extent to communities with well developed model that includes the concept of borehole and allow them to tie features of their model and expose them using the "standard" borehole.

I guess this use case really is, a client should be able to plot a "borehole" dataset, whatever the content.

This use case should also explore the various ways to express relative and absolute geometries and how to encode, and convert from one representation to another one. This might involve proposed API to convert between various representations (OGC Topic 19, Linear Referencing OGC 10-030 , ISO 19148)

Examples

Delivering element of, for exemple, CityGML, in a borehole (drilling underground through floors and walls) . The model should provide a way (or one or more patterns) to wrap (hosted) CityGML into a borehole form.

Exposing a mixture of data from GeoSciML and GWML into a single Borehole

Exposing data that is not following OGC standard (non feature model, or maybe even under an encoding not supported by OGC).

Requirements

• shall not force any modification to hosted model (ie, CityGML)
• the borehole positioning should provide enough information for a client application to plot the extent of the features on a 3D map, regardless of the hosted model
• a data provider shall be able to provide its data using various referencing system and be able to convert from one to the other (so, the positioning system shall provide all the necessary information to do so)

Vocabulary

Term of importance when referring to position of things in the context of a borehole

Collar position (fr: orifice)

The beginning point of a shaft or drill hole, the surface. (Termium http://www.btb.termiumplus.gc.ca/tpv2alpha/alpha-eng.html?lang=eng&srchtxt=collar&i=1&index=alt&sg_kp_wet=64559&fchrcrdnm=21#fichesauve-saverecord21 )

Position (3D Point) of the hole on the surface of the ground.

Borehole trajectory (fr: trajectoire du forage)

Tridimensional path of the hole in the ground. Geometric shape (Curve or tube) representing this path. Geometry can also be represented as a series of distance measurements from the origin and orientation vectors (taken with a tropari for example) from which the positions can be calculated.

syn: borehole path.

Measured Depth (MD) (fr: Profondeur mesurée)

Depth measured along the borehole trajectory. https://en.wikipedia.org/wiki/Depth_in_a_well

True vertical depth (TVD) (fr: Profondeur verticale réelle)

measurement of a straight line perpendicularly downwards from a horizontal plane. https://en.wikipedia.org/wiki/True_vertical_depth

Depth (fr: Profondeur)

Vertical (or "parallel to gravity line") distance from a datum.

Note: depth from Ellipsoid if normally called "Elevation" (fr: Altitude ?) Note: depth is often expressed using a positive number downward, while elevation is upward

Interval (fr: Intervalle)

Linear section of a trajectory , bounded by a start depth and a end depth. Intervals are arbitrary subdivision of a trajectory that may or may not correspond to discontinuities in the bored material or drilling operations. Intervals can be overlap if they are created to group different phenomenons along the trajectories.

Borehole origin

Origin of a local datum for a borehole. Depth, but also relative position, are often expressed relative to an construction element of the borehole or the local elevation (ground level).

Driller use different datum (most of the list of from wikipedia : https://en.wikipedia.org/wiki/Depth_in_a_well)

• ground level (GL) - or Othographic,
• drilling rig floor (DF),
• rotary table (RT),
• kelly bushing (KB)
• curb-stone (fr: margelle) or top of casing (fr: sommet du tubage) - often use for water wells as position of the ground is not precise (or not always apparent, ie: during winter), similar to GL, but with a local offset.

To compare position of features from one borehole to another, they must be converted to a common datum, such as mean sea level (MSL)- or Ellipsoidal datum. Note that, while often called "absolute" elevations, there are not since they are based on a defined datum.