// devMoved tells if a device moved based on the passed latest GPS records.
// At least 2 track GPS records must be present to report moving (to return true).
func devMoved(rs []*ds.GPS) bool {
// Min delta distance that is considered moving
const minDeltaDist = 230 // [m]
var first, last *ds.GPS // First and Last track records
for _, r := range rs {
if !r.Track() {
continue
}
if first == nil {
first = r
}
if last != nil {
if logic.Distance(last.GeoPoint.Lat, last.GeoPoint.Lng, r.GeoPoint.Lat, r.GeoPoint.Lng) > minDeltaDist {
return true
}
}
last = r
}
// Device might be moving very slow, e.g. only 100 m per minute in which case subsequent
// records will not report moving. Also compare the first to the last:
if first != nil && last != nil {
if logic.Distance(last.GeoPoint.Lat, last.GeoPoint.Lng, first.GeoPoint.Lat, first.GeoPoint.Lng) > minDeltaDist {
return true
}
}
return false
}
// checkAlert checks the specified alert.
func checkAlert(c appengine.Context, a *ds.Alert, accKeyID int64) {
const alertDurationMin = 5
const alertDuration = alertDurationMin * time.Minute
// Get latest car GPS records
carRecords, err := getDevRecords(c, a.CarDevID)
if err != nil {
return
}
// Check if car GPS records are received properly:
if time.Since(carRecords[0].Created) > alertDuration {
c.Warningf("No car GPS records found in the last %d minutes!", alertDurationMin)
sendAlert(c, accKeyID, "Car GPS device gone dark!", carGoneDarkAlertMail)
return
}
if a.PersMobDevID == 0 {
c.Debugf("Car GPS records found in the last 5 minutes. No Personal Mobile device specified.")
return
}
carMoved := devMoved(carRecords)
if !carMoved {
// Nothing more to do if car is not moving
c.Infof("Car is not moving. Ok.")
return
}
c.Infof("Car is moving!")
// Get latest personal mobile GPS records
persMobRecords, err := getDevRecords(c, a.PersMobDevID)
if err != nil {
return
}
// Check if personal mobile GPS records are received properly:
if time.Since(persMobRecords[0].Created) > alertDuration {
c.Warningf("No personal mobile GPS records found in the last %d minutes!", alertDurationMin)
sendAlert(c, accKeyID, "Car is moving without you!", carMovingWithoutYouMail)
return
}
persMobMoved := devMoved(persMobRecords)
// Do not draw fast conclusion here if personal mobile is not moving,
// it might be GPS tracking was just turned on and we don't have 2 track records yet
// or they are not at great distance. But if we don't even have 1 track record,
// that's hijacking-suspicious:
if persMobMoved {
c.Infof("Personal mobile is also moving!")
} else {
c.Infof("Personal mobile is NOT moving!")
}
var pg1 *ds.GPS
for _, r := range persMobRecords {
if r.Track() {
pg1 = r
break
}
}
if pg1 == nil || time.Since(pg1.Created) > alertDuration {
// Car is moving and we don't have recent track record from personal mobile!
c.Warningf("No personal mobile GPS track record found in the last %d minutes!", alertDurationMin)
sendAlert(c, accKeyID, "Car is moving without you!", carMovingWithoutYouMail)
return
}
// Check distance:
// We have a track record for both devices for sure (because both moved which also ensures having at least 2!).
var cg1, cg2 *ds.GPS
for _, r := range carRecords {
if r.Track() {
if cg1 == nil {
cg1 = r
} else if cg2 == nil {
cg2 = r
break
}
}
}
cg1.Dd = logic.Distance(cg2.GeoPoint.Lat, cg2.GeoPoint.Lng, cg1.GeoPoint.Lat, cg1.GeoPoint.Lng) // [m]
cg1.Dt = cg1.Created.Sub(cg2.Created) // duration
cv := float64(cg1.Dd) / cg1.Dt.Seconds() // Car speed [m/s]
cpdt := math.Abs(cg1.Created.Sub(pg1.Created).Seconds()) // [s]
dist := logic.Distance(cg1.GeoPoint.Lat, cg1.GeoPoint.Lng, pg1.GeoPoint.Lat, pg1.GeoPoint.Lng)
c.Debugf("Car movement speed: %.1f km/h", cv*3.6)
c.Debugf("Delta T between latest Car and PersMob GPS records: %d s", int64(cpdt))
c.Debugf("Car - PersMob distance: %d m", dist)
var alertMargin int64 = 500 // [m]
// Increase alert margin based on the movement speed of the car and the delta time between
// the last car and personal mobile GPS records.
// Also if this delta time is greater, accuracy decreases/drops.
// So also increase alert margin based on delta time: 6 meters for every second.
// (It is an effect like increasing car speed by 6 m/s = 21.6 km/h.)
// BE RESTRICTIVE: Only do this correction if personal mobile is also moving!
// If not, do not let the car get far away (if for example pers mob is not moving,
// the car could get kilometers away before alert would be sent).
if persMobMoved {
alertMargin += int64(cv*cpdt + cpdt*6)
}
c.Debugf("Using alert margin distance: %d m", alertMargin)
if dist > alertMargin {
c.Warningf("Personal mobile is not moving together with car!")
sendAlert(c, accKeyID, "Car is moving without you!", carMovingWithoutYouMail)
return
}
c.Infof("They are moving together. Ok.")
}