I would like to ask about the relationship between the sign of phase difference and the corresponding ground movement when performing interferometric analysis in SNAP.
(I am Japanese and not a native English speaker, so I apologize if this is unclear.)
For example, let us assume that an earthquake occurred on April 13, 2026.
The pre-earthquake image was acquired on April 2, 2026 (hereafter, Image ①),
and the post-earthquake image was acquired on April 14, 2026 (hereafter, Image ②).
If the calculation is performed with Image ① as the primary image and Image ② as the secondary image, is my understanding correct as follows?
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When the phase difference (phase) is negative: the ground moves toward the satellite (i.e., closer to the satellite line of sight)
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When the phase difference (phase) is positive: the ground moves away from the satellite (i.e., farther from the satellite line of sight)
Conversely, if the calculation is performed with Image ② as the primary image and Image ① as the secondary image, is it correct that the interpretation is reversed?
That is:
-
When the phase difference (phase) is negative: the ground moves away from the satellite
-
When the phase difference (phase) is positive: the ground moves toward the satellite
Is this understanding correct?
Thank you very much.