These guidance notes have been created by experts from RCAHMS for use by Scotland's Rural Past volunteers. They describe a range of archaeological field survey methods, including plane table, alidade and tape and off-set. To view a copy of the document, please click here.
These methods are covered in greater detail in the SRP fieldwork guide A Practical Guide to Recording Archaeological Sites.
There is a growing interest in our built heritage, the subject matter ranging from prehistoric monuments and historic townships to more modern military or industrial sites. Studying a subject can include carrying out documentary research and looking at extant remains. The record can include old documentation and maps, a written description, photography and sketches or measured survey drawings. Most of the examples used in this guide are of post-medieval remains but the same survey techniques can be used to record all types of buildings and sites.
The following pages provide an outline of several survey methods that can be carried out with simple surveying equipment:
Tape and offset survey (extended baseline survey)
Plane table and alidade survey
Each of these methods can provide a very useful record in its own right. However, often the most effective way to survey a site is to use a combination of the different methods.
The purpose of graphic recording is to provide a set of drawn illustrations to provide a record a site at a point in time that can be viewed and used for research by other interested parties.
A graphic record of a building or structure normally takes the form of a combination of plan, elevation and section drawings. Perspective or 3D orthographic views can also be created as required.
A plan, in the case of a building, is a horizontal slice, usuallly above window sill level,to show floor layout, position of doors, windows, fireplaces etc. For an earthwork a plan is a view looking down on to the features from above.
An elevation, is a view looking on to an upstanding structure or wall to show position and height of features.
A section, is a vertical slice through a building or structure to show floor levels, ceiling heights and wall thicknesses. For an earthwork a section would show a ground profile and the height of banks, etc.
A great benefit of graphic recording, often undervalued, is the process of surveying itself. The surveyor is required to spend time looking at and understanding the site or building. Drawing, in either sketch or accurate scale form, is a subjective process requiring a clear understanding of what is to be drawn. If a complex feature is not understood on the ground it is unlikely that the survey drawing will produce a clear depiction. It is necessary to make informed decisions on what the key elements of a structure are and how to depict them using lines or symbols. The amount of detail will vary according to scale.
Understanding the process of generalisation, i.e. using fewer lines to represent a structure at smaller scales, is also crucial to the success of the depiction. The smaller the scale, the more generalisation takes place but overall shape and form must not be lost.
A clear understanding of what a survey is trying to convey is essential in the selection of an appropriate survey scale. Before starting the survey time should be spent walking over the site to determine its extents and boundaries.
What are you trying to illustrate: the site location, position in the landscape, position relative to other buildings, size and form of the structure itself or a detailed part of a building?
Too small a scale can make it impossible to depict important archaeological detail, too large a scale requires far more time and effort, often without any useful gain in information. It is better to show the whole site at a small scale and enlarge specific areas as required to show more complex detail.
Another important consideration is fitting the drawing onto the drawing board. If too large a scale is used, the resulting survey may need to be spread over more than one sheet. This becomes unwieldy and may cause problems if the drawings need to be re-sized for use in a report.
The logical approach is to create a suite of illustrations that may include:
The following range of survey scales is used by RCAHMS:
Should be at an appropriate scale to show the geographical location of the site.
1:1250 - 1:2500 is used to show features within their topographic setting. The level of detail of man-made features at this scale is limited to outline shapes and the relative position of monuments, field banks, etc. Natural features can be illustrated using hachures or contours.
1:200 - 1:1000 is used for a site plan to show the relationship of a group of man-made features, such as a farmstead or prehistoric settlement, with related buildings. This scale allows the illustrator to represent some of the character of the structures, together with their relative positions also structural elements such as blockings and straight joints.
1:50 - 1:100 is used to show the detailed character of a single building or monument, e.g. a hut-circle, cairn, replaces, drains, agstones and stairs can be depicted accurately without recourse to symbols.
1:20, 1:10, 1:5 up to 1:1 or enlargements can be used to illustrate particular features, such as carved stones, moulding profiles and excavation details, as required.
Survey drawings or derivatives are often incorporated into a publication or report. These reports are normally A4 or smaller in size, so consideration has to be given to the size of the original drawings otherwise over reduction will affect the printed quality. RCAHMS generally works to 50% reduction as a standard.
RCAHMS survey drawings are intended to provide a permanent record. To achieve this, Hi-Polymer (eg 6H) lead pencils are used on a polyester film, giving a waterproof, dimensionally stable archive medium.
A specific set of conventions and symbols is used to depict features at various scales. A sheet showing the symbols used by the RCAHMS at various scales is included on the following page.