Analysing (ASCII Volume)

The loader will present the vertical interval and spatial spacings and extents obtained from the file.

Analyse the trace headers
  1. In the Analysis window, click Start.
  2. During analysis, warning Messages may appear in orange at the bottom of the page. It's worth scanning this list to verify that everything is as expected.
  3. If no errors are reported, click Next to move to the next step.

Regular sampling

For regularly sampled ASCII files the loader will match the vertical interval and spatial spacings.

Irregular sampling

ASCII velocity files can vary on both the vertical interval and spatial spacings, this is not allowed in Insight.

The loader will preserve the original velocity pick data by oversampling and choosing a vertical and spatial sampling that captures as much of the original information as possible.

For example:

If the intervals/spacings are 10, 20, 30, 60, 80

  • the smallest interval/spacing will be 10 and will be used as the volume interval/spacing
  • no sample will be missed

Users can later resample in Insight vertically (see Velocity Conversion) and/or spatially (see Volume Resampling) as preferred.

Note: yellow box indicates irregular sampling.

Vertical interval larger than 65 ms

ASCII velocity files can have vertical intervals larger than 65 ms, this is also not allowed in Insight.

Insight will automatically resample the vertical interval to 24 ms.

Users can later vertically resample in Insight (see Velocity Conversion) as preferred.

Duplicates

Data with duplicate CMP (2D) or IL/CL (3D) can't be loaded; only the first value will be kept.

A small number of duplicate traces is not very unusual, but a large number almost certainly indicates a mistake. The most common reason is wrong keyword locations.

Notes: The standard practice in DUG's service division is to use a velocity model sampled at around 100m x 100m x 24ms/20m. If your velocity volume is more dense than this, you may wish to consider downsampling.

Genuine offer of assistance

DUG understands that importing ASCII volume data can be a confusing task.

Whether you are using a trial version or a fully-paid licence, we will help you to import your data to Insight so that you will get the maximum out of your data.

For more information, contact support at [email protected].