Real Time Kinematics (RTK)

What is Real Time Kinematics (RTK)?

Real Time Kinematics (RTK) is a navigation technique that enhances the precision of position data derived from other satellite-based positioning systems, such as GPS. While useful and sufficient in many use cases, GPS alone lacks the precision required for wind turbine inspections and other infrastructure site surveys.

With RTK, centimeter-level accuracy becomes possible by getting an exact date about the physical area in the digital world and, in the case of wind turbines, the exact location of the structure.

How Does RTK Enhance Accuracy and Quality?

How does RTK work so well that it provides location data accurately within a few centimeters? RTK enhances the position of data the Global Navigation Satellite Systems (GNSS) provides by adding a component to the positioning data — the base station.

A stationary GNSS receiver, known as a base station, is set up at a fixed, known location. The station continuously receives satellite signals and calculates the drone’s RTK position. The receiver’s fixed location, combined with the drone’s known location, allows for accuracy correction.

There are two types of base stations, both providing roughly the same benefit in different ways:

  1. Dynamic (D-RTK): This type of system can be operated locally on-site and is deployed near the field of operation. The base station receives GNSS signals, calculates positional errors, and sends real-time corrections to the drone. D-RTK is ideal when operations are concentrated in a specific, localized environment.

  2. NTRIP (Network Transport of RTCM via Internet Protocol): This type of system does not require a local base station. Instead, it operates from a centralized server that collects data from multiple locations spread out over a wide area. NTRIP systems are ideal for regional or even national-scale operations for RTK surveys and maps.

Benefits of RTK Technology for Wind Turbine Inspections

RTK drones can benefit from a new level of accuracy that isn’t possible with GPS, allowing autonomous drones to be useful in various applications — including wind turbine inspections.

Manual drone inspections were an upgrade to rope inspections, and autonomous drone inspections represent another leap forward. This type of inspection requires minimal human involvement and consistently captures data that can be used to evaluate the health of a turbine.

RTK is one of several technologies making autonomous drone inspections feasible and a cornerstone of modern wind farm management. Let’s break down a few of the benefits RTK brings to wind turbine inspections.

Highly Accurate Navigation

RTK provides drones with centimeter-level RTK accuracy, which is critical for navigating wind farms. While the turbine being inspected is taken offline, others nearby might not be. Basing navigation decisions on inaccurate GPS data may result in colliding with a nearby turbine.

Additionally, the same principle applies to other obstacles that may be nearby, like other structures, hills, or rock formations.

Beyond collision avoidance, drones must capture data at specific turbine areas. Accurately navigating to the specified components, such as each turbine blade, to capture data can be challenging for automated systems when relying on GPS data.

Automated Flight Paths

Flight paths for turbine inspections may be pre-programmed rather than the drone making all of the decisions for each inspection. However, these repeatable instructions must still be followed, and doing so requires precise location data.

RTK allows drones to easily follow these instructions even as weather conditions, wind force, or other issues may change the flight conditions

Verification with Ground Control Points (GCPs)

Some vendors may use a Ground Control point (GCP) alongside RTK to verify the accuracy of positioning data further. This added check helps avoid possible issues that may still emerge if the RTK system has an error.

The exact level of accuracy from an RTK system can vary, so the added verification of GCPs can be highly valuable in scenarios where a small error can have disastrous consequences.

Improve Photogrammetry

Although the photogrammetry process itself does not inherently account for RTK, the use of RTC-enhanced photos can lead to more accurate models. The high precision of geotagged images allows for accurate alignment and stitching of photos, resulting in accurate 3D models and maps.

Digital twin platforms can significantly benefit from the added accuracy of the images and other data they receive when building and updating the environment. The high level of precision provided by RTK makes it a critical yet often overlooked capability in the modern landscape of autonomous drones and digital twins.