Unveiling the mystery - an ancient water clock with laser scanning

Author: Reka Vasszi

Inventing devices for keeping track of time is something mankind experimented with for thousands of years before the first digital clocks were invented. Ancient civilisations observed astronomical objects, such as the sun or the moon to determine time, dates and seasons. Along with sundials, water clocks were among the first devices used for measuring time from the 16^th century onwards.

A more complex hydraulic-clock house, as compared to ancient water-clocks, was built attached to the Medersa Bouanania, school of theological sciences and congregational mosque in Fez, Morocco. The educational and religious complex was constructed in 1357 under the Merinid reign of Sultan Bou Inan who commissioned the hydraulic-clock to communicate the correct times of prayer to the muezzin, who leads and recites the call to prayer five times a day for worship in the mosque.

Recently, the Medersa underwent a restoration project by the Agency of Development and Rehabilitation of the city of Fez (ADER-Fès). Together with local artisans, ADER-Fès, reconstructed the Medersa’s unique glazed earthenware mosaics and its fabulous wooden ceiling of carved cedar.

Aided with 3D laser scanning technology, specialists are now restoring the mysterious weight-powered hydraulic clock, which stopped working after it went into disuse when the Saadian dynasty replaced Merinid rulers and moved the capital from Fez to Marrakech. To reveal the mystery of the water clock’s internal mechanism and completely restore it, experts from Geo Lambert, a surveying company in Fez, scanned the façade and interior of the hydraulic-clock house with the Leica BLK360 imaging laser scanner and the Leica RTC360 3D reality capture solution.

Surveying in narrow areas

It is said that a magician created this elaborate hydraulic-powered clock that released metal balls from 12 little doors into brass bowls on the lower beams to chime out the five calls to prayer. This unique technical masterpiece, unfortunately, has not survived the centuries in its original condition.

To bring the clock to life again, Geo Lambert surveyors were requested to scan the clock, produce orthoimages and a 3D meshed model focusing on 2D elevations and cross-sections. Reaching the clock was challenging for the specialists, as it is located vertically on the wall of the Medersa. In addition, the façade has narrow archways where larger laser scanning equipment could not fit.

“The BLK360 made it possible for me to survey a very narrow hall behind the clock thanks to its small size and quick setup,” said Adam Bouramdane, senior surveyor at Geo Lambert.

To come across the challenges, Geo Lambert chose the portable and lightweight BLK360 to capture the clock in detail. Being the first company in the Maghreb to have acquired the BLK360 from leica's new selling unit in Morocco and with a large background in 3D scan, the surveying experts were able to scan the unique time keeping equipment and its environment in a day. To manage project complexities with accurate and reliable 3D representations, the team scanned the heritage building with the RTC360.

Scanning the finest details

After cleaning and registering the captured data, the team created a 3D model of the historic clock that will be the basis of future research and restoration.

“The good point accuracy and density while being very lightweight and portable made the BLK360 and the RTC360 perfect for heritage surveying, especially in narrow areas,” said Raghib Mehdi, associate surveyor at Geo Lambert.

Thanks to its small size, ease-of-use and accuracy, Leica Geosystems’ laser scanning technology opens new horizons in heritage preservation, as in the case of the mysterious clock in Morocco.