Holtwood Marketing Ltd. The Survey Centre, Meridian House,
Stanney Mill Road, Little Stanney, CHESTER CH2 4HX
Tel: 01622 710921  Fax 01622 717945 e-mail

Berntsen Markers & Caps

Berntsen Survey Monument 

Berntsen Installation

3ft

Below 3ft little movement occurs. The rod monuments are firmly anchored into this stable layer by ground friction, and can be driven to refusal if required.

6ft

Rod monuments are a series of 5/8" aluminium rods, usually 3ft long, which are driven into the ground either until they reach refusal, or when it is considered they have reached stable ground.
     They are capped with a domed cap, which can be tapped straight onto the rod.
     The rod can be cut at any stage if refusal is reached.

These are exactly the same as the rod monuments, except that, for the top section, a security rod with 3 aluminium fins is used. This increases the stability of the mark.
     All sections of the monument, including the top security section, can be driven straight into the soil, or alternatively the top section can be isolated from the unstable top soil as shown in the diagram.
     The fins of the top security section can be peeled back with vice grips if it is necessary to cut the top section. This enables the cap to be tapped on.

Where a rod monument is to be used for precise vertical measurements, the top section is encased in a grease-filled plastic sleeve, thus isolating the rod from any movements of the surrounding soil. The sand backfill also helps in this process.
     A stainless steel datum point is usually used instead of a domed cap, and an access cover would usually be fitted to protect the mark.

Experience and tests in USA and Canada show that if rod monuments are installed to manufacturers specifications, only sub-millimeter movements' may be expected in X, Y and Z axes over a period of several years. Sample test results are available from Holtwood on request.