Comparability is not a property waiting inside urban cases; it is an achievement produced through decisions about scale, duration, field boundaries, evidential form and the terms under which difference is allowed to remain legible. A neighbourhood, a mobility trace, a physiological response or a continental comparison becomes comparable only after an apparatus has defined what counts as the same kind of observation across changing circumstances. This does not make comparison arbitrary. It makes its conditions inspectable. The methodological problem is therefore not how to eliminate variation but how to distinguish productive variation from uncontrolled incompatibility. Urban knowledge becomes stronger when the operations that stabilise equivalence are visible enough to be tested, revised or refused.

Scale is one of the first sites at which this instability appears. Residential segregation changes when the analytical unit moves from home address to daily activity space; neighbourhood change looks different when official boundaries are replaced by situated territorial knowledge; affective exposure changes when environmental contact is reconstructed through actual trajectories rather than fixed buffers. Spatial scale is thus not simply a cartographic resolution. It determines which relations can enter the object. The same condition may be legible as a bodily event, a street configuration, a neighbourhood pattern or a metropolitan distribution, but the passage between these levels is never innocent. Every rescaling retains some relations, suppresses others and may generate an object that did not exist at the preceding level. Time produces an equivalent transformation. A cross-sectional measure, an intensive mobile sequence, a repeated visit and a multi-year longitudinal comparison do not merely observe the same urban world for different lengths of time. They constitute different epistemic objects. Movement introduces succession; recurrence distinguishes durable patterns from transient conditions; longitudinality allows institutional and morphological change to become analytically separable. Mobile methods make this especially visible because exposure ceases to be attached to a single location and becomes an ordered relation among person, environment and duration. The city appears not as a container but as a sequence of encounters whose evidential status changes with repetition, latency and return.

Evidence likewise carries its own geometry. Street-view imagery offers scalable visual coverage but uneven temporal and geographic availability; social-media traces enlarge observational fields while embedding severe sampling biases; positioning data produce fine spatiotemporal resolution without explaining experience; physiological data register bodily response but remain difficult to attribute to specific urban stimuli; video preserves behavioural sequences while raising interpretive and ethical problems. None of these sources is simply richer or poorer than another. Each establishes a particular relation between visibility and blindness. Multimodal research becomes rigorous when these asymmetries are treated as constitutive rather than corrected into a false common measure. Translation between evidence forms should therefore record what is preserved, transformed, inferred and lost.

The comparative field is also politically produced. Urban theory cannot claim openness merely by increasing the geographic diversity of its cases if the conceptual vocabulary through which those cases become intelligible remains fixed elsewhere. Situated comparability requires symmetry not of sameness but of epistemic standing: local categories, archives, histories and representational practices must be capable of modifying the comparative framework itself. Methodological transfer then becomes a test rather than a replication exercise. What travels unchanged can be identified as robust; what requires adjustment becomes conditionally transferable; what remains locally meaningful establishes a boundary condition; what fails to translate is evidence of non-equivalence rather than methodological embarrassment. Socioplastics can operationalise this problem as an infrastructure for comparative knowledge rather than a universal descriptive system. Its urban corpus can preserve the chain from embodied encounter to photograph, map, video, text, route, numerical record and derived claim while retaining scale, date, field, provenance and transformation history. Open science matters here because openness is not exhausted by public access. A reusable urban archive must expose the conditions under which evidence was produced, the operations through which one format became another, and the limits within which comparison remains defensible. Serial fieldwork, longitudinal return and distributed media then become complementary devices for maintaining difference while enabling relation. Situated comparability therefore replaces the fantasy of a frictionless urban dataset with a more demanding proposition: knowledge becomes comparative when its transformations remain visible. The strongest urban method is not the one that makes every place fit the same matrix, but the one that can state precisely where equivalence holds, where adaptation begins, where evidence changes status and where comparison should stop. This adds to Socioplastics a rigorous epistemic principle for moving between body and continent, event and archive, observation and dataset: comparison as a traceable production of relations rather than a presumption of sameness.