Transportation Survey Project Lead | Geodesy & GNSS

Distances and bearings from the center are accurateDistortion increases rapidly away from the centerDistances and directions between non-central locations are wrongSo 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 centerThis is why level loops close only when curvature is accounted forIgnore curvature and your elevations driftRule 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 → measurable20+ miles → impossible to ignoreState 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 areaThat excess matches spherical geometry exactlyThis was proven centuries ago and is still used today. If Earth were flat:Control networks would never closeState Plane Coordinate Systems wouldn’t workGNSS solutions would drift uncontrollablyThey don’t.Coordinate Systems Kill Flat Earth Instantly State Plane Coordinate System (SPCS) Every U.S. state uses projected coordinates based on:An ellipsoidA map projection (Lambert, Transverse Mercator)Because Earth is curved and we’re flattening it on purpose, carefully. If Earth were flat:No projections neededNo scale factorNo convergence angleYet we measure:Grid vs ground distance differencesMeridian convergenceScale factor changes by locationYou 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 EarthSignal timing assumes an ellipsoidPositions are solved in 3D spaceIf Earth were flat:RTK corrections would failBaselines wouldn’t resolveVertical solutions would collapseInstead, we routinely get:Horizontal accuracy >> Find more and create a "Seeking Employment" profile:1. CSRS-PPP (Canada): Best-in-Class PPP, No Base Required Natural Resources Canada’s CSRS-PPP is, hands down, one of the most reliable free PPP services available worldwide. This is straight Precise Point Positioning using IGS precise orbit and clock products. No base station required, no reliance on nearby CORS, and no geographic limitation to Canada despite the name. Upload your RINEX, pick static or kinematic, single or dual frequency, and let it run. From a performance standpoint, CSRS-PPP has repeatedly tested at or near the top in independent comparisons. Multiple studies—including CLGE and peer-reviewed academic analyses—have shown it to produce more consistent and repeatable results than most other online PPP engines. Why surveyors should care:Global coverageNo dependency on local CORS densityExcellent long-session static resultsClean reporting and transparent metadataIf OPUS is down and you’re sitting on multi-hour static occupations, CSRS-PPP is usually the first place I send people. 2. AUSPOS: Old-School Relative Positioning Done Right AUSPOS, operated by Geoscience Australia, takes a very different approach—and for many surveyors, that’s a feature, not a bug. This is relative positioning, not PPP. AUSPOS forms baselines from your submitted data to multiple high-quality IGS stations, then performs a network adjustment. Conceptually, it’s much closer to how most of us were trained to think about GNSS control. Requirements are stricter:Static, dual-frequency GPSOne hour minimum (six hours recommended)Best results with long sessions (12–24 hours)But the payoff is stability. Independent evaluations have consistently shown AUSPOS producing extremely reliable coordinates, often outperforming PPP services when long occupations are available. Why surveyors should care:True network-based solutionTied directly to the IGS frameworkExcellent for primary control and long-session workIf you’re comfortable thinking in baselines instead of black-box PPP, AUSPOS is a rock-solid OPUS substitute. 3. Trimble CenterPoint RTX: Commercial PPP Without the Hardware Lock-In Trimble’s CenterPoint RTX post-processing service sits in the middle ground between government-run services and fully commercial workflows. It’s a global PPP service, accessible through a free web portal, and it works with static data from non-Trimble receivers as well. If you’re already running Trimble Business Center or tools like LP360, the integration can streamline processing and coordinate management. A couple of professional caveats:Plan on longer occupations (one hour minimum is a practical baseline).Be aware of reference frame transformations. The RTX web service uses the Morvel56 plate model for NAD83 transformations, while TBC can use HTDP. That matters for control work and multi-epoch consistency.Why surveyors should care:Backed by a major vendorGlobal coverageClean workflow integrationPredictable performanceRTX won’t replace #J-18808-Ljbffr Land Surveyors United