Calibration of vertical aboveground storage tanks 1

[poseilus]

I have found the following standards

ISO 7507

PART 1: STRAPPING METHOD
PART 2: OPTICAL-REFERENCE-LINE METHOD
PART 3: OPTICAL-TRIANGULATION METHOD
PART 4: INTERNAL ELECTRO-OPTICAL DISTANCE- RANGING METHOD
PART 5: EXTERNAL ELECTRO-OPTICAL DISTANCE-RANGING METHOD

which method do you think is the most widely used and more accurate than the others?
I know there are also same standards from API. SHould I consider buying API's standards instead of ISO's

 

[stewbaby]

Off my area really, but I know that all our tanks (small refinery in Mississippi, about 2.5 million bbls total storage) are strapped to API standard MPMS (chapter 2.2 specifically). Plays heavily into billing and acceptance of volumes by U.S. Customs on custody transfer across trade zones.