Where Is My Kid - How To

 

Where Is My Kid Location Tracking

1.0 Location Tracking

Where Is My Kid (WIMK) uses GPS to track users location and movement history.  Apple provides GPS capability to iPhone and other iOS devices to support location information.  WIMK uses this capability to track users location and provide this information to the user and other friends.

Apple have effectively two ways to use GPS tracking:

  1. Continuous detection
  2. Significant movement detection

  Continuous detection provides, by far, the most accurate and detailed tracking data, at the expense of high battery use.  Significant movement detection uses far less battery power, but provides more basic tracking data.  WIMK uses a combination of these two approaches based on user settings and power source.

WIMK has basically 3 ways to track location (with some settings that can affect each)

  1. Significant movement detection
  2. Monitor Movement Details
  3. Continuous tracking on the Tracker tab

1.1 Significant Movement Detection

The default approach is #1 when initially installed from the Apple App store.  This uses the least battery power and provides basic tracking information when a user moves a significant distance.  This works as follows:

  1. About every 30 minutes Apple software does a location check to see if significant movement has occurred, (usually in the range of a few kilometers or so).  Most of these updates are based on cell towers, so as you move around, different towers can be detected and used to determine if a significant distance has been moved.  This approach works best in city areas where there may be more cell towers and less well in country side areas where towers may be further apart
  2. When Apple detects movement, this is reported to WIMK, which begins more detailed tracking.
  3. WIMK then tracks the user movement every few minutes until GPS based location changes stop occuring.
  4. It continues tracking until no further movement is detected in a given period of time.  When this occurs, WIMK goes into a sleep mode and waits for the next update from Apple (step 2 above), which starts the process again.

1.2 Monitor Movement Details

This is an option on the Setting tab of WIMK.  When this is enabled, the following generally occurs:

  1. About every 10 minutes WIMK does a periodic location check to see if any movement has occurred since the last check.  Movement more than about 300 feet will be detected.
  2. When movement is detected, WIMK goes into a higher frequency location tracking mode.  The frequency is based on detected speed of movement and distance from the last check.  It can be as small as every 30 seconds and as long as a few minutes.
  3. It continues tracking until no further movement is detected in a given period of time.  When this occurs, WIMK goes back to step 1 checking location on a more infrequent basis.
  4. WIMK can also sometimes begin tracking when actual phone device motion is detected (for example when it is picked up, set down, or other significant motion events. When this occurs, it triggers step 2 to check more frequently for movement and location changes.

Motion detection (used in step 4) changed somewhat in the Apple iOS 4.2 update.  Previously it worked most all of the time and provided good motion detection for the physical phone device.  With the 4.2.1 update from Apple, this changed (its not clear whether it is a bug or a change in standards), but the result is very limited motion detection.  With the current 4.2.1 update, motion can only be detected when WIMK is in the foreground of the display and the display is visible (not in locked state).  As soon as the app moves to the background or the display locks, all motion detection stops.  Apple may update this in future iOS updates, but that is where it stands today.

1.3 Continuous Tracking

Continuous tracking is an option available from the Tracker tab.  To use this, do the following:

  1. Select the Tracker tab (second from left in WIMK)
  2. Press the Start button (near upper left)

This puts the phone into continuous tracking mode, where any movement beyond about 75 feet, is detected and reported.  When this is enabled, WIMK shows the tracked route overlaid on the map display with a green pin for the start and a red pin for the last location.  This process continues until the Stop button is pressed.

While tracking, the time and distance are shows in the top center of the display.  Each route point is shown as soon as it is detected, based on movement distance.

When the Stop button is pressed, the continuous tracking stops and the resulting route is saved as a route file.  The Prior button (upper left) can be used to access past saved routes and display any of those on the map.

Continuous tracking is useful for joggers, or any other situation where time, distance, and actual route traversed is useful information.  It is a very heavy user of battery power, so keep this in mind when using this option.

2.0 Settings Tab

Various settings and options here determine how location information is detected as well as other features and settings.

Location Accuracy:  Location accuracy determines how close to the actual position GPS tries to determine the users coordinates.  Apple measures this in meters, and the program offers a range from 5 meters (about 15 feet) to 150 meters (about 450 feet).

Lower settings result in better location accuracy as the expense of higher battery use.  Lower settings are generally recommended.

Monitor Movement Details: This determines if the Monitor Movement Details tracking approach described earlier is used.  When this is enabled, the Motion Sensitivity setting is also enabled.

            Disable Screen Timeout:  This applies to the tracker tab and disables any Apple screen timeout setting when the Tracker tab is being shown.  Turning this on makes it easier to see movement and path as the expense of higher battery use as the display is always on when the Tracker tab is visible.

Motion Sensitivity:  This slider sets the motion detection sensitivity.  This feature is only enabled when Monitor Movement Details detection is also enabled.  Motion detection is used to attempt to detect location changes and provide more accurate position tracking.

Higher settings are generally more effective, except in cases where the phone device might be moved very often and that movement does not usually mean significant changes in actual location (for example when using the phone for games or texting).  See the comments section below for limitations in this area for Apple iOS update 4.2.1.  

Temperature Display:  Determines if the current temperature, based on GPS location and local postal code, is display in the left corner of the Location display.  This data comes from www.weatherbug.com and is available through out the USA and some other parts of the world.

3.0 Comments

Motion detection (used in the Monitor Movement Details tracking option) changed somewhat in the Apple iOS 4.2 update.  Previously it worked most all of the time and provided good motion detection for the physical phone device.  With the 4.2.1 update from Apple, this changed (its not clear whether it is a bug or a change in standards), but the result is very limited motion detection. 

With the current 4.2.1 update, motion can only be detected when WIMK is in the foreground of the display and the display is visible (not in locked state).  As soon as the app moves to the background or the display locks, all motion detection stops.  Apple may update this in future iOS updates, but that is where it stands today.

Any time the Tracker tab is selected, WIMK always goes at least  into the Monitor Movement Details tracking mode.  This provides a quick way to track position more easily.  When any other tab is selected, the options from the Settings tab take affect.

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Last modified: April 06, 2011