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How does RTK work?
Certain drone models have real-time kinematic (RTK) capabilities (built-in or as external modules). They can act as receivers to gather data from satellites and reference stations to receive differential corrections in order to achieve absolute centimeter-level accuracy for positioning and mapping data. This removes the need for Ground Control points (GCPs).
Explanation: The remote controller receives differential corrections (via dongle; WiFi hotspot; Cellular data) from a continuously operating reference station (CORS) network (3) and communicate them to the drone (4) to correct location data in real-time for a more accurate positioning and image location.
Subscribe to a NTRIP service
The first step is to subscribe to a Networked Transport of RTCM via Internet Protocol (NTRIP) service.
NTRIP is a RTK positioning correction transmission protocol (via an HTTP Internet service). A reference station at a known geospatial location continuously observes the satellites, calculates position corrections, and transmits them in real-time to the connected remote controller (once every second in a data stream). The drone then uses location information from the satellites and the correctional data to compute its coordinates more precisely.
To gain access to a NTRIP network, register with a local NTRIP provider to create an account. This provides a port, IP address, username, and password to access the network. Once the registration is completed, these credentials can be used to connect the drone base station to the NTRIP network and receive corrections. The cost and coverage area depends on the specific service provider.
RTK account creation
Once a compatible RTK drone model has been selected from the device settings, the Network RTK tab appears in the general settings and a new RTK account can be created:
- Select New RTK account
- Choose an Account name (optional)
- Input the NTRIP details:
- Hostname / IP
- Port number
- Username (optional)
- Password (optional)
- Input Mountpoint
- Press on Save
RTK account connection
When using PIX4Dscan with a compatible RTK drone model, the connection to an existing RTK account can be established from the general settings Network RTK tab or from the map view in the RTK dialog.
The RTK dialog
RTK dialog header
The RTK dialog header is located in the map view top bar. The color of the header is different based on the status of the RTK functionalities:
- Gray: No RTK account connected; RTK positioning functionality disabled.
- Blue: No RTK account connected; RTK positioning functionality enabled.
- Green: RTK account connected; RTK positioning functionality enabled.
When expanding the header, the dialog is displayed. This screen manages the connection to the RTK accounts and displays information that can be used to monitor the status of the connection and the resulting accuracies:
- Account name
- Accuracy: latitude, longitude, altitude
- RTK positioning: ON or OFF
- RTK status: fixed point, float, single point, none
RTK connection dialog
The RTK status
Differential data analysis is completed and RTK can be used for positioning. The drone will only be able to take-off under this status when RTK positioning is enabled. The accuracy of the position can be in the range of a few centimeters.
Differential data is in analysis. The accuracy of the position can be in the range of 1m.
Only GNSS is used for positioning.
No positioning solution. This can be caused by an insufficient number of satellites in view, insufficient time to lock onto the satellites, or a loss of communication between reference station / remote controller / drone.
The RTK positioning functionality enables the use of RTK for navigation.
- When enabled: the drone will use the corrected coordinates to improve flight stability, calculate missions and to write media metadata.
- When disabled: the drone will not use the corrected coordinates to fly nor calculate missions. However, if a valid RTK account is connected, media metadata will apply the corrected coordinates.