3D Model Tutorial - Statue

Shooting 3D model of a statue (or tall objects) can be fairly tricky sometimes depending on height, shape, size, color of the statue and other environmental factors. The sample target Guan Yin (GY - Avalokitesvara) statue is 76m (250ft) height standing on a hill about 56m elevation surrounding by trees. There are a few challenges and need to plan carefully.

  • GY statue is slightly heading down. If we shoot from normal 20°-30° tilt down angle, we would miss a lot of details on her face. We need to figure out the proper aircraft height and angle shooting her face.
  • GY statue is in white color and with strong reflection under direct sunlight when shooting from top down. We would need to adjust EV at each level.
  • As GY statue heading down and her body bending forward, the target center from base to head shift forward about 10m. We need to judge the forwarded target distance at specified height.
  • GY statue is about 800m away from takeoff home point with 2m elevation, we are unable to inspect the statue onsite. We could barely see upper half of the statue from home point. We needed a pre-mission flight studying the terrain and other statue information before mission flights. We also need to fly within 500m to the target in order to start the mission due to DJI firmware restriction.
  • The highest terrain elevation under the orbit is about 70m, plus 15m-20m tall trees. We checked the elevation by placing virtual home point around the orbit to get the elevation figure. Thus, we estimate the clearance height is 90m. Aircraft may physically drop 10m-15m after 10 minutes flight due to IMU discrepancy upon heating up though altimeter reporting the same height. We needed to hover aircraft about 1-2 minute to preheat IMU then land it to reset height back to zero before the mission flight for better altimeter accuracy. 

The model was shot by 4 levels with 2 separate missions (2 levels per mission) as below.   

Level 1 Configuration: This level mainly covers the lower part of the statue and the base.

  • Aircraft height 105m
  • Medium speed (4.7 km/h, 4 Min/Rev)
  • Shot 118 photos, use 59 photos (~1/2) 
  • Radius 50m
  • Target height 80m
  • Tilt angle 27° (EV: -0.3)

Level 2 Configuration: This level mainly covers the face and upper part of the statue.

  • Aircraft height 110m
  • Medium speed (4.2 km/h, 4 Min/Rev)
  • Shot 118 photos, use 59 photos (~1/2)
  • Radius 45m
  • Target height 110m
  • Tilt angle 0° (EV: 0)

 

Level 3 Configuration: This level mainly covers the whole statue to ensure proper 3D model generation.

  • Aircraft height 135m
  • Medium speed (4.2 km/h, 4 Min/Rev)
  • Shot 117 photos, use 58 photos (~1/2)
  • Radius 45m
  • Target height 1100m
  • Tilt angle 29° (EV: -0.3)

Level 4 Configuration: This is a supplemental level and it's optional.

  • Aircraft height 150m
  • Medium speed (3.8 km/h, 4 Min/Rev)
  • Shot 116 photos, use 39 photos (~1/3) 
  • Radius 40m
  • Target height 95m
  • Tilt angle 54° (EV: -0.7)