MultiNav Pro+ GNSS 1sec first fix claim - is that cold start or hot start?

That 1 second figure is definitely hot start - cold start on the MultiNav Pro+ is more like 28-32 seconds in open sky, which honestly tracks with what you'd expect from any decent multi-constellation module. They're a little coy about it in the datasheet but if you ping their support they'll confirm the 1s spec assumes valid ephemeris cached from a recent fix. Design your power-on logic accordingly if cold start TTFF is actually critical for your use case.

Yeah Dawn's right, and worth noting that "recent fix" is doing a lot of heavy lifting there - if your module has been powered off more than ~2-4 hours or moved significantly, you're basically back to cold start territory even if ephemeris is technically cached. Learned that one the hard way on a fleet tracker project where units sat in a warehouse for a week between deployments and we kept wondering why our "hot start" was behaving like cold. Add an RTC with battery backup if you want that 1s figure to actually be reliable in real deployment conditions.

Both great points - just want to add that assisted GNSS (A-GNSS) via a host MCU feeding fresh almanac/ephemeris over UART at boot can get you pretty close to that hot-start performance even after a long power-off, if your application has any kind of connectivity. We did exactly that on a cold-chain tracker and it made a huge difference vs. waiting on the module to sort itself out from scratch.

All solid points above - one thing i'd add is that if you're designing for worst-case cold start and have any flexibility on antenna placement, sky view quality can swing your real-world TTFF by 10+ seconds even on a good module, so don't just bench test and call it done. Tested the MultiNav Pro+ on a rooftop vs. near a building edge and the difference was pretty humbling.

Solid thread - just to tie a bow on it, if you're designing around guaranteed fast acquisition I'd basically treat cold start as your baseline and then layer in RTC backup + A-GNSS as optimizations, so the 1s hot start is a nice bonus when conditions are right rather than something you're depending on. Assuming hot start and getting burned is way more painful than designing conservatively from the start.

Peter's last point is exactly the right mental model imo - design for cold start, let hot start be a pleasant surprise. I'd also just say check the MultiNav Pro+ datasheet directly for the TTFF table, most decent modules will break it out into cold/warm/hot with actual conditions listed, and if that table isn't there that's kind of a red flag in itself.

Yeah that datasheet TTFF table point from josh is worth repeating - if a module vendor can't be bothered to specify the conditions under which they're claiming that number, I'd be pretty hesitant to build a product schedule around it. Seen too many "1 second fix!" claims that turn out to be hot start, clear sky, 8+ satellites, basically best-case-ever conditions that you'll never replicate in production.

Yep, almost certainly hot start - 1 second cold start TTFF would basically require the module to be bending physics. The 1s claim is your "we already know where we are, sky is perfect, ephemeris is fresh" number, not your "powered on for the first time in a parking garage" number. Design to peter's advice and treat cold start as your real baseline, you'll thank yourself later.

Yeah 100% hot start - I've benched a few modules making similar claims and the 1s number is basically "everything went right and we cheated a little." Cold start on the MultiNav Pro+ from what I've seen is more in the 25-35s range depending on sky view, which is totally normal and honestly fine if you design around it like the others said.

Yep, hot start, no question - that 1s number assumes valid ephemeris, recent almanac, and basically ideal conditions. Tod's 25-35s cold start range matches what I've seen on similar chipsets too, so just bake that into your worst-case timing budget and you're good.