A few examples of site and survey matters:

Architect designs a building to the maximum allowed by height to boundary controls.  One or more of the following happens (ie these have all happened on one or more jobs!) and the breach will result in replanning/rebuilding/resource consent with attendant costs and delays:

Owner points out boundary position lies just inside a thick wide hedge.  Regrettably, owner is mistaken, and the boundary is at the other side of the hedge, and at a much lower level.

Architect obtains survey and designs to it.  Surveyor wrongly draws up the site plan (or draftie wrongly reads it) to show the boundary at the top of a retaining wall instead of at its base.

Builder thinks the architect is a wally, and after discussion/agreement with the owner helpfully raises the floor level 200mm without the architect being told or noticing on a site visit.

Boundary levels are more or less consistent, except for a small section which has a pronounced dip about 1.2m across and 400mm deep.  Architect ignores it but the council doesn’t!

Construction proceeding smoothly, framed up with roof about to go on.  Some bright spark in the check-box department of the local council realises that they have not yet got a certificate from a surveyor to verify the HIRB and sends out a routine letter.  Surveyor duly reports to architect that the horizontal dimension between the building and the boundary is 700mm less than the architect used for the roofline.  Architect sadly discovers that at 1:100 scale the dimension line drawn parallel to the boundary is exactly 700mm from it!

Old house in poor condition is to be repiled, refurbished and extended along the boundary. Site levels are taken before the design is started.  Floor level of the extension is later designed to be level through to the existing old house.  After the repiler has straightened and levelled things up, the old house floor level where it meets the new extension is rather higher than before.