Earth observation workspace

Applications library

Twelve NISAR application topics. Each entry separates what a radar time series can genuinely show from what needs a different measurement or an independent source.

Capability labels used here

Learning resource

An educational topic. The repository explains what this kind of observation can show. Nothing on this topic is installed, processed for a real case, or validated.

Exploratory case

Real observations for this topic are installed and can be inspected. Interpretation still needs independent checks, and no scientific claim is settled.

Validated for this case

A documented review exists for one specific case: reviewer, scope, evidence and limitations. The label applies only to that case, never to the topic in general.

Every topic below is a Learning resource. This repository holds no validated real case for any of them, so no topic is labelled exploratory or validated. Using the software successfully is not the same as validating an interpretation.

6 of 12 topics need interferometric phase or offset tracking for their central measurement. This pipeline produces GCOV backscatter and differences, so those topics are explicitly out of reach here.

Topic 01

Flooding

Learning resource

Open water usually returns much less radar energy than the surrounding vegetation or built-up ground, so a date pair around an event can show a large drop in backscatter over inundated ground.

Possible exploration

  • Compare pre-event and post-event backscatter for the same track, frame and polarization.
  • Look at where the drop is coherent across neighbouring pixels rather than isolated speckle.
  • Check whether the low-return area follows terrain, channels or field boundaries.

Interpretation limits

  • A backscatter drop is not a flood map; smooth dry sand, calm water, roads and radar shadow can look similar.
  • Dense vegetation can hide water below the canopy, so under-detection is expected.
  • Wind roughening the water surface raises backscatter and can hide the flood signal.
  • The repository reports a measured difference. It does not classify an event or estimate depth.

Methods a real study would still need

  • Independent reference imagery or ground reports for the same dates.
  • A documented threshold policy and a sensitivity check across thresholds.
  • Terrain and land-cover context to separate water from other low-return surfaces.

Source document: nisarflooding.pdf· fingerprint not recorded in this repository

Central measurement can be approached with backscatter change, with the limits above.

Topic 02

Surface water and soil moisture

Learning resource

Soil moisture changes the dielectric properties of the surface and therefore its radar backscatter, and open water bodies behave very differently from wet soil.

Possible exploration

  • Track how backscatter in a fixed area changes between acquisitions in a season.
  • Check whether the change is consistent across polarizations.
  • Compare the timing of changes with known rainfall or irrigation periods.

Interpretation limits

  • Quantitative soil-moisture retrieval needs calibrated models, field data and correction for surface roughness and vegetation.
  • The repository computes backscatter and differences; it does not retrieve volumetric soil moisture.
  • Surface roughness and vegetation change the signal independently of moisture.

Methods a real study would still need

  • A physical scattering model with local calibration.
  • Field measurements for validation.
  • Correction for vegetation cover and surface roughness.

Source document: NISARwater.pdf· fingerprint not recorded in this repository

Central measurement can be approached with backscatter change, with the limits above.

Topic 03

Coastal regions

Learning resource

Coastal zones combine water, wet sediment, vegetation and infrastructure, and radar is sensitive to all of them at once.

Possible exploration

  • Follow shoreline and intertidal backscatter through a tidal cycle if acquisitions allow.
  • Look for persistent change near river mouths or eroding stretches.
  • Compare low-tide and high-tide acquisitions rather than arbitrary dates.

Interpretation limits

  • Tides, wind and waves change the surface between acquisitions and can dominate the difference.
  • Shoreline position from a coarse grid is not a surveyed coastline.
  • Wet sand and shallow water can produce ambiguous returns.

Methods a real study would still need

  • Tide and weather records for each acquisition time.
  • Higher-resolution shoreline reference data.
  • A documented protocol for separating tidal variation from lasting change.

Source document: NisarCostalRegion.pdf· fingerprint not recorded in this repository

Central measurement can be approached with backscatter change, with the limits above.

Topic 04

Mountain glaciers and snow

Learning resource

Glacier surfaces change brightness with snow cover, melt and roughness, and their motion is measurable with interferometry or offset tracking rather than single-date backscatter.

Possible exploration

  • Compare backscatter over a glacier between seasons to see the snow and melt cycle.
  • Identify areas whose brightness changes repeatedly with the season.

Interpretation limits

  • Glacier velocity is not obtainable from GCOV backscatter differences.
  • Steep terrain causes layover and shadow that change with viewing geometry.
  • Snow wetness changes the signal strongly and is not the same as mass balance.

Methods a real study would still need

  • Interferometry or offset tracking for motion.
  • Elevation models for terrain correction.
  • A glaciological interpretation by a specialist.

Source document: NisarAPPGLacier.pdf· fingerprint not recorded in this repository

Central measurement needs interferometry; backscatter change alone is insufficient.

Topic 05

Landslides

Learning resource

A landslide changes surface cover and geometry abruptly, which can appear as a backscatter change between a pre-event and post-event acquisition.

Possible exploration

  • Compare the same area before and after a known event date.
  • Check that the changed area matches a slope rather than flat ground.
  • Look for a change that persists into later acquisitions.

Interpretation limits

  • Backscatter change locates a difference; it does not identify a landslide mechanism.
  • Vegetation growth, harvest and construction produce similar changes.
  • Slow-moving slopes need interferometric methods, not backscatter differences.

Methods a real study would still need

  • Interferometry or pixel offset tracking for slow deformation.
  • Slope and geology context.
  • Event records to anchor the date pair.

Source document: nisarLandslide.pdf· fingerprint not recorded in this repository

Central measurement can be approached with backscatter change, with the limits above.

Topic 06

Volcanoes

Learning resource

Volcanic surfaces change with eruptions, ash, lava and hydrothermal alteration, while magma movement produces ground deformation that requires interferometry.

Possible exploration

  • Compare backscatter on the edifice before and after a documented eruption.
  • Track seasonal snow and alteration patterns on the summit.

Interpretation limits

  • Volcanic unrest cannot be inferred from backscatter change alone.
  • Deformation requires InSAR time series and atmospheric correction.
  • Ash fall and lava flows need to be distinguished with independent information.

Methods a real study would still need

  • Interferometric time series for deformation.
  • Thermal or optical imagery for thermal anomalies.
  • Volcano observatory records.

Source document: nisarmonitoringVolcan.pdf· fingerprint not recorded in this repository

Central measurement needs interferometry; backscatter change alone is insufficient.

Topic 07

Sinkholes

Learning resource

Subsidence before a collapse is a millimetre-to-centimetre ground motion, which is a phase measurement rather than a brightness measurement.

Possible exploration

  • Compare backscatter where a collapse has already been documented.
  • Look for surface change around known karst areas.

Interpretation limits

  • Sinkholes cannot be predicted from this pipeline.
  • Small precursors are far below what a backscatter difference can resolve.
  • Coherent InSAR requires stable scattering, which vegetation and excavation remove.

Methods a real study would still need

  • InSAR deformation time series with atmospheric correction.
  • Geological and hydrological context.
  • Ground surveys or borehole data.

Source document: nisarsinkhole.pdf· fingerprint not recorded in this repository

Central measurement needs interferometry; backscatter change alone is insufficient.

Topic 08

Terrestrial permafrost

Learning resource

Thaw changes soil moisture, surface roughness and vegetation, and can cause ground subsidence that is again a phase measurement.

Possible exploration

  • Track seasonal backscatter cycles in permafrost terrain.
  • Compare the same tundra area across thaw seasons.

Interpretation limits

  • Active-layer thickness is not measured by backscatter differences.
  • Freeze-thaw transitions change the signal strongly and quickly.
  • Subsidence requires InSAR and careful correction for vegetation.

Methods a real study would still need

  • InSAR time series for subsidence.
  • Soil temperature and active-layer monitoring data.
  • Land-cover classification.

Source document: nisarterrestialperma.pdf· fingerprint not recorded in this repository

Central measurement needs interferometry; backscatter change alone is insufficient.

Topic 09

Plate tectonics and earthquakes

Learning resource

Coseismic and interseismic deformation are measured from interferometric phase, not from backscatter brightness.

Possible exploration

  • Compare backscatter over a rupture zone where surface material actually changed.
  • Use the installed site to inspect acquisition geometry and coverage over a tectonically active area.

Interpretation limits

  • Ground displacement in centimetres is not derived by this pipeline.
  • Large gradients cause phase decorrelation and unwrapping difficulty.
  • Backscatter change after an earthquake mixes damage, dust and vegetation effects.

Methods a real study would still need

  • Interferometric processing (unwrapped phase, deformation maps).
  • Elastic dislocation or fault models for interpretation.
  • GNSS or survey data for validation.

Source document: nisarEarth.pdf· fingerprint not recorded in this repository

Central measurement needs interferometry; backscatter change alone is insufficient.

Topic 10

Human-induced earthquakes

Learning resource

Induced seismicity studies relate small ground motions to injection or extraction activity, which needs dense deformation measurements and operational records.

Possible exploration

  • Inspect coverage and acquisition cadence over an area with documented induced events.

Interpretation limits

  • Attributing seismicity to human activity requires operational data this repository does not hold.
  • The deformation signals are small and require InSAR time series.
  • Statistical association is not proof of causation.

Methods a real study would still need

  • InSAR time series at high temporal sampling.
  • Injection and extraction well records.
  • Seismicity catalogues.

Source document: nisarinductedearthquake.pdf· fingerprint not recorded in this repository

Central measurement needs interferometry; backscatter change alone is insufficient.

Topic 11

Natural and manmade hazards in Texas

Learning resource

A regional overview covering hurricanes and flooding, subsidence, oil and gas activity and coastal change in one state.

Possible exploration

  • Pick one documented hazard in the region and inspect a matching acquisition pair.
  • Compare urban subsidence areas using InSAR where products are available.

Interpretation limits

  • A regional overview is not a hazard assessment for any specific location.
  • Each hazard type needs its own method; one threshold map does not cover them all.
  • Hurricane effects mix wind damage, flooding and debris.

Methods a real study would still need

  • Per-hazard processing chains.
  • State and local records for event dates.
  • InSAR for subsidence.

Source document: nisarManmadeHasardTexas.pdf· fingerprint not recorded in this repository

Central measurement can be approached with backscatter change, with the limits above.

Topic 12

Disaster damage assessment

Learning resource

Damage assessment compares pre-event and post-event observations of the built environment, ideally with reference imagery and field verification.

Possible exploration

  • Compare a city block's backscatter before and after a documented event.
  • Check whether changes cluster along streets, rivers or construction sites.

Interpretation limits

  • The repository does not produce a damage assessment or a damage grade.
  • New construction, demolition, vehicles and vegetation produce similar changes.
  • Radar alone cannot distinguish structural damage from debris or cleanup.

Methods a real study would still need

  • Very-high-resolution optical reference imagery.
  • Field or authority damage reports.
  • Building-footprint GIS data.

Source document: nisarDisaster.pdf· fingerprint not recorded in this repository

Central measurement can be approached with backscatter change, with the limits above.