CLASSICAL DIFFERENTIAL INSAR

• Classical differential InSAR uses image pairs to reveal ground deformation that has occurred for the specific time span between the first and second image date
• In a basic differential interferogram the ground displacement is indicated in coloured fringes (displacement isolines); each fringe represents a deformation of 2.8 cm.  
• Deformation can be shown as a map of absolute displacements by converting the basic differential interferogram using phase unwrapping techniques
• Advantage: Interferograms can be created with only two images
• Limitation: Classical InSAR limited by atmospheric influence, temporal decorrelation (reduction of coherence due to changes in the nature of the ground, e.g. vegetation growth) and phase unwrapping generally restricted to higher coherence regions

Interferogram 1 Showing displacement signal

Interferogram 2 Notable atmospheric influence

Interferogram 3 Temporal decorrelation