Hi,
you can load custom geoid (ggf) files to TMM.
Simply place them in the 'Geodata' folder of your Android device (statement is true for Android version less then 10).
As an example - I just downloaded the global OSU91A from the Trimble page - this geoid is by default not in the list of TMM. Placing the file in the mentioned folder will show the geoid at the bottom of the list after a TMM restart.
As long as you have a valid ggf file this workflow should do the trick.
![](https://higherlogicdownload.s3.amazonaws.com/TRIMBLE/JiveInlineImages/150770.png)