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June 20, 2025

Premise

You’re somewhere on Earth. The sky is your map.
Measure time, measure angles, observe patterns.
Build position from natural reference points.

Step 1 — What You Have

  • Your clock:
    If you have one, great. If not, we build time from the Sun.

  • Horizon:
    Reliable baseline for angle measurement (sunrise, sunset, star rise/set).

  • The Sky:

    • The Sun moves ~15° west per hour.

    • Stars “fixed” relative to one another.

    • Celestial poles (North Star / South celestial pole).

  • A stick and string becomes a sextant.
    Shadow lengths become a clock.

Step 2 — Find Latitude

Latitude is easy to find, it's based on the height of the celestial pole (or Sun at noon).

  • In the Northern Hemisphere, Polaris (North Star) height ≈ your latitude.

  • In the Southern Hemisphere, you use the Southern Cross or Sun.

No Polaris? Use the Sun:

  1. At local noon (Sun at highest point), measure its altitude above the horizon.

  2. Your latitude = (90° - Sun’s altitude at noon) + Sun’s declination.

    • Declination = distance of Sun from celestial equator. Estimate seasonally:

      • Equinox: ~0°

      • Solstice: ~±23.5°

Method: Shadow Tip Tracker

  • Place stick upright.

  • Mark shadow tip every 10 mins.

  • Shortest shadow = local noon.

Step 3 — Find North/South

  • Watch stars rotate: they move counter-clockwise around Polaris (north).

  • Southern Hemisphere: stars rotate clockwise around an empty point (near Crux constellation).

  • Sunrise = East, Sunset = West (approximate).

Quick: Daytime Method

  • Shadow at noon points due north/south.

  • In the north, noon shadow points north.

  • In the south, it points south.

Step 4 — Estimate Time

  • The Sun moves 15° per hour.

  • Measure Sun’s angle from local noon:

    • East of noon = morning

    • West of noon = afternoon

  • Night: use star positions to track time (constellations rise ~4 mins earlier each night).

Step 5 — Estimate Longitude (Trickier, but possible)

Longitude = time difference from a known reference (Greenwich).

  1. Build local time (by tracking the Sun).

  2. Compare to “universal time” (UTC).

    • No clock? Use lunar distances or moon-star angles over days to build a time reference.

  3. Every hour difference = 15° longitude.

    • E.g., if your local noon is 3 hours after UTC noon, you are ~45° west.
  • Observe moon and stars repeatedly to build a sidereal clock.

Step 6 — Map Building

  1. Mark local features: coastline, mountains, rivers.

  2. Track sunrise/sunset azimuths over time to watch seasonal drift.

  3. Plot Sun’s noon altitude daily: track your drift north/south.

  4. Record star rises/sets relative to horizon points.

  5. After weeks you'll have a rough celestial map and local geography.

Tools:

  • Stick and shadow = clock + compass

  • Horizon = reference line

  • Rock and string = plumb-line quadrant

  • Star charts = memorized / sketched over time