Position specified as absolute distance from a defined origin, 
typically the first coordinate of the LinearExtent. Per ISO 19148, 
absolute methods use distance from a fixed origin point.
                        
DIGGS examples:
- Measured depth from kelly bushing (origin at KB)
- Distance along geophysical trackline from start
- Chainage along pipeline from reference monument
- Distance from top of core sample

Position specified relative to a referent point along the linear 
feature. Per ISO 19148, relative methods express position as offset 
from a reference point that may not be at the origin.
                        
DIGGS examples:
- Depth below ground surface (referent at ground level)
- Distance from line intersection point
- Offset from kickoff point in directional drilling

Position determined by interpolation between known control points 
(anchor points). Per ISO 19148, interpolative methods calculate 
position based on known reference points distributed along the 
linear element.
                        
DIGGS examples:
- Core positions adjusted for stretch/compression between top and bottom
- Trackline positions interpolated between GPS waypoints
- Borehole positions adjusted using downhole survey stations