Rail system for close range photogrammetry

[antoine_morin]

I have a technical photo project that is far from my usual portrait

photography. Maybe some one here can steer me in the right direction.

 

We need to create microtopographical maps of stream gravel beds for a study on

the structure of stream animal communities. We are attemting to apply

photogrammetry techniques to build micro digital elevation models (DEM) of our

gravel beds. Basically, we need series of overlapping photos of the gravel,

taken from above looking straight down.

 

My problem is how to hold the camera still so that:

 

1- it is perfectly level and exactly at the same height for each photo in a

serie

2- photos are taken at exactly regular intervals (say repeated photos at each

12 cm) to create a "row" of overlapping photos

3- a second "row" of photos can be taken at a fixed distance (say 12cm) above

or below the first row.

 

A coarse solution is to use a piece of plywood that I level above the gravel at

the desired height (it will be fun on gravel bars, but I guess a pair of sturdy

tripods can do it). Pierce two rows of holes, each hole wide enough to let the

lens through (presuming I can hold the camera square while shooting through a

hole). Take one picture from each hole position.

 

Any suggestion?

[ben_kriete]

I think you'd get better results from a couple iron (or aluminum) pipes; easier to level, less flex (especially with moisture) and I would think you can get a clamp that will slide along them without too much trouble. Combine it with a level on your camera and you should have a fairly accurate and portable system. I do have some field experience in related projects (New England salmon restoration) if you want to bounce ideas off me via email.

[antoine_morin]

Thanks Ben for the suggestion. I will be experimenting shortly with a pipe and 3 superclamps to hold the pipe on a pair of tripods and the camera. I think that rotating the camera clamp 180 degrees (to the other side of the clamp) will give me just the offset I need.