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Drone Data Accuracy: GCPs, RTK, and PPK Explained

  • Writer: Anvita Shrivastava
    Anvita Shrivastava
  • 1 day ago
  • 4 min read

The use of accurate data provided by drones in the UAV mapping, surveying, and photogrammetry field is imperative for any professional projects. The reliability of your results will depend on the accuracy of the data you receive from the drones when producing your topographic maps, building models of construction sites, and measuring the volume of materials.


There are three primary ways to achieve positional accuracy in your drone mapping: GCPs (Ground Control Points), RTK (Real Time Kinematic), and PPK (Post Processed Kinematic).


Drone Data Accuracy: GCPs, RTK, and PPK
Drone Data Accuracy: GCPs, RTK, and PPK

Why Drone Data Accuracy Matters


There are seven areas that suffer due to drone map accuracy:


  • Survey-grade deliverables

  • Monitoring of construction progress

  • Calculation of earthwork volume

  • Inspections of infrastructure

  • Integration of Geographic Information Systems

  • Documentation of legal boundaries


Without some form of correction process, most commercial-grade drones will produce horizontal accuracy of only 1-3 meters in normal situations and will not be accurate enough for use in an engineering or surveying capacity.


Ground Control Points (GCPs)


What Are GCPs?


Ground Control Points (GCP) are fixed points on the Earth's surface that have been precisely located using high-accuracy GNSS receivers.


They are then used to correct and georeference drone imagery in the process of photogrammetry.


How GCPs Enhance Accuracy


  1. GCPs are treated as targets throughout the survey area.

  2. Each GCP is measured using survey-grade GNSS equipment.

  3. In the processing phase of photogrammetry, the software matches the targets found in the drone images to those found on the ground.

  4. These matches allow for model adjustments to correspond to true coordinates.


As a result, less distortion occurs in the model, improving both horizontal and vertical accuracy.


Typical Accuracy with GCPs


  • Horizontal: 1–3 cm

  • Vertical: 2–5 cm

(Depending on equipment and workflow)


GCP Advantages


  • GCPs provide an extremely reliable method of achieving survey-grade accuracy.

  • GCPs can be used for any drone and do not require a special onboard GNSS receiver.


Disadvantages of GCPs


  • GCPs take a considerable amount of time to set up.

  • GCPs require a significant amount of labor to use across large areas.

  • GCPs can also be challenging to access in some situations, particularly in hazardous or difficult-to-access terrains.

  • GCPs require survey-grade equipment to measure coordinates accurately.


RTK (Real-Time Kinematic)


What Is RTK?


Real-Time Kinematic (RTK) is a method of GNSS correction used for precision positioning during the flying of aerial imagery and obtaining a position accurate to a centimeter.


RTK drones can be used in conjunction with:


  • A local base station or

  • A network correction service (NTRIP)


The corrections are applied in real-time and immediately to the geotag of each image taken, resulting in a high degree of accuracy.


How RTK Works:


  1. The local base station (with its own GNSS receiver) calculates the GNSS errors in its area.

  2. The base station sends the GNSS correction data to the drone via radio.

  3. The drone is able to adjust its GNSS position in real-time using the correction data sent from the base station.

  4. The images taken by the drone are tagged with the high-accuracy coordinates.


Typical Accuracy with RTK:


  • Horizontal: 1–2cm

  • Vertical: 2–4cm


Benefits of Using RTK Drones:


  • No to very few ground control points required

  • Quick field workflow

  • Geotagged coordinates accurate immediately after image capture

  • Best for construction or time-sensitive projects


Drawbacks of RTK Drones:


  • Requires a constant source of correction signal

  • Loss of a corrected signal leads to diminished positional accuracy

  • Expensive equipment

  • Dependent on network coverage when using NTRIP


PPK (Post-Processed Kinematic)


What Is PPK?


PPK works in much the same way as RTK, but uses corrections from the processing stage of the flight rather than during it. In the PPK method, the drone logs raw GNSS data to be later corrected and processed with data from the base station.


How PPK Works (Overview of the PPK Process)


  1. Drone Records Raw Satellite Observations

  2. Base Station Records GNSS Data

  3. After Flight, Software is Used to Process and Apply Correction Data

  4. Image Corrections to Position Find Processed and Map to Corrected Location


Typical PPK Accuracy Levels


  • Horizontal: 1 to 2 cm

  • Vertical: 2 to 4 cm

  • Comparable to RTK Accuracy Under Ideal Conditions


Advantages:


  • No Real-time (RT) Signal Required

  • More Reliable Performance in Remote Mapping Locations

  • Greater Ability to Work in Weak Signal Areas

  • Reduced Field Errors

  • Fewer Ground Control Points (GCPs) Required, Sometimes Only Checkpoints


Disadvantages:


  • Requires a Post-processing Workflow

  • Slightly Longer Data Turnaround Time

  • More Technical Set-up Required


RTK vs PPK vs GCPs: Key Differences

Feature

GCPs

RTK

PPK

Field Setup

High

Low

Low

Real-Time Corrections

No

Yes

No

Post-Processing Required

Yes

Minimal

Yes

Signal Dependency

None

High

Low

Best for Remote Areas

Moderate

Limited

Excellent

Equipment Cost

Lower drone cost

Higher drone cost

Higher drone cost

Which Method Should You Use?


Ground Control Points (GCPs) are best for:


  • Standard Drones

  • Limited budget

  • Need for the highest reliability

  • Small or medium area coverage


Real-Time Kinematic (RTK) is best for:


  • Fast turnaround

  • Active Construction Sites

  • Reliable Real-Time Correction signal possibilities

  • Prioritizing reduction in field time


Post Processed Kinematic (PPK) is best for:


  • Remote Flying

  • Areas without reliable reception and/or signal dropouts

  • Accuracy of RTK-level without real-time risk

  • Ability to Control Accuracy Post Processing


Modern UAV mapping has evolved beyond basic GPS. With GCPs, RTK, and PPK, drone surveyors can achieve centimeter-level precision suitable for engineering-grade applications.

Your ideal choice depends on:


  • Project size

  • Terrain accessibility

  • Accuracy requirements

  • Budget

  • Workflow preferences


For many professionals, PPK offers the best balance of reliability and precision, while RTK excels in speed-focused operations. GCPs remain the gold standard for validation.


For more information or any questions regarding the drone data, please don't hesitate to contact us at:


Email:


USA (HQ): (720) 702–4849



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