Stratigraphic Photogrammetry: Part 1 – Calculations for Photometrics on the Olympus C-750

For the last few months, I have been working on a methodology for using terrestrial photogrammetry techniques in capturing stratigraphic profiles. The original idea for this came on the Wenas Mammoth dig (which I wrote about on 10 August 2005), when we were not sure, at one point, if our trench, cut into a wall of loess, would survive over the weekend. At that point, we were only about halfway through our stratigraphic analysis, and a colapse of the trench over the weekend would have set us back very far. I took systematic close-up photographs of the trench wall, hoping to capture some of the features of the stratigraphy in case we lost the wall.

The trench didn’t fall over the weekend, which was a very good thing: in my ignorance, I made many mistakes taking my photographs, and they were completely unusable. Since then, I have been working on the techniques to make measureable photographs of a wall. Because I am using a digital camera to make digital images, the first step in the methodology is to calculate image size, scale, coverage, resolution and spacing for the camera. Because the focal length and sensor size, as well as the pixel resolution, of each digital camera is different, the calculations have to be made for each model of camera (although cameras with the exact same focal length, pixel resolution, and sensor size would have the same calculations). I have an Olympus C-750, which has a focal length of 7.8mm, and a sensor size of 5.67mm x 4.39mm. I am including here a table of all the different calculations for my camera, assuming a screen and print resolution of 200dpi, which would give a photo size of 8″ x 10″.

Update (11/12/05): Going out in the field today to actually try making metric photographs with my camera, using the calculations from Table 1.1 below, I realised that the calculations I made were actually for the Olympus C-140 and C-160 3.2 MP UltraZoom cameras, and that the model that I actually own is the Olympus C-150 4MP. The origianl table of calculations is of no use to me because I don’t own those cameras, but I will leave it here on the chance that someone might be able to make some use of it. I have added the calculations of the Olympus C-150, the camera that I actually own, as Table 1.2, below.

 

Update (11/14/05): I have posted Part 2 of my discussion of stratigraphic photogrammetry using a consumer-level digital camera.

 

Table 1.1 Coverage, Resolution, and Scale Calculations for the Olympus C-740/760 3.2MP Digital Cameras
Distance from Wall DV Coverage (m) DH Coverage (m) Photoscale (200dpi) Photo Resolution (mm/px) Stereo-pair H-spacing Stereo-pair V-spacing
0.50 0.28 0.37
1 /
1.4 0.18 0.15 0.11
1.00 0.56 0.74
1 /
2.8 0.36 0.30 0.22
1.50 0.84 1.11
1 /
4.3 0.54 0.45 0.33
2.00 1.13 1.48
1 /
5.7 0.72 0.60 0.44
2.50 1.41 1.85
1 /
7.1 0.90 0.75 0.55
3.00 1.69 2.22
1 /
8.5 1.08 0.90 0.66
3.50 1.97 2.58
1 /
9.9 1.26 1.05 0.77
4.00 2.25 2.95
1 /
11.4 1.44 1.20 0.88
4.50 2.53 3.32
1 /
12.8 1.62 1.35 0.99
5.00 2.81 3.69
1 /
14.2 1.80 1.50 1.10
5.50 3.10 4.06
1 /
15.6 1.98 1.65 1.21
6.00 3.38 4.43
1 /
17.0 2.16 1.80 1.32
6.50 3.66 4.80
1 /
18.5 2.34 1.95 1.43
7.00 3.94 5.17
1 /
19.9 2.52 2.10 1.54
7.50 4.22 5.54
1 /
21.3 2.70 2.25 1.65
8.00 4.50 5.91
1 /
22.7 2.88 2.40 1.76
8.50 4.78 6.28
1 /
24.1 3.06 2.55 1.87
9.00 5.07 6.65
1 /
25.6 3.25 2.70 1.98
9.50 5.35 7.02
1 /
27.0 3.43 2.85 2.09
10.00 5.63 7.38
1 /
28.4 3.61 3.00 2.20
Table 1.2 Coverage, Resolution, and Scale Calculations for the Olympus C-750 4MP Digital Camera
Distance from Wall DV Coverage (m) DH Coverage (m) Photoscale (200dpi) Photo Resolution (mm/px) Stereo-pair H-spacing Stereo-pair V-spacing
0.50 0.35 0.46
1 /
1.6 0.22 0.15 0.11
1.00 0.70 0.91
1 /
3.1 0.45 0.30 0.22
1.50 1.05 1.37
1 /
4.7 0.67 0.45 0.33
2.00 1.39 1.83
1 /
6.3 0.89 0.60 0.44
2.50 1.74 2.29
1 /
7.9 1.12 0.75 0.55
3.00 2.09 2.74
1 /
9.4 1.34 0.90 0.66
3.50 2.44 3.20
1 /
11.0 1.56 1.05 0.77
4.00 2.79 3.66
1 /
12.6 1.79 1.20 0.88
4.50 3.14 4.11
1 /
14.2 2.01 1.35 0.99
5.00 3.48 4.57
1 /
15.7 2.23 1.50 1.10
5.50 3.83 5.03
1 /
17.3 2.46 1.65 1.21
6.00 4.18 5.49
1 /
18.9 2.68 1.80 1.32
6.50 4.53 5.94
1 /
20.5 2.90 1.95 1.43
7.00 4.88 6.40
1 /
22.0 3.13 2.10 1.54
7.50 5.23 6.86
1 /
23.6 3.35 2.25 1.65
8.00 5.57 7.31
1 /
25.2 3.57 2.40 1.76
8.50 5.92 7.77
1 /
26.7 3.79 2.55 1.87
9.00 6.27 8.23
1 /
28.3 4.02 2.70 1.98
9.50 6.62 8.69
1 /
29.9 4.24 2.85 2.09
10.00 6.97 9.14
1 /
31.5 4.46 3.00 2.20

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