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Cell Phones & Coordinate Accuracy


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Posted (edited)

Well, folks, it is getting to look like more and more of us are using our cell phones to take the pix for the Waymarks that we submit. 10 or 15 years ago this was still a bit of an issue, as was mentioned in the requirements of several categories, vis a vis "grainy/blurred/low resolution/etc./etc. cell phone photos". Today, the onward march of Science & Technology has managed to mitigate this objection into nothingness. 

 

However, another aspect of cell phone photos, those also used to glean Waymark coordinates, is quite another story. Do you regularly check the accuracy of the coords your cell phone has provided those photo EXIFS? Do you EVER check their accuracy?

 

I had always used a GPSr to take coords. and knew them to be as accurate as could be expected from a hand held consumer unit, in general. Recently I decided, having dealt with another for an unpleasantly long time, that it was time I found me anew & different cell phone. Upon finding a choice I considered workable I discovered that a brand, spanking new version would have set me back ~$900.00. (CDN) Opting for a less onerous outlay of cash, I chose an older version of same which I was able, with MUCH shopping around, to purchase for <$300.00. (CDN)

 

I started taking pix with it, only to find out, when comparing them with my REAL camera pix, that they were, for the purpose of internet uploads, every bit as useable as the REAL camera pix, so I started taking Waymarking pix with the phone. However, before I was reckless enough to post any Waymarks using said pix, AND USING the coords. within said pix, I decided I had best check the accuracy of the coords. they were providing.

 

OOPS! - they were all WAAAAAAAY off, as in about a third of a city block off, some in one direction, some in another direction. How do I fix that?

 

After searching the appropriate app store and downloading and trying out several GPS tools apps I finally found one that was as accurate as is possible with a cell phone (without using rather exotic trickery [~3.2 metres]), was VERY fast at accessing the available satellites, AND was able to (apparently) have its location information used by the phone's stock camera, while the app was (apparently) running in the background, resulting in very accurate coords. transferred to  the photo's EXIF. The app has a very comprehensive display of pertinent parameters, as well as several other useful tools.

 

I should note here that I have just, within the last two days, downloaded said app and tried it out with a very small sample of photos and locations. Coords. for those test photos were never within the 3.2 metre radius, some were slightly outside it and some were right on the perimeter.

 

Hopefully, tomorrow I will be taking it out on a more thorough, but not extensive, field trip (just within the city{if it's not raining [we're getting a bit of that lately]{), then, at the end of the week a larger field trip > 100 km. to the west. I'll append my results in an addendum to this post.

 

This is being written solely as a potential aid to Waymarkers who use their cell phones, so I'm not sure I should be mentioning product names here. After all, should "mentioning product names here" be a No No, I already have one strike against me for another, separate, transgression, so I feel my wisest course of action is to simply ask readers to write me should they feel an interest in, or a need for, the particular product to which I allude here.

 

One reason for my breaching the topic of incorrect coords. is the spate of Waymark Suggestion Edits I'm beginning to receive, essentially all dealing with incorrect coords. If cell phones, are, indeed, capable of tagging photo EXIFs with faulty coordinates, then we may well be seeing more and more of these Waymark Suggestion Edits "As Time Goes By".

Keith

Edited by ScroogieII
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Posted (edited)

In my experience, it depends. And it depends on things outside of your control. So I generally don't trust my smartphone EXIFs, but usually their good enough. It is always important to check with other sources.

 

GPS devices use satellites. The more they can read, the better. Sometimes the situation is not optimal, but you still stay within a certain range.

 

Smartphones also use other technologies like cell phone towers and wi-fi. This is not bad, but they don't tell you what they used and things can happen. I once had an EXIF 600 km off, it was in our local harbour and I guess a transport company relocated parts of their wi-fi infrastructure and the database the phone used was not yet updated. I heard similar stories about wi-fis used in convention centers across several continents.

Edited by fi67
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Posted (edited)

As promised, THE ADDENDUM:

Walked several blocks today to a cemetery in which I needed to get some coords for various WMs. On the way I did a couple of test shots, naturally forgetting to turn location on until after the first shot. Below are the results of my test trip:

 

Test01 - OOPS, forgot to turn location on
Test02 - 49.0223917 -118.4574028 - 20M SE
Trail - 49.0241722 -118.4526500 - 6M E
CEM - 49.0241722 -118.4526500 - very close, < 1metre
UR Here - 49.0213750 -118.4524889 - fairly close, can't tell for certain as the kiosk hadn't yet been installed when the satellite flew over
Steel Cross - 49.0213750 -118.4524889 - same coords as above
Wood Cross - 49.0213750 -118.4524889 - same coords as above
WOW - 49.0213750 -118.4524889 - same coords as above

Beliveau - 49.0237111 -118.4524750 - 10M NE

 

As you can see, the results were not very encouraging. Note the bolded lines. For some reason the phone neglected to update its coords, though it had several minutes to do so. The four locations were sufficiently separated that there's no way their coords could be rounded to give these results. Moreover, I meandered slowly about, allowing (I thought) the phone to easily track my movements and update its GPS data. Throughout I had the GPS utility running in the background as a small window on top of the camera window. That way I could see the accuracy it was professing. Before each shot I waited for it to settle on 3.2 metres.

 

My takeaway here is that the phone's camera isn't really having anything to do with what the GPS utility is doing, as while I walked about I could watch the LAT-LON readout shown by the GPS utility change with great regularity, almost with each step. I didn't pay much attention to the GPS utility's LAT-LON readout, which I should have been doing, as I was really only interested in what the camera's output would be.

 

One note here - I have always kept WiFi and Cell usage turned OFF, so coords would be based solely on data received from satellites. Throughout, there were plenty of satellites within range, with 10 always useable.

 

I guess for now I will continue to rely on my old Magellan GPSr, as it has, as best I can recall, seldom lied to me. Meanwhile I shall try to see if I can find a work around. After all, the phone is close to 10 years newer than the GPSr. In that span of time I really expected that "Smart" Phones would have caught up with dedicated GPS receivers with regard to accuracy and repeatability.

 

Onward & Upward,

Keith

Edited by ScroogieII
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This is how I do it: Usually I go out with my GPS device, which tracks my path and usually has more accurate coordinates than the other devices, and my Smartphone / Camera. Usually the saved track is enough, but at some special places (i.e. at a grave of a centennial on a cemetery) I also take an extra coordinate with the GPS.

 

The EXIF and the time information from the Smartphone picture is mainly used to get the area where the picture was taken. The detail coordinates are then taken from the GPS device for the waymarks. If there is still a doubt, I'll use Flopps map (flopp.net) to take a closer look at the satellite image.

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In the old times I used my camera for the photos and took (ugly!) photos with my Garmin just to have the right coords. Meanwhile my GPS is very old and the batteries seem to run out of energy faster and faster and therefore I hardly use the GPS anymore, but my cell phone. Moreover, the photos of my cell phone are often good enough to be uploaded. Additionally, Mrs. PISA also takes photos with her cell phone (that are sometimes an interesting additional point of view) and I have a few WMs with photos of three different devices. :)

 

However, I always check the coords with Google Maps.

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Photos usually taken on phone these days, coordinates taken from resulting photo information...

Double checked against Google. (Usually correct, but do try to give the satellites a chance to register on the phone before taking photos)

 

Interesting factoid. My phone saves the photo as a larger file than the first professional digital SLR camera I used!

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Posted (edited)
On 6/1/2022 at 2:32 AM, FamilieFrohne said:

This is how I do it: Usually I go out with my GPS device, which tracks my path and usually has more accurate coordinates than the other devices, and my Smartphone / Camera. Usually the saved track is enough, but at some special places (i.e. at a grave of a centennial on a cemetery) I also take an extra coordinate with the GPS.

 

The EXIF and the time information from the Smartphone picture is mainly used to get the area where the picture was taken. The detail coordinates are then taken from the GPS device for the waymarks. If there is still a doubt, I'll use Flopps map (flopp.net) to take a closer look at the satellite image.

 

This isn't yet really telling me much about the accuracy, either overall or instance to instance, of your cell phone's published coordinates, though.

Did the coordinates match those from your GPSr with regularity? When I say "match" I would expect a match within 3.2 metres, which, as last I was aware, was the maximum potential accuracy achievable with handheld consumer devices such as GPS receivers and cell phones.

 

On 6/1/2022 at 8:00 AM, PISA-caching said:

In the old times I used my camera for the photos and took (ugly!) photos with my Garmin just to have the right coords. Meanwhile my GPS is very old and the batteries seem to run out of energy faster and faster and therefore I hardly use the GPS anymore, but my cell phone. Moreover, the photos of my cell phone are often good enough to be uploaded. Additionally, Mrs. PISA also takes photos with her cell phone (that are sometimes an interesting additional point of view) and I have a few WMs with photos of three different devices. :)

 

However, I always check the coords with Google Maps.

 

Not much real help in this vein, Andreas, sorry.

 

On 6/2/2022 at 4:58 AM, Bear and Ragged said:

Photos usually taken on phone these days, coordinates taken from resulting photo information...

Double checked against Google. (Usually correct, but do try to give the satellites a chance to register on the phone before taking photos)

 

Interesting factoid. My phone saves the photo as a larger file than the first professional digital SLR camera I used!

 

Interesting that you find the photos' coords to be  "usually correct". What is the make and model?

Yes, by using the GPS utility I always made sure when testing that some damned utility on the phone had a very good idea of where we were, always waiting until it stated that it had achieved "3.2Metre" accuracy. Unfortunately, the camera, which I have hitherto assumed to be in the employ of the same sensors, GPS chips, software, etc., often had a quite different idea of just where on the surface of this round(ish) ball we were situated!

Frustrating as hell! Mostly because I can't yet understand the reason for the discrepancy.

Keith

Factoids or Plain Balderdash, Take Your Pick:

1 - The odds are that your phone saves a much larger EXIF than did your DSLR, assuming the DSLR has a number of years on it.

2 - Moreover, you must compare actual photo size - pixels wide, pixels high, to be sure one's data size is is comparable to another.

3 - Then you have colour depth to consider, IE the number of bits saved per pixel to define that particular pixel's colour, as defined by the DSLR camera vs the phone's camera. I suspect that the recorded colour depth of even today's phone cameras exceeds that of DSLRs of much age.

4 - Then we must consider aspect ratio. All cameras do not natively shoot using the same aspect ratio. The most common are 4:3 and 3:2. Many people will not appreciate the difference between the two, as they appear reasonably similar when viewed. I'll let you tell me which should consume the greater number of pixels, hence bytes (a measure of your mathematical acuity :D ).

And, BTW, how old is that "first professional digital SLR camera"?

 

Edited by ScroogieII
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5 hours ago, ScroogieII said:

Did the coordinates match those from your GPSr with regularity? When I say "match" I would expect a match within 3.2 metres, which, as last I was aware, was the maximum potential accuracy achievable with handheld consumer devices such as GPS receivers and cell phones.

When I use my Garmin 450 with the Glonass mode it usually has an accuracy of 3m when the surroundings are not shielded by many trees or buildings - otherwise it may go up to a measured max of 32m. The GPS in my smartphone (Samsung A51) usually has a deviation of 20m to 36m in the open field  - in the city of Cologne I was once off more than 400m.  Knowing this I prefer to use the coordinates from the Garmin device.

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On 6/5/2022 at 4:10 AM, FamilieFrohne said:

When I use my Garmin 450 with the Glonass mode it usually has an accuracy of 3m when the surroundings are not shielded by many trees or buildings - otherwise it may go up to a measured max of 32m. The GPS in my smartphone (Samsung A51) usually has a deviation of 20m to 36m in the open field  - in the city of Cologne I was once off more than 400m.  Knowing this I prefer to use the coordinates from the Garmin device.

 

BTW, my phone is a Google Pixel 3 XL. 

On the average I would say that its accuracy is better than yours, if not a lot. One disturbing bit of behavior I noted in my cemetery test was the four identical coordinate sets given for three reasonably disparate locations. The phone was given ample time to reorient itself, yet failed to do so.

Then, of course, a few minutes later (and earlier) it had come up with some quite reasonable estimates of its location.

Prior to my leaving home I did two shots in fairly quick succession that were about 25 metres apart and both were within 3.2 metres of perfection, if only just.

 

To paraphrase Erik, "Knowing this I prefer to use the coordinates from the [Magellan] device."

Keith

 

Off Topic: On Saturday, in Penticton, BC I experienced absolutely the HEAVIEST RAIN I'd seen in my entire life! Driving along a street, we couldn't even read street signs there was so much rain, not even large signs over the middle of the street! It was almost like being in a heavy fog. The REALLY HEAVY rain only lasted a few minutes, but it sure was impressive. Climate change?!?!?!

 

As the local rivers had been rising considerably in the past couple of weeks, rains like that will only exacerbate any flooding we get this year. Since we've had a fairly cool April and May, snow in the upper elevations is just beginning to melt. Looks like quite a few people are in for more sandbagging fun this year, alas. :(

Edited by ScroogieII
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I don't often use the cell phone GPS directly but do use it to tag my photos. When it comes to setting the waymarks, I look at the location tag, drop it into Google Earth, and home in on the correct coordinates that way. Google Earth is quite accurate, by the way, probably more so than a handheld GPS.

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6 hours ago, The Snowdog said:

I don't often use the cell phone GPS directly but do use it to tag my photos. When it comes to setting the waymarks, I look at the location tag, drop it into Google Earth, and home in on the correct coordinates that way. Google Earth is quite accurate, by the way, probably more so than a handheld GPS.

 

Based on personal experience, I find I must agree with the Snowdog's ending sentence, but with regard to Google Maps. I imagine, though, that the two originate at the same source.

Though I'm not absolutely certain, Google Maps has been, in my experience, quite accurate with regard to location.

With regard to accuracy of indicated distances, it is pretty much spot on! I checked it on two football fields using the satellite view, in quite different locations, and each time its estimated distance from goal line to goal line was essentially perfect. Needless to say, I was somewhat impressed.

Keith

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