452 lines
18 KiB
Go
452 lines
18 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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"b612.me/astro/internal/geodata"
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"b612.me/astro/mercury"
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"b612.me/astro/venus"
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)
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const planetTransitEvent = "planet-transit"
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// 标准大气，与 basic 站心凌日的视地平判定及凌日 SVG 一致。
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const (
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planetTransitRefractionPressureHPa = 1010.0
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planetTransitRefractionTemperatureC = 10.0
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minimumPlanetTransitIsochroneStep = time.Second
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)
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// PlanetTransitOptions 是凌日 GeoJSON 导出选项；所有要素都被丢弃时导出失败。
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// PlanetTransitOptions are the planetary-transit GeoJSON export options; the export fails when every
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// Feature is dropped.
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type PlanetTransitOptions struct {
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// BoundaryPoints 是地平线采样点数，同时决定分区的经度列数 max(360, BoundaryPoints)（上限 720）；
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// 小于等于零时使用 360，其他值限制在 [12, 1440]。
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// BoundaryPoints is the horizon sample count and also sets the region longitude columns to
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// max(360, BoundaryPoints), capped at 720. Values <= 0 use 360; others are clamped to [12, 1440].
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BoundaryPoints int
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// IsochroneStep 为正时输出一触到四触的站心接触等时线（掠凌没有二触、三触），至少一秒；零值不输出。
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// A positive IsochroneStep adds topocentric C1-C4 isochrones (no C2/C3 for a grazing transit) and must be
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// at least one second. The zero value adds none.
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IsochroneStep time.Duration
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// TimeMarkers 非空时沿一触到四触的太阳直射点轨迹追加时间标记 Point 要素。
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// TimeMarkers adds time-marker Point Features along the subsolar track from C1 through C4 when non-nil.
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TimeMarkers *TimeMarkerOptions
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// SkipRoles 列出不写进输出的 role；分区三个 role 都跳过时不做分区计算。
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// SkipRoles lists roles to leave out; skipping all three region roles skips the region computation.
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SkipRoles []string
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}
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// planetTransitInput 是水星、金星两种 TransitInfo 的公共视图。
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type planetTransitInput struct {
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planet string
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planetIndex int
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start time.Time
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c2 time.Time
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greatest time.Time
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c3 time.Time
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end time.Time
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hasInternal bool
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separation float64
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sunRadius float64
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planetRad float64
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}
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// MarshalMercuryTransit 将水星凌日的全球可见分区、一触/四触地平线与可选站心等时线编码为 GeoJSON / encode a Mercury transit as GeoJSON.
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func (module *Generator) MarshalMercuryTransit(info mercury.TransitInfo, options PlanetTransitOptions) ([]byte, error) {
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if !info.Valid {
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return nil, fmt.Errorf("geojson: mercury transit is invalid")
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}
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return marshalPlanetTransit(planetTransitInput{
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planet: "mercury", planetIndex: 1,
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start: info.Start, c2: info.InternalStart, greatest: info.Greatest, c3: info.InternalEnd, end: info.End,
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hasInternal: info.HasInternal, separation: info.MinimumSeparationArcsec,
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sunRadius: info.SunSemidiameterArcsec, planetRad: info.PlanetSemidiameterArcsec,
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}, options, module)
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}
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// MarshalVenusTransit 将金星凌日的全球可见分区、一触/四触地平线与可选站心等时线编码为 GeoJSON / encode a Venus transit as GeoJSON.
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func (module *Generator) MarshalVenusTransit(info venus.TransitInfo, options PlanetTransitOptions) ([]byte, error) {
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if !info.Valid {
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return nil, fmt.Errorf("geojson: venus transit is invalid")
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}
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return marshalPlanetTransit(planetTransitInput{
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planet: "venus", planetIndex: 2,
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start: info.Start, c2: info.InternalStart, greatest: info.Greatest, c3: info.InternalEnd, end: info.End,
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hasInternal: info.HasInternal, separation: info.MinimumSeparationArcsec,
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sunRadius: info.SunSemidiameterArcsec, planetRad: info.PlanetSemidiameterArcsec,
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}, options, module)
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}
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func validatePlanetTransitInput(input planetTransitInput) error {
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if input.start.IsZero() || input.greatest.IsZero() || input.end.IsZero() {
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return fmt.Errorf("geojson: %s transit contact times are required", input.planet)
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}
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if !input.hasInternal && (!input.c2.IsZero() || !input.c3.IsZero()) {
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return fmt.Errorf("geojson: %s transit cannot have internal contact times without internal contacts", input.planet)
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}
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ordered := []time.Time{input.start}
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if input.hasInternal {
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if input.c2.IsZero() || input.c3.IsZero() {
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return fmt.Errorf("geojson: %s transit internal contact times are required", input.planet)
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}
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ordered = append(ordered, input.c2)
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}
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ordered = append(ordered, input.greatest)
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if input.hasInternal {
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ordered = append(ordered, input.c3)
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}
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ordered = append(ordered, input.end)
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for index := 1; index < len(ordered); index++ {
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if !ordered[index-1].Before(ordered[index]) {
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return fmt.Errorf("geojson: %s transit contact times are not strictly ordered", input.planet)
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}
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}
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return nil
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}
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func marshalPlanetTransit(input planetTransitInput, options PlanetTransitOptions, module *Generator) ([]byte, error) {
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markerOptions := options.TimeMarkers
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if markerOptions != nil {
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if err := validateTimeMarkerOptions(*markerOptions); err != nil {
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return nil, err
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}
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}
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if options.IsochroneStep < 0 || (options.IsochroneStep > 0 && options.IsochroneStep < minimumPlanetTransitIsochroneStep) {
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return nil, fmt.Errorf("geojson: transit isochrone step must be zero or at least %s", minimumPlanetTransitIsochroneStep)
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}
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if err := validatePlanetTransitInput(input); err != nil {
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return nil, err
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}
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timeScale, scaleErr := timeScaleForMarkers(markerOptions)
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if scaleErr != nil {
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return nil, scaleErr
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}
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// 几何一律用民用时刻，只有写进属性的时刻换时标。
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label := func(value time.Time) string {
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if value.IsZero() {
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return ""
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}
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return formatTime(basic.LabelIn(timeScale, value.UTC()))
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}
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boundaryPoints := normalizeLunarBoundaryPoints(options.BoundaryPoints)
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longitudePoints := lunarVisibilityLongitudePoints(boundaryPoints, LunarEclipseOptions{})
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longitudes := make([]float64, longitudePoints+1)
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for index := range longitudes {
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longitudes[index] = -180 + 360*float64(index)/float64(longitudePoints)
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}
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refraction := basic.RefractionFromApparentAltitude(0, planetTransitRefractionPressureHPa, planetTransitRefractionTemperatureC)
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base := map[string]interface{}{"planet": input.planet, "has_internal": input.hasInternal}
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withBase := func(extra map[string]interface{}) map[string]interface{} {
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properties := cloneProperties(base)
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for key, value := range extra {
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properties[key] = value
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}
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return properties
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}
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features := make([]feature, 0, 12)
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columnsAt := func(at time.Time) [][]lunarLatitudeInterval {
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subsolar := solarSubsolarPoint(at, module)
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columns := make([][]lunarLatitudeInterval, len(longitudes))
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for index, longitude := range longitudes {
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columns[index] = planetTransitSunUpIntervals(subsolar, longitude, refraction)
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}
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return columns
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}
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wantEntire := !skippedLunarRole(options.SkipRoles, "transit-entire")
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wantSunrise := !skippedLunarRole(options.SkipRoles, "transit-at-sunrise")
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wantSunset := !skippedLunarRole(options.SkipRoles, "transit-at-sunset")
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wantRegions := wantEntire || wantSunrise || wantSunset
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needC1 := wantRegions || !skippedLunarRole(options.SkipRoles, "visible-at-c1")
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needGreatest := wantRegions
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needC4 := wantRegions || !skippedLunarRole(options.SkipRoles, "visible-at-c4")
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var c1Columns, greatestColumns, c4Columns [][]lunarLatitudeInterval
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if needC1 {
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c1Columns = columnsAt(input.start)
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}
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if needGreatest {
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greatestColumns = columnsAt(input.greatest)
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}
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if needC4 {
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c4Columns = columnsAt(input.end)
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}
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for _, contact := range []struct {
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role, horizonRole string
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at time.Time
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columns [][]lunarLatitudeInterval
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}{
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{"visible-at-c1", "c1-horizon", input.start, c1Columns},
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{"visible-at-c4", "c4-horizon", input.end, c4Columns},
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} {
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if !skippedLunarRole(options.SkipRoles, contact.role) {
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value, err := planetTransitRegionGeometry(longitudes, contact.columns)
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if err != nil {
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return nil, fmt.Errorf("geojson: %s: %w", contact.role, err)
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}
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features = append(features, newFeature(planetTransitEvent, contact.role, value,
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withBase(map[string]interface{}{"time": label(contact.at)})))
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}
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if !skippedLunarRole(options.SkipRoles, contact.horizonRole) {
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subsolar := solarSubsolarPoint(contact.at, module)
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antisolar := geodata.GeoPoint{Longitude: geodata.NormalizeLongitude(subsolar.Longitude + 180), Latitude: -subsolar.Latitude}
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value, err := geoMultiLineGeometry(geodata.SphericalCircle(antisolar, 90-refraction, boundaryPoints), true)
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if err != nil {
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return nil, fmt.Errorf("geojson: %s: %w", contact.horizonRole, err)
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}
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features = append(features, newFeature(planetTransitEvent, contact.horizonRole, value,
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withBase(map[string]interface{}{"time": label(contact.at)})))
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}
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}
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regionFeatures, err := planetTransitRegionFeatures(longitudes, c1Columns, greatestColumns, c4Columns, options.SkipRoles,
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withBase(map[string]interface{}{
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"time_start": label(input.start),
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"time_end": label(input.end),
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"longitude_points": longitudePoints,
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}))
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if err != nil {
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return nil, err
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}
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features = append(features, regionFeatures...)
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if options.IsochroneStep > 0 {
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isochrones, isoErr := planetTransitIsochroneFeatures(input, options.IsochroneStep, timeScale, options.SkipRoles, withBase, module)
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if isoErr != nil {
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return nil, isoErr
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}
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features = append(features, isochrones...)
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}
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greatest := solarSubsolarPoint(input.greatest, module)
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metadata := withBase(map[string]interface{}{
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"start": label(input.start),
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"greatest": label(input.greatest),
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"end": label(input.end),
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"minimum_separation_arcsec": input.separation,
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"sun_semidiameter_arcsec": input.sunRadius,
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"planet_semidiameter_arcsec": input.planetRad,
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})
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if input.hasInternal {
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metadata["internal_start"], metadata["internal_end"] = label(input.c2), label(input.c3)
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}
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features, err = appendPointFeature(features, planetTransitEvent, "greatest",
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pathSample{Time: basic.LabelIn(timeScale, input.greatest.UTC()), Longitude: greatest.Longitude, Latitude: greatest.Latitude},
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metadata)
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if err != nil {
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return nil, err
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}
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if markerOptions != nil {
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markers, markerErr := planetTransitTimeMarkerSamples(input.start, input.end, timeScale, *markerOptions, module)
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if markerErr != nil {
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return nil, markerErr
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}
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features, err = appendTimeMarkerPointFeatures(features, planetTransitEvent, "subsolar-track", markers, markerOptions.Location)
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if err != nil {
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return nil, err
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}
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}
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return marshalFeatureCollectionWithTimeScale(dropFeaturesByRole(features, options.SkipRoles), timeScale)
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}
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// planetTransitSunUpIntervals 返回 longitude 子午线上太阳中心在视地平上的纬度区间：
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// 地点到直射点的角距小于 90°+折射即可见，即 sinδ·sinφ + cosδ·cosΔλ·cosφ > -sin(折射)。
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func planetTransitSunUpIntervals(subsolar geodata.GeoPoint, longitude, refraction float64) []lunarLatitudeInterval {
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rad := math.Pi / 180
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a := math.Sin(subsolar.Latitude * rad)
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b := math.Cos(subsolar.Latitude*rad) * math.Cos((longitude-subsolar.Longitude)*rad)
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threshold := -math.Sin(refraction * rad)
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visible := func(latitude float64) bool {
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return a*math.Sin(latitude*rad)+b*math.Cos(latitude*rad) > threshold
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}
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boundaries := []float64{-90}
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if amplitude := math.Hypot(a, b); amplitude > 0 && math.Abs(threshold/amplitude) < 1 {
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// a·sinφ + b·cosφ = R·sin(φ+α)，α = atan2(b, a)。
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alpha := math.Atan2(b, a) / rad
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base := math.Asin(threshold/amplitude) / rad
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roots := make([]float64, 0, 2)
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for _, value := range []float64{base - alpha, 180 - base - alpha} {
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for _, shift := range []float64{-360, 0, 360} {
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if root := value + shift; root > -90 && root < 90 {
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roots = append(roots, root)
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}
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}
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}
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if len(roots) == 2 && roots[0] > roots[1] {
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roots[0], roots[1] = roots[1], roots[0]
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}
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boundaries = append(boundaries, roots...)
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}
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boundaries = append(boundaries, 90)
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intervals := make([]lunarLatitudeInterval, 0, 2)
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for index := 0; index+1 < len(boundaries); index++ {
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low, high := boundaries[index], boundaries[index+1]
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if high-low > 1e-9 && visible((low+high)/2) {
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intervals = append(intervals, lunarLatitudeInterval{low: low, high: high})
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}
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}
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return lunarUnionLatitudeIntervals(intervals...)
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}
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func planetTransitRegionGeometry(longitudes []float64, columns [][]lunarLatitudeInterval) (geometry, error) {
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value, err := lunarVisibilityEnvelopeGeometry(longitudes, columns)
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if err != nil {
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return geometry{}, err
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}
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return dropDegenerateMultiPolygonRings(value), nil
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// planetTransitRegionFeatures 按与凌日 SVG 相同的口径分区：全程可见是三刻都在地平上，日出带是四触可见而一触不可见，
|
|||
|
|
// 其余凡有一刻可见的都归入日落带（含凌甚前后可见的极区透镜与两端可见、凌甚不可见的高纬带）。
|
|||
|
|
func planetTransitRegionFeatures(
|
|||
|
|
longitudes []float64,
|
|||
|
|
c1, greatest, c4 [][]lunarLatitudeInterval,
|
|||
|
|
skip []string,
|
|||
|
|
properties map[string]interface{},
|
|||
|
|
) ([]feature, error) {
|
|||
|
|
wantEntire := !skippedLunarRole(skip, "transit-entire")
|
|||
|
|
wantSunrise := !skippedLunarRole(skip, "transit-at-sunrise")
|
|||
|
|
wantSunset := !skippedLunarRole(skip, "transit-at-sunset")
|
|||
|
|
if !wantEntire && !wantSunrise && !wantSunset {
|
|||
|
|
return nil, nil
|
|||
|
|
}
|
|||
|
|
union := func(groups ...[]lunarLatitudeInterval) []lunarLatitudeInterval {
|
|||
|
|
var merged []lunarLatitudeInterval
|
|||
|
|
for _, group := range groups {
|
|||
|
|
merged = append(merged, group...)
|
|||
|
|
}
|
|||
|
|
return lunarUnionLatitudeIntervals(merged...)
|
|||
|
|
}
|
|||
|
|
entire := make([][]lunarLatitudeInterval, len(longitudes))
|
|||
|
|
sunrise := make([][]lunarLatitudeInterval, len(longitudes))
|
|||
|
|
sunset := make([][]lunarLatitudeInterval, len(longitudes))
|
|||
|
|
for index := range longitudes {
|
|||
|
|
bothEnds := lunarIntersectLatitudeIntervals(c1[index], c4[index])
|
|||
|
|
entire[index] = lunarIntersectLatitudeIntervals(bothEnds, greatest[index])
|
|||
|
|
sunrise[index] = lunarSubtractLatitudeIntervals(c4[index], c1[index])
|
|||
|
|
sunset[index] = lunarSubtractLatitudeIntervals(union(c1[index], c4[index], greatest[index]),
|
|||
|
|
union(entire[index], sunrise[index]))
|
|||
|
|
}
|
|||
|
|
features := make([]feature, 0, 3)
|
|||
|
|
for _, region := range []struct {
|
|||
|
|
role string
|
|||
|
|
want bool
|
|||
|
|
columns [][]lunarLatitudeInterval
|
|||
|
|
}{
|
|||
|
|
{"transit-entire", wantEntire, entire},
|
|||
|
|
{"transit-at-sunrise", wantSunrise, sunrise},
|
|||
|
|
{"transit-at-sunset", wantSunset, sunset},
|
|||
|
|
} {
|
|||
|
|
if !region.want {
|
|||
|
|
continue
|
|||
|
|
}
|
|||
|
|
value, err := planetTransitRegionGeometry(longitudes, region.columns)
|
|||
|
|
if err != nil {
|
|||
|
|
return nil, fmt.Errorf("geojson: %s: %w", region.role, err)
|
|||
|
|
}
|
|||
|
|
features = append(features, newFeature(planetTransitEvent, region.role, value, cloneProperties(properties)))
|
|||
|
|
}
|
|||
|
|
return features, nil
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// planetTransitIsochroneFeatures 把每个接触的站心等时线编码为一条带 times 的 MultiLineString：
|
|||
|
|
// 每段是一条支路，times 与坐标对齐，同一支路上所有点同刻。
|
|||
|
|
func planetTransitIsochroneFeatures(
|
|||
|
|
input planetTransitInput,
|
|||
|
|
step time.Duration,
|
|||
|
|
timeScale basic.TimeScale,
|
|||
|
|
skip []string,
|
|||
|
|
withBase func(map[string]interface{}) map[string]interface{},
|
|||
|
|
module *Generator,
|
|||
|
|
) ([]feature, error) {
|
|||
|
|
result := basic.PlanetTransitResultFromTimes(input.planetIndex, input.start, input.c2, input.greatest, input.c3, input.end)
|
|||
|
|
features := make([]feature, 0, 4)
|
|||
|
|
for _, contact := range []struct {
|
|||
|
|
kind basic.PlanetTransitContactKind
|
|||
|
|
role string
|
|||
|
|
}{
|
|||
|
|
{basic.PlanetTransitC1, "c1-isochrone"},
|
|||
|
|
{basic.PlanetTransitC2, "c2-isochrone"},
|
|||
|
|
{basic.PlanetTransitC3, "c3-isochrone"},
|
|||
|
|
{basic.PlanetTransitC4, "c4-isochrone"},
|
|||
|
|
} {
|
|||
|
|
if skippedLunarRole(skip, contact.role) {
|
|||
|
|
continue
|
|||
|
|
}
|
|||
|
|
lines := basic.PlanetTransitContactIsochronesWithInstance(result, contact.kind, step, module.inst)
|
|||
|
|
coordinates := make([][][]float64, 0, len(lines))
|
|||
|
|
times := make([][]string, 0, len(lines))
|
|||
|
|
for _, line := range lines {
|
|||
|
|
at := basic.LabelIn(timeScale, basic.JD2DateByZone(line.JD, time.UTC, false))
|
|||
|
|
for _, segment := range line.Segments {
|
|||
|
|
if len(segment) < 2 {
|
|||
|
|
continue
|
|||
|
|
}
|
|||
|
|
points := make([]pathSample, len(segment))
|
|||
|
|
for index, point := range segment {
|
|||
|
|
points[index] = pathSample{Time: at, Longitude: point.Longitude, Latitude: point.Latitude}
|
|||
|
|
}
|
|||
|
|
pieces, err := splitTimedLine(points, false)
|
|||
|
|
if err != nil {
|
|||
|
|
return nil, fmt.Errorf("geojson: %s: %w", contact.role, err)
|
|||
|
|
}
|
|||
|
|
for _, piece := range pieces {
|
|||
|
|
if len(piece) < 2 {
|
|||
|
|
continue
|
|||
|
|
}
|
|||
|
|
coordinate := make([][]float64, len(piece))
|
|||
|
|
stamp := make([]string, len(piece))
|
|||
|
|
for index, point := range piece {
|
|||
|
|
if err := validateCoordinate(point.Longitude, point.Latitude); err != nil {
|
|||
|
|
return nil, fmt.Errorf("geojson: %s: %w", contact.role, err)
|
|||
|
|
}
|
|||
|
|
coordinate[index] = []float64{point.Longitude, point.Latitude}
|
|||
|
|
stamp[index] = formatTime(point.Time)
|
|||
|
|
}
|
|||
|
|
coordinates = append(coordinates, coordinate)
|
|||
|
|
times = append(times, stamp)
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
if len(coordinates) == 0 {
|
|||
|
|
continue
|
|||
|
|
}
|
|||
|
|
properties := withBase(map[string]interface{}{"step_seconds": step.Seconds(), "times": times})
|
|||
|
|
features = append(features, newFeature(planetTransitEvent, contact.role,
|
|||
|
|
geometry{Type: "MultiLineString", Coordinates: coordinates}, properties))
|
|||
|
|
}
|
|||
|
|
return features, nil
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
func planetTransitTimeMarkerSamples(
|
|||
|
|
start, end time.Time,
|
|||
|
|
scale basic.TimeScale,
|
|||
|
|
options TimeMarkerOptions,
|
|||
|
|
module *Generator,
|
|||
|
|
) ([]pathSample, error) {
|
|||
|
|
step, err := normalizeTimeMarkerStep(options.Step)
|
|||
|
|
if err != nil {
|
|||
|
|
return nil, fmt.Errorf("geojson: transit time markers: %w", err)
|
|||
|
|
}
|
|||
|
|
location := normalizeTimeMarkerLocation(options.Location)
|
|||
|
|
capacity, err := timeMarkerCapacity(start, end, step, location)
|
|||
|
|
if err != nil {
|
|||
|
|
return nil, fmt.Errorf("geojson: transit time markers: %w", err)
|
|||
|
|
}
|
|||
|
|
markers := make([]pathSample, 0, capacity)
|
|||
|
|
for current := firstTimeMarkerAfter(start, step, location); current.Before(end); current = current.Add(step) {
|
|||
|
|
point := solarSubsolarPoint(current, module)
|
|||
|
|
markers = append(markers, pathSample{
|
|||
|
|
Time: basic.LabelIn(scale, current),
|
|||
|
|
Longitude: point.Longitude,
|
|||
|
|
Latitude: point.Latitude,
|
|||
|
|
})
|
|||
|
|
}
|
|||
|
|
return markers, nil
|
|||
|
|
}
|