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Publications

Search Publications by Prem Rachakonda

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Displaying 1 - 25 of 32

A First realization of ASTM E3125-17 test procedures for laser scanner performance evaluation

February 1, 2020
Author(s)
Ling Wang, Balasubramanian Muralikrishnan, Vincent D. Lee, Prem K. Rachakonda, Daniel S. Sawyer, Joe Gleason
Spherical coordinate three-dimensional (3D) imaging systems, such as Terrestrial Laser Scanners (TLS), are already used widely in different fields. Their measurement performance evaluation is a topic of active research. In 2017, the first comprehensive

Methods to calibrate a three-sphere scale bar for laser scanner performance evaluation per the ASTM E3125-17

February 1, 2020
Author(s)
Ling Wang, Balasubramanian Muralikrishnan, Vincent D. Lee, Prem K. Rachakonda, Daniel S. Sawyer, Joe Gleason
A scale bar with sphere targets is one way of realizing the symmetric and asymmetric length tests to evaluate terrestrial laser scanner (TLS) performance per the ASTM E3125-17 standard. The length of the scale bar is required to be known with an expanded

Sources of Errors in Structured Light 3D Scanners

April 16, 2019
Author(s)
Prem K. Rachakonda, Balasubramanian Muralikrishnan, Daniel S. Sawyer
Structured light (SL) scanners have been commercially available for over a decade and some commercial scanners are evaluated using one of two German guidelines – VDI/VDE 2634 parts 2 and/or 3. Several other research groups and NMIs have developed physical

Methods to Characterize 3D Scanners for Forensic Applications

February 22, 2019
Author(s)
Prem K. Rachakonda, Balasubramanian Muralikrishnan
Forensic photography has been one of the most valuable tool for investigators over many decades. They preserve the history of the scene and provide a way for investigators to analyze the scene of interest. However, it is difficult to obtain any objective

Roles and Responsibilities of NIST in the Development of Documentary Standards

July 27, 2018
Author(s)
Prem K. Rachakonda, Balasubramanian Muralikrishnan, Daniel S. Sawyer
The National Institute of Standards and Technology (NIST) is a non-regulatory federal agency of the Department of Commerce and is the national metrology institute of the US. The background of NIST's role in the development of voluntary consensus standards

ASTM E3125 Laser Scanner Standard: Challenges and Role of NIST

July 24, 2018
Author(s)
Prem K. Rachakonda
The Dimensional Metrology Group (DMG) at National Institute of Standards & Technology (NIST), along with various other organizations were involved in the development of the ASTM E3125-17 documentary standard for 3D imaging systems. The ASTM E57 committee

Concept to Commercialization of an Artifact for Evaluating 3D Imaging Systems per the ASTM E3125- 17

June 29, 2018
Author(s)
Balasubramanian Muralikrishnan, Prem K. Rachakonda, Vincent D. Lee, Katharine M. Shilling, Daniel S. Sawyer, Geraldine S. Cheok, Luc Cournoyer, Joe Gleason
The newly released ASTM E3125-17 standard describes several point-to-point distance tests to evaluate the performance of spherical coordinate 3D imaging systems, commonly referred to as terrestrial laser scanners (TLS). The relative-range error test, which

Terrestrial laser scanner geometric error model parameter correlations in the Two-face, Length-consistency, and Network methods of self-calibration

April 26, 2018
Author(s)
Balasubramanian Muralikrishnan, Ling Wang, Prem K. Rachakonda, Daniel S. Sawyer
Terrestrial laser scanners (TLS) are increasingly used in a variety of applications where accuracies on the order of few tenths of a millimeter or smaller are routinely demanded. Self-calibration is a quick and cost-effective way to improve the accuracy of

Method to Determine the Center of a Contrast Target from Terrestrial Laser Scanner Data

November 3, 2017
Author(s)
Prem K. Rachakonda, Balasubramanian Muralikrishnan, Daniel S. Sawyer, Ling Wang
Terrestrial laser scanners (TLSs) are instruments that can measure 3D coordinates of objects at high speed resulting in high density 3D point cloud data without the necessity of a cooperative target. Contrast targets, also known as checkerboard targets

Challenges in measuring spherical geometry using terrestrial laser scanners

November 1, 2017
Author(s)
Balasubramanian Muralikrishnan, Prem K. Rachakonda, Katharine M. Shilling, Vincent D. Lee, Daniel S. Sawyer, Geraldine S. Cheok, Luc Cournoyer
Terrestrial laser scanners (TLS) measure 3D coordinates in a scene by recording the range, the azimuth angle, and elevation angle of discrete points on target surfaces. They are increasingly used in a variety of applications, including manufacturing and

An Overview of Activities at NIST Towards the Proposed ASTM E57 3D Imaging System Point-to-Point Distance Standard

October 16, 2017
Author(s)
Prem K. Rachakonda, Balasubramanian Muralikrishnan, Katharine M. Shilling, Geraldine S. Cheok, Daniel S. Sawyer
The Dimensional Metrology Group (DMG) at the National Institute of Standards & Technology (NIST), along with various other organizations has been involved in the development of a documentary standard for 3D imaging instruments that acquire data in

Methods and Considerations to Determine Sphere Center from Terrestrial Laser Scanner Point Cloud Data

September 6, 2017
Author(s)
Prem K. Rachakonda, Balasubramanian Muralikrishnan, Luc Cournoyer, Geraldine S. Cheok, Vincent D. Lee, Katharine M. Shilling, Daniel S. Sawyer
The Dimensional Metrology Group (DMG) at the National Institute of Standards and Technology (NIST) is performing research to support the development of documentary standards within ASTM E57 committee. This committee is addressing the point-to-point

Techniques to Evaluate Terrestrial Laser Scanner Errors

July 26, 2017
Author(s)
Bala Muralikrishnan, Prem K. Rachakonda
Forensic photography has been one of the most important tool for investigators over many decades. They preserve the history of the scene and provides a way for investigators to revisit the scene. However, it is difficult to ascertain any objective

An Overview of Activities at NIST Towards the Proposed ASTM E57 3D Imaging System Point-to-point Distance Standard

July 21, 2017
Author(s)
Prem K. Rachakonda, Balasubramanian Muralikrishnan, Katharine M. Shilling, Daniel S. Sawyer, Geraldine S. Cheok
Terrestrial laser scanners (TLSs) are a class of 3D imaging systems that measure the 3D coordinates of an object in their work volume. They capture the 3D coordinates using a ranging unit mounted on two rotation stages that are orthogonal to each other

Relative range error evaluation of terrestrial laser scanners using a plate, a sphere, and a novel dual-sphere-plate target

July 21, 2017
Author(s)
Balasubramanian Muralikrishnan, Prem K. Rachakonda, Vincent D. Lee, Katharine M. Shilling, Daniel S. Sawyer, Geraldine S. Cheok
Terrestrial laser scanners (TLS) are a class of 3D imaging systems that produce a 3D point cloud by measuring the range and two angles at different sampling locations. The ranging unit of a TLS realizes the SI unit of length. Relative range error is one

Targets for Relative Range Error Measurement of 3D Imaging Systems

May 1, 2017
Author(s)
Prem K. Rachakonda, Balasubramanian Muralikrishnan, Katharine M. Shilling, Geraldine S. Cheok, Vincent D. Lee, Christopher J. Blackburn, Dennis S. Everett, Daniel S. Sawyer
The Dimensional Metrology Group (DMG) at the National Institute of Standards and Technology (NIST) is performing research to support the development of documentary standards within ASTM E57 for the point-to-point performance evaluation of 3D imaging

Report on the May 2016 ASTM E57.02 instrument runoff at NIST, Part 1 – Background information and key findings

October 19, 2016
Author(s)
Balasubramanian Muralikrishnan, Prem K. Rachakonda, Katharine M. Shilling, Vincent D. Lee, Christopher J. Blackburn, Daniel S. Sawyer, Geraldine S. Cheok, Luc Cournoyer
There is ongoing activity within ASTM E57.02 working group WK43218 [1] to develop a documentary standard for point-to-point distance performance evaluation of 3D imaging systems. The Dimensional Metrology Group (DMG) at the National Institute of Standards

Report on the May 2016 ASTM E57.02 instrument runoff at NIST, Part 2 - NIST realization of test procedures and uncertainties in the reference lengths

October 19, 2016
Author(s)
Balasubramanian Muralikrishnan, Prem K. Rachakonda, Katharine M. Shilling, Vincent D. Lee, Christopher J. Blackburn, Daniel S. Sawyer, Geraldine S. Cheok, Luc Cournoyer
There is ongoing activity within ASTM E57.02 working group WK43218 [1] to develop a documentary standard for point-to-point distance performance evaluation of 3D imaging systems. The Dimensional Metrology Group (DMG) at the National Institute of Standards

Targets for Relative Range Error Measurement of 3D Imaging Systems.

July 25, 2016
Author(s)
Prem K. Rachakonda, Balasubramanian Muralikrishnan, Katharine M. Shilling, Geraldine S. Cheok, Vincent D. Lee, Christopher J. Blackburn, Dennis S. Everett, Daniel S. Sawyer
The Dimensional Metrology Group (DMG) at the National Institute of Standards and Technology (NIST) is performing research to support the development of documentary standards within ASTM E57 for the point-to-point performance evaluation of 3D imaging

Performance evaluation of a laser tracker hand held touch probe

November 5, 2015
Author(s)
Balasubramanian Muralikrishnan, Christopher J. Blackburn, Prem K. Rachakonda, Daniel S. Sawyer
Hand-held touch probes and laser scanners are increasing the scope and applicability of laser trackers. While methods to evaluate the performance of laser trackers in conjunction with spherically-mounted retro-reflectors (SMRs) are well established