Available micro-sized Unmanned Aerial Vehicles (UAVs) in the civilian domain currently make use of common GPS receivers and do not address scenarios where high-precision positioning of the UAV is an inevitable requirement. However, for use cases such as creating orthophotos using direct georeferencing, an improved positioning needs to be developed. This article analyses the requirements for integrating Real Time Kinematic positioning into micro-sized UAVs. Additionally, it describes the data processing and synchronisation of the high-precision position data for a workflow of orthorectification of aerial imagery. Preliminary results are described for the use case of precision farming.

1. High-precision Positioning and Real-time
Data Processing of UAV-Systems
Matthes Rieke,
Theodor Foerster, Jakob Geipel, Torsten Prinz
Institute for Geoinformatics – University of Muenster
UAV-g 2011 Conference – September 16, 2011 – Zurich, Switzerland
http://purl.net/ifgi/copter

2. Sensor platforms
● Current available UAV systems use common GPS receivers
● Not addressing use cases where high position accuracy is inevitable
● Creating orthophos using Direct Georeferencing
2 http://purl.net/ifgi/copter

3. Approach for improving position accuracy
• Micro- or small-sized UAV systems
• Improvement using Real Time Kinematic
• Prototypical realization using a Microdrones md4-200
• Overview of the used hardware
• Conceptual design of data processing software
3 http://purl.net/ifgi/copter

4. Teaser of the used hardware
4 http://purl.net/ifgi/copter

5. Possible use case
• Improve/Enable Direct Georeferencing
• Currently limited due to several aspects
• Exterior orientation (e.g. low-cost GPS/GNSS, IMU)
• Alignment of time of image acquisition and positioning
 Focus on improving absolute positioning using advanced GNSS
techniques + timestamp synchronisation
• Stabilize flight trajectory
• Decrease the position delta between planned and actual image position
5 http://purl.net/ifgi/copter

6. Improving position accuracy on-the-fly
REAL TIME KINEMATIC
6 http://purl.net/ifgi/copter

7. Real Time Kinematic
• Specialized form of Differential GNSS
• Ground based Augmentation System
• Takes phase observations into account for error estimation
• Based on correctional signals from national services
7 http://purl.net/ifgi/copter

8. Real Time Kinematic
• What do you need?
• In general: rather cost-intensive hardware
• GNSS receiver + antenna – processing of RTK corrections
• Radio modem (e.g. GPRS) to retrieve correction signals
• Processing unit for data communication
• Payload!
8 http://purl.net/ifgi/copter

9. Real Time Kinematics
9 http://purl.net/ifgi/copter

10. Benefitting from improved positioning
DATA PROCESSING
10 http://purl.net/ifgi/copter

11. Software approach
● Software running on groundstation
● Support for different UAV platforms
● Synchronization of multiple data streams to enable
real-time measurement capabilities
● Modulized architecture to foster reusability
● Realized using Software Framework
11 http://purl.net/ifgi/copter

12. Framework Approach
● Architecture
12 http://purl.net/ifgi/copter

13. Framework Approach
● Synchronization of sensor streams
● Why synchronize streams?
● Knowledge of exact position at time
of image aquisition
● Currently: interpolation mechanism
● Abstract – easily adjustable for application
13 http://purl.net/ifgi/copter

14. Framework Approach
● Basis is description of Plugin Behaviour
● Input/Output phenomena using XML descriptions
● When to determine a position?
14 http://purl.net/ifgi/copter

15. Applying in real-world situations
RESULTS AND FUTURE WORK
15 http://purl.net/ifgi/copter

16. Hardware integration
• Currently only DGPS receiver used
• Future work involves an RTK-enabled L1/L2 GPS/GLONASS
receiver
• Problem of moved centroid
• Hardware optimization
• Implementation of Direct Georeferencing workflow
• Move to md4-1000 to gain more payload
16 http://purl.net/ifgi/copter

17. Hardware integration
17 http://purl.net/ifgi/copter

18. Use case – precision farming
Monitoring Precision
workflow farming
Push-based
communication
18 http://purl.net/ifgi/copter

19. Source Code available at:
19 http://purl.net/ifgi/copter

20. WHAT IS MISSING?
20 http://purl.net/ifgi/copter

21. Thank you for your kind attention!
Questions?
http://purl.net/ifgi/copter
Matthes Rieke – m.rieke@uni-muenster.de
21 http://purl.net/ifgi/copter