Accuracy to the Point of absurdity

Here you go:
https://www.sparkfun.com/products/1...x7P2oZhfBAsZlRBzMh1-QwZ8moYVXg&_hsmi=66451173

Accuracy to the point of absurdity for rocket tracking. Give it 3 to 5 years and the price will come down.
GPS/GNSS units that are affordable are already out there for a few bucks and there is noticeable improvement over using GPS alone. Kurt

I'd love to see how one would be fully configured with the other bits together!

https://navspark.mybigcommerce.com/ns-hp-gl-gps-glonass-rtk-receiver/
A bit cheaper RTK solution considering both systems work best with 2 units (one as base and one as rover).
NavSpark can accept free corrections from a NTRIP server, not sure if the U-Blox can.

This could lead to super accurate GPS-based apogee detection!

The RTK accuracy is for relative distance to a base station. It relies on the base station and the mobile unit having basically identical RF paths to the GPS constellation. Some people’s flights get far enough away to degrade that benefit. But since a typical rocketry application is mostly just interested in relative distances anyway, that’s not much of a limitation. I used a pair of RTK receivers on a professional project about 4 years ago. Ten years ago this was only available for about $50k. 4 years ago it was about $4k for a pair. Now it’s a hobbyist item on Sparkun. Progress.

GPS is already accurate enough for apogee detection, and also flight path angle checking for airstarts —when the GPS is in lock and the solution is available. The biggest obstacle to using GPS for in-flight decision-making in rocketry avionics is dealing with the times when the GPS receiver says “wait a minute, my calculations can’t be right. I can’t have just gone up 2000 feet in 4 seconds...right?”

In order to get an RTK solution, you need to start with GPS lock in both units. In my last RTK project there were a lot of times when both units had GPS lock, but the software couldn’t generate the RTK solution.