Sometimes it is necessary for navigation applications to calculate precise relative positioning between moving vehicles. Swift Navigation Devices Moving Baseline RTK provides 5 Hz RTK output when both of the paired primary and secondary receivers are in motion. In this configuration, the primary receiver and secondary receiver are installed on separate vehicles to support applications where precise relative positioning is important such as in agricultural and marine towing, UAV heavy lift payloads, formation or swarm focused navigation, and docking or shipboard landing.
Software
Swift Navigation Devices must be configured to allow for Moving baseline usage. First, it must be configured to compute its differential solution in what is called “Time-matched mode”. By default, Piksi operates in “low-latency” mode in which there is an inherent assumption that the base station is stationary. In time-matched mode, each differential GNSS solution epoch is triggered by receipt of the raw observations from the moving secondary receiver. This means that the differential pair of Piksis must have equal observation rates which is configured through the “solution rate” and the “output every N Obs” settings. It also means that there can be significant latency on the navigation output from any communication delay. As such, on should minimize any communication delay between the Primary and Secondary receivers.
Common Settings
These settings are to be configured on both the Primary and Secondary Piksis.
| Name | Value | Units | Description |
Solution | |||
| dgnss_solution_mode | "Time Matched" | n/a | Configures Piksi to compute a time-matched solution on receipt of observations from a base station. |
| soln_freq | 5 | Hz | 5 Hz is the current maximum time-matched solution rate on Piksi Multi. |
| output_every_n_obs | 1 | n/a | Enables 5 Hz raw observations on base and rover. |
Table 1: Swift Navigation Devices moving base required settings: Primary and Secondary receivers
Primary Receiver only
These settings are to be configured on only the RTK heading rover Piksi Multi. In these settings, it is assumed that uart0 is the interface over which observations are shared between primary and secondary receivers.
| Name | Value | Units | Description |
| uart0 | |||
| enabled_sbp_messages | 0 | n/a | Configures Piksi to do not send any message back to the moving base station. |
| solution | |||
| dynamic_motion_model | High Dynamics | n/a | Sets required dynamic motion model. Use the same setting for all types of applications. |
Table 2. Primary receiver only settings
Secondary Receiver only
These settings are to be configured on only the Piksi Multi acting as the Secondary receiver and providing corrections to the primary receiver. In these settings, it is assumed that uart0 is the interface over which observations are shared between primary and secondary receivers.
| Name | Value | Units | Description |
| uart0 | |||
| enabled_sbp_messages | 74,117 | n/a | Configures Piksi to send observation (74) and GLONASS biases (117) messages to the rover. |
Table 3. Secondary receiver only settings