Oil tank construction monitoring in Denmark
The building of engineering facilities often involves constant monitoring of the construction site. The surveyors job is to establish permanent, well stabilised control points on objects of the construction site, for example, its foundation, the terrain and other buildings in the vicinity. With high accuracy, it is necessary to measure their temporal spatial position. To take into account natural movements, monitoring needs to be observed before, during and well after construction. Coordinate placements of observed points are computed, and statistically processed to establish objects stability and detect plausible movements.
ISC Consulting Engineers A/S, one of our Danish customers, provided us with the dataset of the construction of an Oil terminal in Frederikshavn. Frederikshavn is located on the northeast coast of the Jutland peninsula in northern Denmark.
During construction they made three flights over the terminal to observe changes. LE34 conducted survey monitoring. A geodetic network was established, and 250 control points were stabilized. Control points were measured in 19 temporal measurements, at different stages of construction. The tenth measurement was made at the time tanks 1 and 2 were constructed and empty. As tanks were filled, several measurements were made. The nineteenth measurement shows vertical displacements (faint) due to the weight of the filled tanks.
Project tools and specs
- Area of interest: 10.000m2
- Drone: DJI Phantom 4 RTK
- Camera: on board, 300 images with 70% horizontal and vertical overlap
- Number of GCPs: 7
- No. of point cloud points: 113.431.703 empty tanks 1 and 2; 114.287.324 full tank 2
- Made by: ISC Consulting Engineers A/S and LE34
- Location: Oil terminal, Frederikshavn, Denmark
- Date: January – February 2020
Workflow and Processing
For aerial survey, 7 GCPs were used. Their position was measured with total station. Three flights were made. Tanks were measured at various stages:
- Both tanks empty
- Tank 1 full, tank 2 empty
- Both tanks full.
After importing images, the point clouds were computed on an extreme level. To detect structure changes, point clouds of empty and filled tanks were loaded into one project. Longitudinal profiles were computed across both tanks. Full tanks lid raise of 13.6cm and 14.4cm were detected.
Here you can see a comparison of the 10th and 19th measurement. Vertical displacements were detected.
To observe differences, both point clouds were displayed at once. Profile lines were made across tanks. Further inspection shows vertical exaggeration of the tank lid and its wreath. Click on the images below to see the point clouds, textured 3D mesh and CAD.