> For the complete documentation index, see [llms.txt](https://docs.phoenixlidar.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.phoenixlidar.com/3rd-party-software-documentation/bathymetric-lidar-processing-in-riprocess/creating-a-project-in-riprocess/processing-parameters/exponential-decomposition.md).

# Exponential Decomposition

**Exponential Decomposition (XDC)** is typically able to extract bathymetric points further underwater than **Online Waveform Processing (OWP)**. XDC accomplishes this by averaging several waveforms to increase the signal-to-noise ratio in regards to bathymetric returns. 

XDC processing is more intensive and requires processing to be restricted to only areas with water coverage. This is done using a GEOJSON format polygon definition file. See the following Riegl documentation regarding creating a GEOJSON polygon in QGIS and ArcGIS:

{% file src="/files/clTRRMQTLi3piqhuvTn6" %}

Once the polygon is created, you should enable XDC and waveform averaging:

<figure><img src="https://2222094320-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FdEevfLZRIk38LUPwDa4V%2Fuploads%2FzlhKC8evCa51MOYCPV2C%2Fimage.png?alt=media&amp;token=85683f56-3392-4e82-9014-3ca202c79135" alt=""><figcaption></figcaption></figure>

{% hint style="info" %}
Waveform averaging using 15 waveforms (as shown above) records bathymetric lidar returns deeper underwater than OWP processing. The benefit of averaging more waveforms (31, 63) is not quite as significant, so it is generally recommended to use 15.&#x20;
{% endhint %}

Ensure that your **Water Surface Selector** is also set to use the same GEOJSON polygon:

<figure><img src="https://2222094320-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FdEevfLZRIk38LUPwDa4V%2Fuploads%2FI4CXjNG6ylaKJdu7pqAu%2Fimage.png?alt=media&amp;token=21574ead-a966-4b5f-9a9c-4810b792dccd" alt=""><figcaption></figcaption></figure>