Erik Mischiatti

Work / 05

RTK Base Station

A portable GNSS reference station. It surveys its own position at power-on and broadcasts RTCM corrections over LoRa. The aim is centimetre-level RTK positioning for drones and rovers nearby.

My contribution: hardware selection, enclosure design and field deployment. The mechanical design adapts an open GNSS base station by Burks Builds; the adaptation covers the receiver integration, the power system and the radio.

Exploded CAD view of the RTK base station: antenna dome, battery section, electronics case.
Assembled base station with GNSS antenna dome, on a tripod.
Fig. 1 Exploded CAD view: antenna mount, battery and charger, receiver and radio. Fig. 2 Version I, assembled on its tripod.

1 Context and design intent

An RTK base station is a GNSS receiver held at a fixed position. It broadcasts correction data so that a moving receiver nearby, on a drone or a rover, can resolve its own position more precisely. The engineering objective, as stated on the project page, is drone-grade, centimetre-level positioning. That is the design target. What the published material shows is set out under Integration and testing.

This unit is built to be carried and set up in the field. The design features, as documented:

  • Portable. Three printed parts with a standard tripod thread underneath.
  • Self-contained power. Four 18650 cells; runs while charging over USB-C; battery status visible through a window in the case.
  • Automatic start. An Arduino Nano triggers Survey-In on the receiver at power-on.
  • Long-range correction link. LoRa at 900 MHz with an external antenna.

No formal requirements were published. The list records the design as built, not a specification it was tested against.

2 System architecture

RTK base station, power and data paths Four 18650 cells feed an IP5310 charger and boost board that outputs 5 volts. The 5 volt rail powers the Here4 Base, the Arduino Nano and an LM2596 step-down that gives 3.3 volts to the LoRa radio. A metal power button switches the 5 volt output. The antenna connects to the Here4 Base by coax. The Nano starts Survey-In over UART. The Here4 Base sends RTCM to the radio over UART, which broadcasts at 900 megahertz to drones and rovers. coax RTCMUART 900 MHz UART cells 5 V rail 3.3 V switch GNSS antennaCS7624A Here4 Baseu-blox F9P receiver LoRa radioEbyte E220-900T22D Drones, roversreceive corrections Arduino Nanostarts Survey-In Step-downLM2596, 5 → 3.3 V Battery4 × 18650 Li-ion Charger / boostIP5310, USB-C input Power buttonmetal, LED ring Power Data, RF
RTK base station, data path The GNSS antenna connects to the Here4 Base by coax. The Arduino Nano starts Survey-In on the Here4 Base over UART. The Here4 Base sends RTCM over UART to the LoRa radio, which broadcasts at 900 megahertz to drones and rovers. Data path coax UART RTCMUART 900 MHz GNSS antennaCS7624A Arduino Nanostarts Survey-In Here4 Baseu-blox F9P receiver LoRa radioEbyte E220-900T22D Drones, roversreceive corrections RTK base station, power path Four 18650 cells feed the IP5310 charger and boost board. The metal power button switches its 5 volt output. The 5 volt rail feeds the Here4 Base, the Arduino Nano and the LM2596 step-down, which gives 3.3 volts to the LoRa radio. Power path cells switch 5 V rail 3.3 V Battery4 × 18650 Li-ion Power buttonmetal, LED ring Charger / boostIP5310, USB-C input Here4 Base5 V Arduino Nano5 V Step-downLM2596, 5 → 3.3 V LoRa radio3.3 V
Fig. 3 Power and data paths, redrawn from the functional diagram on the project page. Heavy line: power. Dashed line: data, RF and the switch signal. All modules share ground. On narrow screens the drawing splits into its two paths.

Data path

  1. Antenna to Here4 Base over 30 cm coax, TNC to SMA.
  2. At power-on the Nano starts Survey-In over UART.
  3. Here4 Base streams RTCM over a 3.3 V UART link to the E220.
  4. The E220 broadcasts the corrections at 900 MHz.

Power path

  1. 4 × 18650 cells into the IP5310 charger and boost board.
  2. 5 V rail to the Here4 Base and the Nano.
  3. LM2596 derives 3.3 V for the radio.
  4. The metal button switches the 5 V output; its LED ring is on the same rail.

3 Mechanical and electronic implementation

Three printed parts stack on the tripod. The bottom case holds the Here4 Base and the LoRa radio, with the radio antenna mounted outside. The middle section holds the four cells and the IP5310 charger and boost board. The top carries the GNSS antenna.

The IP5310 board's own button is removed, so the external metal button switches the 5 V output, and its LED ring is wired to the same output. A USB port at the base allows charging from a power bank.

Open bottom case: Arduino Nano, receiver and LoRa module wiring.
Fig. 4 Bottom case: Nano, Here4 Base, LoRa radio.
Battery section with four 18650 cells in a holder and the charging module wiring.
Fig. 5 Middle section, 4 × 18650.
Side view of the assembled base station on its tripod, with antenna cable.
Fig. 6 Side view, antenna connections.
Table 2 Components and where they sit in the case
FunctionPartLocation
GNSS receiver CubePilot Here4 Base, u-blox F9P Bottom
Correction radio Ebyte E220-900T22D, external SMA antenna Bottom
Controller Arduino Nano –
Energy 4 × 18650 Li-ion cells and holder Middle
Charger and boost IP5310 (LX-LBC3.1) Middle
3.3 V regulator LM2596 step-down –
GNSS antenna CS7624A Top

Bench notes

  • Set the LM2596 to 3.3 V before connecting the radio.
  • Connect both antennas before power-on.

4 Integration and testing

The published record is one reported field result. The test record keeps what is documented apart from what is only reported, line by line.

Table 1 Version I, field test record
ItemRecordStatus
Unit under test Version I, fully assembled. Documented
Setup Base station broadcasting RTCM over LoRa to drones, in “real drone localization setups”. The drone or rover used is not named. Partly documented
Conditions Site, date, sky view and distance to the rover are not documented. Not documented
Procedure Survey-In starts automatically at power-on. Survey-In settings, and how positioning accuracy was assessed, are not documented. Partly documented
Observations [object Object]Fully assembled, validated, and tested during field experiments.Source: project page [1] Reported
Result [object Object]Stable centimeter-level accuracy in real drone localization setups.Source: project page [1]. No values, logs or plots are published. Reported, no data
Limitations The result cannot be checked from published material. Version II has not been tested. Documented

Documented in the project materialReported, or only partly documented

5 Results and limitations

Objective. Centimetre-level RTK positioning for drones and rovers, from a base station that can be carried and set up in the field.

Result. Version I is fully assembled and was used in field experiments. The project page reports stable centimetre-level accuracy in drone localization setups.

Limitations. No measurements, logs or test conditions are published, so the accuracy claim cannot be checked from this page. Version II is documented as work in progress and has not been tested. No CAD files, firmware or wiring files are published.

6 Resources and references

  1. [1] Original RTK Base Station project page, source of the quoted results (archived version)
  2. [2] Burks Builds, GNSS Base Station Prototype: the mechanical design this adapts
  3. No repository, CAD files or firmware published