Drone Data Accuracy: What You Need to Know
- Hammer Missions
- Sep 16
- 4 min read
Updated: Oct 8
When it comes to drone inspections, one of the most common misconceptions in the industry is that using RTK automatically guarantees highly accurate measurements. While RTK and other positioning methods certainly play a role, they are only part of the story. In reality, data accuracy in drone inspections is influenced by multiple factors — and understanding the difference between relative accuracy and absolute accuracy is critical for getting the results you need.
At Hammer Missions, we regularly work with engineering firms, surveyors, and property managers who depend on accurate data. In this post, we’ll break down the two types of accuracy, explain why GSD (Ground Sampling Distance) matters so much, and help you determine what level of accuracy is right for your project.
What Is Relative Accuracy in Drone Data?
Relative accuracy, also known as internal accuracy, refers to the consistency of measurements within the drone map or model itself. If you’re trying to measure the distance between two points in a 2D map or 3D model, relative accuracy determines how reliable those measurements are in relation to each other.
The most important factor driving relative accuracy is GSD (Ground Sampling Distance) — the distance between two consecutive pixel centres on the ground. To understand GSD in more detail, read our blog on the subject here. Put simply:
Flying closer to the subject = finer GSD = more detail per pixel.
Flying further away = coarser GSD = less detail per pixel.
If your data is captured at 1 cm per pixel, your relative accuracy will typically be within 2–3 cm. This level of accuracy is often more than sufficient for tasks like roof measurements, facade inspections, or volume calculations.
Key takeaway: For accurate measurements, focus on GSD and camera quality, not just on positioning systems.
What Is Absolute Accuracy in Drone Data?
Absolute accuracy is about how well the drone data aligns with the real-world coordinate system. In other words, if you overlay your drone-generated map with a surveyor’s plan, does it line up correctly in geographic space?
The main challenge here is GPS error. Most drones have an inherent GPS error margin of up to a meter, meaning their reported positions can deviate from their true positions. That’s why additional methods are often required to correct absolute positioning:
GCPs (Ground Control Points): Physical markers measured with survey-grade equipment and used to correct drone models during processing.
RTK (Real-Time Kinematics): Provides real-time GPS correction through a base station or network connection.
PPK (Post-Processed Kinematics): Similar to RTK, but corrections are applied after the flight, reducing the risk of signal issues on site.
Absolute accuracy is crucial for projects where drone data must align with design drawings, site plans, or other georeferenced datasets — for example, in construction monitoring or as-built verification.
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When Do You Need Each Type of Accuracy?
In many projects, you don’t need both at the same time. The key is to match the level of accuracy to the outcome you’re trying to achieve.
Relative Accuracy: Ideal when your goal is to obtain precise measurements within the model itself — e.g., measuring roof areas, identifying facade defects, or estimating volumes.
Absolute Accuracy: Essential when your data needs to align with external datasets — e.g., construction progress tracking, BIM integration, or topographic surveys.
Want to see these accuracy levels applied in practice? Watch our case study video on measuring a roof using drones for a step-by-step breakdown:
The Role of Cameras and Flight Planning
It’s not just about distance to the subject. Camera quality also plays a significant role in determining GSD. A higher-quality camera with the right focal length can capture more detail at the same flight altitude, improving both efficiency and accuracy.
Effective flight planning, combined with the right equipment, ensures you’re striking the right balance between coverage and resolution.
Why This Matters for Your Drone Operations
Too often, teams invest in expensive positioning systems without fully considering whether they actually need absolute accuracy for their use case.
By understanding the difference between relative and absolute accuracy, and by planning flights with GSD in mind, you can:
Capture the level of accuracy that’s fit for purpose.
Avoid unnecessary costs and complexity.
Deliver data that’s directly usable for your stakeholders.
How Hammer Missions Can Help
At Hammer Missions, our software is designed to help you plan, capture, and analyse drone inspection data with precision. Whether you’re an engineer measuring building facades, a property manager inspecting roofs, or a surveyor capturing site data, our platform helps you:
Optimise flight planning for the right GSD.
Streamline data capture across different inspection types.
Generate actionable insights that save both time and cost.
If you’re looking to get more from your drone inspections, we’d love to help. Book a call to see how our platform supports accurate, efficient inspections.
About Us
Hammer Missions is a software AI firm helping companies in the built environment leverage drones and AI for assessing existing conditions. Having seen 5000+ projects, we're pleased to be working with leading firms in AEC to streamline and scale the process of facade inspections. If you're looking to learn more about how AI can automate and accelerate your building assessment projects, please get in touch with us below. We look forward to hearing from you.
