By Maja Urbas
Architects are often dealing with heritage conservation projects. The fundamental need of any conservation project is understanding the object and gathering data about its physical condition prior to any action and intervention that might change the object. Each object has its own unique characteristic and based on its physical condition, time and needed accuracy for the project, architects decide which documentation approach or tool is the most appropriate.Read more
In the city centre of Ljubljana, the capital city of Slovenia, there is the Ljubljana Central open market, designed by the famous architect Jože Plečnik, built in 1942. The design of the complex reflects Renaissance influences and it is a cultural monument of national importance. For the purpose of renovation, the Architectural office Kramar had to capture all the elements of the building (walls, columns, retaining walls, wreath, windows, doors, roof, openings, …). The result of the capture is a point cloud on the basis of which BIM modelling is then performed.
Architects had 2 ways on how to approach this project most efficiently:
TLS Terrestrial Laser Scan, it gives great results, but lasers cost more than 60k EUR, plus specific software for processing has to be used which comes with extra cost
Photogrammetry, a great cost-efficient option, perfect for rocky buildings, because of the incredible texture. For this kind of project, only a hand camera is needed.
Their decision was to use a hand camera and 3Dsurvey. Total investment was 500 EUR for the camera and 3000 EUR for the software.
Advantages of using photogrammetry for 3D documentation:
Using an ordinary digital camera, 320 photos were captured and used in 3Dsurvey for the calculations of a textured 3D model. Once the textured 3D model was created, the architect was able to calculate the orthophoto from any arbitrary side in a very fast time. The latest version of 3Dsurvey allowed them to also calculate the "Custom plane" orthophoto shot from the side, the Facade Orthophoto.
With this 3D documentation, the building is archived and can be used for all reconstructions in the future.
With this solution, the architects were able to precisely measure the dimensions of the building and were able to make a good estimation of needed material to create an offer for the client.
How to best capture all the necessary details using a hand camera:
Equipment: Standard digital camera Olympus EP2 (12Mpix camera)
Number of GCPS: 12 (local coordinate system; GCP measured with the total station).
Area of interest: 200m x 20m
Time on the field: 4 hours
Location: Ljubljana Center
Date: August 2020