RTK drone photogrammetry over tea terraces: ground control points on steep contours?

Conducting high-precision RTK drone surveys across steep mountain tea estates (like Nuwara Eliya or Talawakelle) presents severe multipath signal reflection issues caused by steep granite ridges and dense Grevillea shade trees. Surveyors must mount GNSS base stations on high ridge vantage points with unobstructed 360-degree sky views. Ground Control Points (GCPs)—high-contrast black-and-white checkered targets measuring 60x60cm—must be pinned onto concrete estate boundary stones and road culverts at varying elevation bands across contours to prevent vertical z-axis warping in photogrammetric point-cloud reconstructions.