# Phase to elevation vs phase to height

Hello
I Have this DEM and I am wondering which one is correct
by using Phase to elevation or phase to height
it is the same area with same data just one by elevation and the other is to height
if you look well there is a deference between ?

Thank you

phase to height converts the unwrraped phase to the heights in the radar coded system so you need ground points with known altitude to converts your results into real ground values.
phase to elevation uses a digital elevation model in reference height calculation. This operator converts interferometric phase to digital elevation map.
Both operators are correct.

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Thank you Mr,
So in the phase to height how do I add GPCs directly in SNAP or there is another way to do?

and you think both operators are good to generate a DEM?

hi, have you sovled this problem? To add GPSs to get DSM from the results of phase to height.

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Smail, did you find any ways to solve it? Or any other know how to do it?

if you mean adding GPSs no I didn’t solved it. But if you want to generate DEM it’s better to use phase to elevation as they said the experts above .

I am using phase to elevation, but I have obtained kind of ondulation in the estimated height

Would you please to share screenshot, if that possible to understand more the matter,

Which DEM, did you use?

Seemingly the result referred to not well unwrapped phase, and this most probably comes back to the low coherent between the two acquisitions, jump phase is the case, but, would you please to check up the coherence map,

By the way, would you please to remove the same redundant topic you created.

I have used th ophase to elevation with the srtm as reference. To be honnest, I still don’t know what the output, iT should be the surface ( top of buildings, top of trees) ?

Which SRTM 1sec or 3sec,?

This DEM is created by this procedure is DTM, Digital Terrain Model, for two reasons the first one The available DEM DTM is used to correct the one is being created, so the features above the surface are already removed, While DSM , Digital Surface Model , could be created, in case convert phase to height by providing the GCP’s of the features.

Thanks, It is the SRTM 3sec. Phase-to-elev provides the DTM and to get the DSM, I have to make a summation of both outputs of phase to elev and phase to height ?

Let’s solve one by one to figure out the reason of undulating phase , firstly please use SRTM 1sec,

As I explained getting DSM, phase to heigh you should have GCP ,

Thank you
I have reestimateed the dtm using the 1 second SRTM. So now I will look for the ground control points for the dsm. It is the estimated DTM map. It is more noisy than the preveous one, but it is normal, I have used a single baseline… But we see less the effect of ondulation and it is mainly due to the unwrapping step… But what I don’t like and I like to share with SNAP experts is the range of estimated hegits, it is -400 and 1400…

What are the parameters applied in the unwrapping step?

Following is good example of SNAPHU parameters change to create DEM,

Source of the post

statistical cost mode : DEFO
Inirtial method: MCF
number of rows: 10
number of columns: 10
number of processing: 4
row overlap: 0
columns overlap: 0
Tile cost treshold: 500

Please take a look at my previous post, I already edited it,