Dibujante CAD & GIS: Geodesy‑Driven Drafting Pro

Distances and bearings from the center are accurate

Distortion increases rapidly away from the center

Distances and directions between non-central locations are wrong

So while the map can function as a practical educational or navigational tool from the pole, it fails for comparing distances or routes elsewhere — exactly what geodetic theory predicts.

The modern interactive version by Khaled Mimoune, including adjustable daylight overlays, further illustrates how cartographic projections can visualize real-world phenomena (like illumination and seasons) on a flat surface. From a surveying perspective, this reinforces the distinction between:

The Earth (a globe)
A map (a mathematical projection of that globe)
In short, Gleason’s map doesn’t demonstrate a flat Earth. It demonstrates that projecting a curved surface onto a plane requires distortion, a foundational principle in surveying, geodesy, and every State Plane Coordinate System used in professional practice today.

Flat Earth does not survive real-world surveying practice. Not philosophically, not mathematically, and definitely not in the field. Surveying is one of the oldest applied sciences on Earth, and we measure curvature whether we intend to or not.

What Surveyors Actually Observe (Not Theory) 1. Level lines are not parallel On a flat plane, level lines would remain parallel forever. In reality:

Level lines converge toward Earth’s center

This is why level loops close only when curvature is accounted for Ignore curvature and your elevations drift

Rule of thumb every surveyor learns:

Curvature drop ≈ 0.667 ft per mile²That’s not a NASA number — that’s a surveying correction.
2. Long-distance leveling proves curvature If I run a precise level line:1 mile → negligible difference5 miles → measurable
20+ miles → impossible to ignore

State DOTs, USACE, and geodetic surveys require curvature and refraction corrections. If Earth were flat, these corrections would introduce errors — but instead they remove them.
3. Triangulation doesn’t work on a flat Earth In geodetic control:

Large triangles do not sum to 180°The excess increases with triangle area

That excess matches spherical geometry exactly

This was proven centuries ago and is still used today. If Earth were flat:

Control networks would never close

State Plane Coordinate Systems wouldn’t work

GNSS solutions would drift uncontrollably

They don’t.Coordinate Systems Kill Flat Earth Instantly State Plane Coordinate System (SPCS) Every U.S. state uses projected coordinates based on:

An ellipsoid

A map projection (Lambert, Transverse Mercator)
Because Earth is curved and we’re flattening it on purpose, carefully. If Earth were flat:

No projections needed

No scale factor

No convergence angle

Yet we measure:

Grid vs ground distance differences

Meridian convergence

Scale factor changes by location

You can verify this with a total station and two benchmarks. GNSS Is the Nail in the Coffin Survey-grade GNSS works because:

Satellites orbit a curved Earth Signal timing assumes an ellipsoid

Positions are solved in 3D space

If Earth were flat:

RTK corrections would fail Baselines wouldn’t resolve

Vertical solutions would collapse

Instead, we routinely get:

Horizontal accuracy < 0.03 ft Vertical accuracy < 0.06 ft Every day. By county surveyors, not space agencies. “But I Can See Farther Than Curvature Allows” Surveyor response:

Refraction is real Elevations matter

Atmospheric ducting happens

Line of sight ≠ line of level

Surveyors distinguish between:

Optical visibility

Geometric line of sight

Level surface

Geoid vs ellipsoid

Flat Earth arguments usually mix all four into one sentence. Historical Surveying Perspective Long before satellites:

Surveyors in the 1700s measured meridian arcs Found Earth’s radius within a fraction of a percent

Using chains, theodolites, and stars

No rockets. No CGI. Just math and patience. Professional Reality Check Here’s the blunt PLS truth:

If Earth were flat, surveying as a profession would not work.

Boundary surveys wouldn’t close

Control networks would fail Elevation datums would drift

Engineering projects would not align

Yet highways meet. Bridges connect. Pipelines close. And property corners agree. Why Flat Earth…