Quality control in geophysical surveying

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Quality control in geophysical surveying
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Background

• You wrote a bid for a project in the last week
  assignment. During the presentations we realized
  many good points but also flaws in the given
  information. The written proposals were of
  similar quality.
• Following you will find guidelines for future
  improvement in projects

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Quality control

• General Quality Guidelines 
• Important to implement in all stages of a
  geophysical project, from start to end, from
  invitation for to archiving of project
• Invitation to bid
• Order
• Acquisition
• Reporting
• Archiving

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Invitation to bid

• The invitation to bid is one of the most
  important documents in the preparation of a
  project. Within this document, the client defines
  the guidelines and boundary conditions for the
  project. Precise definitions in this document
  will allow an adequate comparison of the
  different bids and is a good basis for an order
  or contract.
• Question what should be included in a good bid?

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Invitation to bid

• Specifications
• Overall objectives of the proposed project
• Goals of the specific investigation
• Links and interrelation to other investigations
• Proposed methods
• Site map
• Boundary conditions (time window, access to
  ground, infrastructure etc,)
• Project organization (project manager,
  directions)

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Invitation to bid

• Methods and / or targets
• Dependant on the know-how of the client, the
  target for the investigation and/or the proposed
  method must be specified.
• Target
• Size, depth, continuity, contrast of physical
  parameters to the surrounding rock
• Expected accuracy of the result (quantitative or
  qualitative)
• Method
• general description
• measurement design (2D or 3D investigation,
  measurement points or lines and spacing)
• measurement parameters (e.g. minimum recording
  length, resolution)
• processing parameters
• interpretation method
• Even if the method is specified, it should be
  explicitly allowed that the contractor offers an
  alternative method or lay-out in addition to the
  specified one.

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Invitation to bid

• Existing information
• existing geological maps and cross sections of
  the area
• results from other measurements
• known problems at the site (electrical or seismic
  noise, difficult terrain, soft ground etc.)
• information on possibly buried dangerous
  materials (explosives, chemicals, waste etc.)
• Results
• specification of report outline and format
• expected products (e.g. maps or cross sections
  with scales)
• raw data presentation and formats (analog,
  digital)
• data processing and display specification

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Invitation to bid

• QC
• required QC level
• equipment tests and certifications
• on site quality checks
• Quotation
• The general basis for the quotation has to be
  defined. Possibilities are
• turn-key projects (with costs per measurement or
  test)
• effective time (with costs based on hourly rates
  for personnel and equipment)
• lump sum (for the execution of the predefined
  project)

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Invitation to bid

• The different types of quotation have different
  risks for client and contractor. Quotations based
  on effective costs should only be chosen if an
  adequate surveillance by the client or his
  consultant is guaranteed. For the other cases it
  is necessary to precisely define the measurement
  design and the products. In all cases, it is
  necessary to define
• cost of stand-by times which are out of the
  responsibility of the contractor
• force majeur
• possibility and costs for interruption or
  cancellation of work

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Order

• General
• An order for geophysical study (survey) is
  usually based on bidding and the proposal of the
  best value competitor.
• Small order
• Small order are usually ordered written or by
  letter. Oral order can be accepted as provisional
  or only in urgent case.
• Contract
• For greater surveys, a contract for services in
  connection with the project between the Customer
  (organization) and Contractor will be
  concluded.The contract should contain following
  items next page

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Order

• Purpose and programme of the survey
• Work and Services to be executed by the
  Contractor
• Equipment, materials and supplies to be provided
  by the Contractor
• Participation in the performance of the contract
  by the Customer (organization)
• Time schedule of performances
• Reporting (progress reports, interim reports,
  final report)
• Remuneration and method of payment
• Security guidelines (Quality control)
• Defining of field tests
• Modality for break-off or extension of
  measurements
• Regulations for data storage and Archives
• Changes and Amendments
• Regulations in case of disputes and arbitration
• Termination of Contract

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Acquisition

• General
• To inspect a geophysical crew during field work,
  the following points need to be checked
• Acquisition scheme
• Is fieldwork conducted according to the
  specifications in the quotation?
• Exist deviations from the acquisition scheme
  proposed due to unexpected incidences? If yes,
  why?
• How are potential sources of noise and systematic
  errors considered (e.g., ambient seismic or
  electromagnetic noise, metallic objects, etc.)

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Acquisition

• Field Crew
• Does a qualified geophysicist lead the crew?
• Are the helpers instructed adequately?
• Do qualified personnel check the work of the
  helpers?
• Is the field crew working efficient?
• Has one of the crew members the necessary licence
  (e.g., to handle explosive)
• Equipment and field computers
• Are the instruments specified in the quotation
  employed for the measurements? If no, what are
  the consequences in terms of acquisition speed
  and data accuracy?
• Are the instruments working properly?
• Are the computers suitable for fieldwork?
• Are backups performed regularly?

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Acquisition

• Surveying
• How are the source and receiver coordinates
  determined (measuring tape, theodolite, GPS)?
• Is topography considered adequately?
• What is the coordinate accuracy? Is this accuracy
  sufficient for the geophysical method used?
• How is the recording, storage of the geometrical
  data? (Redundant?)
• QC in the field
• How often are the data recorded checked?
• How are the data checked?
• Exists a detailed field log-book, in which all
  significant incidences are documented?
• How are the data stored?

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Acquisition

• Permitting, damages
• Was a permitting performed prior to the field
  campaign (if required)?
• Were the landowners informed about potential
  damages?
• Have any damages already occurred?
• Has the geophysical contractor an appropriate,
  liability insurance (should be checked prior to
  the field campaign)?
• All permissions existing? (explosives,
  radioactive sources?)
• Timing
• Corresponds the acquisition speed with the
  specifications in the quotation?
• Is the acquisition speed adequate, i.e., is the
  acquisition speed such that reliable measurements
  can be expected?

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Reporting

• General
• Client decides (in according to the contract) in
  which way a geophysical report should be done. It
  can be a great difference in report extent
  depending on a type of geophysical survey and its
  size. Geophysical report contains usually the
  following parts
• Abstract
• Contents
• Table of Contents
• Appendix
• Introduction
• Objectives of the survey
• Former investigations
• Reports, List of maps etc.

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Reporting

• Geological overview
• E.g., geological situation, borehole profiles
• Field investigations
• Site and measurement location
• Field and weather conditions
• Time table of activities
• Incidents

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Reporting

• Geophysical processing
• Data acquisition parameter
• Copy of raw data (if necessary)
• Quality of raw data (reproducing precision
  resolution)
• Processing software
• Processing steps
• Results
• Qualitative results e.g. electrics resistivity
  profiles or sections (2-D or 3-D), resistivity
  maps, transversal resistance-, longitudinal
  conductance maps
• Quantitative results time-depth sections
  (reflection seismic), interpretative sections or
  maps

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Reporting

• Interpretation in terms of geology (if required)
  
• Conclusions
• Reliability of results
• Recommendations
• Unresolved problems

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Archiving

• Data
• Raw data
• Geometry files (Surveying)
• Processed data
• Interpretation (Profiles Maps)
• Data formats
• Analogue Copies on document paper or transparent
  (e.g., Geometry and calibration data)
• Digital use standard formats (e.g., ASCII no
  binary files) and use Floppy disks or CD
• Archives
• Company data and reports must be archived for at
  least 10 years (archiving of important data
  spatial separated)

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Additional resources

• There are a few very good resources available for
  assisting you in choosing the right field
  technique and assessing how much time and costs
  it will take you to study a certain object
• Geopass (NITG-TNO)
• http//www.nitg.tno.nl/eng/projects/geopass/
• Quality Control (Swiss Geophysal Commission)
• http//www.aug.geophys.ethz.ch/gpmapping/

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Mise-a-la-masse