Geo Week News

July 11, 2007

New Construction Technology: CAD-Guided Dimensional Control from BuildExact

New Construction Technology: CAD-Guided Dimensional Control from BuildExact - Image 1

New technology that uses CAD geometry and twin robotic total stations to locate points in space was unveiled by BuildExact, Pleasanton, CA. A construction tool for translating CAD designs into physical space, the BuildExact system is based on patented software technology that lets users navigate 3D CAD models and identify points for location. The software then drives a pair of robotic total stations operating in slave mode to generate visual cues for positioning building materials. To locate a point in the real world, the user selects a point on a 3D CAD model. The total stations then move until their beams cross each other at the point in space that corresponds to the point selected in the model. The laser crosshair is seen with the aid of a viewing device. For example, to position a form for pouring a column on a construction site, the user selects a corner point on a 3D CAD model of the column. The total stations move until their beams intersect at the point where the corner of the form should be positioned. Pierre Bierre, CEO of BuildExact and inventor of the technology, says position accuracy is 1/16 inch.

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Practical construction tool

The software reads DXF files and renders them in solid or wireframe mode with layer filtering. Intended as a practical construction tool, the software is designed to let non-CAD users easily manipulate the model and navigate to any desired point. For “gaze control,” a 3D attention cursor is dragged to the general area of interest; model orientation relative to this gaze point is controlled by three sliders. Another plus for non-specialist users – structures always remain upright.

Setting up the total stations relative to “CAD space” is done via a system of automated triangulation on a set of three control points enveloping the workspace. This allows the total stations to be set up by non-technical workers at unspecified locations, instead of pre-specified locations as with total stations, Bierre explains, and the three-point setup works without leveling the total stations.

The system can also be used for as-built dimensional verification and reporting. In this mode, the user steers the laser intersection to the desired point on a structure or object, then clicks a button to record it. This approach to capturing object edges and corners has some advantages over a single total station, according to Bierre, because total stations use laser distance ranging and thus can suffer from depth ambiguity when the beam straddles an edge.

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Field trials starting – participants welcome

BuildExact’s first public showing took place last month at Stanford’s Center for Integrated Facility Engineering (CIFE). Dr. Martin Fischer, CIFE’s respected director, is bullish on the new technology, saying it makes possible an aspect of fully integrated digital construction he has long advocated.

Founder and CEO Bierre is a software engineer whose specialty is algorithmic geometry, an approach to solving difficult spatial problems using direction vectors and rotators instead of angles. Bierre recently completed a textbook on the subject for software developers, Flexing the Power of Algorithmic Geometry, which includes exercises for solving 2D and 3D robotics problems as well as GPS self-location. Before founding BuildExact, Bierre was a senior project manager at Tecan Systems, a maker of precision liquid-handling instruments for the laboratory market, and had also been Automation R & D Lab Manager at Becton Dickinson Biosciences.

BuildExact is already winning some popular attention – it was chosen as one of the Top 25 New Inventions of 2007 by the Modern Marvels Invent Now Challenge, an annual invention contest developed by The History Channel and Invent Now, Inc., a division of the National Inventors Hall of Fame Foundation. Our thanks to Parsons Brinckerhoff CTO Doug Eberhard for first drawing our attention to this new tool.

Indoor field trials of BuildExact are planned for this summer. Bierre invites interested builders to contact him about participating at [email protected] or tel. 925-200-1558.

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