On the lower tab bar, select the Map icon. From the Map screen, tap the Date button on the upper tool bar. Use the picker to pick a date. Location data will be searched from midnight to midnight (per the device's current timezone) on the selected date. If locations are found on that date, the map will show red circles around the data points, and will pan the map from wherever it last was centered. If no locations are found, no circles will be drawn, and the map will not pan.

On the lower tab bar, select the Map icon. From the Map screen, tap the Area button on the upper tool bar. Next, drag your finger across the screen to identify the map region (rectangle) to search. If locations are found within the search area, a list view of data points will be opened up, showing the time (per the device's current timezone) at which data in that area was recorded. Click on a row to drop a pin back on the map identifying the precise location. The map will also show red circles around the other data points from the list, and will pan the map from wherever it last was centered.

On the lower tab bar, select the Database icon. Next, choose either the Delete button, or the Random button. Delete will clear out all location data in the device's database. Random will alter the device's location data by inserting random location errors. This will not leave the database empty, but will contain locations the device was never at. Be careful, as these actions are permanent, unless you have previously backed up the database ...

In iOS update 4.3.3 (GSM) and 4.2.8 (CDMA), Apple reduced the amount of location history saved. If you don't like this change, you can use Footprintz to keep more history. The default behaviour is for Footprintz to not save any more history than iOS normally does. You must choose to enable this feature.

To do so, on the lower tab bar, select the Settings icon. Within the settings, turn on the switch labeled Retain History. This will cause Footprintz to start keeping a separate history file, that contains a superset of the data it has ever found on your phone. If iOS later shrinks the built-in database, Footprintz's copy will still retain the full history. Note that this feature cannot recover lost data. If you did not email yourself a backup of your history, and iOS deleted it, then it's gone.

Also important to note is that if you want to retain a full history, but also want to upgrade to 4.3.3/4.2.8 (or later), you must turn the Retain History switch on before you upgrade your device. If you wait until after the upgrade to turn on the switch, it will be too late.

On the lower tab bar, select the Database icon. Next, choose the Email button. Follow the process to send yourself the attached file, in an email. The file may be several megabytes in size, so make sure the sending and receiving email accounts can accept large files. You may wish to do this while connected via WiFi, rather than a carrier network.

If you save the attachment on the other computer, you will be able to later restore your device's location data by emailing it back to your device, and opening the file as an attachment. For this step, you must make sure the file still has the .fpz extension, before emailing it from your computer, back to your iOS device.

Warning: If you wish to have location history backed up, and available after an iPhone restore, you need to use the feature described above. Normal iTunes backups do not backup the location history on iOS 4.3.3 and above (4.2.8 and above for CDMA phones). So, you must manually email yourself the backup file, and then open the attachment on your phone, after performing a restore on your device.

On the lower tab bar, select the Database icon. Next, choose the Export button. Follow the process to send yourself the attached file, in an email. The file may be several megabytes in size, so make sure the sending and receiving email accounts can accept large files. You may wish to do this while connected via WiFi, rather than a carrier network. The attachment will be a human-readable CSV (comma-separated value) file, that you can open up in your favorite spreadsheet program for further charting or analysis.

Be sure to see the built-in Settings app for ways to customize Footprintz's user experience.

More information about Footprintz can be found online.

Two clever researchers stumbled on to it mapping nuclear radiation. See their story here.

A link to their official statement.

Footprintz is still undergoing testing with iOS 4.3.3 (4.2.8 for CDMA phones). The reason for Apple to release iOS 4.3.3 was to reduce the amount of location data stored internally. So, if you really want to see the stored data, which Footprintz allows you to do, then you have no good reason to upgrade to iOS 4.3.3.

These location data are points near where your device was, not necessarily where it was exactly. This is a database of cell towers and WiFi hotspots that your device came reasonably close to. The data are used to help the device more quickly determine your position while using location-enabled apps, without relying too much on GPS, which is slow and battery-intensive. So, some points may be further away from your location, especially cell sites.

The size of the circle doesn't actually correspond to the accuracy of the location data. There is accuracy information in iOS's database, but there's no public documentation as to what the accuracy values mean (feet, meters, HDOP?) If you know, please feel free to email me. and I'll update the app.

See the previous response. Also, this app searches three different tables of data kept by your iOS device. GSM vs. CDMA vs. WiFi locations will inherently differ in their accuracy. You can experiment with Settings to see which location source gives you the best results.

Your data really has been cleared out. The database format that iOS uses for this does not shrink files when data is deleted. It holds on to empty space to reserve it for future growth. Footprintz could have "vacuumed" up that unused space, but that just takes more time for the app to run.

I don't know. This is Apple's algorithm. However, it's probable that this location data is only collected when location-enabled apps are run. If you didn't use any location-enabled apps for a couple days, there might not have been any data collection. Or it could be that the device already had data for the nearby WiFi hotspots and cell towers, from a previous date. If iOS really is only collecting this data to improve the speed of location fixes, then they shouldn't need to record the location of a given tower/hotspot more than once or twice.

Your location history may be quite large. You can try to limit the number of search results via the Settings screen.

The playback feature waits for a given number of seconds between each day, as it plays back your history. Sometimes, especially if there are a large number of locations stored, or if you have an older iPhone, it can take a while for the map to draw the red dots. This can cause the playback to skip to the next day before the previous day's dots are drawn on the map. You can slow down the playback by increasing the playback step/delay, via the Settings screen. Older iPhones (e.g. iPhone 3G) will probably need a longer delay, as will phones with more location data.

A full restore would probably wipe out your location history data. However, prior to iOS 4.3.3, the location database was actually part of iTunes backups. So, if you performed a full restore to a clean state, and then recovered a previous backup, to bring back your apps, location data should be part of that. Again, prior to 4.3.3.

I actually have a lot of location data from a previous iPhone, that apparently got migrated when upgrading to an iPhone 4. All location data from the previous device were timestamped with the date I restored the new phone from iTunes backup.

Footprintz does not collect the location data. iPhone does. So, I can't be sure. However, one possible way this might happen is if WiFi hotspots are being used. WiFi sources are identified by unique numbers, called MAC addresses. These numbers don't change if an IP address changes. They are like serial numbers for pieces of hardware. If a given WiFi source is moved (for example, someone sells their WiFi router on eBay), that could cause the location database to show one datapoint that is completely in the wrong location. Over time, new locations for WiFi sources should be stored by your iPhone, but it's certainly possible to have out-of-date WiFi data, and therefore points on the Footprintz map that you have never been to. This should not happen with cell tower locations, however.

In the Footprintz application settings, you can choose to turn off WiFi location sources, if you find WiFi data to be too unreliable.

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If you have a problem running Footprintz, please tap here to email me the application logfile and describe your problem as precisely as possible.

This is Footprintz 2.1