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linestring_builder.go
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/
linestring_builder.go
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package main
import (
"flag"
"log"
"time"
"github.com/paulmach/orb"
"github.com/paulmach/orb/geo"
"github.com/paulmach/orb/geojson"
)
type LineStringBuilder struct {
Interval time.Duration
LineStringFeature *geojson.Feature
LineStringFeatures []*geojson.Feature // the points represented by the linestring
lastNFeatures []*geojson.Feature
intervalFeatures []*geojson.Feature // points
linestringsCh chan *geojson.Feature
}
func NewLineStringBuilder(interval time.Duration) *LineStringBuilder {
return &LineStringBuilder{
Interval: interval,
lastNFeatures: make([]*geojson.Feature, 0),
intervalFeatures: make([]*geojson.Feature, 0),
linestringsCh: make(chan *geojson.Feature),
}
}
func (t *LineStringBuilder) LastFeature() *geojson.Feature {
if len(t.lastNFeatures) == 0 {
return nil
}
return t.lastNFeatures[len(t.lastNFeatures)-1]
}
func (t *LineStringBuilder) Flush() {
if t.LineStringFeature != nil {
t.linestringsCh <- t.LineStringFeature
}
close(t.linestringsCh)
}
func (t *LineStringBuilder) AddFeatureToState(f *geojson.Feature) {
t.intervalFeatures = append(t.intervalFeatures, f)
for i := len(t.intervalFeatures) - 1; i > 0; i-- {
if timespan(t.intervalFeatures[i], f) > t.Interval {
t.intervalFeatures = t.intervalFeatures[i:]
break
}
}
t.lastNFeatures = append(t.lastNFeatures, f)
for len(t.lastNFeatures) > 10 {
t.lastNFeatures = t.lastNFeatures[1:]
}
}
func (t *LineStringBuilder) ResetState() {
t.lastNFeatures = []*geojson.Feature{}
t.intervalFeatures = []*geojson.Feature{}
}
// calculatedAverageSpeedAbsolute returns the average speed in meters per second
// between the first point and last. Round trips will theoretically return 0.
func calculatedAverageSpeedAbsolute(pointFeatures []*geojson.Feature) float64 {
if len(pointFeatures) < 2 {
return 0
}
firstTime := mustGetTime(pointFeatures[0], "Time")
lastTime := mustGetTime(pointFeatures[len(pointFeatures)-1], "Time")
timeDelta := lastTime.Sub(firstTime).Seconds()
distance := geo.Distance(pointFeatures[0].Point(), pointFeatures[len(pointFeatures)-1].Point())
return distance / timeDelta
}
func calculatedAverageSpeedTraversed(pointFeatures []*geojson.Feature) float64 {
if len(pointFeatures) < 2 {
return 0
}
sum := 0.0
for i := 1; i <= len(pointFeatures)-1; i++ {
sum += calculatedAverageSpeedAbsolute(pointFeatures[i-1 : i])
}
return sum / float64(len(pointFeatures))
}
func calculatedAverageSpeedTraversedLinestring(lineString *geojson.Feature) float64 {
if len(lineString.Geometry.(orb.LineString)) < 2 {
return 0
}
distance := 0.0
for i := 1; i < len(lineString.Geometry.(orb.LineString)); i++ {
distance += geo.Distance(lineString.Geometry.(orb.LineString)[i-1], lineString.Geometry.(orb.LineString)[i])
}
return distance / lineString.Properties["Duration"].(float64)
}
func averageReportedSpeed(pointFeatures []*geojson.Feature) float64 {
if len(pointFeatures) < 2 {
return pointFeatures[0].Properties["Speed"].(float64)
}
sum := 0.0
for _, f := range pointFeatures {
sum += f.Properties["Speed"].(float64)
}
return sum / float64(len(pointFeatures))
}
func timespan(a, b *geojson.Feature) time.Duration {
if a == nil || b == nil {
return 0
}
firstTime := mustGetTime(a, "Time")
lastTime := mustGetTime(b, "Time")
return lastTime.Sub(firstTime)
}
func getAbsoluteDistance(features []*geojson.Feature) float64 {
if len(features) < 2 {
return 0
}
var start orb.Point
var end orb.Point
if _, ok := features[0].Geometry.(orb.Point); ok {
start = features[0].Point()
} else {
start = features[0].Geometry.(orb.LineString)[0]
}
if _, ok := features[len(features)-1].Geometry.(orb.Point); ok {
end = features[len(features)-1].Point()
} else {
end = features[len(features)-1].Geometry.(orb.LineString)[len(features[len(features)-1].Geometry.(orb.LineString))-1]
}
return geo.Distance(start.Point(), end.Point())
}
func getTraversedDistance(pointFeatures []*geojson.Feature) float64 {
if len(pointFeatures) < 2 {
return 0
}
sum := 0.0
for i := 1; i < len(pointFeatures); i++ {
sum += getAbsoluteDistance(pointFeatures[i-1 : i+1])
}
return sum
}
func calculatedAverageAccuracy(pointFeatures []*geojson.Feature) float64 {
if len(pointFeatures) == 0 {
return 0
}
sum := 0.0
for _, f := range pointFeatures {
sum += f.Properties["Accuracy"].(float64)
}
return sum / float64(len(pointFeatures))
}
func (t *LineStringBuilder) AddPointFeatureToLastLinestring(f *geojson.Feature) {
t.LineStringFeature.Geometry = append(t.LineStringFeature.Geometry.(orb.LineString), f.Point())
t.LineStringFeatures = append(t.LineStringFeatures, f)
// TODO: update properties properly
for k, v := range f.Properties {
t.LineStringFeature.Properties[k] = v
}
t.LineStringFeature.Properties["PointCount"] = len(t.LineStringFeatures)
t.LineStringFeature.Properties["Activity"] = activityModeNotUnknown(t.LineStringFeatures).String()
t.LineStringFeature.Properties["AverageAccuracy"] = toFixed(calculatedAverageAccuracy(t.LineStringFeatures), 0)
t.LineStringFeature.Properties["Duration"] = timespan(t.LineStringFeatures[0], f).Round(time.Second).Seconds()
t.LineStringFeature.Properties["DistanceTraversed"] = toFixed(getTraversedDistance(t.LineStringFeatures), 2)
t.LineStringFeature.Properties["DistanceAbsolute"] = toFixed(getAbsoluteDistance(t.LineStringFeatures), 2)
t.LineStringFeature.Properties["AverageReportedSpeed"] = toFixed(averageReportedSpeed(t.LineStringFeatures), 2)
t.LineStringFeature.Properties["AverageCalculatedSpeed"] = toFixed(calculatedAverageSpeedTraversed(t.LineStringFeatures), 2)
}
func (t *LineStringBuilder) AddPointFeatureToNewLinestring(f *geojson.Feature) {
// Send the last linestring to the channel.
if t.LineStringFeature != nil && len(t.LineStringFeature.Geometry.(orb.LineString)) > 1 {
t.linestringsCh <- t.LineStringFeature
} else {
// Otherwise the target linestring will be overwritten with the new feature
// without sending the last feature.
}
t.LineStringFeatures = []*geojson.Feature{f}
t.LineStringFeature = geojson.NewFeature(orb.LineString{f.Point()})
t.LineStringFeature.Properties = map[string]interface{}{}
for k, v := range f.Properties {
t.LineStringFeature.Properties[k] = v
}
t.LineStringFeature.Properties["StartTime"] = f.Properties["Time"]
t.LineStringFeature.Properties["Duration"] = 0.0
t.LineStringFeature.Properties["MotionStateReason"] = f.Properties["MotionStateReason"]
}
var flagLinestringDisconinuityActivities = flag.Bool("linestring-discontinuity-activities", false, "If true, linestrings will be split on activity changes.")
// IsDiscontinuous returns true if the last point is discontinuous from the previous interval.
// According to some paper I found somewhere onetime, it's generally better
// to break more than less. Trips/lines can then be synthesized later.
func (t *LineStringBuilder) IsDiscontinuous(f *geojson.Feature) (isDiscontinuous bool) {
// A failsafe in case something goes wrong.
// We assume that t.LastFeature() returns a non-nil value.
if len(t.lastNFeatures) == 0 {
return true
}
if f == nil {
return true
}
// Split any tracks separated by the DWELL INTERVAL in time,
// or any non-chronological points.
span := timespan(t.LastFeature(), f)
if span < 0 {
log.Println("WARN: linestring feature not chronological",
mustGetTime(t.LastFeature(), "Time"),
mustGetTime(f, "Time"),
span.Round(time.Second))
return true
}
if span > *flagDwellInterval {
return true
}
// // If the activity type changes, we should start a new linestring.
if *flagLinestringDisconinuityActivities {
incumbent := activityMode(t.intervalFeatures)
next := activityMode(append(t.intervalFeatures, f))
if !incumbent.IsContinuous(next) {
return true
}
}
return false
}
func (t *LineStringBuilder) AddPointFeature(f *geojson.Feature) {
defer t.AddFeatureToState(f)
// This will be ONLY the first point the builder sees
// since the deferred AddFeatureToState will get called for all points.
if len(t.lastNFeatures) == 0 {
t.AddPointFeatureToNewLinestring(f)
return
}
if t.IsDiscontinuous(f) {
t.ResetState()
t.AddPointFeatureToNewLinestring(f)
return
}
t.AddPointFeatureToLastLinestring(f)
}