Established survey practice is to show all survey measurements on the survey plan. However, in the case of GNSS surveys, showing measured GNSS vectors on survey plans can cause excessive clutter.

Even though vectors can now be easily excluded from plan generation, the captured vectors can still clutter the spatial view in Landonline and LandXML data extracts.

It is acceptable to replace some or most of the measured GNSS vectors from base stations with calculated vectors between adjacent PRM, witness, non-boundary and boundary marks. For capture purposes, vectors derived from GNSS measurements made in conjunction with the survey are considered measured. The Equipment Type must be captured as "GPS" (Standard for lodgement of cadastral survey datasets LINZS70000 Requirement 4.2(c)).

However, this practice does create some additional risks for both surveyors and LINZ that need to be carefully managed.

Managing risk

The omission of some measured vectors and substitution of calculated vectors can increase the risk of errors going undetected. This means that Landonline validation checks could give a false indication of accuracy even with a significant degree of network redundancy. It may also affect Landonline network adjustment and make it more difficult to resolve errors discovered by subsequent surveys.

Surveyors are expected to demonstrate that they have adequately managed the accuracy risks. This should be covered in the survey report.

A tabulation of the measured GNSS vectors or a summary of the adjustment results can be submitted as a supporting document. This is not routinely used by LINZ for validation purposes but could be useful for demonstrating risk mitigation and for resolving any subsequent data conflict or data integration issues.

Please note that surveyors can always capture measured GNSS vectors if they choose to.