Casablanca’s Medina buildings monitored during tunnel construction

March 6, 2020  - By
Photo: ETAFAT/Spectra Geospatial

Photo: ETAFAT/Spectra Geospatial

Engineers are monitoring in real time the effects on Casablanca’s aging buildings during tunnel construction using a Spectra Precision GNSS receiver.

Vibrations during the construction of a new 1,890-meter tunnel adjacent to Casablanca’s Old Medina, the 250-year-old section of the famed Moroccan city, challenged the stability of its historically important buildings.

To monitor in real time the effects on the Medina’s aging buildings and to confirm that the construction work meets all engineering standards and guidelines, ETAFAT, a geospatial information acquisition and processing company, used the Nikon XF Total Station to perform more than 100 daily inspections. The ETAFAT team relied on optical targets placed on building facades whose coordinates were determined by forced centering to complete the inspections.

The new Les Almohades tunnel, beneath the Boulevard des Almohades, runs parallel and adjacent to the old Medina. Together with its 380 meters of access roads, the twin-tube tunnel, which carries traffic in two unidirectional lanes in each tube, was constructed to reduce traffic congestion.

According to ETAFAT engineers, the Nikon XF 1” with its fast autofocus function, saved considerable field time. The Nikon XF enabled fast collection of highly accurate observations throughout the monitoring and control of the planimetric and altimetric locations of the structure. The monitoring of the buildings during the various phases of the tunnel’s construction generated a large amount of data essential for understanding the consequences of the work and defining any necessary corrective measures.

The Nikon FX 1,” with its advanced options and Survey Pro software, enabled survey teams to quickly yet accurately perform a variety of other essential field tasks.

These tasks include digital terrain modeling (DTM), cubature calculations, coordinate geometry (COGO) topometric calculations and layout control with customized report generation. The use of Survey Pro software enabled ETAFAT engineers to fully integrate their total station work with their fleet of Spectra Geospatial SP60 GNSS receivers.

The Nikon XF 1” is a mechanical total station that stands up to tough worksite conditions. It is designed to quickly capture accurate measurements, and it offers crisp, clear optics for sighting in both bright and low-light conditions.

Its dual-color touchscreen displays run Survey Pro, Survey Basic and Layout Pro.

It is also equipped to take advantage of the optional Trimble Protected L2P device for asset security to locate lost, stolen or missing equipment. Its hot-swappable batteries reduce downtime and a PIN enhances security in the field.

About the Author: Tracy Cozzens

Senior Editor Tracy Cozzens joined GPS World magazine in 2006. She also is editor of GPS World’s newsletters and the sister website Geospatial Solutions. She has worked in government, for non-profits, and in corporate communications, editing a variety of publications for audiences ranging from federal government contractors to teachers.