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Cape Coral Ground Subsidence Investigation Series
By Jose Alberto Suarez | Evidence reviewed through October 12, 2026

Do the newest satellite observations show that Cape Coral’s previously mapped deformation continued into 2026?

Since Part 5, our investigation has completed two important checks: a three-pair processing-consistency test and a geographic comparison between six recent InSAR pilot products and historical OPERA displacement maps.

The results strengthen one part of the evidence while leaving another question open.

The historical maps show a strongly recurring regional pattern. The August–September 2026 pilot does not yet reproduce that pattern consistently enough to establish continued subsidence.

Understanding that distinction is essential to interpreting the latest findings.

What OPERA adds to the investigation

NASA’s Observational Products for End-Users from Remote Sensing Analysis—OPERA—provides satellite-derived surface-displacement products. Its DISP-S1 products use Sentinel-1 radar observations to measure displacement along the satellite’s line of sight. These measurements are relative and are not automatically equivalent to vertical sinking. NASA/JPL: OPERA displacement products

Our broader review includes 34 downloaded OPERA products across two satellite tracks. The new geographic comparison uses a study-era subset of 20 products, covering:

• Track 48: July 5, 2016–February 4, 2022.

• Track 121: October 8, 2016–May 4, 2022.

These historical maps were compared with the approximate deformation area illustrated in the 2023 Cape Coral study by Aslan and colleagues, and with our six pilot intervals from August–September 2026.

The periods matter. The OPERA measurements used here do not cover the pilot dates. This is a comparison of spatial patterns across different periods, not a same-date validation of the pilot.

The historical pattern appears on both tracks

To compare the maps on a common geographic basis, the analysis grouped observations into 500-meter blocks. At the principal pilot coherence threshold of 0.30, 612 blocks had sufficient coverage across both historical maps and all six pilot products.

Across those blocks, the historical OPERA maps had a spatial correlation of approximately 0.89.

In plain language, locations showing relatively greater movement away from the satellite on one historical map generally showed a similar pattern on the other.

That supports the presence of a recurring historical regional deformation pattern, broadly consistent with the area highlighted in the published Cape Coral investigation.

It does not mean “89% certainty,” prove a particular cause, or establish an exact vertical settlement rate. The analysis is descriptive, and neighboring blocks are not statistically independent.

The study-area outline also requires care: it was approximately aligned from the published figure. It is not an authoritative hazard boundary or a parcel-level map.

What the six 2026 comparisons show

The pilot now includes these intervals:

• August 1–13.

• August 13–25.

• August 25–September 6.

• August 1–25.

• August 13–September 6.

• September 6–30.

These are six combinations of five acquisition dates, not six independent confirmations.

The strongest resemblance to the historical OPERA pattern occurs in the August 13–September 6 interval. Its spatial correlations with the two historical maps are approximately 0.55 and 0.61.

The next interval, September 6–30, shows an opposing pattern, with correlations of approximately −0.46 and −0.55.

Meanwhile, the August 1–25 comparison—which shares no acquisition date with September 6–30—has weak correspondence with the historical maps, approximately 0.18 and 0.06.

The practical finding is that the pilot’s apparent movement changes between intervals. It has not yet produced a consistently repeated pattern demonstrating ongoing subsidence.

Why September 6 deserves closer examination

September 6 is the ending observation in one comparison and the starting observation in the next.

An atmospheric or other acquisition-specific contribution associated with that scene could therefore appear with opposite signs in the two results. Atmospheric differences are a recognized source of apparent deformation in radar interferometry. ASF: InSAR interpretation limitations

This is a possible explanation, not an established diagnosis. Real transient or seasonal movement also remains possible.

The observed reversal tells us where to investigate next. It does not, by itself, distinguish among those explanations.

The closure test passed—what does that establish?

The completed three-pair test compared:

August 13–25 + August 25–September 6
against
August 13–September 6

The reviewed closure record reports:

• 283,362 pixels meeting the test’s three-product coherence criteria, representing 52.72% of the area-of-interest pixels.

• A median closure residual of approximately +0.019 millimeters.

• A robust residual spread, measured by normalized median absolute deviation, of approximately 0.904 millimeters.

• 91.1% of tested residuals within ±2 millimeters.

These are encouraging measures of consistency between the processed products.

They are not measurements of settlement or proof of millimeter-level ground-motion accuracy. Shared atmospheric contributions and other acquisition-related effects can also satisfy closure. The successful test strengthens confidence in processing consistency while leaving physical interpretation unresolved.

Regional movement and local differences are different questions

The OPERA review also clarified an important issue at NW 16th Terrace and the L-4820 well location.

Comparing a site with nearby ground asks whether it behaves differently from its surroundings. It does not necessarily reveal movement shared by the entire surrounding region.

Imagine two neighboring areas settling together. Their difference could remain small even though both are moving.

Our sensitivity checks found that removing a broad spatial gradient substantially reduced L-4820’s apparent local contrast. NW16 retained a smaller negative contrast under the tested models.

Those results do not establish that L-4820 is stable or that NW16 has a confirmed vertical settlement rate. Removing a broad trend can remove genuine regional deformation as well as measurement error.

The recent pilot comparisons also show changes in direction at both locations. These are neighborhood-scale observations, not measurements of individual roads, foundations, or buildings.

What the evidence supports today

The findings support three distinct conclusions:

Historical regional deformation: The two OPERA maps show strong spatial agreement, supporting a recurring historical pattern consistent with the published subsidence interpretation.

Recent processing consistency: The three-pair closure test passed, strengthening the technical basis for further analysis.

Continued 2026 subsidence: The six pilot comparisons remain inconsistent. They do not yet establish that the historical deformation persisted into August–September 2026.

The satellite results also do not establish groundwater pumping as the cause of a particular feature, determine the effectiveness of roadway repairs, or resolve property-specific safety questions.

The next test should compare the same dates

The clearest next step is to process a historical interval through our pilot that is also covered by OPERA.

Using comparable dates, reference areas, and measurement directions would test whether the pilot can reproduce the historical product under more closely matched conditions.

Additional work should examine the September 6 acquisition, extend the pilot time series, and evaluate intervals that do not share images. Independent surveying or other ground measurements would provide a separate check on physical movement.

Part 6 therefore marks meaningful progress: we now have a stronger historical comparison and a successful consistency test. The remaining task is to establish which recent signals represent ground movement and which reflect the limits of the observations.

Read the complete series at Coral Coast Developers — Insights.

Sources & Documentation

• Cape Coral: Sentinel-1 Pilot / OPERA / Aslan Cross-Reference, computed October 12, 2026. Supporting materials include the comparison maps, 612-block dataset, source-raster hash checks, and sensitivity results.

• Cape Coral August–September 2026 InSAR Three-Pair Closure Record, October 12, 2026.

• OPERA spatial-gradient and temporal-comparison records, reviewed October 12, 2026.

• Aslan et al. (2023), Cape Coral ground-deformation study. Published paper.

• NASA/JPL, OPERA DISP Product Suite.

• Alaska Satellite Facility, InSAR Product Guide.

Editorial & Technical Disclosure

This installment presents an independent initial review of the available evidence. The project’s analyses have not undergone independent peer review. Correlations, closure residuals, and reference-sensitivity tests do not establish vertical settlement, causation, or property safety. Historical annualized measurements and short-interval pilot measurements use different periods and units and should not be compared as equivalent rates. AI tools assisted with analysis and editorial preparation. The header is a conceptual illustration, not a displacement map.