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

# 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., 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('3f649a2b-e2ef-4f5e-bd50-6ad91522e30f'),
  'Channels': [],
  'Input type': 'Rx and base stations',
  'Property groups': [],
  'Receivers': UUID('58d46f94-1aa5-4521-a7a5-2931dec8599f'),
  'Survey type': 'ZTEM',
  'Unit': 'Hertz (Hz)'}}

Channels

List of frequencies at which the data are provided.

receivers.channels = [30., 45., 90., 180., 360., 720.]

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
data_fun = lambda c, f: (c+1.) * (f+1.) * np.sin(f * np.pi * (x_loc * y_loc).ravel() / 400.)

# 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 0x7feac7d0f040>,
 <geoh5py.groups.property_group.PropertyGroup at 0x7feabc3af580>,
 <geoh5py.groups.property_group.PropertyGroup at 0x7feabc250940>,
 <geoh5py.groups.property_group.PropertyGroup at 0x7feabc3afe20>]

Metadata are updated immediately to reflect the addition of components:

receivers.metadata

{'EM Dataset': {'Base stations': UUID('3f649a2b-e2ef-4f5e-bd50-6ad91522e30f'),
  '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('58d46f94-1aa5-4521-a7a5-2931dec8599f'),
  '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 0x7feac7d0eb60>,
  <geoh5py.data.float_data.FloatData at 0x7feac7d0fe50>,
  <geoh5py.data.float_data.FloatData at 0x7feac7d0e4d0>,
  <geoh5py.data.float_data.FloatData at 0x7feac7d0c760>,
  <geoh5py.data.float_data.FloatData at 0x7feac7d0eb90>,
  <geoh5py.data.float_data.FloatData at 0x7feac7d0f8e0>],
 'Txz (imaginary)': [<geoh5py.data.float_data.FloatData at 0x7feac7d0eaa0>,
  <geoh5py.data.float_data.FloatData at 0x7feabc3afa60>,
  <geoh5py.data.float_data.FloatData at 0x7feabc3afa00>,
  <geoh5py.data.float_data.FloatData at 0x7feabc3afc10>,
  <geoh5py.data.float_data.FloatData at 0x7feabc3aeb90>,
  <geoh5py.data.float_data.FloatData at 0x7feabc3af550>],
 'Tyz (real)': [<geoh5py.data.float_data.FloatData at 0x7feabc3af460>,
  <geoh5py.data.float_data.FloatData at 0x7feabc250ac0>,
  <geoh5py.data.float_data.FloatData at 0x7feabc250220>,
  <geoh5py.data.float_data.FloatData at 0x7feabc250280>,
  <geoh5py.data.float_data.FloatData at 0x7feabc2506d0>,
  <geoh5py.data.float_data.FloatData at 0x7feabc2511e0>],
 'Tyz (imaginary)': [<geoh5py.data.float_data.FloatData at 0x7feabc251a80>,
  <geoh5py.data.float_data.FloatData at 0x7feabc3af9d0>,
  <geoh5py.data.float_data.FloatData at 0x7feabc3afc70>,
  <geoh5py.data.float_data.FloatData at 0x7feabc3afd90>,
  <geoh5py.data.float_data.FloatData at 0x7feabc3af880>,
  <geoh5py.data.float_data.FloatData at 0x7feabc3afe50>]}

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()