RTK, PPK, and GCP Explained: Choosing the Right Positioning Method for Your Drone Survey

If you’ve been working with or researching drone-based data collection, you’ve probably come across terms like RTK, PPK, and GCP. These acronyms can be confusing or even overwhelming if you’re new to the field. In this article, we’ll walk through what these techniques are, how they work, and when to use them.

RTK (Real-Time Kinematics) is a correction technique used to improve the accuracy of GPS positioning systems and is commonly employed in drone operations. It involves using a fixed GNSS base station to establish a known reference point. This base station sends correction data in real time to mobile GPS receivers (rovers) on the drone, allowing them to correct for errors and achieve centimeter-level positional accuracy during flight.

A GNSS RTK base station is commonly used on surveying sites.

PPK (Post-Processed Kinematics) is a GNSS correction technique typically applied on the payload side, where raw satellite data is logged during the flight and processed after the mission to compute precise positions. By decoupling correction from real-time constraints, PPK enables centimeter-level accuracy even in environments where RTK (Real-Time Kinematics) is unreliable or unavailable, making it ideal for mapping, surveying, and other high-precision applications.

GCPs (Ground Control Points) are widely used in photogrammetry and surveying. These are physical markers placed at known, surveyed locations within the mapping area. Their precise coordinates—measured using a base station or high-accuracy GNSS equipment—are later input into photogrammetry software to improve the geometric accuracy of the resulting map or 3D model.

Ground Control Point (GCP) markers are commonly used in mapping and surveying.

What are the Pros and Cons of Each Method?

Type of Correction	Pros	Cons
RTK	Real-time, high accuracy positioning No post-processing steps	Requires a stable base to maintain accuracy Accuracy can vary depending on signal quality
PPK	Doesn’t require real-time communication with the base station Can be more reliable than RTK in some conditions	Requires post-processing, can be time-consuming Depending on the payload, some require upfront setup to use PPK corrections
GCP	Improves accuracy of the final deliverables Doesn’t depend on signal quality such as RTK/ PPK corrections	Require additional setup and surveying steps Not as scalable for large areas

When to Use RTK, PPK, or GCPs?

RTK is a correction technique used for the drone itself. All Arcsky drones are equipped with GNSS modules capable of RTK corrections. To use RTK, you simply need the RTK Base Module or an internet-based RTK correction service (NTRIP). One of the key advantages of using an internet-based service is that it requires no on-site setup. However, the trade-off is that you need reliable internet access. In contrast, the RTK Base Module does not require an internet connection, but must be “surveyed-in” for a long time period in order to get an accurate positioning estimation.

RTK is particularly useful for inspection work, as it improves the drone’s relative positioning accuracy in real time. This is especially beneficial when zooming in to inspect or monitor specific areas of interest, helping to minimize positional drift which can be caused by GPS inaccuracies.

RTK vs Non-RTK Flight Comparison

PPK, on the other hand, is a correction technique applied to the data itself. As long as the hardware is able to collect the GPS data in the required format, and you are able to collect GNSS observations from a fixed base station, you’ll be able to post-process your GPS data to dramatically increase accuracy. Not all payloads support PPK, but if you’re a LiDAR operator, the good news is that most LiDAR payloads come with the ability to do PPK corrections. For camera systems like the Sony ILX or Phase One P3, additional setup is required to enable PPK corrections.

PPK is ideal for LiDAR applications, and most LiDAR sensors have a PPK correction workflow to achieve higher accuracy. This reduces the sensor's dependency on external corrections while maintaining high data accuracy.

GCPs are particularly effective for small to mid-sized surveys, where they can be quickly deployed and easily accessed. In these scenarios, they provide excellent ground-truth data to anchor aerial imagery during photogrammetric processing, significantly improving georeferencing accuracy. However, GCPs become less practical for large-scale surveys, where placing and measuring enough points across expansive or difficult terrain can be time-consuming and labor-intensive. In such cases, you'll have to rely more on positioning methods like RTK or PPK.

Overall, GCPs are best suited for localized projects where survey teams can establish and record control points efficiently, delivering high-accuracy outcomes with minimal equipment. However, this all depends on the accuracy required of the final deliverable. An experienced surveyor will generally know what sites and projects require the usage of GCPs, how many to use, and their ideal placement within a data capture project.

RTK, PPK, and GCPs each offer unique advantages depending on your hardware, workflow, and the scale of your project. Many surveyors find that combining methods—like using RTK for real-time corrections and GCPs for post-flight accuracy—produces the best results. Understanding when and how to use each technique is key to optimizing your data quality and workflow efficiency.