Non-gps long range position hold

Hardware Multirotors
1

Hi everyone!
I’m looking for non-gps solution for position hold in a high altitude(30-100m) Ardupilot documentation has a list of vendors which implement visual odometry/optical flow algorithms.
https://ardupilot.org/copter/docs/common-non-gps-navigation-landing-page.html
Every device seems can work only on limited altitue 8-15m, I didn’t expolre all of them though, so I could be wrong. I’m wondering why there is a limitation on altitude and are there any exisitngs soutions or suggestions that can work on a higher altitude?

2

Fairly obvious why when they are optical based devices.

Optical flow

3
4

So in this post its said that PX4flow was tested at 100m. However link is redirects to 404 and and cant find any proves in documentation