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Introduction to the INTREPID database (G20)

Overview

This chapter outlines the structure of the binary database that underlies all INTREPID operations. The INTREPID database:

  • Supports all INTREPID data formats,
  • Underlies all INTREPID tools,
  • Uses a binary format to efficiently store data,
  • For practical purposes, has no size limits.

INTREPID uses this standard database structure for all data. If your data is not in a supported format, you must import it into an INTREPID dataset. Once the data is in this format you can process it with the full range of INTREPID tools.

This tour is an overview of the INTREPID database structure. For full information, see INTREPID database, file and data structures (R05).

The following diagram illustrates the INTREPID process.

INTREPID dataset types

The INTREPID database format accommodates several types of data. Each data type has a corresponding INTREPID dataset format. The following table summarises the data types and dataset formats.

Data Type

Application

INTREPID dataset

Vector

Line data collected as sequences of readings by a sensing craft along traverse paths

Line dataset

Point data—sets of readings each associated with one geographic location

Point dataset

Regions of interest defined by the geographic coordinates of the vertices of a polygon

Polygon dataset

Raster

Grid overlaid on the survey area, each cell having a value (or several values)

Grid dataset
(can be multiband)

Line datasets

INTREPID constructs a line dataset from the data collected by a sensing craft (such as a ship or aircraft) systematically traversing an area of land or sea in a set equally spaced parallel lines. The survey may be completed over a number of excursions (usually flights). The sensors on the craft collect data at set time intervals. The on-board fiducial clock synchronises the readings. Each time the fiducial clock ‘ticks’, the recording devices record a set of readings. In the simplest case a set of readings (data point) would include

  • The fiducial clock reading
  • The flight (excursion) number
  • The traverse line number
  • A pair of geographic coordinates (nowadays obtained from Global Positioning Satellites) (often called X and Y fields)
  • Values for the phenomena being measured (e.g., magnetic field strength), often referred to as signal fields.

Each data point therefore has a number of values. Each set of values (e.g., the set of X values) forms a field of the dataset.

Because the dataset consists of data points each with several values we call it a vector dataset.

The traverse lines along which the craft collects data for use in the dataset are called acquisition lines. It is normal practice to traverse several lines at right angles to the acquisition lines. We can use these tie lines for cross-checking the acquisition lines data.

Here is an illustration of some flight paths showing acquisition and tie lines.

gtdbappx1.png

We do not normally use tie line data except for levelling the data. To distinguish tie lines from acquisition lines we firstly give them characteristic line number values. The convention for numbering lines varies amongst organisations. A common convention is to number acquisition lines <7000 and tie lines >7000.

To assist INTREPID with rapid processing we normally create the line type field containing a simple code indicating the type of line. INTREPID uses the value 2 for an acquisition line and 4 for a tie line.

After performing corrections and a projection conversion on the data we may end up with several versions of some fields, especially the geographic location fields. We therefore need to specify which fields are the ‘official’ ones for use in INTREPID processes. The INTREPID standard information (.isi) file contains these specifications. It specifies the names of the ‘official’ fiducial, flight number, line number, line type and X and Y geographic location fields. An ‘official’ field label is called an alias. Examples of aliases are X, Y Fiducial, LineType.

Point datasets

Point datasets are vector datasets whose data points do not have a sequential relationship, although they may be grouped. They are simply sets of data points. The simplest point dataset would consist of X and Y geographic location fields and a signal field. Point datasets have aliases identifying their ‘official’ X and Y fields.

Polygon datasets

We use Polygon datasets to define sub-regions of a dataset. They have X and Y fields only.

Grid datasets

Grid datasets consist of rows and columns of cells. Geographic location information included with the grid allows you to determine the size and location of each cell. Each cell has one or more Signal values. Each set of Signal values forms a band of the grid dataset.

Metadata

INTREPID can capture and deliver extensive detailed information about all datasets, including where they come from, how they were created and their statistics. This information is stored in the .isi file.

Structure of INTREPID Datasets

An INTREPID grid dataset consists of three files. An INTREPID vector dataset consists of a directory containing the fields as separate files, with a small marker file outside the directory to indicate the presence of the vector dataset.

You will normally store all of the datasets associated with a survey in a single directory called the project directory.

Marker files

INTREPID datasets and dataset components are identified by marker files, which have suffixes .ers, ..DIR, ..LINE, ..PNT and ..POLY. INTREPID uses them to assist you to locate the data you require. The marker files identify INTREPID data structures as follows:

Suffix

Dataset or component

Inside or outside Dataset directory

.ers

Grid dataset

(no directory)

..DIR

Vector dataset

outside

..LINE

Field of line dataset

inside

..PNT

Field of point dataset

inside

..POLY

Field of polygon dataset

inside

Dataset files and directories

INTREPID datasets have a number of files associated with them. The description in this guided tour is simplified. For a more detailed description, see INTREPID database, file and data structures (R05).

A grid dataset consists of three files. One is the binary data file, the other two contain meta-data. Usually grid datasets would be stored in the project directory itself.

When you wish to load a grid dataset, look for its metadata file, which has the suffix .ers.

Example of a grid dataset marker file: raw_magnetics.ers.

Important: Do not store a grid dataset inside a vector dataset’s directory. This may cause confusion for you and sometimes prevent INTREPID from working properly.

Each vector dataset has its own directory. A marker file (..DIR) outside the directory indicates the presence of a vector dataset. Inside the directory each field of the dataset essentially occupies a separate file. Each field has a marker file with a suffix that depends on the type of vector dataset (..LINE, ..PNT or ..POLY).

Line datasets have at least one ‘group by’ field—the line number field. Using this feature INTREPID can easily display or process all data for a given line. Point and polygon datasets do not have a ‘group by’ field.

When you wish to specify a whole vector dataset, look for its ..DIR marker file. When you wish to specify a field of a vector dataset look for its ..LINE, ..PNT or ..POLY marker file.

Here is an example of a line dataset including its directory and marker files. Point and polygon datasets have a similar structure.

ebagoola_e..DIR

dataset marker file

ebagoola_e/

dataset directory

fiducial..LINE

fiducial count field marker file

flightnumber..LINE

flight number field marker file

linenumber..LINE

line number field marker file (‘group by’ field)

linetype..LINE

line type field marker file

x..LINE

x (easting) coordinate field marker file

y..LINE

y (northing) coordinate field marker file

raw_magnetics..LINE

magnetic data (a ‘Signal’ field) marker file

mlev_magnetics..LINE

magnetic data (another ‘Signal’ field) marker file

Masks, suffixes and specifying input

As part of the process INTREPID uses the marker file suffixes as masks to offer only certain file types in Load dialog boxes. The Windows version of INTREPID will not display these masked suffixes in the Load dialog boxes.

Sample datasets

Location of sample data for Guided Tours

We provide two complete sets of sample datasets, one in INTREPID format and one in Geosoft format. INTREPID works equally well with both formats. When you want to open a dataset, navigate to the directory containing the required data format.

Where install_path is the path of your INTREPID installation, the project directories for the Guided Tours sample data are
install_path/sample_data/guided_tours/Intrepid_datasets and
install_path/sample_data/guided_tours/Geosoft_datasets.

For example, if INTREPID is installed in
C:/Intrepid/Intrepid 6.0.4.304babe910c_x64
then you can find the INTREPID format sample data at
C:/Intrepid/Intrepid 6.0.4.304babe910c_x64/sample_data/guided_tours/intrepid_datasets

For more information about installing sample data, see “Sample datasets—installing, locating, naming” in INTREPID Guided Tours Introduction (G01)

For a more detailed description of INTREPID datasets, see Introduction to the INTREPID database (G20). For even more detail, see INTREPID database, file and data structures (R05).

Location of sample data for Cookbooks

In the adjacent folder to Guided Tours data is a collection of more exotic geophysics datasets and grids already prepared for the cookbook training sessions. You may also gain some insights into the capabilities of the software by testing the Project Manager’s ability to preview and describe the attributes of each of the cookbook datasets.

For an introduction to the Cookbooks, see Using INTREPID Cookbooks (C12).

For a list of available Cookbooks, see Cookbooks.

Sample data for batch processing

Yet more sample datasets are available in install_path/sample_data/examples/datasets. We have provided these for users to learn about batch processing with .task files. For more information, see: