starainrt
3ffdbe0034
- 新增日食、月食、本地可见性、中心线、半影区域、SVG 图示与沙罗周期信息 - 新增行星冲合、留、方照、物理星历、视直径、相位、亮肢角、轨道节点等计算 - 新增木星伽利略卫星位置、现象与接触事件计算 - 新增恒星星表、星座判定、自行修正与观测辅助能力 - 新增 coord、formula、orbit、sundial、lite/sun、lite/moon 等扩展包 - 完善农历年号、月相英文别名、视差角、大气质量、折射、日晷与双星计算 - 增加 NASA、JPL Horizons、IMCCE 等回归测试数据与基线测试 - 重构基础算法文件组织，补充大量公开 API 注释和语义回归测试 - 更新中文和英文 README，补充示例、精度说明、SVG 配图
112 lines
2.6 KiB
Go
112 lines
2.6 KiB
Go
package planet
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import (
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. "b612.me/astro/tools"
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"math"
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)
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// WherePlanet returns the full VSOP result for the selected body and coordinate.
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func WherePlanet(xt, zn int, jd float64) float64 {
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return WherePlanetN(xt, zn, jd, -1)
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}
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// WherePlanetN returns the VSOP result for the selected body and coordinate.
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// When n < 0, all terms are used. Otherwise n follows the original eph0.js
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// truncation semantics: keep roughly n principal terms from the 0th order
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// series and scale higher-order series proportionally.
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func WherePlanetN(xt, zn int, jd float64, n int) float64 {
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sata := 0
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if xt == -1 {
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xt = 0
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sata = 1
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}
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rad := 180.0000 * 3600.0000 / math.Pi
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t := (jd - 2451545) / 36525.0000
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t /= 10 // 转为儒略千年数
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body := planetViews[xt]
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coord := body.coords[zn]
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baseOrderTerms := len(coord.orders[0])
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tn := float64(1)
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var v float64
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for i, series := range coord.orders {
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seriesLength := len(series)
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if seriesLength == 0 {
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continue
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}
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termLimit := seriesLength
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if n >= 0 {
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termLimit = int(math.Floor(3*float64(n)*float64(seriesLength)/float64(baseOrderTerms) + 0.5))
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if i != 0 {
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termLimit += 3
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}
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if termLimit > seriesLength {
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termLimit = seriesLength
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}
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}
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var c float64
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for j := 0; j < termLimit; j += 3 {
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c += series[j] * math.Cos(series[j+1]+t*series[j+2])
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}
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v += c * tn
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tn *= t
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}
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v /= body.scale
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if xt == 0 { // 地球
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t2 := t * t
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t3 := t2 * t // 千年数的各次方
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if zn == 0 {
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v += (-0.0728 - 2.7702*t - 1.1019*t2 - 0.0996*t3) / rad
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} else if zn == 1 {
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v += (+0.0000 + 0.0004*t + 0.0004*t2 - 0.0026*t3) / rad
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} else if zn == 2 {
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v += (-0.0020 + 0.0044*t + 0.0213*t2 - 0.0250*t3) / 1000000
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}
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} else { // 其它行星
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planetCorrections := []float64{
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// 经(角秒), 纬(角秒), 距(10-6AU)
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-0.08631, +0.00039, -0.00008, // 水星
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-0.07447, +0.00006, +0.00017, // 金星
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-0.07135, -0.00026, -0.00176, // 火星
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-0.20239, +0.00273, -0.00347, // 木星
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-0.25486, +0.00276, +0.42926, // 土星
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+0.24588, +0.00345, -14.46266, // 天王星
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-0.95116, +0.02481, +58.30651, // 海王星
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}
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dv := planetCorrections[(xt-1)*3+zn]
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if zn == 0 {
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v += -3 * t / rad
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}
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if zn == 2 {
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v += dv / 1000000
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} else {
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v += dv / rad
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}
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}
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if zn == 0 && xt == 0 {
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if sata != 0 {
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return Limit360(v * 180 / math.Pi)
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}
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return Limit360(v*180/math.Pi + 180)
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}
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if zn == 1 && xt == 0 {
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if sata != 0 {
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return v * 180 / math.Pi
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}
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return -(v * 180 / math.Pi)
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}
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if xt > 0 && zn == 1 {
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return v * 180 / math.Pi
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}
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if xt > 0 && zn == 0 {
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return Limit360(v * 180 / math.Pi)
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}
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return v
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}
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