Berntsen Sectional Rod Monuments for Control
The rotating sectional rod monument concept originated with Berntsen in the mid-1970's and has since developed into a wide variety of products. Although the rod monument can be used for nearly any type of survey, it was designed to meet the requirements of survey projects that involve a high degree of precision. Rod monuments and markers are often used for vertical control work and are also used for GIS/LIS. Rods are usually driven deeply into the ground to the point of refusal.*
This survey monument is assembled as it is installed. It consists of a simple series of sectional rods available in 1 foot (305 mm) to 5 foot (1524 mm) lengths, in even - foot lengths. The rods are coupled together with a floating thread that aligns and connects the rods. Additional sections can be added, as required, to achieve the required depth or stability of the monument. The thread is also used to connect the point to the rod series. The unique spiral penetrating point rotates the rod series slightly as it is being driven into the ground. This slight rotation is very important as it assures that the series stays connected. The tap-on cap has a hex-socket specially designed for a compression fit when tapped onto the rod. The socket interior is fluted to allow air escape. A permanent ceramic magnet is affixed to the inside of the cap socket.
Rods are made of either 6000 series aluminum or 304 series stainless steel. Aluminum rods are available in 3/4" (19 mm) diameters. Stainless steal rods are available in 9/16" (14 mm). All rods are machined with appropriately sized vibration resistant precision threaded connections on each rod end. Rod ends are machined-faced flat and perpendicular to the centerline of the rod. Threaded connectors are made from 300 series stainless steel and are of appropriate size and length for joining the various rod diameters. Plastic color-coded end caps (9/16" (14mm)- Yellow identify and protect and keep clean the rod end(s) and the threaded bore, or connecting threaded stud.
* "Refusal" for a rod monument is defined by most federal agencies as "No more than one (1) foot (305mm) of further penetration of a rod monument in one (1) minute of impacting with a gasoline powered reciprocating impact hammer.