In the surveying profession, unmanned aerial systems (UAS), also known as drones, offer an opportunity to augment existing conventional tools with hardware and software that minimize risk of injury, reduce data collection time and lower cost.
Although not suitable for every project, such as boundary work and construction staking that require conventional surveying, drones are perfectly suited for topographic surveys in areas that are difficult to access on the ground.
For example, a project in a busy transportation corridor carries a high risk of injury to surveyors and causes lengthy delays in traffic, and an irrigation ditch has lots of twists and turns that would be time consuming to survey manually. Collecting data with a drone expedites the work and reduces inconvenience for everyone.
“We follow best practices for reliable and accurate data collection to meet the standards set by ASPRS ─ it’s important to be able to verify the data quality,” says Jonas Collier, LSIT. “We also use the drone for site scouting before we carry out a conventional survey. It is a great supplementary tool.”
To achieve centimeter-level accuracy with a drone, survey control points and check shots are collected with a survey-grade GPS receiver. The points are used to tie the drone dataset to the real world and check for errors.
This data can produce an orthomosaic, a digital surface model (DSM) and other deliverables. For additional quality assurance, real-time kinematic (RTK) data is accessed through a base station and rover and corrections are sent throughout the flight. A Points to Surface report verifies the accuracy of the final project.“Every survey has its own unique requirements,” Collier explains. “We use a drone when it’s the best fit for the job, when it will save time and money while delivering the accuracy we need – otherwise conventional surveying is the way to go.”