Solmeta GMAX-GD Photo/Video GPS BDS Dual-positioning Geotagger & Bluetooth Shutter Release for Nikon D5, D810, D800, D4, D3, D700, D300S...with 4GB Flash,1900mAh Li-ion, Altimeter, eCompass, LCD...

Bought for use on z8, works as expected.Was a little surprised when it came with a £46.17 extra charge from customs.

I have tested it with my D810 and it works perfectly.Lock time is fast even indoor by the window - about 10 sec. After the it keeps lockedWhen I keep my camera without batteries for some time, the camera date and time is reset to default values in the past. GMAX-GD is setting the camera's date and time as soon as the camera is turned on.Geotagging is working just fine. No additional settings of the camera are necessary to be done.

The Solmeta GMAX is the best GPS product yet the company has produced. The unit has many new features and improvements: I love that it locks onto the camera hot shoe, I love that the 10-pin cable threads onto the camera and the unit itself and can't come loose, and I especially LOVE the remote app for my iPhone which can now function as a remote shutter release! I don't have to carry another remote with me since I always have my iPhone with me anyway. Great idea. The GMAX is a little larger but I also love the larger screen it has. It's much easier to read. I think it's easily the best GPS unit available from Solmeta or any other manufacturer.

This is a somewhat tentative review, as I haven't had the chance to really use & abuse this yet. I'm optimistic that I'll revise my rating upwards in time, once I get that chance.In summary:Pros:• Seems to work very reliably.• Seems to be accurate.• Certainly has lots of capabilities, many unique.• Built-in battery enables much more accurate tagging, especially if you take photos without warning often.Cons:• Pretty heavy.• Very pricey.• Doesn't support all the positioning systems that competitors support.In [much] more detail:The first thing to note is that it's *big*. Much bigger than I expected. I don't know what it is about the various product photos, but they just did not convey to me nearly how big this thing is. It's bigger in volume than my phone, by far. Probably two or three times the volume. It's *big*.It's not super heavy, but it's not light by any means. If you're used to having speedlights (or similar) in your hotshoe, this will be no problem in comparison, but if this is the first thing you've put in the hotshoe, you're going to notice it in regular use, for a while.GPS acquisition isn't exceptionally fast - and certainly slower than a typical smartphone, which has the benefit of wifi & other assistances - but isn't unusually slow, either - about the usual sixty seconds or so, in most cases.I haven't tested it rigorously, but thus far I haven't noticed any GPS accuracy issues. It's infinitely better than Nikon's SnapBridge tagging mechanism, which is ridiculously flawed and will misplace you as miles and miles away from your real location.The heading functionality is a little squirrelly, though - as with pretty much all electronic compasses, it's not all that accurate out of the box. Calibration is fairly simple, but of course requires you to have a more accurate compass to begin with (or some other kind of accurate means for determining true north). I haven't really checked the real-world results yet, but in some in-home testing I saw it often reporting the wrong heading. Again, though, certainly no worse than a typical smartphone's electronic compass, so it all depends on your expectations.It's got a *lot* of config options, most of which are truly optional, so you need only worry about them in certain edge cases (or if you're just geeking out on them).The user interface isn't as awkward as I expected. It is of course a bit limited, with only a couple of buttons and that "old fashioned" LCD display, but it actually works quite nicely once you get a little used to it. And it is nice to have the display visible to you at all times - I use a Cotton Carrier chest harness for my camera, which is a very nice combo with this since I can just glance down at my holstered camera to read my GPS coordinates, my heading, the current time - whatever I choose to have displayed on there. If you're actually out navigating by GPS it's actually a really convenient setup.I have not yet explored it's off-camera capabilities, nor its built-in GPS logging function (other than to check it out once, just to see that it was working & recording something). It's a nice to have for me, but I typically have my phone recording my travels already. It will be interesting to compare them for accuracy and reliability at some point, though.The built-in battery is nice. It allows me the peace of mind to just set it to always-on and thus always get accurate GPS stamps in my photos. The alternative, which is basically your only practical option for any GPS dongle that doesn't have an independent battery supply, is to have the GPS attempt to rapidly reacquire signals when your camera starts metering (e.g. half-press of the shutter button). But if you're doing wildlife photography, as I usually do, you might go from holstered to snapping away in literally two seconds, which is simply way too fast for GPS reacquisition and position updating. So I fully expect this, in its always-on mode, to be dramatically more accurate in those situations in particular. But again, I haven't enough experience with it to judge, yet.Lastly, there's the price. It is about the most expensive GPS dongle you can get, short of Nikon's official ones. And nobody should ever buy Nikon's official ones, because they're insanely expensive for what they do - this one is far more capable, but with the aforementioned trade-offs in weight & size etc, so maybe not the right one for you if you just essentially want a cheap version of Nikon's, but there are several other manufacturers that make much smaller ones that have all the same functionality as Nikon's, at an order of magnitude less cost.