  We use the latest parallaxes measurements from Gaia DR3 to obtain a geometric
calibration of the tip of the red giant branch (TRGB) in Cousins $I$ magnitudes
as a standard candle for cosmology. We utilise the following surveys: SkyMapper
DR3, APASS DR9, ATLAS Refcat2, and Gaia DR3 synthetic photometry to obtain
multiple zero-point calibrations of the TRGB magnitude, $M_{I}^{TRGB}$. Our
sample contains Milky Way halo stars at high galactic latitudes ($|b| > 36$)
where the impact of metallicity, dust, and crowding are minimised. The
magnitude of the TRGB is identified using Sobel edge detection, but this
approach introduced a systematic offset. To address this issue, we utilised
simulations with PARSEC isochrones and showed how to calibrate and remove this
bias. Applying our method within the colour range where the slope of the TRGB
is relatively flat for metal-poor halo stars (1.55 $<$ $(BP-RP)$ $<$ 2.25), we
find a weighted average $M_{I}^{TRGB} = -4.042 \pm 0.041$ (stat) $\pm0.031$
(sys) mag. A geometric calibration of the Milky Way TRGB has the benefit of
being independent of other distance indicators and will help probe systematics
in the local distance ladder, leading to improved measurements of the Hubble
constant.
