geotag pic taken when not connected to wi-fi?

[Sam]

I am very interested in the geotagging functionality of the eye fi explorer but some of the posts here are rather discouraging and I am curious what happens when the card does not have wi-fi access at the time a picture is taken. I found the quote below in a review at http://www.wired.com/gadgetlab/2008/05/eye-fi-adds-geo/ that seems to indicate that even if the card is not connected to wi-fi at the time the picture is taken that the card will still store enough data so that later when the pictures are uploaded to your computer the pics will be successfully geotagged.

Can anyone please confirm this quote, can the eye fi explorer geotag a pic even if that picture was taken when the eye fi card was not connected to a wi-fi access point?

Thanks,

Sam

quote from http://www.wired.com/gadgetlab/2008/05/eye-fi-adds-geo/
"And if the card can’t connect to a WiFi access point to grab the info it needs to geotag the photos, it will store a snapshot of the access points it sees and work things out later when you get back to your PC or Mac." http://www.wired.com/gadgetlab/2008/05/eye-fi-adds-geo/

[hyachts]

That quote's a little misleading in that it suggests that geotagging is dependent on the card accessing networks at all. That's not the case. The geotagging is done solely on the basis of netowrks the card can "see" - it scans for networks every so often (once a minute, I think?) and caches the list of networks it detects (by the AP's MAC address). It's that list of networks that Eye-Fi (via Skyhook) uses to geotag the photo. That part of the function is in no way affected by whether you can connect to any of those networks or not.

The only time you need to be connected to a wireless network in order to get geotags is when you transfer the pictures. The photos have to transfer automatically (wirelessly) in order for Eye-Fi to apply the tags to the photo EXIF. In other words, if you remove the images from the card manually (via a normal file interface) they'll never get tagged, even if there were wireless networks visible at the time the picture was taken.

[Sam]

I think I did not ask my question in a technically correct way so I will ask again with just a slight change to the wording to clarify. I understand from your response that the geotagging takes place when the pics are transferred from the card to the computer and that this must be done wirelessly, the pics cannot be geotagged if the pictures are manually copied from the card to the computer.

In my origional question it appeared that I was asking about the geotagging process but what I am more concerned with is what happens when the pic is taken if the card cannot "see" a wi-fi access point or what would happen if the last "seen" wi-fi access point was 50 miles away.

Can the eye fi explorer accurately geotag a pic even if that picture was taken when the eye fi card did not "see" a wi-fi access point?

What would happen if the last wi-fi access point the card saw was now 50 miles away when a pic is taken, would the pic be geotagged as being at the location of the last wi-fi access point that was seen?

Thanks for your help...

-Sam

[hyachts]

The card must have seen a wifi point within an hour either side of the picture being taken in order for there to be any chance that the photo will be tagged. Additionally, the network(s) the card sees must be mapped in Skyhook's database to convert the network data to a geographic fix.

So.. no wi-fi, definitely no fix. If the last AP seen is 50 miles away at the time of capture, but within an hour, and that AP is in Skyhook's database, then the tag will be 50 miles off.

[toomer]

If this is the case, then the Eye-Fi is a little bit disappointing ... and will probably end up getting returned to Amazon.

If the location "granularity" is truly +/- 30 minutes ... then I don't really think this is all that useful for sightseeing trips - where you might see several interesting landmarks over the course of an hour, often many times miles apart from each other. So now if I snap a few shots of the Coloseum in Rome ... then taxi over to the Trevi Fountain and take a few more shots, it's entirely possible that my Coloseum shots will be geotagged at the Trevi Fountain location? That's useless to me...

I knew that the Eye-Fi's accuracy would not be as good as GPS (range of a few hundred feet) but was willing to live with that tradeoff for not having to carry a separate GPS for geotagging. But if this is how the logic works in the card, it's going back...

I just tested this out by taking a 1 hour trip around my town, snapping photos of various businesses and shops ... so that I knew where all the locations were. Sure enough ... even though I took photos in about 10 discrete locations around town, all several miles apart from each other ... once I brought the camera home and let it do its WiFi upload magic, all the photos ended up geotagged into two spots once they got up to SmugMug. Completely incorrect -- photos were tagged miles away from where they were actually taken.

Nice idea ... but if this is how it's implemented, the geotagging is pretty much useless. Why the card can't be programmed to take a quick "wifi snapshot" of the MAC(s) visible in the area, any time a new file is created ... puzzles me.

[hyachts]

It scans for networks every sixty seconds, IIRC. If you only got two locations for your ten stops, that means that it was only at those two locations that the card saw networks that are in the Skyhook database. Even if it saw wifi networks the rest of the time, if they're not in the Skyhook database, they aren't any good for a tag so the routine expands its search until it finds APs that are in the database (up to an hour +/-). It's a trade off - accuracy for number of "hits".

If you want reliable geotagging, get a GPS. WPS is no match; not even close.

[toomer]

Thanks hyachts ... yeah, read through a few more threads here - and think I have a grip on how it's working. I had already purchased a Garmin Colorado 400t for some trekking in the Grand Canyon next month anyway (knew I wouldn't have Wifi locations there), but was hoping this might work well enough that I didn't have to carry the Garmin around as a datalogger every time I wanted some geo data...

It's not necessarily the way I would have designed the algorithm - seems they've overlooked a rather obvious use case by not making this behavior a bit more flexible. Personally, if the card hasn't seen a AP within a minute or two, I'd not want it to stamp anything on there and I'll do it later myself ... as opposed to depending on a scan possibly 60 minutes old and thereby stamping the wrong location on a photo.

Oh well ... just have to keep reminding myself ... it's only $99.

[hyachts]

I think there might be a thread in the feature request forum to make that time window configurable. If not, you should start one - I'll second it.

[toomer]

Done.

Couldn't find an existing thread in the Feature Request forum, so I started a new one: viewtopic.php?f=10&t=1057

[talula11]

Thank you!!!
we really needed such a thread