What's new
Essays arrive in groups rather than one at a time, and a group usually opens up a subject the collection had not covered before. Between one group and the next nothing changes, so a reader who has seen the most recent group has seen everything.
5 September 2026
13 essays on the impossibility, the families, what is taught wrongly, what each projection optimises, what the numbers refer to, what a machine does with it and measuring distortion
What a cut buys
Six rungs count cuts and none measures one. A cut is a curve on the sphere with a length in kilometres, the shape distortion it removes is a falling function of that length, and the interruption everybody prints spends a hundred thousand kilometres to reach a figure the even-lobed curve reaches with sixty.
How many triangles it takes
Rung eleven priced one triangle and recorded that a survey observes hundreds. Averaging n of them divides the noise by √n, and n is not free: a chain of fixed length holds fewer big triangles than small ones, so the accuracy improves as the side to the power three halves rather than two. Struve's 141 triangles of forty kilometres are worth exactly Gauss's seven of eighty-five.
Four radii of the Earth
Ten rungs handle the ellipsoid with an auxiliary latitude. Every one of those constructions also needs a radius, and the radius that makes each property exact is a different number: the published 6371 km is right for an area to half a part per million and wrong for a meridian distance by 559 — while the radius a conformal map needs is not a constant at all, and spans 6,739.
The average was a choice of norm
Ten projections, one region, one measured quantity, and the only free decision left is how to turn a field into a number. Over the world's scale departure the ordering at the mean and the ordering at the worst case have a rank correlation of −0.04, all ten maps change position, and the exponent that produced each answer is stated nowhere.
The pooled score abandons a region
Fifteen rungs optimise for one region. An atlas is several, and pooling their samples into one area-weighted score is what everybody does — which on Britain and New Zealand serves Britain 1.2 times worse than it could be served alone and New Zealand 125 times worse. The worst-case objective makes them equal at 33 and 59, and the cost of sharing rises with separation from 1.4 to 59.
On a body with a hole, north can be up everywhere
Twelve rungs vary the body's shape and none varies its topology, which is what every impossibility here actually rests on. A torus has a nowhere-zero tangent field, a total curvature of zero rather than 4π, and a conformal world map with no cut and no singular point — and it still cannot be flattened, for the one reason that survives.
The height a coordinate does not carry
Ten rungs treat a datum shift as a map from one pair of angles to another. It is not one: the transformation runs through Cartesian coordinates, so the answer depends on the height — by 7.7 to 121 millimetres per kilometre depending on the datum and the place, which puts Lhasa 432 millimetres from where a height of zero would have said.
The orientation is a policy
A polyhedral cell system has three free angles nobody scores. They cannot improve it: rotating the solid rotates every cell rigidly, so the distribution of cell areas is identical for every orientation there is. What they decide is who stands on the bad cells — and the eight cities measured here get a spread of cell area of 1.00 under the best turn and 1.50 under the worst.
The sample was drawn on the page
Every mean in this collection integrates over the sphere, because that is where the ground is. A raster, a pixel loop and any figure that walks its own canvas integrate over the page instead, and the difference is exactly the covariance between the quantity being measured and the map's own area distortion — 7.2° of mean angular deformation on Miller becoming 18.0°.
Two indicatrices do not make a third
Reprojecting is composing, and the composite's indicatrix is not a function of its parents'. Mollweide followed by Hammer is gentler than either map over eighty per cent of the sphere; the sinusoidal followed by Gall–Peters is worse than both everywhere. What separates them is one angle, and it is the number rung ten showed the ellipse does not carry.
A cartogram keeps the shapes it inflates
Seven rungs build cartograms and none reads one back. Reading means recognising a region and dividing its drawn area by its base area, and the construction is against the reader twice: the correlation between how much a region grows and how much of its shape it keeps is −0.996, and the base area a reader has to divide by is the map the cartogram replaced.
A current drawn on a page has sources
Seven rungs project a scalar field and ask what the page does to its gradient. A wind or a current is the other half of what gets mapped, and the operator that matters for it is the divergence — which is preserved by an equal-area map exactly, by no other map at all, and by a conformal map least of anybody's expectation.
Rounding is not noise
Eight rungs treat a coordinate's error as noise that averages down. A published coordinate has a second error that does not: it is deterministic, it is shared between every point in the same cell, and at five centimetres apart ninety-three per cent of pairs come out as the same place — which no amount of independent noise can produce.
Before that
Everything published earlier, newest first. Titles only — the cards are on the full listing.
1 September 2026
20 essays on the impossibility, paths and directions, grids, and what a survey does, the families, what is taught wrongly, what each projection optimises, what a machine does with it and measuring distortion
- How big a triangle it takes — the impossibility
- The most compact shape depends on the paper — paths and directions
- The score is not stable at any scale — paths and directions
- Two charts are enough, and one is not — the impossibility
- One pair of numbers, a hundred and twenty places — grids, and what a survey does
- The exact map says the seam is smooth — the families
- The ranking is not an order — what is taught wrongly
- The answer is a set — what is taught wrongly
- The first break is mostly its denominator — what each projection optimises
- The nodes were evenly spaced — what each projection optimises
- A tolerance in map units is not a tolerance — what a machine does with it
- The worst point is not on the grid — measuring distortion
- A mean that does not exist can still be printed — measuring distortion
- There is no equal-area lattice on a sphere — measuring distortion
- A refinement that stops moving — measuring distortion
- Which of these numbers are the sampler's — measuring distortion
- One number changed and the whole map moved — measuring distortion
- The lines where the bending vanishes — measuring distortion
- The area is unbiased and the perimeter is not — measuring distortion
- The fourth number the ellipse does not carry — measuring distortion
31 August 2026
20 essays on paths and directions, the families, grids, and what a survey does, what each projection optimises, what is taught wrongly, what the numbers refer to, what a machine does with it and measuring distortion
- The shortest route a vehicle can fly — paths and directions
- The corner is not at the midpoint — the families
- A family is not closed under averaging — the families
- The network's answer is decided before it is measured — grids, and what a survey does
- The threshold is not a percolation — what each projection optimises
- Which small quantity the series is in — what is taught wrongly
- A condition imposed at points is not a condition — what each projection optimises
- A vertical rate needs a height system — what the numbers refer to
- A cell's children do not fit inside it — what a machine does with it
- Every country's zero is a different surface — what the numbers refer to
- A label belongs to no tile — what a machine does with it
- The parameters are not independent — what the numbers refer to
- A ray from the centre hits the surface twice — what the numbers refer to
- Which features survive is not a sample — what a machine does with it
- Two routes to one scale — what a machine does with it
- A choropleth is read by area — measuring distortion
- A symbol has a size on the page and an area on the ground — measuring distortion
- A dot map's density is partly the projection's — measuring distortion
- The class breaks were computed on the page — measuring distortion
- What the page cannot move — measuring distortion
30 August 2026
20 essays on paths and directions, the impossibility, the families, grids, and what a survey does, what is taught wrongly, what each projection optimises, what the numbers refer to, what a machine does with it and measuring distortion
- A reach set with a cost that depends on direction — paths and directions
- Four colours, and what a cut cannot do to them — the impossibility
- The set that can be reached is not the set that can reach — paths and directions
- Where the surface curves the other way — the impossibility
- The gnomonic crosses a seam without a corner — the families
- Further north on the grid is not further north — grids, and what a survey does
- A rotation is not absorbed the way a shift is — what is taught wrongly
- The basins have widths as well as depths — what each projection optimises
- Which projection a weighting can make best — what is taught wrongly
- The ground has an indicatrix too — what the numbers refer to
- A velocity needs a frame and a strain rate does not — what the numbers refer to
- A grid stops fitting the ground it was laid on — what the numbers refer to
- The strain a map adds to the ground's — what the numbers refer to
- The query a fast path actually answers — what a machine does with it
- The cheapest map that meets its areas — measuring distortion
- A density that asks for no room at all — measuring distortion
- The ellipses are a sample, drawn at a size somebody chose — measuring distortion
- The error that does not average down — measuring distortion
- A length measured from noisy points is too long — measuring distortion
- The best compromise for angle is not the best for bending — measuring distortion
28 August 2026
35 essays on paths and directions, the impossibility, grids, and what a survey does, the families, what each projection optimises, what is taught wrongly, what the numbers refer to, what a machine does with it and measuring distortion
- A circle of a distance is not a circle — paths and directions
- Nearest of many is a partition — paths and directions
- A corridor has a width the page cannot keep — paths and directions
- How many times, not whether — the impossibility
- The places where a map is exactly right — the impossibility
- Sixty zones was a decision about one latitude — grids, and what a survey does
- What the net heuristic cannot find — the families
- Where the valley breaks in two — what each projection optimises
- The nearest map to an impossible request — what each projection optimises
- The tolerance that decides the verdict — what is taught wrongly
- The geoid model stops at a degree — what the numbers refer to
- The attribute is a claim about the geometry — what a machine does with it
- The second derivative cannot classify — measuring distortion
- The error ellipse is not an ellipse — measuring distortion
- Whether the ellipses point the same way — measuring distortion
- The line drawn straight on the page is a route — paths and directions
- A projection defined by a table has an interpolation in it — the families
- The blunder the network cannot see — grids, and what a survey does
- The datum hides inside the projection's parameters — what is taught wrongly
- The height of the pass between two basins — what each projection optimises
- The nearest equal-area map to an impossible request — what each projection optimises
- A longitude that drifts with the rotation rate — what the numbers refer to
- The rotation has two sign conventions — what the numbers refer to
- The radius of curvature is two numbers — what the numbers refer to
- The correlation is not the same in every direction — what the numbers refer to
- A thousand features are wrong in the same direction — what a machine does with it
- How many features a scale can carry — what a machine does with it
- The answer depends on the cells it was counted in — what a machine does with it
- A map drawn to a density it was handed — measuring distortion
- The renderer runs out of numbers before the zoom does — what a machine does with it
- Every density can be met and none is free — measuring distortion
- A map that meets its target can fold — measuring distortion
- Everything else on the page pays for the areas — measuring distortion
- The light comes from a page direction — measuring distortion
- The curvature of a field is not the curvature of its picture — measuring distortion
26 August 2026
15 essays on paths and directions, the impossibility, what is taught wrongly, the families, grids, and what a survey does, measuring distortion, what the numbers refer to and what a machine does with it
- The shortest route is not at sea level — paths and directions
- No map of the whole sphere is one to one — the impossibility
- North cannot be up everywhere — the impossibility
- Two opposite places on the same spot — the impossibility
- The equator is not a circle either — what is taught wrongly
- Where the control points are — what is taught wrongly
- The family is a symmetry, not a shape — the families
- The weights are a guess the solve believes — grids, and what a survey does
- An average of ellipses is not an ellipse — measuring distortion
- The slope of a field that was measured — measuring distortion
- A long window and a square one — what the numbers refer to
- What another common point buys — what the numbers refer to
- When the edges do not line up — what a machine does with it
- The road is drawn two pixels wide — what a machine does with it
- A boundary that two features share — what a machine does with it
24 August 2026
15 essays on the impossibility, what is taught wrongly, measuring distortion, what each projection optimises, the families, grids, and what a survey does, what the numbers refer to and what a machine does with it
- Impossible in two derivatives, possible in one — the impossibility
- The projections that are beaten on both counts — what is taught wrongly
- A slope is not a shape — measuring distortion
- Not every distortion can be asked for — what each projection optimises
- A net can land on top of itself — the families
- The contour is right and the reading is wrong — measuring distortion
- A grid reference names a square — grids, and what a survey does
- The shape of the valley — what each projection optimises
- Water runs downhill on the ground, not on the page — measuring distortion
- The size at which the second derivative arrives — measuring distortion
- The difference of two coordinates — measuring distortion
- Cuts of the same size in different places — what the numbers refer to
- A mountain is not a buried sphere — what the numbers refer to
- A polygon on a sphere has no outside — what a machine does with it
- The same number of cells, in two shapes — what a machine does with it
23 August 2026
15 essays on paths and directions, what is taught wrongly, the families, measuring distortion, what each projection optimises, grids, and what a survey does, what the numbers refer to and what a machine does with it
- Where the shortest route stops being the only one — paths and directions
- A residual has more than one explanation — what is taught wrongly
- The inverse of the series is not the series of the inverse — the families
- The indicatrix at a point that has none — measuring distortion
- The developable surface was never necessary — the families
- Report the map, not the parameters — what each projection optimises
- A coordinate is the output of a solve — grids, and what a survey does
- The seven parameters have their own uncertainty — what the numbers refer to
- A vector tile has an integer grid — what a machine does with it
- The map depends on where it was cut — what the numbers refer to
- Cells that are rectangles in no coordinate — what a machine does with it
- How far the plumb line bends — what the numbers refer to
- A line has a length only at a scale — what a machine does with it
- Simplification does not commute with the projection — what a machine does with it
- A tolerance is a promise about the picture — what a machine does with it
22 August 2026
15 essays on the impossibility, what is taught wrongly, measuring distortion, what each projection optimises, the families, grids, and what a survey does, what the numbers refer to and what a machine does with it
- Two surfaces with the same curvature — the impossibility
- The rule scored out of sample — what is taught wrongly
- The second derivative is not an invariant — measuring distortion
- When the answer is not in the library — what is taught wrongly
- A coordinate is a number with a width — measuring distortion
- An error ellipse is an indicatrix — measuring distortion
- Every equal-area map is every other one — what each projection optimises
- The net that loses the fewest neighbours — the families
- The average of noisy positions moves — measuring distortion
- The landscape the search walks on — what each projection optimises
- The bound on the body the country is on — grids, and what a survey does
- The line a height is measured along — what the numbers refer to
- A conformal map of a body that is not a quadric — what the numbers refer to
- A real edge has a width — what a machine does with it
- The same data on two grids — what a machine does with it
20 August 2026
15 essays on paths and directions, what is taught wrongly, measuring distortion, the families, what each projection optimises, grids, and what a survey does, what the numbers refer to and what a machine does with it
- The quickest route is not the shortest — paths and directions
- The rule of thumb, scored — what is taught wrongly
- A map does not say what it is — what is taught wrongly
- Two projections that cannot be told apart — what is taught wrongly
- What a careless copy hides — what is taught wrongly
- A projection between two projections — measuring distortion
- Where the series stops being the map — the families
- The condition does not always decide the map — the families
- The third parameter, run — what each projection optimises
- The best grid a country could have had — grids, and what a survey does
- The chain the satellite does not have — grids, and what a survey does
- A chain of transformations does not close — what the numbers refer to
- A conformal map of a body with three axes — what the numbers refer to
- A tilted view has no zoom level — what a machine does with it
- One edge is not an edge — what a machine does with it
19 August 2026
15 essays on the impossibility, what each projection optimises, measuring distortion, the families, what the numbers refer to and what a machine does with it
- Curvature that varies from place to place — the impossibility
- Solving for the map instead of choosing it — what each projection optimises
- The second derivative over a region — measuring distortion
- A conformal map onto a face — the families
- A local model has an order — measuring distortion
- A map with no formula — what each projection optimises
- More faces, less distortion, more cutting — the families
- The aspect has three numbers, not one — what each projection optimises
- The sphere is not the plane at small counts — what each projection optimises
- A map of a body with three axes — what the numbers refer to
- A body with no sea level — what the numbers refer to
- A query is a disc, and a disc is not a cell — what a machine does with it
- A deflection is the slope of a mass — what the numbers refer to
- The address is a curve through the sphere — what a machine does with it
- An edge has no order of convergence — what a machine does with it
18 August 2026
15 essays on what each projection optimises, measuring distortion, the families, what the numbers refer to and what a machine does with it
- A projection written as a condition — what each projection optimises
- Tissot stops at the first derivative — measuring distortion
- Bending and stretching are one failure — measuring distortion
- The globe on a solid — the families
- Three conditions are one too many — what each projection optimises
- A map that cannot be read backwards — what each projection optimises
- The cut has to go somewhere — the families
- The second derivative has its own ranking — measuring distortion
- What a face can preserve — the families
- A coordinate on another body — what the numbers refer to
- An address is an area — what a machine does with it
- The same projection on a different body — what the numbers refer to
- A body that is not an ellipsoid — what the numbers refer to
- Hexagons cannot tile the sphere — what a machine does with it
- A cell system trades area for shape — what a machine does with it
16 August 2026
15 essays on the impossibility, paths and directions, what each projection optimises, what is taught wrongly, measuring distortion, the families, grids, and what a survey does, what the numbers refer to and what a machine does with it
- A direction carried round a loop — the impossibility
- A route that must go round — paths and directions
- The average of two projections — what each projection optimises
- Equal-area on the wrong body — what is taught wrongly
- How many sheets an atlas needs — what each projection optimises
- The indicatrix is a limit — measuring distortion
- The azimuthal family is one function — the families
- The normal section is not the geodesic — what is taught wrongly
- An area on the grid is not an area on the ground — grids, and what a survey does
- Two parameter sets, one transformation — what the numbers refer to
- Zoom is a ladder — what a machine does with it
- A centroid belongs to a plane — what a machine does with it
- A height that is not a length — what the numbers refer to
- What a closed figure cannot see — grids, and what a survey does
- Inside is a claim about the edges — what a machine does with it
15 August 2026
15 essays on what a machine does with it
- A screen map is a pyramid of tiles — what a machine does with it
- The scale of a screen map is not one number — what a machine does with it
- A scale bar is right in one place — what a machine does with it
- The square costs the poles — what a machine does with it
- The pixel is a place with a size — what a machine does with it
- A tile is drawn without its neighbours — what a machine does with it
- The pyramid did not have to be Mercator — what a machine does with it
- A coordinate without its system is not a location — what a machine does with it
- A degree is not a unit of length — what a machine does with it
- Computing an area needs a surface — what a machine does with it
- A straight segment is a claim about a plane — what a machine does with it
- The antimeridian is a cut in the numbers — what a machine does with it
- Nearest is a question about the metric — what a machine does with it
- Reprojecting a raster invents values — what a machine does with it
- The operation decides the coordinate system — what a machine does with it
14 August 2026
15 essays on grids, and what a survey does
- A grid has an origin that is not there — grids, and what a survey does
- What a grid is made of — grids, and what a survey does
- The scale factor of a line — grids, and what a survey does
- The scale factor was chosen — grids, and what a survey does
- The units are part of the coordinate — grids, and what a survey does
- Designing a grid for one region — grids, and what a survey does
- Where two zones meet — grids, and what a survey does
- A grid scaled to the ground is not a map — grids, and what a survey does
- What a tape measures — grids, and what a survey does
- A traverse must close — grids, and what a survey does
- The two ways to spread a misclosure — grids, and what a survey does
- Setting out runs the chain backwards — grids, and what a survey does
- Two grids over the same ground — grids, and what a survey does
- The tolerance decides the model — grids, and what a survey does
- A published coordinate is a result — grids, and what a survey does
11 August 2026
15 essays on what the numbers refer to
- What a coordinate refers to — what the numbers refer to
- The seven parameters, and what each one does — what the numbers refer to
- A datum is fitted to a region — what the numbers refer to
- Where a fit leaves residuals — what the numbers refer to
- Molodensky's shortcut — what the numbers refer to
- When a formula is not enough — what the numbers refer to
- The epoch is part of the coordinate — what the numbers refer to
- Height above what? — what the numbers refer to
- The ellipsoid is a level surface — what the numbers refer to
- A levelled height is not a distance — what the numbers refer to
- The plumb line is not the normal — what the numbers refer to
- The ground is not the grid — what the numbers refer to
- The third coordinate moves too — what the numbers refer to
- The flattening is not a free parameter — what the numbers refer to
- The figure of the Earth was measured — what the numbers refer to
10 August 2026
12 essays on what each projection optimises, the impossibility, paths and directions, the families, measuring distortion and what is taught wrongly
- Fitting the aspect to the region — what each projection optimises
- How small is flat enough — the impossibility
- The route with no shortest path — paths and directions
- Choosing for a line, not a region — what each projection optimises
- Flying a curve in straight legs — paths and directions
- The conic is the whole family — the families
- The curvature of the Earth is not one number — the impossibility
- Where the worst point is — measuring distortion
- Conformal does not mean the angles are right — what is taught wrongly
- Distortion has a direction — measuring distortion
- Where a pseudocylindrical puts its error — the families
- Grid north is not north — the families
5–8 August 2026
34 essays on the families, what each projection optimises, the impossibility, paths and directions, measuring distortion and what is taught wrongly
- Cylinders, cones and planes — the families
- Every projection minimises something — what each projection optimises
- No map is faithful — the impossibility
- The shortest route is not straight — paths and directions
- Tissot's indicatrix — measuring distortion
- Web Mercator is not conformal — what is taught wrongly
- Mercator against Peters — what is taught wrongly
- What a standard parallel buys — the families
- What can be unrolled — the impossibility
- What survives a change of coordinates — measuring distortion
- Which projection is best — what each projection optimises
- Why Mercator exists — paths and directions
- Compromise projections — what each projection optimises
- The aspect is a free choice — the families
- The gnomonic companion — paths and directions
- The projection that shows true size — what is taught wrongly
- The trade-off is two lines — the impossibility
- The two ways a map is wrong — measuring distortion
- Chebyshev's criterion — what each projection optimises
- Measuring instead of naming — measuring distortion
- The Earth is a sphere, and when it is not — what is taught wrongly
- The great-circle vertex — paths and directions
- Total curvature and the scale rule — the impossibility
- Transverse Mercator and the series that computes it — the families
- Geodesics on the ellipsoid, and why they are hard — paths and directions
- Geodetic against geocentric latitude — what is taught wrongly
- Giving up continuity — what each projection optimises
- Measuring curvature from inside — the impossibility
- Scale distortion is the third failure — measuring distortion
- UTM and the zone system — the families
- Datum shifts dwarf projection errors — what is taught wrongly
- Distortion over a region — measuring distortion
- The projections that gave up being one thing — the families
- The plate carrée, the projection nobody chooses — what is taught wrongly