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.

import numpy as np

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


# Create a new project
workspace = Workspace("my_project.geoh5")

# 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 TipperReceivers, the metadata contains all the necessary information to define the geophysical experiment.

receivers.metadata

{'EM Dataset': {'Base stations': UUID('bf9541c4-268b-4f1b-90f9-3d95ba6d059f'),
  'Channels': [],
  'Input type': 'Rx and base stations',
  'Property groups': [],
  'Receivers': UUID('e2e1883a-9463-482f-9710-73aaf2585835'),
  '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 PropertyGroups 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 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 0x7f53dcbe6c20>,
 <geoh5py.groups.property_group.PropertyGroup at 0x7f53f27ae470>,
 <geoh5py.groups.property_group.PropertyGroup at 0x7f53dc347100>,
 <geoh5py.groups.property_group.PropertyGroup at 0x7f53dc346f50>]

Metadata are updated immediately to reflect the addition of components:

receivers.metadata

{'EM Dataset': {'Base stations': UUID('bf9541c4-268b-4f1b-90f9-3d95ba6d059f'),
  '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('e2e1883a-9463-482f-9710-73aaf2585835'),
  'Survey type': 'ZTEM',
  'Unit': 'Hertz (Hz)'}}

Data channels associated with each component can be quickly accessed through the BaseEMSurvey.components property:

receivers.components

{'Txz (real)': [<geoh5py.data.float_data.FloatData at 0x7f53f27eee60>,
  <geoh5py.data.float_data.FloatData at 0x7f53dcbe6d10>,
  <geoh5py.data.float_data.FloatData at 0x7f53f27eea70>,
  <geoh5py.data.float_data.FloatData at 0x7f53f27ee890>,
  <geoh5py.data.float_data.FloatData at 0x7f53f27eed70>,
  <geoh5py.data.float_data.FloatData at 0x7f53dc3474c0>],
 'Txz (imaginary)': [<geoh5py.data.float_data.FloatData at 0x7f53dc346bf0>,
  <geoh5py.data.float_data.FloatData at 0x7f53dc347e50>,
  <geoh5py.data.float_data.FloatData at 0x7f53dc347e20>,
  <geoh5py.data.float_data.FloatData at 0x7f53dc347fa0>,
  <geoh5py.data.float_data.FloatData at 0x7f53dc210070>,
  <geoh5py.data.float_data.FloatData at 0x7f53dc2101f0>],
 'Tyz (real)': [<geoh5py.data.float_data.FloatData at 0x7f53dc347850>,
  <geoh5py.data.float_data.FloatData at 0x7f53dc3473d0>,
  <geoh5py.data.float_data.FloatData at 0x7f53dc347940>,
  <geoh5py.data.float_data.FloatData at 0x7f53dc347970>,
  <geoh5py.data.float_data.FloatData at 0x7f53dc347d30>,
  <geoh5py.data.float_data.FloatData at 0x7f53dc347910>],
 'Tyz (imaginary)': [<geoh5py.data.float_data.FloatData at 0x7f53dc346b60>,
  <geoh5py.data.float_data.FloatData at 0x7f53dc2113f0>,
  <geoh5py.data.float_data.FloatData at 0x7f53dc211360>,
  <geoh5py.data.float_data.FloatData at 0x7f53dc2114e0>,
  <geoh5py.data.float_data.FloatData at 0x7f53dc211630>,
  <geoh5py.data.float_data.FloatData at 0x7f53dc211750>]}

Receivers

Generic label used in the geoh5 standard for EM survey to identify the TipperReceivers entity.

Base stations

Generic label used in the geoh5 standard for EM survey to identify the 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()