Empirical Earth · Shape, Curvature & the Horizon
Calibrated instruments vs. a superzoom camera
The claim
“Zoom in with a Nikon P1000 and a city that should be hidden by the curve comes back — proof there’s no curvature.”
What is measured
A camera zoom is a magnifier, not a measuring tool. The curve and your latitude are pinned down with calibrated angle-readers (theodolites to about 1–6″, sextants to about 0.1′). And past 125× the P1000’s “zoom” is just guessed-in pixels, which is invented data.
What would show this is wrong
a calibrated, leveled theodolite or sextant reading zero horizon dip from altitude, or a demonstration that optical zoom alone (with refraction controlled) brings back an object whose base is below the line of sight.
Sources
- Refraction, Snell's law & refractive index of air/water. Standard optics; refractive index of air via the Ciddor/Edlén equations. E. Hecht, Optics ; NIST refractive-index references. Snell's link
- Nikon COOLPIX P1000 — 125× optical zoom (24–3000 mm equiv.). Optical zoom tops out at 3000 mm; f/2.8–8, 16 MP 1/2.3″ BSI-CMOS sensor. Beyond 125× the camera switches to digital zoom.. Nikon link
- Nikon Coolpix P1000 review — the 250× “Dynamic Fine Zoom” is digital. Reviewers advise against the digital zoom for image quality; digital zoom interpolates pixels and adds no real optical d link
- Theodolite — precision angular surveying instrument. Measures horizontal and vertical angles to seconds of arc on a leveled, calibrated circle; the basis of geodetic triangulation.. Theodoli link
- Marine sextant — celestial-altitude accuracy to ~0.1′ of arc. Micrometer-drum sextants read to a tenth of an arc-minute; measured altitudes yield latitude (Bowditch, American Practical Navig link
- Curvature & refraction correction in levelling. Surveying practice applies a standard correction to long sights: curvature lowers the apparent target by about 0.0785 D² meters and refraction link
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