We had our last day of digging last wednesday, followed by a lot of sweeping, photography, packing, and cleaning. We left Karmiel on saturday, and now most of our students and some of our staff have already returned home.
Here is a short video of time lapse photographs, taken during the field season, that shows some of what it is like to work at Marj Rabba. Thanks so much to all of our students, staff, volunteers and interns for a successful 2013 season!
Last season we began using aerial photography and photogrammetry to document excavation at Marj Rabba. We used a quadcoptor, an r/c plane, and a pole aerial photography rig to record images of the site at several altitudes. The pole was great for low level recording of features and individual squares, the quadcoptor was great for getting photos of the entire excavation area, and the plane was getting aerial photos of the entire area around the excavation. Our original plane, however, was only set up for carrying a GoPro Hero camera which takes great pictures but is not ideal for doing 3d photogrammetry because of its extremely wide angle lens. This set up gave us some good initial results and some excellent individual images of the site, like this:
This year we are using a larger model that has a better payload carrying capacity. It can fly longer, carry 2 cameras simultaneously, and is more robust:
Today we had the first successful flight of the season. The 2 camera setup means that we can get a nice video recording of what the landscape looks like from above while simultaneously recording vertical images that will be utilized for 3d modeling and mapping.
Here is a video of what the site looks like from onboard the plane:
As was discussed in the earlier post, the vertical still images provide the basis for 3d modeling. Here is a composite image (an ortho-mosaic) of the field system surrounding our site. This composite image is fairly low resolution, as it was constructed from a small subset of the total images to check how well the image recording went. However, this is a distortion free image and can be exported directly into our GIS map of the site. By doing a few more flights, processing the photographs more intensively, and combining them with data collected with our Total Station, we will be able to generate a complete high resolution composite image of the area as well as a high resolution digital elevation mode (DEM):
We have several Unmanned Aerial Vehicles at the site. While they are primarily used to take vertical still images, they can sometimes be used to record videos of the site. Here is a short flyover of parts of areas CC and BB taken from our quadcoptor. This was recorded on a windy part of the day, so I did not fly particularly high or far, it just gives a brief glimpse of work at the site. The quadcoptor does not have any stabilization, so this video is somewhat unsteady:
Videos like this are of limited utility for anything other than recording pretty images of the site. What the UAVs are normally used for is to build 3d models of the site from sets of still images. These 3d models are powerful tools for research, mapping, and publication. They ALSO provide a way to see the site from above. Here is a quick, low resolution model of area CC, the same area that I was flying over in the video above. This is just a screen recording demonstrating how you can navigate around a 3d model in Photoscan (the software used to make these). After this stage, the 3d models will be geo-rectified and exported to arcGIS.
Today was day one of Marj Rabba, 2013. We started with a short tour of the site, to get our new crew members oriented. Short talks were given by all the directors and supervisors about various areas and features:
MK talking about the first season
YMR giving an overview of the main excavation area
The site looked a little beat up after sitting for a year, but this did not deter us, and we got to work clearing away vegetation, burst sandbags, and loose soil:
Cleaning up area BB
Here are aerial shots of the main excavation area from the quadcoptor, just after we got to work:
By the end of the day, the site was looking much better and ready for real excavation to begin tomorrow: