Velocity measurement techniques
Day 1
Day 24
Feature Retracking
100 mDay 1 Day 24
10 m
Day 1 Day 24
10 m
InSAR Speckle Retracking
1
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21
x
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Azimuth Corrections• Azimuth pixel spacing goes as prf as well as orbit height, terrain elevation, look angle
and latitude. Consequently two slightly different orbits will have slightly different azimuth spacings given approximately by
For a purely vertical separation, corresponding to about 14 m in height, the azimuthDisplacement will change about 3 parts in 10^6. There will be an accumulating Error such that after about 500 km, the azimuth will be incorrect by a measurable .3 pixels.
Ionospheric Streaks
• For C-band Radarsat, A SAR footprint is illuminated for about 0.5 sec. The satellite travels about 3.5 km.
• If the integrated electron density changes along the line of sight, while the footprint is illuminated, then the phase history built from about 600 pulses will be corrupted
• The consequence is incorrect azimuth placement.
• The effect is smaller in the range direction.
Streaks
• Idea tested by – Comparing streak density with ionospheric
activity– Simulations using a phase screen– Relationships to streak density and magnetic
poles
Option 1 – azimuth offset, range phase; azimuth offset, range offsets; ascending descending range;
Option 3 – only ascending descending range products.
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• Plug Vr into Vf and differentiate along flow direction
We assume that several terms are small: change in look direction is small; changes in flow directions are small for large glaciers over 0-30 km, Large scale strain rates not effected by surface slope.