Tipper

This object can be used to store tipper (ZTEM) surveys - a natural-source geophysical method. Data are provided in the frequency-domain as point source measurements of tipper data.

The following example shows how to generate a tipper survey with associated data stored in geoh5 format and accessible from Geoscience ANALYST.

from pathlib import Path

import numpy as np

from geoh5py.objects import TipperBaseStations, TipperReceivers
from geoh5py.workspace import Workspace


# Create a new project
h5file = Path("my_project.geoh5")
workspace = Workspace(h5file) if h5file.exists() else Workspace.create(h5file)

# Define the pole locations
n_stations = 64
n_lines = 2
x_loc, y_loc = np.meshgrid(
    np.linspace(0, 60, n_stations), np.linspace(-20, 20.0, n_lines)
)
vertices = np.c_[x_loc.ravel(), y_loc.ravel(), np.zeros_like(x_loc).ravel()]

# Assign a line ID to the poles (vertices)
parts = np.kron(np.arange(n_lines), np.ones(n_stations)).astype("int")

# Create the survey from vertices
receivers = TipperReceivers.create(workspace, vertices=vertices, parts=parts)
base = TipperBaseStations.create(workspace, vertices=vertices)

We have so far created two seperate entities, one for the receiver locations and another for the base station(s). In order to finalize the survey, the association must be made between the two entities:

receivers.base_station = base

or equivalently

base.receivers = receivers

Only one of the two options above is needed.

Metadata

Along with the geoh5py.objects.surveys.electromagnetics.tipper.TipperReceivers, the metadata contains all the necessary information to define the geophysical experiment.

receivers.metadata

{'EM Dataset': {'Base stations': UUID('f5a58666-add6-41ee-bd0b-9155a9536e2a'),
  'Channels': [],
  'Input type': 'Rx and base stations',
  'Property groups': [],
  'Receivers': UUID('9e753865-8a63-494b-9c49-07044cb2bba9'),
  'Survey type': 'ZTEM',
  'Unit': 'Hertz (Hz)'}}

Channels

List of frequencies at which the data are provided.

receivers.channels = [30.0, 45.0, 90.0, 180.0, 360.0, 720.0]

Input type

Generic label used in the geoh5 standard for all EM survey entities. Restricted to Rx and base station in the case of a tipper survey.

Property groups

List of geoh5py.groups.property_group.PropertyGroup instances defining the various data components (e.g. Txz (real), Tyz (imag), …). It is not required to supply all components of the impedence tensor, but it is expected that each component contains a list of data channels of length and in the same order as the Channels (one Data per frequency).

The class method geoh5py.objects.surveys.electromagnetics.base.BaseEMSurvey.add_components_data() can help users add data from nested dictionaries. Below is an example using four components:

# Arbitrary data generator using sine functions
def data_fun(c, f):
    return (c + 1.0) * (f + 1.0) * np.sin(f * np.pi * (x_loc * y_loc).ravel() / 400.0)


# Create a nested dictionary of component and frequency data.
data = {
    component: {
        f"{component}_{freq}": {"values": data_fun(cc, ff)}
        for ff, freq in enumerate(receivers.channels)
    }
    for cc, component in enumerate(
        [
            "Txz (real)",
            "Txz (imaginary)",
            "Tyz (real)",
            "Tyz (imaginary)",
        ]
    )
}

receivers.add_components_data(data)

[<geoh5py.groups.property_group.PropertyGroup at 0x7752ca4b2330>,
 <geoh5py.groups.property_group.PropertyGroup at 0x7752ca4faf30>,
 <geoh5py.groups.property_group.PropertyGroup at 0x7752ca4fbda0>,
 <geoh5py.groups.property_group.PropertyGroup at 0x77531815dcd0>]

Metadata are updated immediately to reflect the addition of components:

receivers.metadata

{'EM Dataset': {'Base stations': UUID('f5a58666-add6-41ee-bd0b-9155a9536e2a'),
  'Channels': [30.0, 45.0, 90.0, 180.0, 360.0, 720.0],
  'Input type': 'Rx and base stations',
  'Property groups': ['Txz (real)',
   'Txz (imaginary)',
   'Tyz (real)',
   'Tyz (imaginary)'],
  'Receivers': UUID('9e753865-8a63-494b-9c49-07044cb2bba9'),
  'Survey type': 'ZTEM',
  'Unit': 'Hertz (Hz)'}}

Data channels associated with each component can be quickly accessed through the geoh5py.objects.surveys.electromagnetics.base.BaseEMSurvey.components() property:

receivers.components

{'Txz (real)': [<geoh5py.data.float_data.FloatData at 0x775318741430>,
  <geoh5py.data.float_data.FloatData at 0x775318117800>,
  <geoh5py.data.float_data.FloatData at 0x7752cb3d3260>,
  <geoh5py.data.float_data.FloatData at 0x775308189670>,
  <geoh5py.data.float_data.FloatData at 0x77531848ac00>,
  <geoh5py.data.float_data.FloatData at 0x7752ca499340>],
 'Txz (imaginary)': [<geoh5py.data.float_data.FloatData at 0x77530815a870>,
  <geoh5py.data.float_data.FloatData at 0x7753186e0b60>,
  <geoh5py.data.float_data.FloatData at 0x7752ca4fa480>,
  <geoh5py.data.float_data.FloatData at 0x7752ca4fad50>,
  <geoh5py.data.float_data.FloatData at 0x7752ca4faed0>,
  <geoh5py.data.float_data.FloatData at 0x7752ca4fa720>],
 'Tyz (real)': [<geoh5py.data.float_data.FloatData at 0x77530815abd0>,
  <geoh5py.data.float_data.FloatData at 0x7752ca4f99a0>,
  <geoh5py.data.float_data.FloatData at 0x7752ca4f9be0>,
  <geoh5py.data.float_data.FloatData at 0x7752ca4f92e0>,
  <geoh5py.data.float_data.FloatData at 0x7752ca4fb830>,
  <geoh5py.data.float_data.FloatData at 0x7752ca4fbb60>],
 'Tyz (imaginary)': [<geoh5py.data.float_data.FloatData at 0x77530815ab70>,
  <geoh5py.data.float_data.FloatData at 0x7752ca4fb0b0>,
  <geoh5py.data.float_data.FloatData at 0x7752ca364440>,
  <geoh5py.data.float_data.FloatData at 0x7752ca364590>,
  <geoh5py.data.float_data.FloatData at 0x77531815dee0>,
  <geoh5py.data.float_data.FloatData at 0x77531815f560>]}

Receivers

Generic label used in the geoh5 standard for EM survey to identify the geoh5py.objects.surveys.electromagnetics.tipper.TipperReceivers entity.

Base stations

Generic label used in the geoh5 standard for EM survey to identify the geoh5py.objects.surveys.electromagnetics.tipper.TipperBaseStations entity.

Survey type

Label identifier for ZTEM survey type.

Unit

Units for frequency sampling of the data: Hertz (Hz), KiloHertz (kHz), MegaHertz (MHz) or Gigahertz (GHz).

workspace.finalize()