Replace x_coord, y_coord, z_coord in the Node and Location tables with the well-known-text (wkt) representation of a point

[ssmith55]

This is to provide greater consistency with the representation of lines in the link and geometry tables. Instead of x_coord, y_coord, z_coord, one would have
POINT (x_coord, y_coord) or
POINT Z (x_coord, y_coord, z_coord)

Furthermore, wkt provides an option for linear references
POINT M (x_coord, y_coord, lr) or
POINT ZM (x_coord, y_coord, z_coord, lr)

Do PMC members think this change would provide significant benefit?

[pedrocamargo]

This would conversion code simpler and visualization (e.g. on QGIS) MUCH simpler.