I did buy the Groundvue 3A ground penetrating radar cart that I discussed in my earlier post, and have been giving it a go at Oaklands Park, where I did a large magnetometer survey with IHRG a while back. There were a few areas where we thought that there might be a possibility of buildings. The results have been very positive. The two survey areas we covered, outlined in red in the image below, are 40x40m and overlap as we found that the building was on the edge of the first grid we did. The first area, to the north-east, was recorded down to 70ns. The second area, to the south-west, was recorded down to 50ns.
GPR survey areas. Click to enlarge.
There are interesting features at various levels, and to get a full idea of them all, you need to look at different depths. Below are features from 10ns and 13ns followed by an interpretation. To get a better picture of what is going on, you can look at the whole lot on youtube. The video for the first survey is here and for the second survey is here.
Features at 10ns. Click to enlarge.
Features at 13ns. Click to enlarge.
Interpretation over magnetometry. Click to enlarge.
You can see in the above image the location of features on the GPR surveys overlaid on the magnetometry results. The most important feature is the building in dark blue. This shows up fully on the magnetometry, but the west wall and a second north wall are missing on the GPR results. This may be due to robbing. The green feature seem to be metalling on a trackway, most likely iron slag. It doesn't extend all of the way along the track, but seems to have been placed outside of the building, which may indicate that this section of the track was busy and in need of repair. The two light blue features are very strong both magnetically and very dense on the GPR results. They may be where the iron was processed. The yellow lines are boundary features, which mark out an enclosure around the building and a further enclosure to the north-east, the other side of the track. The orange areas are large pits. On the GPR results, these can be seen to reduce in size as they go deeper. Light purple areas seem to be dumps of material with no pit. Finally, the small dark purple feature to the north-east seems to be a well. It is circular, with a small L shaped feature attached at higher levels, which disappears further down. While all other features disappear by 30ns, the well keeps going all the way down to the 70ns recording limit.
These GPR results are great. I'm looking forward to using it on a lot more sites in the future.