Always comes in 3s

Author: Bora Yavuz

3 days. 3 laser scanning instruments. 3D model.

The cultural heritage project of capturing the Ottoman-period Bursa Grand Mosque in Turkey certainly came as a three – and then as a six.

Built between 1396 and 1399, one of the most unique features of the mosque is its Minbar or pulpit. Designed in 6,666 interlocking pieces of walnut wood with nil a piece of metal or nail used during assembly, each piece represents one of the verses of the Quran.

The Leica Geosystems UAE Office was tasked with capturing a 3D model of the Minbar and front interiors of the 2,215 sq m structure by Burset Project & Engineering. The project was commissioned by the Merinos Atatürk Congress & Culture Centre as an exhibit for the museum’s Ottoman era section.

“We have reached a high quality dataset within a short time with the Leica T-Scan and C10 ScanStation combination,” said Cihan Özüisik, Burset Project & Engineering design engineer. ”This was the best fitting solution for our reverse engineering project, which we will definitely use again in the future."

Merging laser scanners for one model

The general scan of the building was captured with a Leica C10 ScanStation. With the mosque’s 20 domes and 2 minarets, the C10’s full dome and 360º focused areas scans saved the team great amounts of time, enabling the complete project to be finished in only 3 days.

Working with another Hexagon business, the Minbar was captured with the Leica T-Scan and tracked with Leica Absolute Tracker AT402 by the Hexagon Manufacturing Intelligence scanning team in Turkey.

“With the supreme precision of the Absolute Tracker, I was able to capture every detail of the intricate woodwork in the Minbar,” said Gökhan Sunar, Hexagon Manufacturing Intelligence application manager - portable systems. “Combined with the detailed scan of the interior of the mosque by the C10, we were able to provide a full 3D model of such a historical and culturally important site.”

Bringing several point clouds into one

The point clouds captured by different instruments were registered and overlapped in 3D Reshaper softtware and modeled.

Total data size and modeling accuracy:

• Around 1GB for high resolution C10 scans at 2 mm
• 3 GB for T-Scan and Absolute Tracker scans 20 micro-metres

The scan data from T-Scan was given in millimeters scale in order to work in a metrology market, however, the unit of C10 scan data was in metres.

To achieve a registration of the multiple data, T-Scan results were scaled in 3DR software with x1000 factor. The datasets then became the same scale, and the best fit registration function was applied to the data.

This enabled registration of the multiple point clouds in the same coordinate system. As a result, 3D models created by meshing command in 3DR and models reconstructed and edited for better quality.

With this 1-2-3 solution, the Bursa Grand Mosque is now digitally preserved for generations to come. With the 3D model on display in the museum, people are able to enjoy its beauty and cultural significance.