What are the exact speed limits for charging and hacking/deploying/xmp firing?

Almost everyone knows that there are speed limits for actions in Ingress. You can't hack, deploy, or damage resonators at and above the speed of 35-50 km/h, and you can't recharge Portals at and above the speed of 60-80 km/h.

There are still ongoing discussions on many different platforms (reddit, g+ etc). What I want to know is, if Niantic ever published the exact speeds for these limits. Did anyone ever experiment and find the exact speed limits?

I've been involved in Ingress almost since its release, so I have a lot of experience to draw upon. Unfortunately Niantic have never published details on the speed limits, and it's unlikely they ever will.

The limitation on game actions appears to be based on straight-line (well, shortest-geodesic) distance from your last action and the time between actions.

Imagine a circle expanding out from your last action, with the radius growing at 35mph (just over 55km/h). As long as your next action is within this circle, you'll be fine. There have been some reports that you get one "free" action if you've been under the speed limit for a while, but there's some debate about this.

There is also a maximum time that your actions are remembered for. Reports place this between 30 and 60 minutes. This feature allows you to hack a portal in city A, then fly to city B and still be able to hack virtually immediately, without having to wait for the 35mph limit to catch up to you.

Not all actions count towards the speed limit though. COMM is one example.

Having said all this, Niantic may have taken the time to implement something more complex by now.

Why 35mph? It's a common speed limit on a large number of residential roads in the US, particularly in California and around Mountain View.

The existence of speed limits has been known for a while (I asked about those more than a year ago) but, as usual, Niantic never disclosed the exact values. Experimenting would require a lot of trial and error and, as far as I know, has never been attempted. Also, I would advise against playing Ingress while driving.

There's an idea anyway that has been floating around, that I've found matches quite well my observations on the field: it's not exactly a matter of speed, but of radius around your last action. I'll try to explain this better:

Everytime you do an action in game, an invisible circle begins expanding from your current location, moving at the still currently undisclosed speed limit. Any other action done inside this radius, indipendently from your speed, will succeed. Any action done outside of that radius will fail. My experience, as I've said, seems to give strength to this theory, but I have only a very small sample to say it's surely like this.

TLDR: YMMV, but stay under 30 mph for best results.

Nobody but Niantic really knows the answer. It is most likely 30-35 mph, but even that limit is inconsistent, as it seems that some actions occasionally succeed while over the limit, and others fail under the limit. For example, rapidly spamming actions can be effective even well above the speed limit. One theory is that there may be a race condition such that an action is normally validated against the location of the last valid action, but instead, the location of the immediately previous action may be used if it had not yet been invalidated. On the other end, another theory for the fuzzy speed limit may have to do with the latency between when we initiate the action on the client and when it is timestamped on the server. The server may register the action even after we seem to receive a response from it (e.g., items, AP). If there is a long delay on one action then a shorter delay on a later action, you will have appeared to move faster and be incorrectly speed limited.