I've an AnyTone 878uv pluss and I want to know if roaming is only a DMR feature or if it can be used with analog repeaters?
This handheld radio requires you program in all the repeaters you want to use, so it already knows what is available and could, in theory, check GPS or it could check to see if there's a usable signal on a given channel. ...but it already knows the channels.
So, that'd be nice and all, but that wouldn't be enough to be useful.
Imagine this: you're in coverage area of one repeater. Now you're getting closer to a different repeater and want to use that instead.
To be useful, you need a lot more than switch your radio's own channel: the moment you roam, you don't want to become "disconnected" from your original communication partner, and that means that you either need to stay on the same relay "output channel" on these two different relays, or you need to tell your partner that you're now on a different channel. Both impossible with an analog system, because:
Staying on the same relay output channel is impossible, because these two relays are analog and hence shouldn't share the same channel if they're so close to each other.
Signalling that you'll be receivable on a different channel is impossible because an analog network doesn't have the signaling backend for that.
Auto-discovery would be one Hell of a feature, though, huh?
Not very complex to implement if your signal was digital. So anyone would do that with a digital signalling protocol, because:
To implement such a complex system as hand-off between relays, you'd need to have all the tools to do digital speech. So you'd do just that.
To give you a bit of historical insight:
Germany used to have C-Netz, from around 1984 to 1990, with about 750000 subscribers. That was the third generation of analog telephony networks, and the first one to support handover between different relays (which would be called base stations in cellular telephony parlay).
It was also the the last analog cellular network (that was 29 years ago, so we can safely assume it's pretty obsolete, even by ham standards). And it was the only generation to support handover – because you really needed digital signalling to achieve that, and as soon as Siemens and others really had that technology figured out, it became obvious that a digital system would be vastly superior. So, C-Netz became a tremendously popular, but quickly superseded (only after six years – imagine that speed for a behemoth like the German Postal service, which run it) system. Simply because that if you have the digital signal processing capability to do the call management in a handset, you'd really want to make use of that and do digital voice, which has several advantages over analog.
TL;DR: You want to build something like a trunked/cellular analog network. You need to go digital to achieve that. So you usually drop the analog speech in the process.
Hence, your handset is unlikely to support anything like that. It's not a feature of DMR alone (any cell phone standard does that since '90), but it's certainly not an analog thing.