How to have a DEM for plant height

[laura_p]

Hello everyone,

 

I'm here to post a very basic question about DEMs.

 

Can a DEM be derived only with Lidar\Radar technologies? Or are there ways to elaborate a DEM also from optical?

I am working on crop classification and it would be extremely useful for me to be able to derive plant height from the optical data I'm working with (both Landsat8 and Sentinel2).

 

Thank you for your attention,

Laura

[Art409]

Hi Laura:

 

You want to calculate tree heigths? Or just want a DEM?

Some info now:

 

Optical data can't go below trees or any other coverage.

You just can use patches with crear view o terrain to extract DEM

 

LIDAR can reach the ground going trough "holes" between foliage, in a way that we can ASSume the last echo as a terrain echo.

Very dense foliage don't allow lidar reach ground.

 

Radar... (ouch!) I'n out of date about SAR new satellites, or aerial ones., but:

REMEMBER, inside the SAR minimal data (let's call it a PIXEL, for now) you got a lot of responses added from everithing that reflect te signal.

 

Note: Landstat 8 is no good for stereo, so  LANDSAT8 discarded for DEMs

 

Art

Edited September 30, 2016 by Art409

[mamadouba]

The distinction here is Digital Surface Model (DSM) vs Digital Elevation Model (DEM).  I think of the DEM as the bare surface elevation and the DSM as heights above that surface.  Taking the difference between these two models gives a normalized DSM.  You can create electro-optical (EO) point clouds from imagery, but you will not be able to do this with Sentinel or Landsat because only Nadir data are provided.  EO point clouds require multiple collects at multiple look angles to apply photogrammetric techniques for deriving heights.  Only agile commercial sensors like Worldview provide this capability, and UAS.

 

Here's some information: http://www.harrisgeospatial.com/Home/NewsUpdates/TabId/170/ArtMID/735/ArticleID/14517/3D-Point-Cloud-Generation-from-Stereo-Imagery.aspx

[meodensi]

You may be interested in this paper "Mapping forest canopy height globally with spaceborne lidar"

 

http://onlinelibrary.wiley.com/doi/10.1029/2011JG001708/pdf

 

Cheers

[laura_p]

Hello everyone,

 

thank you very much for your replies, you clarified my doubts. 

 

Mamadouba, I used the distinction provided by the Italian Wikipedia (which, of course, is not the most reliable source...). But you are right, I was referring to DSM.

 

Meodensi, thank you for sending me this link: I will have a closer look at it ;-)