The major change to the height Orders is that they now provide information about the accuracy of the height, whereas the previous height Orders were based on the method of survey.
LINZ does not describe the accuracy of ellipsoidal heights using these Orders. Instead the vertical accuracy of the control mark Orders is used for ellipsoidal heights because they are determined in conjunction with the horizontal position.
The height Orders and the changes from the previous system are summarised in the following table:
| Order | Purpose | Network Accuracy | Local Accuracy | ||||
|---|---|---|---|---|---|---|---|
| Tier | (m) | Class | Constant (m) |
Proportion (m/m) |
Relative Accuracy (old) | ||
| 1V | National Height Network | E | 0.30 | VI | 0.01 | 3x10-6 | 1st and 2nd order precise levelling |
| 2V | - | F | 0.35 | VII | 0.01 | 1x10-5 | 3rd order precise levelling |
| 3V | Cadastral Vertical Control | F | 0.35 | IX | 0.02 | 1x10-4 | Less accurate techniques with 1V or 2V origin |
| 4V | - | G | 0.50 | X | 0.02 | 1.5X10-4 | Systemic techniques with poor origin or correction |
| 5V | - | H | 1 | XII | 0.30 | 6x10-4 | Unknown or unreliable accuracy |
| 6V | - | - | - | - | - | - | - |
Previous values are shown in italics. The terms 1st and 2nd Order precise levelling refer to the misclose of the levelling observations.