NZ Trig Beacons (May 09)

Trig points with 2 metre or 4 metre high beacons on the top of prominent features. They have a survey mark code and common topo name and the height is the orthographic height compatible with the topo elevations, not the datum height reported by your GPS.

These points supplement the spot heights in the topographic database. Spot heights are not duplicated at trig points to remove redundancy. Trigs may not be the highest point because they are placed for visibility when surveyors needed them for backsights to orientate their theodolites for survey bearings.

Type: Height of beacon structure. If there is no beacon, the mark is not in this database, but there may be a concrete mark. Beacons are not being replaced, vegetation is not being trimmed so they are harder to see.

Elevation: Orthographic height in metres

Name: Official mark code (unique 4 character code)

Label: Old name or hill name previously on old topographic maps. Not all trigs have a name, and many are a single letter or a number easily confused with the elevation. Hills may be named separately from the trig common name. Many hills are not named, hence the trig name is used for describing features when mapreading.

SDist: Survey district to resolve duplicate names. This was part of the label, but it is too much information for a map label.

There is a lot more in the LINZ database, available for download at

www.linz.govt.nz/geodetic/geodetic-database/downlo...

Source: LINZ Survey Marks maintenance database Feb 2009