iPhone geo-tracking database

April 20, 2011
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[This article was first published on simon jackman's blog » R, and kindly contributed to R-bloggers]. (You can report issue about the content on this page here)
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So the web lit up a little today with news that iPhones are collecting time-stamped location data, and in a form that isn’t particularly hard to look at (and even with some nice apps to make animated maps of your travels etc):

The database is SQLite, and I used R (and the RSQLite package) to open it up and see what is there. In my case, I found a database with 35,297 records, with timestamps ranging from June 22, 2010 to 4 days ago (the date I last synced my phone). That said, there are only 726 unique timestamps in the database, which makes me wonder what is going on. Incidentally, the time-stamps are seconds since 2001-01-01 (I don’t know which TZ): in R, I converted with:


as.POSIXct(data$Timestamp,origin=c("2001-01-01")

There is a little weirdness in the data: the iPhone thinks I was in Scotland last August (when in fact I was no further north than Colchester), and a few other instances of the geo-data being off by as much as 100 kilometres or so. There are also 68 records with lat/long recorded as 0/0, almost all of which are records from when I was in England last August.

There are also fields whose names I can’t fathom, nor does a quick look suggest that any of them might be offsets to the timestamps:

> names(data)
[1] "MCC" "MNC" "LAC"
[4] "CI" "Timestamp" "Latitude"
[7] "Longitude" "HorizontalAccuracy" "Altitude"
[10] "VerticalAccuracy" "Speed" "Course"
[13] "Confidence"

Does anyone know what the fields with non-obvious names might be?

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