Geotagged photos can pin-point your every move. Dr Karl takes a close look at how this sneaky snap technology works.

In the vast majority of cases, your smartphone will automatically embed your location into every photograph you take. (Source: fotostorm/iStockphoto)

If you don’t understand the technology you use, every now and then your ignorance will come back and bite you.

One expensive example of this happened back in 2007 on a US military base in Iraq. Because some soldiers took photographs and posted them on the web, the US taxpayer lost over $100 million.

This new-ish technology that the soldiers didn’t fully understand is called ‘geo-tagging’. What it means is that when you take a photograph or video, your geographical location is almost always embedded in the digital files of that photograph or video. This happens automatically with practically all smart phones that have a camera built in, and with a few specific digital cameras.

This geographical identification data is usually stored as ‘metadata’ in what is called an EXIF file, as part of your digital photograph.

EXIF stands for exchangeable image file format. It is an industry standard that specifies the format for images and sound used by digital cameras. But it doesn’t store only images and sound. It also stores date and time information, the camera settings that we use to take a photograph or video, a small thumbnail picture to preview the image on the camera’s LCD screen, and so on.

But EXIF files are now being used to store extra information, such as your latitude and longitude coordinates. Furthermore, the geo-data stored can also include your altitude above sea level, the direction the camera was facing when it took the photograph, how accurate is your camera’s estimate of your location, and even place names.

But how does your smart phone know where you are?

There are a few different ways. They all involve the 2000-year-old technique called ‘triangulation’. In triangulation, if you have three known locations, and if you know your exact distance from each of them, then there’s only one place you can be.

The first modern method of triangulation uses ‘real’ GPS, and gets location and time information from GPS satellites orbiting some 20,000 kilometres overhead. But that’s expensive. So you don’t have to use the satellites. Instead, your smart phone can also work out your whereabouts by knowing the location of the nearest mobile phone towers, or any Wi-Fi hotspots, including the one in your house.

But regardless of how your smartphone knows where you are, the important thing to realise is that in the vast majority of cases, it will automatically embed your location into every photograph you take. If you want to stop it from doing this, you have to dive deep into the settings of your smart phone. However, if you did accidentally imprint geotags on your photos when you took them, you can later remove them with the many so-called ‘metadata removal tools’ available on the web.

This has “interesting” privacy considerations. If you take a photograph of a painting on your bedroom wall, and then post that photograph on Facebook, anyone can work out the location of your bedroom. A thief can work out that you have gone on holidays by checking your location via the photos you post on the web.

Getting back to the snap-happy soldiers who cost the US taxpayer lots of money, back in 2007 at a military base in Iraq, they took delivery of some AH-64 Apache helicopters. These are not cheap choppers. In 2012, the price of a brand-new one was $38 million. The soldiers proudly took pictures of their new attack helicopters, and then uploaded them onto the web. Almost certainly, the soldiers did not realise that geo-location tags were embedded in those photographs.

According to Steve Warren, a US Army Manoeuvre Centre Of Excellence intelligence officer, “the enemy was able to determine the exact location of the helicopters inside the compound and conduct a mortar attack, destroying four of the AH-64 Apache”.

That was an expensive $150 million mistake but I guess that the soldiers now have had drilled into them just what geo-tagging is. I wonder how long before all us civilians learn about the “Oh My God”s or “OMG”s of geo-tagging.

Tags: mobile-phones, computers-and-technology, information-technology

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Published 05 June 2012

2012 Karl S. Kruszelnicki Pty Ltd

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06 Jun 2012 12:04:35am

Not sure whether the EXIF data actually gets copied to Facebook.
When you upload something to Facebook, it is compressed and resampled where necessary.
I also believe Facebook removes this data – I just tested this on a few of my friends photos.
So before frightening everyone that photos you put on Facebook can be used to track you down – double check! 🙂
Obviously, if you were to upload the raw unmodified photo from you phone or camera, to a website or hosting service, the EXIF data would still remain.

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11 Jun 2012 10:21:47pm

karl, can we get a reply that addresses whether you agree with ronald – that facebook does not enable access to exif data? i think clarity on this is pretty vital considering the alarming hypotheticals you cite so it seems odd you’ve answered only a later query to me…

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26 Jun 2012 3:18:30pm

The article did not specify Facebook. While I do not doubt that your experiments are accurate for Facebook, there are a number of Photo sharing sites on the web that DO include geo tags – Picasaweb and Flickr being two examples. The implied fact is that ANYONE to whom you give your photos, be it via web, email, or by thumbdrive, will get the EXIF data which includes the geo tags, unless you specifically remove it.

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03 Jul 2012 9:34:04pm

the article clearly does specify facebook pete – ‘If you take a photograph of a painting on your bedroom wall, and then post that photograph on Facebook, anyone can work out the location of your bedroom.’

i’m still waiting for karl to address ronald’s comment.

karl – does geotagging occur in facebook photos as you have claimed or not?

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06 Jun 2012 2:21:38pm

Excellent article.

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07 Jun 2012 2:18:26pm

Seems alarmist to me.

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08 Jun 2012 12:49:47am

My camera is a “primitive” on that does not store location data. Sometimes it’s better not to be the “first kid on the block” to use the latest technology!

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07 Jun 2012 7:10:39pm

When you triangulate from 3 known points there are 2 possible locations you can be not one. To get it down to only one possible position you need to know your exact distance from 4 known points.

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08 Jun 2012 7:10:57pm

Dear Jason,

Howdy, and thanks for the comment. You might be correct, but I am not sure.

If you have ONE known point, you have to be on the circumference of a circle centered on that point.

If you have TWO known points, then there are two circles (each around their own known point). These circles intersect at only two places. Therefore you have to be at one of those two places.

If you have THREE known points, the third circle will intersect the two previous circles at only one point – which is where you have to be.

At least, this is my interpretation of the geometry. Can you tell me where I have made my mistake?

Thanks again.


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20 Jun 2012 1:45:10pm

When using mobile phone towers you also need to think in 3D, if I’m in a lift or perhaps on an overpass then the distance from each tower will put me at either a point above or below relative to the towers transmission/transponder centers.

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21 Jun 2012 6:08:22am

Depends on whether you are talking in 2 dimensions or 3. If we are talking in 3 then Karl has missed the first step – a fixed distance from a point in space creates a sphere. Knowing your distance from 2 points in space then locates you on a circle, the third distance gives you 2 points in space and the 4th distance gives you the fix. GPS doesn’t need 4 however, only 3 – it automatically rejects the position that is way out in space.

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21 Jun 2012 10:03:07pm

Hi Dr Karl

I think Jason is correct because three dimensional geometry means that one point defines the centre of a sphere not a circle – I think we need 4 intersecting spheres to define a unique point. Being on the surface of the earth doesn’t help much if you are in the Himalayas or at the bottom of death valley although in most circumstances knowing you are placed somewhere along a line of the earth’s radius will allow a good approximation to one’s position if we assume you are within a few hundred metres of sea level. I doubt it would allow an accurate mortar attack without additional data such as altitude.

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09 Jun 2012 3:26:26am

Triangle of error
1. If the triangle of error is inside the triangle formed by three features (ABC), your true position will be inside the triangle of error. If the triangle of error is outside the triangle ABC, then your true position will be outside the triangle of error;
2. If the triangle of error is outside the triangle formed by the three features, ABC, then your true position will be either to the left or the right when facing fixed points of all the lines drawn on the map from the respective features through the triangle of error; and
3. Regardless of whether your true position is inside or outside the triangle of error, the distance from that position to the lines will be directly proportional to the length of the lines(that is, your position will be nearest to the shortest line and furthest from the longest line). Depending on the size of the triangle of error, your position within the triangle can be worked out exactly by this method. By approximations, your true position can be confirmed by relating the map to the ground.

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09 Jun 2012 9:01:19am

How so?
If you know your exact distance from two points then there are two possibilities for a third pont that will satisfy the distances from the first two points(one on either side of a line that joins the two points). But if you know the exact distance from a third point then there is only one location that will satisfy all three known lengths. (the location is not one of the points unless one of the distances is zero). It is called TRIangulation not quadrangulation for a reason.

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09 Jun 2012 9:12:23am

In a void or in flight this is true, but when you know you are on a surface three should usually be sufficient.

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09 Jun 2012 4:38:20pm

If you needed four positions to get your exact location, it would be called ‘quadrilateration’. The only timme you get more than one (two)intersection point for three circles is when the three points are co-linear. If you then add a fourth point, you can do away with one of the others, leaving three.

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10 Jun 2012 2:10:22pm

If you assume the point is on the earth, then the earths radius is the fourth distance, hence only three others are required.
Incidentally we are talking about trilateration which is location by measurement of distances – triangulation involves the measurement of angles (plus at least one distance).

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09 Jun 2012 6:14:07pm

I found this article interesting, coz i too was shocked when i realised the location of the pics i was taking on my phone was available for ppl to see.

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14 Jun 2012 3:28:23am

Who relies on the internet for facts?

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