Faster yellowing of pea plants mark the line of a Roman ditch. In the background, the large earth levee of the "Camp of Caesar" can be seen. La Chaussée-Tirancourt (Somme). Port-le-Grand (Somme). Here, it is the frost that reveals the location of a protohistoric circular enclosure.
 
Port-le-Grand (Somme). Here, it is the frost that reveals the location of a protohistoric circular enclosure.
 
Neufmoulin (Somme). Early morning dew traces the location of a Bronze Age ditch. This type of phenomenon has fueled legends about nocturnal witching ceremonies!
Checking on the ground
In the landscape
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Faster yellowing of pea plants mark the line of a Roman ditch. In the background, the large earth levee of the -Camp of Caesar- can be seen. La Chaussée-Tirancourt (Somme).
Port-le-Grand (Somme). Here, it is the frost that reveals the location of a protohistoric circular enclosure.

Port-le-Grand (Somme). Here, it is the frost that reveals the location of a protohistoric circular enclosure.

Neufmoulin (Somme). Early morning dew traces the location of a Bronze Age ditch. This type of phenomenon has fueled legends about nocturnal witching ceremonies!
When it comes to more extensive leveled-off remains, they are only partially perceptible at ground level, which can be a source of confusion. A line of crops that appears greener or more yellow can simply be the result of a trail of manure. Nevertheless, if the phenomenon occurs several seasons in a row, or if the same line appears on bare ground in winter, in another form, it could be a clue to the presence of a buried archaeological site.

In both cases, recourse to aerial photography can give an overall view of these anomalies. In the same way, looking down on a site from high enough to have the necessary perspective often considerably lessens the confusion.

The ground-based prospector should explore the fields bordering sites known through bibliographic research, and particularly in the vicinity of raised earthworks that are very visible: ancient or medieval entrenchments, tumuli, etc. For thousands of years, people have been drawn to the same types of places — hills, exposed slopes, confluences of rivers, and above all the heights that overhang them. As everyone knows, oppida, feudal mounds, etc. are generally mentioned and even depicted on 1:25,000 scale maps from the IGN. Taking this as a starting point, it is in the interest of the "history investigator" to scour the countryside. He or she could also look into significant named-places, and talk to old farmers — legendary sites are always archaeological ones.


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