# Phase to Displacement Units?

Thank you for your explanation. the temporal baseline is about 1 year (master 20160604 and slave 20170611). based on the following equation : Φdefo = 4ΠvΔt/λ
Φdefo : displacement-related phase
v : surface displacement rate
Δt : temporal baseline
λ : wavelength
small deformation rates v requires long temporal baselines Δt to make sure that the displacement phase signal ϕdefo raises above the noise floor. therefore if also the temporal baseline is high, there is decorrelation. I am struggling to choose pair of image for Insar to measure slow displacement such as land subsidence

yes, that’s a dilemma. You need short temporal baselines for high coherence but long temporal baselines for subtle displacements.

What is the amount of displacement you expect in your area? If the quality of the interferogram is good, InSAR can measure at the sub-centimeter level.

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the expected amount of displacement is about 5 to 10 cm. I am planning to reduce the temporal baseline but another constraint is that the area is covered by snow from about December to April. I afraid about the noise created by the snow

With such large displacements you should also be fine witg a 12 or even 6 day pair from outside the snow season.

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After we convert the LOS displacement into vertical displacement, can we create a displacement contour map out of the phase-to-displacement map?

not in SNAP, but QGIS offers to display rasters as contours: https://www.youtube.com/watch?v=0oyZ0gwLKXY

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Dear Johngan
I need the source for the formula you mentioned about the vertical displacement, please.
I also need the formula for the horizontal displacement too, if possible.
Thank you.

There is not just one formula, many approaches exist.

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Dear ABraun

I read this comment for you previously, in which you wrote that there are many approaches. I was going to ask you if you may refer the most popular one, please?. And do we always need in-situ measuremnets or this analytic way is quite enough?.

All the best

Sorry I can’t tell which is the most popular. The simple ones are often less correct.
A compromise between complexity and accuracy is used in this study by @mdelgado: Remote Sensing | Free Full-Text | Measuring Urban Subsidence in the Rome Metropolitan Area (Italy) with Sentinel-1 SNAP-StaMPS Persistent Scatterer Interferometry

In situ measurements help to assess the accuracy of your calculation so that you can report which error range has to be expected.

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Thank you so much.

Dear ABraun,

I am searching for an article or a tutorial that explains the practical steps of any appoach of LOS decomposition (I mean like the usual way you do in the tutorials), but I found nothing. Can you help me with this please?. Thank you.

All The Best

Hii I am very new in this field, please let me know from where we will get the incidence angle?

This master’s thesis is very helpful too.

https://repository.tudelft.nl/islandora/object/uuid%3A9bea6424-c03b-4e0b-95b9-cc6871959f2d

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Thank you!

Thank you Sir.

Hello, thank you very much for your explanation, I just have a question…How can I get these ‘‘accurate GPS measurements’’? please.(any useful link or document)

Hi jam1,

I do not know what your research topic is and what results you are trying to validate.

Accurate geodetic GPS measurements for validating results derived by Remote Sensing are usually taken by the person who carries out the research (in this case its you). If you are unable to get those GPS measurements, maybe a government body (the country you are working in) used GPS receivers over the same AOI you are working on and made those data available.