How do I filter large amplitudes, extreme values and spikes from my data?
Volume Maths is a very usefull process in Insight that allows manipulation of seismic data (to a certain degree). In this instance, we will use Volume Maths to identify large amplitudes, extreme values and/or spikes and replaced it with NaN values. We can then interpolate these NaN values using the NaN Removal process to repair the volume.
![Volume maths to fix spikes](https://media.screensteps.com/image_assets/assets/003/326/695/original/cbb2de40-2a37-4263-b255-4f559fe55822.png)
For this situation, we use the logic that if values in volume v1 are greater than 900 (or a more suitable extreme number for the volume) replace it with NaN, if not use v1 (input values).
- Open the Process tab and click the "+" button to add a New Process. Search and select Volume Maths.
- Type in a name for this Volume Maths process.
- In the Volume Maths panel, click the "+" button and select the abnormal volume.
- In the Formula text box, enter the formula: if (abs(v1) > 900, NaN, v1).
![Volume maths for maxmin fix](https://media.screensteps.com/image_assets/assets/003/326/697/original/93bba7b1-712c-41b3-94a2-3b37577954a9.png)
To crop on specific high min and max values, use the logic that if input volume v1 is greater than 75 (or a suitable max value) OR if v1 is less than -75 (or a suitable min value), replace with it NaN, othewise use v1 (original value).
- Add formula if (v1 > 75 || v1 < -75, NaN, v1) in the Formula text box of the Volume Maths panel.
![NaN Process](https://media.screensteps.com/image_assets/assets/003/326/699/original/0f2f0a6e-6cf0-4544-add4-e8f8aa40e60d.png)
Interpolate NaN values using the NaN Removal process.
- In the Process tab, click the "+" button and add a new process. Search and select NaN Removal.
- Type in a name for this NaN Removal process.
- Under the NaN Removal panel, select the volume created from the above Volume Maths process in the Volume text box.
- Select Linear Interpolation from the Action drop box. Read more about NaN Removal process.
- A volume is created and is available in the Volume tab.
![](https://media.screensteps.com/image_assets/assets/000/232/841/original/9a7126e4-ac7d-4f53-80e5-261998f6456d.png)