Short Drill-Braced Monument

The short drill-braced geodetic monument is perfect for:

 Remote locations only accessible by helicopter or 4WD vehicle
 Environmentally sensitive sites
 Rapid deployment after large earthquakes
 Funds are not available to install a deep-anchored drilled-braced monument

The short, drill-braced monuments is a smaller, hand-drilled geodetic monument design that we use for rapid installations of continuous GPS sites. The monument consists of 1-inch diameter stainless-steel rods forming a quad-pod that stands about 3 feet above the ground surface and is anchored 3 to 6 feet into bedrock. A generator-powered handheld rotary drill using a 1.5-inch diameter drill bit is used to prepare the holes. Epoxy is used to anchor the stainless-steel rod in the holes.

This page provides installation instructions for the SCIGN short, drilled-braced monument. The original design was a collaborative effort between S. Dockter, D. Elliot, and F. Wyatt (UCSD/SIO), and J. Galetzka and K. Hudnut (USGS Pasadena). Below are links to the USGS/SCIGN installation guide.

 USGS/SCIGN short, drilled-braced monument design instructions

Installation and Guide

In the aftermath of the 2001 Nisqually earthquake, PANGA used this monument design because of its low cost and ease of installation. It takes about two days to install the monument and ancillary electronic equipment. Each site uses a FreeWave radio modem or a land-line telephone for data communications and a solar panel array with eight gell-cell batteries for power.

Materials, Costs and Drawings

 Monument assembly drawing
 Monument leg drawing
 Interconnection details
 Installation costs (courtesy of John Galetzka (SCIGN/USGS)
 Equipment list (courtesy of Mike Jackcon (UNAVCO)

Ancillary Equipment

We used Trimble SSI or Ashtek Z12 receivers and choke ring antennas with stainless steel recoverable antenna mounts. The antenna mount is the standard SCIGN-type anentta adapter, using SCIGN-type radomes.

All of our sites have secure and covered facilities. We use NEMA/EEMAC Type II enclosures with bulkhead fittings. The enclosures contains the GPS receiver, U.S. Robotics 56 kbs modem or Freewave radio modem and heavy duty surge protectors. The surge protectors isolate all components from lighting strikes or AC power surges.

Photos


Welding the stainless-steel pipe.
Installing the copper ground rod next to the utility boxes.

Short drilled-braced monument. View to the north.
Lake Chaplain solar panels and GPS antenna. View towards the north.