Monument type
Scattering of shards indicating a villa rustica in a vineyard

Survey data
Area investigated: 110 m x 157 m
Resolutions:    diverse (a = 1,0m) : 17.270 m2                  

Array configuration: Square array (a = 1.0m)
Measuring instruments: Lippmann 4point light MC
Imaging software: SURFER (Golden Software)
Survey period: 07. 2013

Comments
The presence of iron rods and wires make it impossible to use geomagnetics in the vineyard and Georadar is also easily disturbed by too much metal. For this reason earth resistance surveys are the best method for geophysical prospecting in the vineyard due to their insensitivity to metal objects.

The following conditions must be observed when taking measurements in the vineyard:
- Since the entire area is already deep-plowed  between 60 cm and 90 cm before planting a vineyard, the archaeological structures contained therein are often largely disturbed.
- After planting, the soil in the vineyard is only superficially and slightly loosened. Over time, this creates a heavily compacted subsoil that can weaken the value of measurable contrast.
- Vineyards usually consist of several plots with different vine row and vine spacing (Fig. A). On the survey area steel rods and wires arranged in rows to attach the vines, only allow moving along the rows of vines. A movement transverse to the rows of vines is not possible.

- Every second lane between the rows of vines is regularly driven over by machines and is therefore particularly heavily compacted. These compactions form a stripe-shaped pattern on the measurement image, which must be subsequently removed again through image processing. (Fig. B)

Despite these limiting conditions, geoelectric prospecting in the vineyard is rarely inconclusive. It can even be extremely rewarding at times. An insight into the range of possible measurement results is documented by the author in several examples: (Langenlohnsheim, Niederkirchen, Großwinternheim, Königsbach, Weyher, Wachenheim, Gönnheim)

Special features of measurement technology in the vineyard:

If you tried to measure the vineyard, as usual, in an even, precise grid, this would lead to an extremely time-consuming measurement because of the extremely restricted freedom of movement on the measuring area. It therefore makes much more sense to first carry out a less precise overview measurement as a basis for possible subsequent detailed measurements. Fig. C shows the different sizes of plots, their vine row distances (lane sizes), their vine spacings and the resulting measurement grid of each individual plot. Fig.D shows the resulting measurement images of the individual plots.

In order to be able to walk the measuring tracks in both directions, as usual, a twin arrangement with a trailing cable to be tracked to the stationary electrodes cannot be used. The reason is as follows: the trailing cable would have to be routed around the row of vines at the end of each lane and pulled in the opposite direction. On the one hand, this fails because it would get stuck at the deflection points because there is a lot of friction there, and on the other hand, the line would have to be extremely long, heavy and unwieldy, since it would have to be pulled along all the lanes one after the other...
With a square electrode arrangement, however, you have complete freedom of movement and you can measure back and forth in the lane between the vine rows or, depending on the situation, back in the following lane. In this way, wider lanes of vine rows can be divided into two or more measuring tracks and narrow lanes of vine rows can be covered in just a single measuring track. The number of measuring tracks in the lanes must be decided on site. Careful documentation of the number of measuring tracks caried out in the lanes of every plot is important for subsequent image processing. This documentation provides, along with the width of the lanes and plots, the necessary correction values ​​for subsequent image processing.

The with of the lanes, which changes from plot to plot, usually varies between 2 m and a maximum of 5 m. Since the square array frame has a fixed size of 1m  by 1m and only rarely corresponds to the paths run in the lanes without gaps or overlaps, a certain inaccuracy arises in the grid, but this does not affect the reliable recognition of archaeological structures.
By horizontally compressing or stretching the individual plots, a measurement image that is sufficiently true to scale with regard to the image width, is generated in subsequent image processing with the help of the correction values ​​(Fig. E).

Since the spacing between the vines within a plot are uniform, i.e. always the same distance, you can work in each lane without laying out a tape measure by simply measuring from vine to vine. The different spacing distances between individual plots lead to different numbers of measuring points per measuring track. They are subsequently adjusted to the true-to-scale image height during image processing by stretching or compressing them vertically (Fig.E).