Internal GPS is inaccurate. Does this mean I need to buy external GNSS for vGIS to work? (KB-FQ003)

No. vGIS has two calibration methods: patented vGIS calibration that can achieve 5cm/2in accuracy and an external GNSS/RTK-supported location calibration with up to 1cm horizontal accuracy. Both have their own advantages and use cases. Most of our clients—over 95% of users—use vGIS as is without additional GNSS hardware, which helps them minimize or completely eliminate hardware costs.