As for the handheld units I was looking at something like this, or similar
Creaform | Online Resources, Inc.
I'm not going to put myself out as an expert in metrology, so take what I say with a grain of salt. I'm a bit skeptical about the results you would get scanning a full car with the Go!Scan or any other handheld scanner less than 50k USD. The reason being as follows:
1) all optical scanners work with the same principle: project a series of lines onto an object with a light source (e.g. a projector or laser) and record that line with a camera physically offset from the light source (the line will no longer be a straight line due to the shape of the object and the offset of the camera). Then do the math to turn the distortions of the recorded line into 3d points of the object surface.
2) because the geometry of the handheld scanners is inevitably fixed, so is the scanning field and because it is handheld, that field is inevitably small.
3) to scan a large object, you therefore need to combine many small scans into one large scan, but you lose accuracy every time you merge two scans (you need a significant amount of overlap of the scans and fixed reference points). More merged scans = less accuracy.
4) the expensive handheld scanners, e.g. FARO or Creaform's HandyScan combine the handheld scanner with a system to track the 6D position of the scanner to improve the accuracy of the merging process. But then we are talking about BIG BUCKS.
5) The advantage of the structured light scanner solution (not handheld) is that the geometry is not fixed: With the same hardware you can make single scans as large or as small as the hardware permits. With my hardware I can do a 3mx4m scan in one go (to go larger, you just need a brighter projector). So to scan a full car, I am stitching together 5 scans instead of 500 scans. But with the projector I am using, I can also make a 30cmx40cm scan (shortest focal distance of the projector lens).
6) A structured light scanner is very cost effective. To put together a structured light scanner, you just need software ($400), a projector, a camera that can output live video to your computer, a tripod, and bits and pieces to hold it all together. More money = more accuracy, of course. However, you are still way ahead of the other solutions. A top quality solution: $1200 for the camera, $400 for the lens, $1000 for the projector, $800 for the tripod and head, plus another $200 for the various bits to hold everything together. You can definitely go a lot cheaper than that too.
