Build of engineering facilities predicts constant monitoring of construction location. Surveyors job is to establish permanent, well stabilised control points on objects of construction, its fundations, terrain and other buildings in vicinity. With high accuracy, measures their temporal spatial position. To abide natural movements, monitoring needs to be observed before, during and well after construction. Coordinate displacements of observed points are computed, and statistically processed, to establish objects stability and detect plausible movements.
ISC Consulting Engineers A/S, one of our Denmark customers, provided us with the dataset of construction of an Oil terminal in Frederikshavn. During construction, they made three flights over the terminal, to observe changes. LE34 conducted survey monitoring. Geodetic network was established, 250 control points were stabilized. Control points were measured in 19 temporal measurements, at different stages of construction. Tenth measurement was made at the tame, tanks 1 and 2 were constructed and empty. As tanks were filled, several measurements were made. Nineteenth measurement shows vertical displacements(faint) due to weight of 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
For aerial survey, 7 GCPs were used, their position was measured with total station. Three flights were made. Several cases of tanks were measured:
- Both tanks empty
- Tank 1 full, tank 2 empty
- Both tanks full.
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 13.6 and 14.4cm were detected.
Comparison of 10th and 19th measurement, and detected vertical displacements.
To observe differences, both point clouds were displayed at once to observe differences. Profile lines were made across tanks. Further inspection shows vertical exaggeration of the tank lid and its wreath.
Point cloud from the first measurement
Point cloud from the second measurement with the newly built pipeline basin.
Section comparison of Fully textured 3D mesh of empty and filled tank 2.
Section comparison of two perpendicular profiles of empty and filled tank 2.