When satellite analysis should be combined with field inspection

Satellite analysis covers wide areas, reaches years into the past, and treats every location consistently — but observes only surface movement of radar-visible features. Field inspection observes condition directly, below-ground and in detail — but only where and when someone goes, at a cost that scales linearly with sites visited.

The economics are therefore complementary: use the satellite layer to decide where field effort is justified, and use field findings to interpret what the satellite layer means.

Satellite results that should prompt engineering involvement include: movement rates clearly above local background, especially if accelerating; differential movement across a single structure or between a structure and adjacent ground; movement onset correlating with nearby construction, dewatering, or extraction; and flagged assets that are safety-critical regardless of signal strength. Conversely, field observations of distress at a site the satellite record shows as long-stable are themselves diagnostic — pointing toward causes that develop faster than the acquisition interval, or that are invisible to radar.

The strongest monitoring programmes close the loop: satellite screening establishes the baseline and ranks attention; targeted inspection and instrumentation (levelling, GNSS, crack monitoring) validate and localise; and continued satellite updates track whether interventions changed the trend. Each data source covers the others' blind spots, and the documentation trail — measured, consistent, independent — is exactly what regulators, insurers, and asset committees want to see.