Occupation length has the most influence on the accuracy of PositioNZ-PP coordinates, excluding factors common to other GNSS (global navigation satellite system) survey methods such as equipment, set up and observation environment. The longer the occupation time, the more accurate the final coordinate will be.
When testing against Geospatial Accuracy Framework, stations must be separated by an appropriate distance for assigning coordinate orders. Stations which are too close or too far apart will not meet the distance-dependent accuracy standards.
Standard for the geospatial accuracy framework - LINZS25005
Occupation length and accuracy
The table below outlines the occupation length (for each of two independent occupations) and distances between stations for the various levels of accuracy commonly required.
East and north accuracy (95% confidence level) (m) Local (vector between control marks) | 0.010 | 0.010 | 0.020 | 0.020 | 0.030 | 0.040 |
|---|---|---|---|---|---|---|
East and north accuracy (95% confidence level) (m) Network (coordinate in terms of PositioNZ stations) | 0.005 | 0.005 | 0.015 | 0.015 | 0.020 | 0.030 |
Height accuracy (95% confidence level) (m) Local (height change between control marks) | 0.015 | 0.015 | 0.030 | 0.030 | 0.050 | 0.060 |
Height accuracy (95% confidence level) (m) Network (height in terms of PositioNZ stations) | 0.010 | 0.010 | 0.020 | 0.020 | 0.040 | 0.050 |
| Minimum distance between control marks (m) | 4000 | 1500 | 3000 | 300 | 700 | 1500 |
| Minimum time for each occupation (2 occupations for each mark required) (hours) | 16 | 16 | 4 | 4 | 3 | 2 |
| Order: NZGD2000 | 3 | 4 | 4 | 5 | 5 | 5 |
| Order: NZVD2016 | 1V | 2V | 2V | 3V | 3V | 3V |
Example 1
If you require heights with network accuracy of 2cm or better and there is 500m between control framework marks, then two 4-hour occupations at each mark are required, and the coordinates will achieve Order 5 (NZGD2000) and Order 3V (NZVD2016).
Example 2
If the height change accuracy between control marks (that is, local accuracy) needs to be better than 3cm and there is 3km between marks, then two 4-hour occupations at each mark are required, and the coordinates will achieve Order 4 (NZGD2000) and Order 2V (NZVD2016).