TL;DR

Your cell phone, yes even your expensive iPhone, is only accurate down to a few meters/15'. It is estimated - and often not a bad job - to a more accurate location over time as it gets multiple readings, but they can suddenly be off again if insufficient satellites have been seen 'recently'.

Google gives cut and paste values accurate down to the distance that is the membrane of a cell. If you are typing values instead of copy paste, just type in the numbers in front of the decimal and then 5 or 6 more that it gives you and ignore the rest. (If you type 6 you can ignore rounding rules because the data from Google isn't that accurate to start with.)

Intro

On your cell phone, if you look at the numbers and calculate the distance, you might think that the GPS is giving you accuracy down to a cm (1/2 inch). If you think about it though, the first concern would be - but what point on my many cm/inch sized phone is that location for? It turns out it really doesn't matter - the resolution shown is far more specific than your device can accurately report.

See also our doc on Accuracy vs Precision: accuracy vs Precision

How many decimals do I have?

According to testing done How accurate is the iPhone GPS? - California Learning Resource Network In 2025, an iPhone 14 Pro has an accuracy of about 4.5 meters (about 15') in an open field in best case weather conditions and about 12.5 meters (about 40 feet) in an urban setting. Testing on the iPhone 16 in 2025 showed it to be less accurate than the iPhone 14 although I'm told Apple claims the 16 is slightly better.

Samsung S25 Ultra tested in the 3-5 meter range so essentially the same as the iPhone.

Both Samsung and IPhones have from time to times had software upgrades where the precision got worse, and then patches where they got better again.

For CMMS purposes though, you should probably just keep in mind that circa 2025, the GPS systems on phones are working in the 4-20 meter (15-70') accuracy, meaning if you are standing in a spot looking at the GPS - you might be many feet away in any direction from where your phone says you are.

So if your GPS team has located a valve in the road, a high end phone will normally get you within about 15' of it. If you are trying to correct readings on a map, and the current value is within 15-65' in a city of where you are finding it 'actually' is … don't bother changing it unless you are sure that your device is more accurate than the device used to locate it.

What if I am indoors near a Window? With WiFi triangulation you might get within 25 meters (80')

What if you have a dedicated device? Here are a couple with the same testing as the iPhone 14:

Note that the Garmin is not really enough better for most purposes than a high end cell phone. But the Trimble, it is 2.5 magnitudes of order better - or what people would normally call "200x's better"

But my experience is that MY phone is much more accurate than that.

The phones that are both ingenious and generally useful to improve the accuracy most of the time. This is good, and in many circumstances is beneficial, but be aware that most of the time is not all of the time. Different phones use different tricks, most now-a-days start with GPS, and if you have a vast clear sky (no buildings, trees in the way) you start with the accuracy noted above. But then as you move, the device can use accelerometers and other devices to increase the accuracy over time, as they get more GPS readings, averaging out readings to try to pinpoint where you are.

On a recent hike with my kids (2025), most of the time the readings seems to be accurate to within a couple metres (6 feet), then suddenly - it showed me I was standing 5 metres (15') off the trail. I knew I hadn't jumped 5 metres to the left and I could see that I was standing on the trail - not standing 2 metres off of the cliff (well I guess that would mean I was plummeting to my death) as the map said I was. Then over the next 15 seconds it said I moved from being out in the air falling to back onto the cliff.

Another time on the same hike, it showed me slowly going off the trail, again claiming that I was out walking on thin air, I suspect that, because I was on a trail on a cliff, with a mountain cliff wall beside me, that I had been out of site of most GPS satellites for too long, and I was getting 'drift' with the accelerometer readings in my phone. So use common sense with the readings, they might be very accurate, but don't trust your life or expensive equipment to what might be a very inaccurate reading.

You might not be beside a mountain, but you might be beside a building, or in a building or have signals blocked by other objects.

If there are WiFi signals, those may be used to triangulate based on where, based on lots of previous readings, the software thinks those WiFi devices are. But if someone moves one or more of those WiFi receivers, your position may be wildly off for a period of time until databases get corrected for the new location.

It may also use cell tower locations (those are less likely to move, though once based on that, I was told I was miles away from where I actually was - a tower had been relocated many miles to the South)

So yes, it may seem like tha accuracy is much better than it sounds from the science, and you can take advantage of that now that you know not to trust it to always be correct.

How many decimals do I need?

Having more than your device accuracy doesn't improve accuracy, it just shows more nonsense numbers. So if your device can give you accuracy of 4-10 meters, anything more than 5 decimals is fictional data.

Resolution

Any in the chart below the red line, 6 decimals, are guaranteed in almost every system to be useless data, no one in the EAM CMMS world is using equipment able to be accurate down to 7 decimals. Even 6 decimals will normally be beyond the accuracy of the data.

If you have top end cell phones and are lucky, you might from time to time get accuracy to the line with 5 decimals, the line above the red line, but usually you'll be in the 4 - 5 decimal range, so record 5 and that will be more than the accuracy of your device.

Resolution for degrees latitude at the equator and degrees longitude everywhere

These are accurate for all longitude values. Why? Because longitude values as a distance stay consistent as you move from the equator to the poles.

These are 'worst case' for latitude values. Why? Because these are the distances for latitude values at the equator. the distance between values of latitude approach 0 as you head towards the poles.

The arctic and Antarctic circles are ±16,000 kms long, so the purported resolution is a little better than double the chart above, but it doesn't mean the accuracy of your device in metres/feet change, indeed near the poles it may get worse due to the difficulty in having polar orbits for satellites.

The Tropic of Capricorn an Tropic of Cancer is ±36,800 (though it varies as the tilt of the earth changes and the Tropics move up or down towards and away from the poles and equator. So the resolution isn't very different from the equator. Most of the USA contiguous states only gives about a 10% better resolution on latitude than the equator, so not enough for us to worry about, Most of inhabited Canada is a little more precise again, but still not enough to change how many decimals of data matter.

Mapping and GIS readings

With GIS, check with your data team to determine how accurate readings are. It will depend on how they collected the data, some may be cm or inch accuracy, others significantly less.

Now imagine you are reading a Google maps value of 51.3942355583999, -114.216758879722 ( which I got most recently by r-mouse copy from Google Earth circa 2026) , Google is giving you a reading of location that, at the equator, is precise down to the membrane of a cell. But it's accuracy is at most 5 decimals.

This means you can ignore almost all the values Google gives you and, in the case above type in 51.39424,-114.21576 (±4"). In visual displays on Google maps 2025 they now show only 5 decimals of accuracy though copy/paste gives you the values above.

If you are concerned about the position of a door or window, type in just the 1st 5 or 6 and you'll likely be more precise than the data. (See the link above for discussing precision vs accuracy - you won't be that accurate, you'll just be more precise with wrong and meaningless data.)

If you type in 6 you don't have to worry about rounding the 6th value - you're already more precise than any data backing it up. But most of the time you don't have to worry about rounding with 5 decimals either.

If you are only trying to locate a city - don't bother with more than 1 decimal.

If you are trying to locate a building, enter up to 4 decimal places.

But my Phone is returning 15 digits

So doesn't that mean it is telling me it is really precise? like the position of molecule compared to another molecule, or where the tip of your fingernail was a second ago, it grows at about 1nm/second.

No, it just means it is giving you random numbers after the 3rd 4th or 5th decimal, depending on circumstances as above.

More Accuracy

what if you want more accuracy than your cell phone is giving?

You could try taking several readings spread out over several hours or days, then plot them and take the mean, but the evidence suggests that this is unlikely to help especially in urban settings due to 'bias' factors (the buildings blocking the signal tend not to move.) But if you do try it, use several different cell phones and move around (so your body isn't blocking it from the same place every reading and so errors in the direction your phone is facing don't become a factor. So this 'smart sounding' solution is of dubious value especially when you add in the human cost of doing it. Better off just accepting the limitations of the device.

Ideally start from a knows location, then move, trusting the accelerometers to figure out where you moved to. If you don't move much, your readings are truly more likely to be accurate.

So while there is some evidence this will often slightly enhance the accuracy of the reading, the cost in human time if you are doing for many items will likely be more than buying a more accurate device and calibrating it to known locations.

Tall objects like buildings can cause errors by signals bouncing and therefore taking longer to arrive. To avoid this problem whenever possible, have your device high enough to see most of the sky 'direct line of sight' so that it gets straight line signals from enough satellites. There are only 24-32 operational at a time, so you need to see most of the sky to get high quality readings.

What about when experience says that the phone readings are more accurate than above?

As discussed above, you may feel that at times you are getting more accurate data than above, this is possible due to several factors. Your phone may be averaging out readings, your phone may be adding in info like WiFi signal latency and/or dead reckoning, accelerometers, gyroscopes, magnetometers and even AI to improve the frequency of more accurate readings. This is why in a tunnel or in a building you see it tracking you even when no GPS satellites are visible. This is usually great - the point is to not rely on it in any critical situations, don't step off the roof of a building because the GPS tells you that you are 2 metres from the side when you can see you are on the side. Your experience of 'higher accuracy' in the past does not change the fundamentals, and the longer you are out of sight of too many GPS satellites, these factors can drift and become less and less reliable, check with the device manufacturer to see if the devices you are looking at getting use additional tools like this to give more frequently higher accuracy. The author of this article had a hard time reconciling the sometimes 1 meter accuracy (hiking path) with the 'facts' that the readings weren't supposed to be that accurate … until readings drifted several meters to one side, showing that the experienced accuracy couldn't be relied on, walking off the cliff because the GPS said to was not a good choice.

If you need more accuracy before digging a hole in a road, or punching a hole in a wall or ceiling - use the GPS to get you close, then other measurements to get things exact. Remember you can easily be 4-15 meters (3.5-50 feet) or more off, even if 'most' of the time you are within a few meters/feet.