Evaluating Orthophoto Mosaic Accuracy Using RTK UAVs and AeroPoints 2 Ground Control Points: A User’s Perspective

Abstract

With the growing use of Real Time Kinematics (RTK) Unmanned Aerial Vehicles (UAVs) and advancements in ground control points (GCPs), assessing positional accuracy of UAV derived orthophoto mosaics is crucial. This study aimed to improve UAV aerial image accuracy for more reliable orthophoto mosaics by examining the positional accuracy of orthophoto mosaics derived with (1) an RTK UAV; and (2) an RTK UAV combined with AeroPoints 2 GCPs. We tested two GPS base station methods for the RTK UAV: self-determined and manually assigned coordinates. The manually assigned coordinates resulted in significantly lower root mean square error (RMSE = 0.0729 m) compared to the self-determined method (RMSE = 1.9762 m), indicating improved accuracy. For the AeroPoints 2 GCPs, we recorded coordinates from a central GCP at a known location and four additional GCPs placed in each cardinal direction. The AeroPoints 2 system showed lower RMSE at all points compared to the RTK, with the central GCP at 0.0136 m, indicating high accuracy. These findings suggest that while RTK UAVs improve accuracy with manual base station assignment, incorporating AeroPoints 2 GCPs provides consistently higher precision across multiple locations. The study highlights the potential of AeroPoints 2 GCPs and suggests further research opportunities to enhance RTK UAV accuracy in areas lacking GPS correctional networks.

Keywords

Real-time kinematic (or RTK) / Unmanned aerial vehicle (or UAV) / AeroPoints 2 / Ground control points (or GCPs) / GPS / Positional accuracy

Acknowledgments

We would like to thank everyone who made this study possible. We are especially grateful to Clayton Collier at Hydrex Environmental, and John Chapman at Hydrex Environmental, for providing orthophoto mosaic imagery for the study. Kenneth Farrish provided an Environmental Science Graduate Research Assistantship to E. Shupe through the McIntire-Stennis Cooperative Forestry Research Program. We would also like to thank Isaac Smith, Jacob Boatman, Canon Gainer, and Alexandria Cook for their help in collecting the field data. Finally, E. Shupe would like to thank Martin and Lori Shupe for their support and encouragement.

Author Contributions

Conceptualization, E.S., D.U., D.K., I.-K.H. and Y.Z.; Methodology, E.S., D.U., D.K., I.-K.H. and Y.Z.; Software, E.S., D.U., D.K., I.-K.H. and Y.Z.; Validation, E.S., D.U. and D.K.; Formal Analysis, E.S.; Investigation, E.S., D.U., D.K., I.-K.H. and Y.Z.; Resources, E.S., D.U. and D.K.; Data Curation, E.S.; Writing—Original Draft Preparation, J.K.; Writing—Review & Editing, E.S., D.U., D.K., I.-K.H., Y.Z. and J.K.; Visualization, E.S.; Supervision, D.U., and D.K.; Project Administration, D.K.; Funding Acquisition, D.U., D.K., I.-K.H. and Y.Z.

Ethics Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data will be made available on request.

Funding

McIntire-Stennis funds (Grant Number: NI24MSCFRXXXG037), administered by the Arthur Temple College of Forestry and Agriculture at Stephen F. Austin State University (SFA), were used for the completion of this project for E.S. Dr. Kenneth Farrish, Director of the Division of Environmental Science at SFA, provided an Environmental Science graduate assistantship for this project for E.S.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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