BEARING-ONLY LINES

In Landonline it is possible to capture a line which has a bearing only and no distance. This can be used, for example, for bearing control lines across a survey or to distant NZGD2000 geodetic control.

The survey must have sufficient information to coordinate or re-coordinate all points which are not survey-accurate (NZGD2000 geodetic control or cadastral points with SDC status). Therefore, bearing-only (or equivalently, distance only lines) lines must fit one of the following criteria:

• Between points on the survey that can be coordinated through other survey data. For example, a check bearing observed between traverse marks or from an origin mark to traverse marks.
  
• One-way observations to NZGD2000 geodetic control points (5th order or better) or other traverse or boundary points with survey accurate (SDC) status.
  
• Points that are already in Landonline but not survey accurate and that can be re-coordinated by well-configured intersection, resection, or trilateration.

Bearing-only observations to NZGD49 control marks can cause difficulties because a significant number of these NZGD49 control marks have not yet been upgraded to geodetic quality NZGD2000 coordinates. The surveyor should check the NZGD2000 order or SDC status before capturing a bearing-only line to control marks.

In other cases, both the bearing and distance is required in order to allow the Landonline capture tool to coordinate the points and to allow LINZ to generate new coordinates after approval. Even where only the bearing has been measured, it is possible to specify a distance as adopted or calculated. In these cases, the distance required is the spheroidal (sea-level) distance and not the projection distance. If calculated from coordinates, it is important to ensure that the coordinates are in terms and the distance has correctly been reduced from the projection to the spheroid. Otherwise, re-coordination of this point may result in it being incorrectly moved as a result of an incorrect distance.