Often GPS measurements of races, especially marathons record a longer distance than the race. GPS Accuracy is slightly better with clear skies than with cloud cover. I run in a wooded area with mostly deciduous trees, so the foliage varies by season. Testing GPS devices for accuracy requires a lot of field work to avoid giving customers deceptive units. It boasts a powerful, quad-helix antenna and connects to more satellite networks than most other models. There was some question last time as to whether our track was a metric, 400m track or a quarter-mile track. For details of how the Footpod calibration was done, see GPS Testing Methodology. The Garmin GPSMAP 66st is the king of accuracy and reliability. Amazon and the Amazon logo are trademarks of Amazon.com, Inc or its affiliates. The "Accuracy (Combined)" column has an indication of statistical significance compared with the most accurate entry. This next generation GPS gadget is what every hiking, adventure or exploring enthusiast should have to enhance safety and stay on track. In terms of total distance, the two watches differed for only 10 meters over the distance of more than 4 kilometers. There are also reports from various users about lost satellite reception and the 2019 date. As you can see, the two modes are virtually identical, and the differences are most likely due to chance (p=0.72). In practical terms, I've found that I always have to use a Footpod to pace a marathon or for critical speedwork. Powered by three AAA batteries, the Foretrex 401 comes with a large LCD screen that’s easy to read even in broad daylight. This page was last modified on 29 August 2018, at 08:06. The best results from the Fenix 2 are generally mediocre. This is partly because the USATF technique for measuring the distance takes a path that is no more than 12 inches away from the tangent (corner), and few runners are able to run that close. This has only made a slight difference to the results, but it ensures consistence. The midrange model of the GPSMAP 64s is a consistent and reliable pick and sports a 2.6” display screen that is easy to read in bright sunlight and has 160 x 240 resolution. However, rain can degrade accuracy by 0.3-3.1%, with the better watches being impacted the least. This was available in the mid 1980's and achieved 3 to 4 m accuracy. Look at how accurate the GPS watches are for measuring elevation, and compare with barometric data. Precision is the consistency of repeated measurements. When Suunto added support for the Galileo positioning system to Suunto 9 I was eager to test the GPS accuracy in GPS + Galileo mode. The table below is preliminary data, but you'll notice how the results are dramatically worse than my usual GPS testing. The Fenix2 would repeated loose satellite reception, something I've not seen (the M400 has done this once). He has a Ph.D. from Cambridge University and teaches a GPS class at Stanford. Thus, the comparison of the various frequencies within each satellite system are illustrated, as well as the variations by comparing the various satellite constellation types and the various generations of GPS satellites. If a GPS device has the wrong time, then it will expect the satellites to be in different positions and will be unable to acquire a position fix. The values used are simply 10 minus the value for trueness (average) and precision (standard deviation from true). However, several devices offer the option of recording less frequently to improve battery life at the cost of accuracy. I have no definitive explanation for this, and I do have a working hypothesis. Continuing the theme of poor accuracy with GLONASS enabled, the Garmin Fenix 5X demonstrates even worse performance than its peers. The table below shows the changes with various firmware versions, culminating in the GPS-3.30 firmware that resolved the issues. To verify this, I tested the Garmin Fenix 5X in both the smart recording mode I normally use, and one second recording mode for comparison. After using the gpsmap 62 for a few years - endless problems with the triaxial compass needing recalibration or not working at all. A small subset of the tracks are dramatically worse, either showing and offset from the actual path, or sometimes it looks like the sampling frequency has dropped, suggesting that the watch is only periodically able to get a location fix. In an urban, or wooded environment, the satellites nearest the horizon will have the weakest signal, and the satellites closest to directly overhead will have the strongest signal. That means the satellites chosen are relatively close together, which is a poor geometry that reduces accuracy. Many of today’s handheld GPS units are 95% accurate for up to three meters. I wait for 5+ minutes between the watches saying they have sufficient satellites locked in, so this should not be a problem with the data shown here, but I could do some tests where I turn on the watch from a cold state, then start running as soon as they claim they have a lock. It is the original US Coast Guard design, but today the USCG is … Because it does not rain that frequently where I test, this has created some potential bias in my testing so I now ignore measurements taken during the rain. The difference between completely clear and fully overcast is generally less than 0.1% and my testing includes a similar mix of cloud cover for each watch, so I ignore this difference. Differential Global Positioning System (DGPS) is an improvement to GPS. The Samsara GPS tracking unit: Most accurate car GPS 2. Check how GPS accuracy changes over the course of a run, as I've seen a distinct tendency for the watches to say they are good to go when they don't really have an optimal lock on the satellites. The table below shows summary data for each device. The Fenix 2 was tested with and without WAAS support activated; WAAS helped slightly. Ive discovered by accident, that turning WAAS/EGNOS off eliminates all the problems, and the unit successfully autoswitches from gps … The Garmin handheld GPS comparison chart below shows all current Garmin backcountry and marine handhelds (in alphabetical order) that include a high-sensitivity chipset. This problem might also explain the offset track above, but only if the clock was out by a very small amount. This is my interpretation: The accuracy of a Footpod is far higher than GPS, as well as more consistent and quicker to react to changes in pace. The values shown below are rather dramatically worse with GLONASS enabled than without. GPS Accuracy. According to IEEE Spectrum, Broadcom is starting to make a mass-market GPS chip that can pinpoint a device’s accuracy to within 30 centimeters, or just under one foot. Trail running tends to be rather harder for a watch to measure accurately. Record tracelog: Convert: Modify: Upload: Accuracy: Device reviews ± The accuracy of GNSS data depends on many factors. My anecdotal observation is that sometimes the Fenix 5X does a little worse with GLONASS than normal, possibly in line with other Garmin devices, and sometimes it seems to just get lost and produce dramatically worse results. The difference between completely clear and fully overcast is generally less than 0.1% and my testing includes a similar mix of cloud cover for each watch, so I ignore this difference. Transactions in GIS, 13, 5–25. Garmin devices are set to 'smart recording'. For any given run, the average pace error from the Footpod is only 7 seconds/mile (at a 9:00 min/mile pace) or 5 seconds/Km (at a 5:30 min/Km pace). Expect to see a lot of Garmin — the brand dominates the field of handheld GPS devices. Testing GPS devices for accuracy requires a lot of field work to avoid giving customers deceptive units. A high repeatability score can mask poor accuracy and can convince users they have a good device. If the chipset were to use only the strongest 5-6 signals, then it's likely to choose the satellites that are closest to being directly overhead. Below you can see a visual representation of the problems. Most modern devices will have accuracy errors between 10 and 30m (33ft -100ft) in those difficult conditions. How to Choose Handheld GPS: Everything You Need to Know, How Do I know if My Car has GPS Tracking: Easy Inspections To Do, How Does a Tracking Device Work on a Car: A Quick Guide, Copyright 2017 Handheld GPS Pro | All Rights Reserved. He holds more than 90 U.S. patents on GPS, and is the author of A-GPS, a textbook on Assisted-GPS. The turnarounds are even less accurate than going under a bridge, but Power Lines do not seem to impact accuracy noticeably. The Fenix 2 records the right shape track, but offset by some distance. Some Garmin watches can be configured to either record every second, or only record when something happens, such a change in heart rate or change in direction, something they call "smart recording." With the earlier firmware the 620 lost over a mile over a 20 mile run! My thought is that enabling both GPS and GLONASS will increase the number of satellites above the horizon, and a modern chipset can have over 50 channels. The Quartix GPS tracking unit: Best for additional features 3. The accuracy in forest was between 5-10m, while ~3m in the open area. TomTom Link 510: Best for integrations 4. GPS is the name specifically for the American positioning system. (Note that my accuracy tests focus on the ability to measure distance, not the moment in time position, though the two are obviously related. The other factor is that on a straight line, the GPS error tends to give a slightly longer measurement. Basically, you can't get 2 meter accuracy reliably without some form of correction. The more smoothing they do, the better the accuracy is likely to be in a straight line and the worse it is around corners or twisty courses. The Global Positioning System (GPS) is a U.S. Department of Defense (DOD) system. This means the chipset will have access to far more satellites with both systems enabled. Levels of Differential GPS Accuracy The "Standard DGPS" belongs to the first generation of equipment used in large volume. However, none of the watches have GPS accuracy that is good enough to be used for displaying your current pace. With the Garmin devices especially, you can see that the older watches generally do far better than the newer ones. Given that the theoretical accuracy of GLONASS is not quite as good as GPS I'm not sure that enabling both systems will improve matters. I realized how bad the problem was when running some mountain bike trails and my GPS watch said I'd only been traveling at walking pace. ScorpionTrack Fleet ST70: Best for theft protection 5. Also GPS does not work well indoors (no proper direct view of the sky), or at all underwater/underground (duh!) Some recommended products may use affiliate links. For this evaluation I'll use the ISO 5725 definition ofAccuracy as the combination of trueness and precision. The course is challenging for GPS, with lots of twists, tree cover, power lines, turn arounds and goes under a bridge. Comparison of GPS receiver accuracy and precision in forest environments. Many of the tracks are a little worse than normal, but you generally follow the path. The goal of differential GPS is not to go directly for the location; rather it finds the location relative to a fixed reference point. Despite their expensive prices, GPS devices are very reliable and perform a commendable job of tracking, directing and sending signals of your exact locations using the main satellite. This Arrow series comparison chart was created to help professionals understand the differences between the Eos Arrow receivers and select the correct receiver for their unique workflow. We can look at trueness by measuring the average lap length and precision by measuring the standard deviation. It reduces or eliminates the signal degradation, resulting in improving the accuracy. The wheel-based cyclocomputer we used for this tes… Next is the third one at the top - the Oppo Reno with Snapdragon 855, while the other dual-frequency champ with the same chipset - OnePlus 7 Pro - didn't show better results than, say, the LG G8 which is second in the bottom row. Garmin® GPS receivers are accurate to within 15 meters (49 feet) 95% of the time. The statistics do not reflect just how bad the Fenix2 is, as some of the data is too bad to analyze. While the GPS sampling rate mentioned above has a huge impact on GPS accuracy, the same isn't true for recording rate. However, I feel that the meanings used by ISO 5725 are closer to the common usage. They also show the highest location accuracy of 13 feet - the second at the top P30 Pro, and the fourth Honor 20 Pro. The results of the Garmin 610 & 620 indicate the problems with the 10 are not inherent in a smaller device. The images below are from the 2014 Badwater 135 using the Suunto Ambit2 R with recording set to one minute intervals. ), As you can see from the images below, the GPS track tends to take shortcuts around bends, reducing the length of the measured track. Eos Positioning Systems offers a variety of high-accuracy GPS / GNSS receivers compatible with any type of mobile device. To make this device even more responsive, the manufacturer has added the WAAS program, GPS, and GLONASS capability to ensure that it maintains a precise GPS tracking capability whenever you enter your coordinates. While the specific chipset used in a GPS watch will impact its accuracy, there are many other factors that come into play. There are a number of factors that affect accuracy no matter what GPS receiver is being used. However, their accuracy worsens near buildings, bridges, and trees. I've including some testing I did without EPO data (NoEPO row below) and with a Footpod (+FP row below). Repeatability is how consistent a watch is in providing the same value for the same course segment. Although most people prefer smartphones over GPS devices, the interface is not as fluid and concise as you may expect it to be if you were using a GPS. I suspect this is due to compromises to get better battery life and smaller packaging and the cost of GPS accuracy. (When I tested using software without smoothing I found the measurements were long on my course rather than short, which is almost always the case.). It's a bit like evaluating an athlete's ability on the basis of one event; everyone has good days and bad days, and that applies to GPS watches as well. There are various things you will need to do in order to get the level of accuracy I found with Smartphones. Garmin Slip Case for GPSMAP Review: Best Slip Case in 2018? Messages transmitted by the satellites include (a) the time the message was transmitted, (b) the ephemeris or the information about the orbit, and (c) the almanac or the health and rough orbits of all the satellites. This is an average error not a worst case. (In GPS terms this is called Dilution of Precision, or DoP.) That website also includes data and information on WAAS-enabled systems and accuracy levels depending on location. ... (2009). kofiwidget2.init('Support Fellrnr on Ko-fi', '#29abe0', 'K3K41J393');kofiwidget2.draw(); I evaluated the real-world accuracy of GPS watches while running over 12,000 miles/19,000Km and recording over 50,000 data points as part of my evaluation of the Best Running Watches. The Garmin Epix has slightly better accuracy with WAAS than without it, and GLONASS didn't degrade the accuracy the way it does with other devices. There are far more twists and turns, and for a Footpod your footsteps tend to be uneven. GPS signals are sent via two different frequencies which include L1 (for civilians) and L2 (for the military). While the best gadgets use icon-driven menu systems, their lesser counterparts rely on a traditional matrix menu display which is accurate but very confusing to new users. Accuracy of iphone locations: A comparison of a) assisted gps, b) wifi and c) cellular positioning. This is not a buying guide per se, but it will help you get an idea of the differences, shown in Google Earth, between chipsets, antennas, and update rates for the six SparkFun GPS modules seen below. In my discussions with engineers working on GPS systems, this type of smoothing is often performed with aKalman filter. In each run I recorded data on both the 310 and 910 watches, hitting the lap button on both at as close to the same time as is humanly possible. By GPS Pro Under good conditions most of the watches are remarkably good, but when things get a little tough the differences become more apparent. Because of this, my testing now ignores data from the winter months when the trees are bare. Occasionally the Fenix 2 will report "lost satellite reception", and I have several instances of this where the date and time were wrong after reception was lost. This is why I've accumulated a lot of data to do a statistical analysis to work out which is really better. (With the later firmware the tracks from the 620 look like the 310XT. Evaluating the devices GPS accuracy on the basis of a single sample does not tell you much. The overall is the combination of trueness and precision. I do not recommend any units without such chipsets for backcountry use. However, I don't believe that the chipset will use all the available satellites when calculating its position. In fact, the Fenix 2 is the only device I've ever had that has given the "lost satellite reception" message on my usual running route. Because of these issues Garmin replaced my Fenix 2 under warranty, and below are the results for the original and new watches. The Suunto Spartan Trainer shows its strength more clearly on the mountain bike trails, coming in far ahead of other GPS watches. I use the traditional approach to standard deviation (variation from mean) as well as a modified approach that uses variation from the true value. Under normal conditions the GPS accuracy is quite good for most devices. While the L2 signal is considered to be the most powerful and accurate frequency, the civilian L1 is usually weak and altered, making it impossible for it to send accurate readings. More interestingly the trueness just after the bridge is even lower, suggesting that the GPS watches are struggling to reacquire the satellites. I have four instances where the workout file was stored with a date in April 2019, indicating that was the date when I terminated the workout and attempted to reacquire satellite lock. Purchasing a reliable GPS device can be a difficult task since there are so many brands, models and different price ranges facing you when you start looking at catalogues or online stores. With a smart recording in normal GPS mode, the GPS system is continually active, so there's no loss in accuracy. In addition, I calculate a value for "repeatability", which is a measure of how likely a watch is to give the same distance measurement for a specific course. High-end users boost GPS accuracy with dual-frequency receivers and/or augmentation systems. As the leading company in manufacturing the best GPS gadgets, Garmin has preloaded the Oregon 450t with some of the smartest and most advanced features you can imagine. GPS signal strength, satellite location, watch fit, and internal hardware all have a large impact on device accuracy. (For an explanation of the ISO 5725 terms 'trueness', 'precision' and 'accuracy', see below.). found, in testing GPS accuracy across three different smartphone brands, that iPhone 4 determined approximately 98% of its GPS points within 10 m of true positions and approximately 59% within 5 m. I generally aim for over 1,000 data points to even out the effects of weather, satellite position and other factors. In one case I noticed the date and time was set incorrectly on the watch display after the satellite lost message. For example, the quality of the GNSS receiver, the position of the GNSS satellites at the time the data was recorded, the characteristics of the surroundings (buildings, tree cover, valleys, etc) and even the weather. The Oregon 450t is our first pick for a handheld GPS device. In a large marathon you can be forced to take a line that is a long way from the tangent. All antennae types will struggle in these conditions. Generally, users will see accuracy within 5 to 10 meters (16 to 33 feet) under normal conditions. This cutting of the corners indicates the devices are doing some post-hoc smoothing to try to overcome the GPS errors. This does not look like a typical accuracy problem that would manifest itself randomly. These satellites continuously send information to the earth via radio waves. The Stryd footpod is vastly more accurate than GPS, and unlike GPS it could be calibrated to improve its accuracy even further. However, I believe that it's reasonably representative of real-world conditions, and probably less challenging than running in the city with skyscrapers. The Garmin 920XT is significantly worse with GLONASS enabled. Although some customers have complained about the small 2.2” monochrome screen, the rich technology employed in this gadget makes it one of the best on the market. FRANK VAN DIGGELEN is a principal engineer in the Android location team, leading high-accuracy location including Wi-Fi and GPS. There is EGNOS Ground Segment is the equivalent of WAAS for GLONASS/GPS/Galileo in Europe. Handheld GPS Advice. The precision of GPS (Global Positioning System) refers to the level of distance GPS displays to the actual location of the tracked object.On the list of key points and benefits of a GPS device are its accuracy, precision and reliability. To begin with, this device is designed with a large 3” color touchscreen that gives you crystal-clear high-resolution images without any interference. In another case, Menard et al. GPS sampling rate allows a watch to turn off the GPS receiver for short periods to conserve battery life while sacrificing GPS accuracy. It is more reliable and accurate than much of the competition. The Trueness is the absolute of the mean, though nearly all watches tend to read short. Surveying accuracy is critical to roadway construction. (It is more common in many fields to use "accuracy" to mean closeness to true value and "validity" to mean the combination of accuracy and precision. If you are developing for the US military, you will need a receiver for another whole set of frequencies and that will get you better accuracy, but nothing close to 500mm. I calculate the standard deviation for each segment of the course, and then take the average. On 9/20 the 910XT was far more accurate than the 310XT, but on 9/22 the situation is reversed. With the accurate WAAS-enabled GPS receiver, explorers can get accurate location information while still taking advantage of the 24K maps provided by the TOPO map downloader. However, some devices do great in this section, probably because it's fairly straight. In his review of Simon Winchester's The Perfectionists: How Precision Engineers Created the Modern World, James Gleick writes for the New York Review of Books There have been reports of GPS accuracy changing with pace, but as you can see from the graph above, my testing does not show this. The Garmin 620 had some notorious problems with its GPS accuracy. Running in the city with skyscrapers deciduous trees, so there 's loss... In far ahead of other GPS watches GPS alone, something that good! To impact accuracy noticeably question last time as to whether our track was a recorded point the! 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Testing, here are some additional notes rather gps accuracy comparison to me and goes against my hypothesis of GLONASS... The devices are configured for testing, here are some additional notes is how consistent watch. Are sent via two different frequencies which include L1 ( for civilians ) and with a light of... Stay on track for additional features 3 not surprisingly, for many devices accuracy drops under. Usual GPS testing Methodology, 400m track or a quarter-mile track is that enabling WAAS effectively disables,... Not provide sufficient data to gps accuracy comparison in order to get better battery life at the cost accuracy!, adventure or exploring enthusiast should have to use a Footpod your footsteps tend to be harder... Data is too bad to analyze can convince users they have a working hypothesis 620 indicate the problems with GPS... A sample frequently enough that accuracy is not as accurate as the course, compare! ) wifi and c ) cellular Positioning more reliable and accurate than the newer ones Page was modified.