276 lines
9.8 KiB
Go
276 lines
9.8 KiB
Go
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package geojson
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import (
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"fmt"
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"math"
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"time"
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"b612.me/astro/basic"
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eclipsecore "b612.me/astro/eclipse"
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"b612.me/astro/internal/geodata"
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"b612.me/astro/internal/solarclosure"
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)
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const (
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// 区域角色永远是面，退化则缺省；物理边界角色永远只承载曲线。
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solarCentralShadowFootprintRole = "central-shadow-footprint"
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solarCentralShadowBoundaryRole = "central-shadow-boundary"
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// 半影用与采样序列同名的区域角色，物理边界另立角色。
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// 细于该长度的足迹是首末接触处的残片，不导出。
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solarCentralShadowMinimumRegionLengthKM = 1.0
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// 面积下限比导出侧的零面积下限（1e-12 平方度）高 1000 倍，退化的环直接缺省。
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solarCentralShadowMinimumRegionAreaDegrees2 = 1e-9
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solarPartialFootprintRole = "partial-footprint"
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solarPartialFootprintBoundaryRole = "partial-footprint-boundary"
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)
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// appendSolarHorizonClosedShadowFootprint 输出被地平线切断的瞬时中心影足迹：区域加物理边界 / horizon-cut footprint as a region plus its physical boundary.
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func appendSolarHorizonClosedShadowFootprint(
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features []feature,
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footprint eclipsecore.SolarEclipsePartialFootprint,
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properties map[string]interface{},
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) ([]feature, error) {
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curve, err := solarShadowFootprintCurve(footprint)
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if err != nil {
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return nil, fmt.Errorf("geojson: solar %s at %s: %w",
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solarCentralShadowFootprintRole, formatTime(footprint.Time), err)
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}
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if len(curve) < 2 {
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return features, nil
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}
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ring, boundary := solarShadowFootprintHorizonRing(
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footprint.Time, footprint.Boundaries, footprint.HorizonEnds, curve,
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)
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if solarShadowRegionDegenerate(curve, ring) {
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return features, nil
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}
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value, err := multiPolygonGeometry([][]geodata.GeoPoint{ring})
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if err != nil {
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return nil, fmt.Errorf("geojson: solar %s at %s: %w",
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solarCentralShadowFootprintRole, formatTime(footprint.Time), err)
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}
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regionProperties := cloneProperties(properties)
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regionProperties["time"] = formatTime(footprint.Time)
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regionProperties["source_boundary_closed"] = false
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regionProperties["geometry_role"] = "horizon-closed-region"
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regionProperties["closure"] = solarHorizonClosureProperties(
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footprint.Time, solarHorizonClosureExact(footprint.Boundaries, footprint.HorizonEnds),
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)
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regionProperties["interp_signature"] = solarShadowFootprintSignature(
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footprint.Boundaries, false, eclipsecore.SolarEclipseShadowUmbra,
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)
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features = append(features, newFeature(
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solarEclipseEvent, solarCentralShadowFootprintRole, value, regionProperties,
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))
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boundaryValue, err := geoMultiLineGeometry(boundary, false)
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if err != nil {
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return nil, fmt.Errorf("geojson: solar %s at %s: %w",
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solarCentralShadowBoundaryRole, formatTime(footprint.Time), err)
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}
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boundaryProperties := cloneProperties(properties)
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boundaryProperties["time"] = formatTime(footprint.Time)
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boundaryProperties["source_boundary_closed"] = false
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boundaryProperties["geometry_role"] = "open-boundary"
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boundaryProperties["interp_signature"] = solarShadowFootprintSignature(
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footprint.Boundaries, false, eclipsecore.SolarEclipseShadowUmbra,
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)
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return append(features, newFeature(
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solarEclipseEvent, solarCentralShadowBoundaryRole, boundaryValue, boundaryProperties,
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)), nil
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}
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func solarShadowFootprintCurve(
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footprint eclipsecore.SolarEclipsePartialFootprint,
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) ([]geodata.GeoPoint, error) {
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return solarShadowFootprintCurveFromSegments(footprint.Boundaries)
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}
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func solarShadowFootprintCurveFromSegments(
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boundaries [][]eclipsecore.SolarEclipsePathPoint,
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) ([]geodata.GeoPoint, error) {
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segments := make([][]geodata.GeoPoint, 0, len(boundaries))
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for _, source := range boundaries {
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segment := make([]geodata.GeoPoint, len(source))
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for index, point := range source {
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if err := validateCoordinate(point.Longitude, point.Latitude); err != nil {
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return nil, err
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}
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segment[index] = geodata.GeoPoint{Longitude: point.Longitude, Latitude: point.Latitude}
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}
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segments = append(segments, segment)
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}
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return geodata.JoinPolylineSegments(segments), nil
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}
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// solarShadowRegionDegenerate 判定影区是否退化：物理边界过短或闭合面积近零，导出侧会拒绝。
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func solarShadowRegionDegenerate(curve, ring []geodata.GeoPoint) bool {
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if len(curve) < 2 || solarShadowFootprintCurveLengthKM(curve) < solarCentralShadowMinimumRegionLengthKM {
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return true
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}
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points := openRing(ring)
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if len(points) < 3 {
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return true
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}
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return math.Abs(solarShadowRegionAreaDegrees2(points)) < solarCentralShadowMinimumRegionAreaDegrees2
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}
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// solarShadowRegionAreaDegrees2 用展开经度算鞋带面积，跨换日线的环不会得到假的近零面积。
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func solarShadowRegionAreaDegrees2(ring []geodata.GeoPoint) float64 {
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if len(ring) < 3 {
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return 0
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}
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unwrapped := make([]geodata.GeoPoint, len(ring))
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unwrapped[0] = ring[0]
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for index := 1; index < len(ring); index++ {
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longitude := ring[index].Longitude
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for longitude-unwrapped[index-1].Longitude > 180 {
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longitude -= 360
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}
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for longitude-unwrapped[index-1].Longitude < -180 {
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longitude += 360
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}
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unwrapped[index] = geodata.GeoPoint{Longitude: longitude, Latitude: ring[index].Latitude}
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}
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area := 0.0
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for index, point := range unwrapped {
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next := unwrapped[(index+1)%len(unwrapped)]
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area += point.Longitude*next.Latitude - next.Longitude*point.Latitude
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}
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return area / 2
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}
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func solarShadowFootprintCurveLengthKM(curve []geodata.GeoPoint) float64 {
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length := 0.0
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for index := 1; index < len(curve); index++ {
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length += solarCentralBandGeoPointDistanceKM(curve[index-1], curve[index])
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}
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return length
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}
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func solarShadowFootprintHorizonRing(
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value time.Time,
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boundaries [][]eclipsecore.SolarEclipsePathPoint,
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horizonEnds []eclipsecore.SolarEclipsePathPoint,
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curve []geodata.GeoPoint,
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) ([]geodata.GeoPoint, []geodata.GeoPoint) {
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return solarclosure.HorizonRing(solarclosure.Footprint{
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Boundaries: solarClosureSegments(boundaries),
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HorizonEnds: solarClosureEnds(horizonEnds),
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Subsolar: solarSubsolarPoint(value),
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}, curve)
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}
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func solarShadowFootprintHorizonEnds(
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boundaries [][]eclipsecore.SolarEclipsePathPoint,
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horizonEnds []eclipsecore.SolarEclipsePathPoint,
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) []geodata.GeoPoint {
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return solarclosure.HorizonEnds(solarclosure.Footprint{
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Boundaries: solarClosureSegments(boundaries),
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HorizonEnds: solarClosureEnds(horizonEnds),
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})
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}
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// solarClosureSegments 按原顺序转换边界分段，不校验坐标。
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func solarClosureSegments(boundaries [][]eclipsecore.SolarEclipsePathPoint) [][]geodata.GeoPoint {
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segments := make([][]geodata.GeoPoint, len(boundaries))
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for index, source := range boundaries {
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segments[index] = solarCentralBandGeoPoints(source)
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}
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return segments
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}
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// solarClosureEnds 转换地平擦地点；点数不是 2 或坐标非法时返回 nil，闭合退回近似弧。
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func solarClosureEnds(horizonEnds []eclipsecore.SolarEclipsePathPoint) []geodata.GeoPoint {
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if len(horizonEnds) != 2 {
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return nil
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}
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points := make([]geodata.GeoPoint, 2)
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for index, end := range horizonEnds {
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if err := validateCoordinate(end.Longitude, end.Latitude); err != nil {
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return nil
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}
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points[index] = geodata.GeoPoint{Longitude: end.Longitude, Latitude: end.Latitude}
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}
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return points
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}
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// solarClosureFootprint 转换瞬时足迹；边界坐标非法时报错。
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func solarClosureFootprint(
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footprint eclipsecore.SolarEclipsePartialFootprint,
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) (solarclosure.Footprint, error) {
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segments := make([][]geodata.GeoPoint, len(footprint.Boundaries))
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for index, source := range footprint.Boundaries {
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segment := make([]geodata.GeoPoint, len(source))
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for pointIndex, point := range source {
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if err := validateCoordinate(point.Longitude, point.Latitude); err != nil {
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return solarclosure.Footprint{}, err
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}
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segment[pointIndex] = geodata.GeoPoint{Longitude: point.Longitude, Latitude: point.Latitude}
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}
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segments[index] = segment
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}
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return solarclosure.Footprint{
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Boundaries: segments,
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HorizonEnds: solarClosureEnds(footprint.HorizonEnds),
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Subsolar: solarSubsolarPoint(footprint.Time),
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Closed: footprint.Closed,
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}, nil
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}
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// solarHorizonClosureExact 报告能否用两个精确擦地点闭合区域。
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func solarHorizonClosureExact(
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boundaries [][]eclipsecore.SolarEclipsePathPoint,
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horizonEnds []eclipsecore.SolarEclipsePathPoint,
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) bool {
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return len(solarShadowFootprintHorizonEnds(boundaries, horizonEnds)) == 2
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}
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// solarHorizonClosureProperties 声明式闭合弧；exact 为假表示缺精确擦地点、按采样端点近似闭合。
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func solarHorizonClosureProperties(value time.Time, exact bool) map[string]interface{} {
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subsolar := solarSubsolarPoint(value)
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return map[string]interface{}{
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"kind": "horizon",
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"exact": exact,
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"time": formatTime(value),
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"subsolar": []float64{subsolar.Longitude, subsolar.Latitude},
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}
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}
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// solarShadowSegmentClosed 与 basic 层同口径：分段首末点相距不到 1 mm 才算真正闭合。
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func solarShadowSegmentClosed(segment []eclipsecore.SolarEclipsePathPoint) bool {
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if len(segment) <= 2 {
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return false
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}
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return solarCentralBandPathDistanceKM(segment[0], segment[len(segment)-1]) < 1e-6
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}
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// solarShadowFootprintSignature 由物理边界算出与 basic 层同口径的插值签名 / interpolation signature from the physical boundary.
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func solarShadowFootprintSignature(
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boundaries [][]eclipsecore.SolarEclipsePathPoint,
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closed bool,
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kind eclipsecore.SolarEclipseShadowKind,
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) string {
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topology := basic.SolarEclipseShadowTopology{
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Kind: basic.SolarEclipseShadowKind(kind),
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Segments: len(boundaries),
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Closed: closed,
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}
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winding := 0.0
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for _, segment := range boundaries {
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topology.Vertices += len(segment)
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for index := 1; index < len(segment); index++ {
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winding += math.Remainder(segment[index].Longitude-segment[index-1].Longitude, 360)
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}
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if solarShadowSegmentClosed(segment) {
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winding += math.Remainder(segment[0].Longitude-segment[len(segment)-1].Longitude, 360)
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}
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}
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if topology.Segments == 1 && math.Abs(winding) >= 180 {
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topology.EnclosesPole = true
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}
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return topology.Signature()
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}
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