Overview #
Approximate contexts were not a part of the originally defined recording system and were introduced in 2015 to account for small objects that could not be modeled and for objects that had been moved from their original locations and for which we could only produce “approximate” spatial data. Whereas the spatial data for a spatial context is recorded volumetric via photobatches, the spatial data for approximate contexts is recorded by one dimensional point coordinates, around which a volume could theoretically be constructed in the future, if the exact volume of the item removed is known.
When to Open an Approximate Context #
As described above, approximate contexts are most often opened for objects of interest which are too small to model or which are typically moved accidentally before their exact location can be recorded, but for which spatial information is necessary. These include things like small metal objects (e.g., needles, awls, weights, slag); ceramic objects associated with textile production (e.g., spindle whorls); grinding stones; and poorly understood objects of interest like “pierced sherds” (circular ceramic objects with holes drilled through them) and “buttons” (circular ceramic objects with two or more holes drilled through them).
You should also take approximate contexts for all carbonized samples collected for radiocarbon or anthracological analyses. These are usually wood charcoal samples, but you should also keep an eye out for carbonized seeds. You might also take an approximate context for a 30 L sediment sample for flotation if you find a particularly interesting concentration of sediment that you determine should not be its own context (but this is not preferred). Approximate contexts are also used to collect spatial data for samples taken for sediment chemistry analysis. Finally, you may take an approximate context for mostly whole vessels, figurines, or other objects of interest if they have been moved from their original location. If these types of objects have not been moved when they were uncovered, they should be removed as a spatial context rather than an approximate context.
How to Record an Approximate Context #
Taking an approximate context is very straightforward. First, you should open a new context in the database (see instructions here) and set the supra-type to “Approximation.” Fill out the other necessary fields, including opening/closing data, excavator, contamination, etc. Then use the GNSS and connected mobile phone to select the right survey project for the excavation area’s approximate contexts and then record its point coordinates.