AG Surveys collects topographic beach surveys throughout England

Prepping for flight: Andreas Garbe, AgSurvey, sets up the UX5 HP for a topographic survey at Severn Beach, a village in South Gloucestershire. (Photo: Trimble)

Based in Bristol, AG Surveys has been collecting topographic beach surveys around the country as part of England’s Environment Agency’s coastal monitoring campaign.

In the first integrated approach of its kind in the program, AG Surveys uses the Trimble UX5 unmanned aerial system (UAS) equipped with a Trimble/Applanix GNSS receiver along with photogrammetry software. The UAS-based system has not only confirmed its viability for coastal monitoring, it has been bringing new business opportunities ashore since 2017.

For each beach, AG Surveys must provide one baseline survey based on a 5-meter grid with a height accuracy of 3 centimeters. Also required is a series of profile line surveys. Profile surveys follow pre-defined lines set every 50 meters from the back of the beach to the low tide line, with GNSS measurements taken within 10 centimeters of each side of the line.

Crews typically cover 3 square kilometers a day, flying four to five Delair drone flights at an altitude between 100–120 meters, at speeds of 80 kph and a lateral overlap of 80%. To ensure the reliability and accuracy of the UAS data, they use a minimum of 10 ground control points (GCPs) for each flight block and measure each target’s position with a GNSS receiver.

Once flights are complete, the team imports into Trimble Business Center (TBC) the flight and GNSS data and the base station survey data. Using both on-board GNSS positioning data and the ground control data, they process precise, short baselines between the base station and each photo point. All images are then integrated into Trimble’s Inpho UASMaster software to create a dense point cloud and a seamless orthophoto of the entire area of interest. (UASMaster is now integrated into the TBC Aerial Photogrammetry Module). If needed, they can also use UASMaster to produce a seamless, georeferenced orthophoto directly from the point cloud.