What are the input files to and output results from VELMAP?

The input files to VELMAP are common-shot or common-receiver SEGY gathers recorded from a VSP survey.  They can be single or multiple components.  In the end, VELMAP will produce 2D or 3D migration images and the migration velocity models.

What processing functions does PreProcess module include?

It includes the following: FX Decon, Decon, Trace Mute, Time Scaling, Time-Variant Spectral Whitening, Bandpass Filter, AGC, F-K Filter, Median Filter, Statics, and Regularization.

What migration algorithms are included in VELMAP?

For 2D, VELMAP applies a prestack wave-equation depth migration method (PSPI) for processing common-receiver or common-shot gathers.  For 3D, it employs a 3D Kirchhoff prestack depth migration method.

What processing functions does PostProcess module include?

It includes: FX Decon for Common-Reflection-Point (CRP) gathers, residual statics estimation using stack-power maximization method, and restack.

How can I build a migration velocity model for the portion between the surface and the top receiver in well?

This top zone cannot be reconstructed from VSP tomography, but it does significantly affect the VSP migration.  You will need to use GeoTomo’s VECON program to build the top model from surface seismic images, and fix the top portion during VSP tomography when updating the lower velocity model.

How can I compare the VSP image with the surface seismic image?

You will need to use GeoTomo’s VISUS software package.  VISUS is designed for 3D VSP visualization and interpretation.    Comparison of seismic images is just one of the many analysis tools available in VISUS.