Objective:

Volta River Estates has opted to convert an existing banana plantation into a real estate.

They request for a topographical map with levels and contours of the land with its surroundings so as to enable an appointed planner design a masterplan for the commencement of the land development as well as carry out further design works.

 

Project Description:

Location: Akosombo, Ghana.

Total Site Area: 49 Ha (approx.)

Total surveyed area: 116ha

Total extracted 3D ground data area: 78Ha

 

Housing/Estate development is to be located along the Volta River downstream from the Akosombo dam, with utility services, infrastructure and parking facilities.

 

 Scope of survey:

The following deliverables were required:

  • Production of a grid map of 25m x 25m
  • Contour map
  • Detailed map with existing features, buildings, roads, utilities and Trees/vegetation
  • Longitudinal sections North-south and X sections
  • A height discrimination model showing the terrain slopes and water runoff tendency

Methodology:

A Phantom 4 Pro Drone with a 1” sensor was used for image capture

20 GCP (ground control points) were installed and surveyed with a pair of RTK DGPS.

20 targets visible on the imagery at 100m were fabricated and placed on the GCP.

The DGPS loop closure triangulated accuracy with the DGPS was 43mm.

A flight altitude of 100m was selected to provide an average ground sampling of 2.68cm/pixel

The corresponding anticipated accuracy was 5.36cm in northern & eastern, and 8.04cm in height.

All imagery was captured in regular corridors with a 80% longitudinal overlapping and 70% transversal

A total of 1135 images were taken in a pattern of 1745 m x 536m in a multiple flight pattern of 1hour

Imagery was processed with a photogrammetric software generating an orthomosaïc and a DSM.

A DTM was generated and a 5m x5m grid levels was extracted.

A GIS software enabled a selective extraction of ground levels below the banana trees, selecting the existing ground and removing interference by the tree canopy and vegetation.

Subsequent data was analyzed with a digital ground modelling software (PDS causeway) and the topographical maps were extracted in ACAD.