TRY THE ASSUMPTIONS

The Neighbourhood Watch

Computed synthetic demonstration. No HSI benchmark data, no neural network and no invented accuracy.

Shared test-patch support
Coordinate-only 1NN accuracy
Field spatial autocorrelation
Distance to nearest training centre
1. Synthetic class map

Green = class 0 · Gold = class 1

2. Split and example patch supports

● Blue = train · × Orange = test
Grey = buffer exclusion · Pale edge = no full patch

Same field, same label budget, different test geography

Matched training budget, different test geography
SplitTrainRetained testShared support1NN accuracy

What this experiment can and cannot show

Training labels are used only by a Euclidean coordinate-only nearest-neighbour classifier. Ties use the smallest row-major training index. Patches are audited geometrically but never supplied to this learner. Score differences cannot be attributed causally to patch overlap. Smoothing changes the generating field; changing patch width changes which interior centres are eligible. At fixed settings the random and blocked rows use identical field values, class labels and training counts before buffering, but different training locations and test populations.

Buffer b excludes a test centre if its Chebyshev distance to any training centre is ≤b. Setting b=p−1 eliminates all shared raw support for equal odd-width p patches. It does not eliminate longer-range dependence. No padding, fitted feature transforms, spectral data, hyperparameter selection or test-label-based training is used. Moran’s I uses unit weights for both directions of horizontal/vertical adjacency on the scalar field. It is descriptive; no p-value is calculated. Next seed varies the generated scene and random split together, not only optimiser initialisation.

Download the experiment source, CLI and tests (ZIP)