Seen & Found

magicbastarder wrote: »

cheers, i hadn't - but i'm curious as to whether if i do find something which is visible on satellite, but not marked on the archaeology viewer, whether there are any easy or rough guidelines to point to the antiquity of them?
i kinda just picked that field at random.

I waited a while to see if anyone else wanted to offer help on this subject.

There is a wealth of online resources to check the 'antiquity' of features.
The first port of call is undoubtedly the Historic Environment Viewer provided by the National Monuments Service. This is an online resource cataloguing all monuments known to date from before 1700 AD.* It is the online version of the Sites and Monuments Record (SMR) and is maintained by the Archaeological Survey of Ireland (ASI) with 'new' sites added as they are reported.

The records from the SMR are replicated on two other sites:
http://map.geohive.ie/mapviewer.html
and,
https://heritagemaps.ie/WebApps/HeritageMaps/index.html

Both of these sites have the considerable advantage that it is possible to work backwards from the potential discovery of a feature through aerial imagery. In other words: if you think you may have found something interesting, it is important to check if it persists in earlier aerial imagery. If it does, then it is more likely to be something of substance rather than an illusion.
The ASI webviewer is limited to recent aerials and historic mapping. Geohive and Heritage Maps include imagery from 1995 (B/W), 2000, 2005 and more up to date imagery as well as the Historic Maps. These layers can be switched on as necessary and their transparency adjusted which can be very useful.

Then there are a number of satellite imagery resources like Google Earth, Bing Maps and others.
The time slider on Google Earth is a really useful tool. If a potential feature appears on the current imagery, it's always a good idea to slide back in time and see if the feature persists. There are a number of other processes that can create features that appear to be something from antiquity, especially if your eye is tuned in to circular features. Agriculture is probably the primary source but nature can throw up some convincing shapes too in the form of 'fairy rings' created by fungal growth and other quirky formations. Drains in fields can often form puzzling arrangements and create the impression of something from antiquity. Often too, earlier field fences/boundaries were removed to create more open fields and sometimes the isolated remains create a false impression. It is crucial to always compare up to date imagery with the historic maps. Another aspect of agriculture that can easily deceive is animal feeders. They can often look extremely like barrows.



It's not easy to distill down a whole aspect of archaeology into a single post but I hope that this has given you some pointers. It's really all about becoming familiar with the resources and getting an eye for the right things.

One last thing to remember is that genuine cropmarks that indicate the presence of something archaeological vary in how they were formed. There are 'positive and negative' cropmarks. These are formed by either building something up or digging down. Positive cropmarks tend to be lighter in colour because the dry more rapidly and do not retain moisture - they indicate the presence of something that was above original ground level and possibly a higher concentration of stone. Darker cropmarks indicate the existence of something below original ground level that retains moisture - usually something like a ditch.
Or you might find something like this as yet unrecorded feature which has both positive and negative cropmarks. The positive cropmarks have been ploughed out and distributed but the surrounding ring ditch survives well.



Archaeologists always undertake an intensive desktop survey in advance of any excavation and these resources form the backbone of that survey; along with documentary evidence and analysis of previous excavations. It really is a whole set of skills unique to the profession but the contribution of non-professionals in recent years has been outstanding.


* There is some confusion about the so-called post-1700 AD cut off point. This cut-off applies only to the schedule of listings on the ASI. It does not imply that anything dating to after 1700 AD is not archaeological and does not imply that anything from after 1700 AD is not afforded the same protection as anything dating from 1700 BC. All archaeological objects have the same level of protection no matter when they date from.

magicbastarder wrote: »

cheers - much appreciated.

one thing i was wary of, and i don't even know if the effect of it would last long in the soil, would be circular feeders a farmer would drop in a field for feeding cattle; but i suspect these would be uniformly small (only 2 or 3m across)?

Check out the first photo in the post above. The rings are from cattle feeders.
If rings like this are close to farm buildings, then there is a greater chance they are the result of animal feeders