Google Earth Revisited: Case Studies at the Plain of Larissa (Thessaly, Greece)

Introduction

The '' image '' of a covered monument from the soil or / and crop, embedded in the analogue or digital image, is the result of the interaction of the covered monument with the prementioned elements. This '' image '' is internationally called '' mark ''. The covered monument may be a '' solid construction '', e.g. the foundations of a building or an '' open construction '', e.g. an ancient ditch or an old stream (Figure 1). The result is, in the first case, the appearance of a negative soil or crop mark (light color or light gray in relation to the surroundings of the mark) and, in the second case, the appearance of a positive soil or crop mark (dark color or dark gray). The interaction of the covered monuments with the above elements (soil or crop) is very complex. The form of the event (kind of marks) and the intensity of its observation depend on dozens of factors, such as the type, size and depth of the covered monument, the amount of soil moisture, the temperature of the air, the soil, the type of cultivation or vegetation, the period and intensity of rainfall, the depth of the aquifer, etc. These factors cause, on the one hand, different soil moisture and temperature between the material covering the monument and the material on either side and, on the other hand, qualitative (height, density, color) and temperature difference between vegetation.

Thus, the amount of electromagnetic energy reflected or emitted by these materials (soil or vegetation) is different and is recorded by remote sensing systems (analogue photography, multispectral and panchromatic images, thermal images, etc.), allowing observations to be made on the '' images '' of the covered monuments (Kaimaris, 2006).

Figure 1.

Anatomy of a mark (Kaimaris, 2006)

The tools for archaeologic forecasting are surface survey, historical sources, testimonies, field survey, historical map, aerial photography, satellite imagery and geophysical interruptions.

Google Earth (GE) can be characterized as a complementary and thus helping tool in the frame of a systematic survey of aerial and remote sensing archaeology (Kaimaris et al., 2011). More specifically, apart from the main use of GE imagery in archaeology, which is the observation and further study of known archaeological positions, in some occasions the imagery itself has led to a “random” tracing of unknown covered constructions.

For example, in the Philippi Plain (Macedonia, Greece) the editorial team is conducting systematic aerial and satellite archeology research since 2002. In 2011, during a periodic monitoring of the variation in the magnitude and number of traces of the covered ancient Via Egnatia and other laterally covered monuments, “random” were detected in GE light-colored linear marker images (Kaimaris et al., 2011), which show up on crops and on bare ground (soil). The marks (Figure 2) are 4-7m wide, ~ 5000m long and are located south of the Philippi Plain, between the ancient city of Philippi and the modern settlement of Antiphilippi. No markings or roads were observed at the mark positions on the historic maps of 1901, 1910, 1916, 1925 scale 1: 50,000 and 1: 200,000 and contemporary maps of 1980, scale 1: 5,000 and 1: 50,000. Therefore, they are not the “image” of a road of the early 20th century that was later covered by the ground. The mark may be the result of a covered fortification or a covered historic road that secured communication between the ancient city of Philippi and the settlement-locations that had developed in the area of ​​the modern settlement of Antiphilippi.