Changes

The My initial disappointment with the {{Polar M400}} has changed over time. There are a number of factors, not least of which is a disappointing watchthat it's now on sale far cheaper than its release price, with poor GPS accuracy and limited support for making it far more competitive. Its [[CadenceGPS Accuracy]]has also improved, though it still mediocre. Even at This accuracy problem is offset by its low price point it I don't think it reasonable support for the [[Best Running Watch| offers good value for moneyStryd]]Footpod that is extremely accurate. If you're after a midrange GPS watch, I'd suggest looking at The main competition the M400 faces is the [[Garmin 610Vivoactive]]. While it's an older watch, it offers far more features than the M400. The Garmin 220 Vivoactive is more expensivea better watch in virtually every respect, but offers better functionalityexcept for its Stryd support. For a simple evaluation of a In order to get the Vivoactive to get pace and distance information from Stryd you have to turn off GPS watch, I look at how well it while the M400 can answer some basic questions:use Stryd for pace and distance whilst still recording a GPS track.* '''How far did I run?''' This is the most basic question, and the M400 has stunningly bad poor GPS accuracy, but this can be offset by using the Stryd Footpod. It may seem odd to spend more on a Footpod than the watch, but I've had the M400 be out by d argue this is actually a mile on an 18 mile run, which could really screw up your marathon trainingreasonable compromise. * '''How fast am I running?''' Knowing how fast you're running can be a nice to know, or it can be vital for your training or race performance. Because of the nature of GPS, watches that rely on GPS signal alone tend to have serious problems with current pace. Without With the ability to display current [[Pace From A Stryd Footpod]] while getting all other data from GPS, combined with such poor GPS accuracyyou can get extremely accurate pace information, but without it, the M400 can't answer this questionis pretty hopeless.

* '''What's my cadence? '''[[Cadence]]''' '''is one of the most critical and often overlooked aspects of running. If you get your Cadence right, many other things naturally fall into place. The M400 has limited support for a other [[Footpod]]s besides Stryd, no plus it has support for Cadence from the internal accelerometer, and . There are no Cadence alerts. It's better than nothingwhich is a shame, but it's not greattypically this feature is only available on more expensive devices.

* The M400 can act as a simple activity monitor, but it only has only an internal accelerometer which provides poor accuracy. If you need an activity monitor, I'd recommend the [[Basis Activity Tracker]] which has sensors for heart rate, skin temperature and perspiration.

* Unlike the [[Polar V800]], the M400 has poor [[GPS Accuracy]]; see below for a detailed discussion.

** The Polar Stride Sensor is fully supported by the M400, with automatic calibration and it will display stride length as well as cadence. However, the Stride Sensor is huge and heavy when compared with modern Footpods, weighing over three times as much as a Garmin Footpod. Because of its size and weight, it requires lacing into the shoelaces, making it a real pain to move between shoes. <jfs id="B00CCASIMS" noreferb="true" n="Polar Stride Sensor"/>** The [[Stryd]] Footpod and the [[MilestonePod]] work well with the M400.

** The Adidas miCoach Speed Cell will work with the M400, but it's not easy. By default it will pair with the M400, but you can't set the calibration factor nor can you set the M400 to use GPS for pace/distance. You have to pair the M400 with the Polar Speed Sensor to activate the menu items you need to configure the Adidas Footpod, which is far from ideal. However, the Adidas Footpod is then a reasonable size and provides cadence (though not stride length). <jfs id="B00FEJ7FBO" noreferb="true" n="adidas miCoach Speed Cell "/>.** Even though the M400 has an internal accelerometer, this is not used to display cadence.

** Polar states they use [http://www.u-blox.com/en/assisted-gps.html AssistNow], a technology from u-blox] which does satellite prediction. AssistNow can use a downloaded prediction file or simply calculate the positions offline. With version 1.4 of the firmware, the synchronization software was updated to indicate that the offline file had been downloaded, and the watch will now indicate how long the file is valid for. However, even with version 1.4, the TTFF is still slow compared with competing devices. * The M400 uses Bluetooth sensors rather than the more common Ant+, limiting the choice and quality of sensors. This is likely to change over time as more devices are produced and compatibility issues are resolved. * The M400 will only upload the data to the Polar website. Polar has introduced to the export of TCX format data, but this export is incomplete (no laps). You can work around this by using the open source projects [https://github.com/pcolby/bipolar Bipolar] and [https://github.com/profanum429/v800_downloader M400_downloader], but this is a far cry from the open approach that Garmin has taken.

The For quite some time, the M400 has had the worst GPS accuracy of any device I've tested, worse even than the Garmin 620 was before the but recent firmware fixes upgrades have improved things. * Both Trueness and Precision are remarkably poormatters somewhat. The M400 GPS accuracy is nearly always giving a shorter distance than I actually ranstill rather mediocre at best, over 250 feet/mile short on average. * The M400 does a better on repeatability, which is a measure of how likely but at least it is to give the same indicated distance on a particular part of the course. This tends to give an illusion of being correct, 's not as appalling as it is easy to mistake consistency for accuracyonce was.* An out-and-back turnaround is challenging for any It looks like Polar are using an unusual GPS watch, and this often shows up the difference between a good and bad a device. A really good GPS watch will typically be out by 2 to 3%, but the M400 does particularly badly with an error of over 13%. * Running chipset in a straight line on the other hand, is a fairly easy task for most GPS watches, and hear the M400 does vastly better than in other conditions. However, when itI's compared to ve not seen any other devices, it's still one of device using the worst.* Rather strangelyu-blox chipset, the M400 does remarkably well going under the bridge. It's almost like it does better without the GPS signal than with it. If you look at the image below and compare it with the V800, you can see replacement for the M400 does much better when emerging from under the bridge.* While I rely on detailed measurements and statistical analysis (M430) returns to evaluate GPS accuracy, it's worth mentioning that on one 18 mile run using the M400 has lost over a mile. This is the worst a level of error I've seen, even worse than same chipset manufacturer as the [[Garmin 620Polar V800]] before Garmin fixed their problems with a Firmware upgrade. (I tested the M400 with version 1.4 of the firmware and the which has outstanding GPS accuracy is unchanged.)* It looks like Polar are using a different GPS chipset in the M400. The V800 uses firmware upgrade is also fixed the SiRF chipset, problem where the M400 uses [http://www.u-blox.com/en u-blox].* I have seen the Polar M400 would report losing satellite signal with the message "There's no GPS signal". This occurred was occurring under conditions where another device is doing fine and there are not circumstances that would should cause a problem.

|[[File:BridgePolar M400v1.9.600.jpg|none|thumb|x300px|This image shows Here's the tracks from the M400 with the 1.9 firmware. This diagram has tracks color coded for with green indicating good accuracy through to red indicating poor accuracy, and the lap markers as blue dots.]]|[[File:BridgePolar M400.jpg|none|thumb|x300px|For comparison, this is the M400 with the earlier 1.4 firmware. You can see a few tracks where the M400 has shifted out of position even though the shape of the course is maintained. The blue lap markers are quite spread out, suggesting some positional accuracy problems. You can see from the green lines going under the bridge that the M400 does quite well in that situation, and there are no sudden changes in position on emerging. I suspect this is because the M400 is doing a lot of smoothing, which works well in that situation. The middle segment that is quite curved is nearly all red, and this is one of the areas where the M400 is a smoothing too much and cutting the corners. You can see the M400 does worse here than in the sharp turn to the right of the image. ]]|- valign="top"