Selective sections from GSA BIM Guide Series 03 – BIM Guide For 3D Imaging
Calibration
Errors from an improperly calibrated instrument are systematic errors and result in an offset or bias in the measurements. This offset may be constant, linear, nonlinear, or periodic. The offset may be determined by an accredited test facility, the manufacturer of the instrument, or by a user following a formal/standard test method. If a manufacturer performs the calibration, the manufacturer can change hardware settings and alignment of instrument parameters to optimal levels to eliminate or reduce the error. In the other cases, a correction factor is often applied to the measurements to reduce the calibration error.
For 3D imaging systems that acquire color information in addition to 3D data, calibration of the color information with the 3D data is also required.
3D imaging instruments
The 3D imaging instrument should be proven to be in calibration before the start of the project and should have been calibrated within the 12 months prior to the project start date. The calibration should be performed by the manufacturer of the instrument or by a qualified third party. The calibration should be performed using standard test procedures, if available, traceable to a national standard.
Some instruments have a self-check process to determine if the instrument is within calibration. This capability provides the service provider a means of checking the instrument in the field. For instruments without the self-check capability and even for instruments with the capability, it is strongly suggested that some field check be performed to ensure that the instrument is functioning properly. The service provider should describe any field checks that will be performed.
Survey instruments
Any other survey instruments (e.g., theodolites, total stations, levels) that will be used in the project should be proven to be in calibration before the start of the project and should have been calibrated within the 12 months prior to the project start date. The calibration, traceable to a national standard, should be performed by a qualified third party or the manufacturer of the instrument.
For further information about this GSA BIM Guide Series 03 – BIM Guide For 3D Imaging visit the National 3D-4D-BIM webpage: http://www.gsa.gov/graphics/pbs/GSA_BIM_Guide_Series_03.pdf
Sheri Blackford is the owner of Lanmar Services. Registered as a Licensed Architect (TX 16753) and Interior Designer in Texas. She is LEED accredited. She has worked internationally in Europe, Africa, North America and the Bahamas. Prior to Lanmar Services she was Project Architect on Schools, Large Resorts, Hotels, Condominiums and Schools. Her current role as owner of Lanmar Services is to manage projects, direct the LiDAR scanning of the buildings and their documentation.