>> Why should I need a Geophysics Survey?
>> What happens if DVAS find something?
>> How long does it take?
>> What procedure can I expect from DVAS?
>> How does the equipment work?
>> How accurate is DVAS' equipment?
>> Do you work internationally?

Q1. Why should I need a Geophysics Survey?
A. If you are planning a construction project on land that has (or is near) any features of archaeological or historical significance, your local planning authority will be keen to ensure that the land is evaluated before work starts. A Geophysical Survey is a non-invasive way of doing this whilst producing a report that will satisfy the authority.
If you are involved in an archaeological dig, a 'Geo-fiz' survey can point you in the right direction, enabling your team to concentrate efforts more effectively and economically.

Q2. What happens if DVAS find something?
A. What happens next depends upon the significance of the feature. You may:-
i) Get planning permission to proceed
ii) Get planning permission to proceed with a 'watching brief' ( an archaeologist must oversee the excavation part of the project), OR
iii) Be required to have the site examined archaeologically before construction begins.
IT IS FAR BETTER TO SATISFY THIS REQUIREMENT BEFORE THE PROJECT STARTS, RATHER THAN HAVE THE PROJECT STOPPED SHOULD FEATURES COME TO LIGHT DURING DEVELOPMENT.

Q3. How long does it take?
A. Many factors influence the time taken to complete a survey and report. However DVAS will always try to work within your time-scale for the project.

Q4. What procedure can I expect from DVAS?
A.

Stage 1.

This would consist of a preliminary visit to your site, in order to meet the project manager and to assess the scale of the area to be surveyed. A surface walk may be undertaken to visually determine the suitability of the land to the different types of surveying equipment we have available and to develop a ‘minds-eye’ plan of action. The requirements of the contractor would be discussed, with referral to the requirements of PPG (15/16) / MAP2 Photographs may be taken of any areas, buildings and features of particular interest and soil samples may be collected.

Stage 2.

From the results of stage1, a draft schedule will be prepared, detailing the series of procedures that DVAS would need to carry out in order to complete a successful survey. This schedule would also indicate the likely timescale and costs of carrying out each of the following stages, including a contingency for unexpected additional work. Should the schedule be acceptable, the survey will then begin.

Stage 3.

A desk-based survey would be undertaken. This survey delves into the historical and archaeological records for the area under consideration. Local buildings and on-site features are researched at this stage to identify their historical value and their past and present interaction with the development site, in order to give indications of the likelihood of any significant features being concealed beneath the area intended for development.

Stage 4.

Using information from stage 3, a Geophysical Survey of the area is then carried out. Depending upon surface conditions on site this could include: Field-walking, Magnetometer survey, Resistivity survey and Core sampling. Also available are techniques such as Electromagnetic Surveying, GPR (Ground Penetrating Radar), and remote sensing procedures such as aerial photography.

Stage 5.

The results of the surveys are analysed and compiled into a report, to be archived at DVAS and copied to the contractor, the local planning authority and the historical archives for future reference.  DVAS’ report will include recommendations relevant to the requirements of P.P.G. 15/16  planning guidelines.

Q5. How does the equipment work?
A. Our most frequently used items of equipment are the Resistivity Meter and the Fluxgate Magnetometer. Resistivity works by measuring the resistance of the ground to an electric current. Different types of buried features resist the current to varying amounts, giving clues to what may be buried below the surface. Magnetometry works by measuring fluctuations in the magnetic field near the surface of the ground, which is also influenced by buried features.

Q6. How accurate is DVAS' equipment?
A. At the moment, our equipment is 'state of the art'. The resistivity meter can pinpoint to within 0.25metres, while the magnetometer can work to 0.125m. Neither machine can tell us exactly what lies buried beneath the surface however; they both produce sub-surface 'maps' (see example), which then need to be interpreted by our archaeologists.

Q7. Do you work internationally?
A. As well as carrying out work anywhere in the U.K.., DVAS is happy to discuss international contracts. Please contact us with your requirements.