thinking about archaeology

Night at the Museum 2

A chance to give Hoa a quick dust

Last night we finished the job of recording the British Museum’s large Easter Island statue (see here for the first post). As with photogrammetry, the really clever stuff with PTM lies mostly in the software and not the kit. The two most important things here were a shiny little black ball, and a piece of string (the latter was the only thing that gave any grief, when the knots came undone).

James sizes up the statue. Not the largest, but still impressive

James and Hembo took photos for four images of the back, showing separate zones from top to bottom (they finished off the first night by doing this for the hands area at the front). For each one, they set the camera up on a tripod at different heights, from the floor to high on the scaffolding (handy stuff when you’ve got it next door with two nice men to put it all together). Then Hembo took lots of photos while the camera stayed fixed, moving the flash around to alter the lighting angles. The really useful kit here was the wireless trigger that enabled him to fire the camera, which itself tripped the flash. The piece of string ensures the flash is always the same distance from a selected point on the statue, so the light has an even intensity – when the flash was in position, James had to duck out of frame so the shot could be taken. And the black shiny ball reflects back from the flash (creating a specular highlight) so the light direction can be calculated by the software.

Positioning the flash with a piece of string. The camera is on the scaffolding out of shot to the left

A shiny ball at a fixed spot in each PTM image allows the light direction to be calculated

Now comes the slow stuff, as we examine the images and work towards a full description of the carvings, and any damage or dressing marks.

You can read more about the Archaeological Computing Research Group at Southampton here, and here is Graeme’s staff page.

2 responses

  1. Greetings Mike, This is something that has always held my imagination. Is there any Information regarding the tools available to the carvers? considering the density of the stone the detail achieved was an incredible feat..Thank you for sharing, this mst have been a fascinating project.

    February 17, 2012 at 6:54 pm

  2. mikepitts

    That’s a good question. Most of the island’s statues are made from a tuff which is really quite soft (at its most weathered it reminded me of weetabix, and some of the remains really are weathering). The quarries are littered with rough stone tools that look as if they were held in the hand. They’re made of basalt, which begs the question how did they shape a basalt statue like Hoa? My guess is they would have used a similar rock that was just that little bit harder. The statue looks as if it was hammered and pecked out of the rock, and finished by grinding and smoothing, as you’d expect.

    February 17, 2012 at 7:25 pm

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