Curvature

Name: Curvature
Price: 1.99 USD
Rating: 5 (2 reviews)
Author: Steven Wilkinson

Earth geometry & curvature

$1.99 · Designed for iPad. Not verified for macOS.

2 Ratings
Age Rating

4+
Years
Category

Utilities
Developer

Steven Wilkinson
Language

EN
English
Size

121.9
MB

New: the 3D Model Explorer. Compare polar flat-disc models with a WGS84 globe driven by real dated astronomy, then stand in the observer's sky at true scale. Curvature is a geometry and visibility toolkit for anyone who wants to test what a curved or flat Earth would predict, with every formula documented and every assumption stated. THE CALCULATOR Enter observer height, target height and surface distance. Curvature returns the surface horizon, tangent-plane drop, midpoint bulge, horizon dip, surface tilt and the hidden and visible portions of the target, in metres or feet, kilometres or miles. Choose refraction off, four published coefficients or your own k from 0 to 0.5, and compare any result side by side with the pure geometric case. Drag the observer, target and distance directly on an exaggerated profile, or switch to a true-scale view with a magnified detail inset. Uncertainty ranges recalculate across your stated input tolerances so you can see whether a sighting is robust. THE MAP Drop rulers and points of interest on standard, satellite or hybrid maps. Rulers report geodesic surface distance and initial bearing in degrees or NATO mils, search for places, fit the view and send endpoints straight to the calculator. Optional terrain lookup prefills ground elevations from SRTM data with the datum and limits spelled out. THE 3D MODEL EXPLORER (NEW) Explore three scenarios with the same observer, date and time: the classical north-polar disc, a south-polar projection comparison and a WGS84 reference ellipsoid. The globe uses dated geometric ephemerides from the open-source Astronomy Engine, including sidereal rotation, precession, nutation, seasons, real Earth-Sun and Earth-Moon distances and lunar illumination, validated against JPL Horizons and US Naval Observatory data. Place the observer anywhere, read elevation, bearing, slant distance and angular diameter for the Sun and Moon, then open the observer sky to see both at their calculated angular size. A comparison sheet lists all three models for the same inputs. Each scene labels what is sourced, what is an app assumption and what is not simulated. REPORTS AND ANALYSIS Export an illustrated PDF report with inputs, coordinates, assumptions, uncertainty bounds and the calculation version, or copy a structured text summary. On supported devices, Apple Intelligence can draft a plain-language analysis that never alters the calculated numbers. REFERENCE LIBRARY Read bundled historical and technical PDFs with page bookmarks, find and go-to. Browse fifty curated web links covering tools, research, forums and video from every perspective, plus references, worked formulas for the calculator, map and explorer, and an indexed glossary of more than eighty terms. YOUR DATA Saved observations, rulers, points, links, imported PDFs and reading positions sync privately through iCloud on signed-in devices, with portable backup and restore. No account, tracking or advertising. Curvature does not tell you what to believe. It shows what each model predicts, how that was calculated and where the model stops.

Ratings & Reviews

5.0

out of 5

2 Ratings

Real Science
11/16/2022
Firmanent Lover
This app is extremely accurate and provides actual data instead of fairy tales. Our eyes can’t see curvature, only straight lines. It’s pretty fun to do experiments with it. I suggest using it over water. From San Mateo shore to Treasure Island is about 18 miles. With my telescope 4 feet above the water it says there is about 160 feet hidden behind the curve which means most of the island shouldn’t be visible. In reality through our telescope we could see the water splashing on the shore, so yeah… Real science.

Developer Response
Thank you. I recently updated the app with lots of new features and accuracy and had a full design from the ground up. Please update and wish you all the best!
Real Science
11/16/2022
Firmanent Lover

This app is extremely accurate and provides actual data instead of fairy tales. Our eyes can’t see curvature, only straight lines. It’s pretty fun to do experiments with it. I suggest using it over water. From San Mateo shore to Treasure Island is about 18 miles. With my telescope 4 feet above the water it says there is about 160 feet hidden behind the curve which means most of the island shouldn’t be visible. In reality through our telescope we could see the water splashing on the shore, so yeah… Real science.
Developer Response Mar 6
Thank you. I recently updated the app with lots of new features and accuracy and had a full design from the ground up. Please update and wish you all the best!

3D MODEL EXPLORER • Compare a north-polar disc, a south-polar projection and a WGS84 globe with one observer, date and time. • The globe is driven by dated astronomy: sidereal rotation, axial tilt, precession, seasons and real Sun and Moon distances, checked against JPL Horizons and USNO data. • Observer sky view shows the Sun and Moon at their true angular size, with elevation, bearing, slant distance and lunar illumination. • Solar-orbit overview, equinox and solstice presets, and a side-by-side comparison sheet you can share. ACCURACY REVIEW • Every calculator, map and explorer formula was re-derived and cross-checked; worked examples on the Formulas page match the engine to the last digit. • The observer sky now renders with correct left–right orientation. REFERENCE LIBRARY • 27 new verified web links, including NGA WGS84, USNO, JPL Horizons, NOAA, Stellarium and Bowditch; dead links replaced or retired. • New formula cards for map geometry and the Model Explorer, 25 new glossary terms and a Sun and Moon constants table. • Source attributions for every bundled PDF. ALSO • New app icon. • Now supports iOS 17 and later. • Version and build numbers report correctly.

Version 3 Oct 12

Data Not Collected

The developer does not collect any data from this app.

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Supported Features
- Dark Interface

Information

Seller: Steven Wilkinson
Size: 121.9 MB
Category: Utilities
Compatibility: Requires iOS 17.6 or later.

iPhone
Requires iOS 17.6 or later.

iPad
Requires iPadOS 17.6 or later.

Mac
Requires macOS 14.6 or later and a Mac with Apple M1 chip or later.

Apple Vision
Requires visionOS 1.3 or later.
Languages: English
Age Rating: 4+

4+

Learn More