# LOS to horizontal displacement

Hi all,

I want to know how can I convert the LOS displacement to horizontal displacement in glacier. I know the tool is not available yet in SNAP. But if any one has done this by using the LOS displacement map generated from SNAP please share on how is it possible?

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to my understanding, this depends on the movement direction of the glacier and the pass (ascending or descending) of the image.
I donâ€™t think it is possible in SNAP without generating whole DEMs of the glacier at two times (which isnâ€™t less challenging).

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Often the assumption is surface-parallel flow so a DEM is needed to derive that as well.

thank youâ€¦ yes, i think using an external DEM and assuming surface parallel flow, horizontal displacement can be calculatedâ€¦ i just know the theoryâ€¦ if someone who has done practically would be of helpâ€¦

So for external DEM, if i use SRTM DEM (even though precise DEM would be aspired) do you know how I can derive the horizontal displacement?

The formula to be used is:

where Îľ is the angle of the flow direction, Ď† of the surface slope and Ď‘ is the local incidence angle respect the range
direction.

I do not know how to derive the term Îľ. Any help shall be appreciated.

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You need to determine the flow direction vector â€śby handâ€ť by examining the glacier geometry and then assume either horizontal or surface-parallel flow.

thank you so muchâ€¦ so its going to be only in the line that I draw by handâ€¦ like the centerline of the glacierâ€¦ than I should make the assumption and make the calculation??