GPS 失败后的兜底方案，必须你点"使用"才生效。固网出口 IP 常汇聚到地级市或省会（例：新泰的宽带可能落在济南，约 100 km）；手机流量的 IP 库里注册地可能完全错乱（实测有山东用户被定位到海南），故本工具只做提示、不自动应用，并在与上次位置相差过远时直接警告
地图搜索 / 手动输入
取决于所选点
最可靠。搜索地名或直接在地图上点选，坐标由你决定
定位优先级：① GPS（最多等 12 秒；9 秒时就会提示"不必等，可直接手输"）→ ② GPS 不行则自动尝试网络 IP（仅提示，须你点"使用"才生效，与上次位置差 >300 km 会直接警告）→ ③ 都不行就手动输入经纬度或在地图搜索框输地名。
IP 定位会向第三方服务（ipwho.is）查询，仅发送你的 IP 地址，不发送其他任何信息；查询结果只在本机使用，不写入"上次位置"记录。
对太阳高度角的影响：纬度每差 1°，正午高度角约差 1°；经度每差 1°，日出日落时刻约差 4 分钟。因此 100 km 的 IP 误差约带来 1° 高度角、3–4 分钟时刻偏差。
Most accurate. Tap "Allow" on the prompt and go outdoors / near a window; the first fix indoors can take 10–30 s
Browser location (desktop)
Tens of m – a few km
Desktops have no GPS; the browser uses nearby Wi-Fi networks plus IP. Enable OS location services: Windows → Settings → Privacy & security → Location → On. Better with a Wi-Fi adapter
Network IP
10–100 km
Automatic fallback after GPS fails. Carrier exit IPs aggregate at city or provincial level and may put you in a different city
Place search / manual
As chosen
Most reliable. Search a place name or click the map; you control the coordinates
Location priority: (1) GPS (waits at most 12 s; at 9 s it already tells you that you need not wait and may type coordinates) → (2) if GPS fails, network IP is tried automatically (hint only — applied only when you tap "Use", and a warning appears if it is >300 km from your last position) → (3) otherwise enter coordinates manually or search a place name.
IP lookup queries a third party (ipwho.is) and sends only your IP address — nothing else — and the result stays on your device and is never saved as your "last location".
Effect on results: 1° of latitude changes noon altitude by about 1°; 1° of longitude shifts sunrise/sunset by about 4 minutes. So a 100 km IP error means roughly 1° of altitude and 3–4 minutes of timing error.
🌙 Moon data
Item
Meaning
Notes
Phase
Sunlit shape of the lunar disk
From Sun–Moon ecliptic longitude difference: 0° new, 90° first quarter, 180° full, 270° last quarter
Moon age
Days since last new moon
0–29.5 d (mean synodic month 29.53 d)
Illumination
Lit fraction of the disk
0% new, ~50% quarters, 100% full
Moonrise / Moonset
When the Moon's centre reaches the horizon
The Moon rises ~50 min later each day, so some days have no rise or no set
Moon algorithm: simplified lunar theory from Meeus, Astronomical Algorithms (29 longitude terms, 13 latitude terms, 15 distance terms).
Phase times accurate to about ±1–2 min; moonrise/moonset about ±2–5 min (limited by parallax, terrain and air temperature — a physical limit).
Cross-checked against pyephem: altitude/azimuth agree within 0.02°, and phase angles at six solar/lunar eclipses (2024–2026) within 0.1°.
Fig 1: left — elevation (side view); right — azimuth (top view)
📐 Key parameters
Parameter
Meaning
Range / note
Elevation
Angle between the sun and the horizon (vertical direction) — how high the sun is.
0° at sunrise/sunset, highest at noon; negative = below horizon.
Azimuth
Clockwise angle from North to the sun's horizontal projection.
0°=N, 90°=E, 180°=S, 270°=W. Northern H.: sun is in the south at noon; Southern H.: in the north.
Sunrise / Sunset
Clock times when the sun's upper edge crosses the horizon.
Standard zenith 90.833° (refraction 34′ + solar radius 16′).
Solar noon
When the sun crosses the local meridian (highest point of the day).
Usually not 12:00 — shifted by longitude and equation of time.
Day length
Duration from sunrise to sunset.
Polar day/night shown for polar regions.
Max elevation
Highest elevation the sun reaches at noon that day.
Determined by latitude + season (largest at summer solstice).
Declination
Latitude of the subsolar point in the celestial coordinate system.
≈0° at equinoxes; ≈+23.44° at June solstice; ≈−23.44° at December solstice.
Equation of time
Difference between apparent and mean solar time.
About −14 to +16 minutes; why solar noon ≠ 12:00.
Shadow length / direction
Shadow of an obstacle of given height.
Shadow direction = azimuth + 180°; lower sun → longer shadow.
🗺️ Reading the charts
Map rays: colored rays = sun direction at sunrise / 09:00 / 12:00 / 15:00 / sunset and the selected time (dashed = below horizon).
Polar chart: center = zenith (90°), outer ring = horizon (0°); radius = elevation, angle = azimuth. Dark gray = summer solstice, light gray = winter solstice, orange = selected date (dots = hours), yellow dot = current sun; the dark line from center to South (180°) is the azimuth reference line. For the Southern Hemisphere the solstice dates swap automatically (summer = Dec 21, winter = Jun 21).
3D dome: sky as a hemisphere; the orange arc is the selected day's path.
Why is solar noon not 12:00? Longitude offset from the timezone meridian (China uses 120°E) plus the equation of time (±14 min).
Why is the sun in the southeast at 8 AM? In the Northern Hemisphere the sun's path is south of the zenith; it rises in the SE and sets in the SW.
Negative elevation? The sun is below the horizon (night / polar night).
Southern Hemisphere? Noon sun is in the north; seasons are reversed (December = summer).
Which datum? Use WGS84/CGCS2000 (default) for GPS/maps; use GCJ-02 for coordinates copied from AMap.
📏 Accuracy
NOAA solar position algorithm (Meeus). Error < 0.01° for 1900–2100; max deviation ≈ 0.008° vs pyephem. Sunrise/sunset times iterated for declination, typically < 0.5 min error.
