TLV Twistloc prism pole by SECO.

Surveyors sometimes attach importance to equipment with respect to its cost. That is understandable, but the importance of particular equipment can outweigh their cost. Case in point: prism poles. Examples abound of pole glitches with incorrect heights, level bubbles out of adjustment, or those that “slip” from the locked, extended position.

SECO Manufacturing Co., Inc. of Redding, Calif., a longtime manufacturer of prism poles, has improved the prism pole to avoid these glitches and developed its new TLV Twistloc prism pole. SECO offers tailored models of this rod for specific applications, such as GPS and robotics. Our review model was the basic total station version. (For specifics on the application-specific models, see SECO’s website at SECO also provides this pole in two generic construction materials: aluminum and carbon fiber. Our test unit was of the aluminum variety, which has a number of outstanding features. Of particular interest to the user will be its weight, durability and usability.

Twistloc Prism Pole Features

This pole, while by no means excessively heavy, has a heft and solidity that shouts “quality.” It comes across as durable and well-built. One crew chief called it “the Rolex of poles.” The durability aspect would apply mostly to the “top end,” the fittings that connect to whatever the pole is supporting, typically a prism housing. On the SECO Twistloc, those fittings are all made of solid brass. We often see a hard plastic used in the construction of these threaded components, and the brass version is vastly better for the comfort level.

As to usability, this is where the Twistloc really shines. The TLV Twistloc has a built-in yellow vial that is more visible for fast leveling. The top end fittings are simply the standard 5⁄8" x 11" screw and the two locking nuts to secure the screw at a particular height. The screw part is unusually long at about 4 1⁄2", which provides plenty of room for adjusting the height. Equally important is that there is plenty of screw left in the pole to maintain stability. The level bubble is an integral part of the locking device, which is itself a fairly substantial assembly. In fact, that locking assembly is the star of the show and where the Twistloc pole gets its name. In past models of poles, the locking of the telescoping action was accomplished via a friction nut sleeve encircling the pole. With its knurled surface, users needed to loosen and tighten the nut with a circular motion about the circumference of the rod. This one is different. It is a substantial five-sided rubber knob that directly screws the two halves of the lower segment around the upper segment. The concept is a simple one (see photo) and seems to work quite well. Once that knob is tightened and the segments locked together, it is hard to imagine the upper segment slipping down into the lower. What’s more, the user can work with gloves on.

Prism poles have long featured graduated markings on the inner segment that would supposedly represent the correct rod height. This feature was frequently ignored because of the aforementioned slippage of the telescoping mechanism. The Twistloc pole may well provide the assurances to avoid those concerns. The brass fittings, the extra long screw and the very positive locking mechanisms seem quite reliable and stable. Of course, constant checking is a part of surveying, but every little bit of reliability helps.

The list price for the model reviewed here, the 5500-11, is $160. The TLV poles run up to $254. SECO has done a commendable job of designing and producing a prism (or GPS or robotic) pole that directly addresses many of the concerns surveyors have about these sometimes taken-for-granted, but never insignificant accessories.