Frequently Asked Questions
What is the minimum possible size of an object to digitize?
What is the Maximum size of the object to digitize ?
Can I scan an object ?
Can I use my own printer for print coded targets ?
Can I use my own camera ?
Can I use several cameras with the same software ?
Can I "zoom" between photos of the same project ?
And what about accuracy ?
How many targets can I use in a single project ?
Is there a limitation to the number of photos ?
What is the minimum possible size of an object to digitize?
The minimum size is limited by the size of the coded targets you can position on the object. Generally speaking, a 100x100x100mm object is the minimum size.
What is the Maximum size of the object to digitize ?
There is no limit to the size of an object, the only thing is that the coded targets must be visible on the photo and "readable".
If you can print and place large coded targets, and if the black center circle of the target has a diameter of more than 6-8 pixels on the photo, our software can reconstruct the 3D scene.
We have made successful reconstruction with parts measuring 20.00 meters x 5 meters.
Can I scan an object ?
Except for Orthopaedic application where we have a special command for rebuilt organic part, no, you cannot scan an object. Photogrammetry is not a scanning technology like a laser scanner. It creates Points in 3 Dimensions, where you need points
Can I use my own Printer for print coded targets ?
Yes, of course you can print your own coded targets with all standard Windows printer Inkjet, laser... (from A4 size to A0++)
Can I use my own camera ?
Theoretically yes if your camera is recent and have more than 5 Mega Pixels sensor (our softwares have difficulties to read target on images with less than 5 MP), all the digital cameras will be usable, but taking into consideration the ever increasing number of cameras available on the world market, we cannot unfortunately test them all, nor guarantee that your camera will enable you to obtain the precision which you require.
It is necessary that your camera records certain “EXIF” data in each image (to our knowledge all the “modern” cameras record EXIF data - EXangeable Image spins Format).
You will find more information on EXIF data on the following website:
Exchangeable image spins format. (2006, September 20). Wikipedia, the free encyclopaedia http://en.wikipedia.org/wiki/EXIF.
Can I use several cameras ?
As you would expect, our softwares works with an unlimited number of cameras.
Software will automatically look for an existing calibration file for a given camera in its database. If it doesn't find a calibration file it will automatically use the camera's data stored in the EXIF of each image. In this case measurements will be less precise but you will obtain at least an estimation of 3D points.
Can I "zoom" between photos of the same project ?
No, for the moment you cannot change the zoom level between photos.
In the same manner, it is essential to use exactly the same zoom level as the one used when calibrating the camera (usually the lowest zoom level).
And what about accuracy ?
Accuracy is relative to the size of the part.
The accuracy of the 3D reconstruction depends off several factors :
* The resolution of the digital camera and quality of the lens.
* The quality of the Camera calibration.
* The number of photos (more photos gives better accuracy).
* The number of targets positioned on the part to digitize (more targets gives better accuracy).
Current tests gives an accuracy of 5/1000 to 2/10000 depending on the camera and lens.
Accuracy test sample with a entry level Digital SLR camera :
Camera : Nikon D40 (6Mp)
Lens : AF-S NIKKOR 18-55 ED (Locked to 55mm and calibrated)
Camera Setup :
* Manual Mode
* Apperture : F/8.0
* Integrated Flash : On
* ExposureTime : 1/160Sec
* ISO : 400
Object : Cube 100x100x100 mm
Material : Steel (XC48)
Accuracy of Object : +/- 0.015mm (grinding-machined)
Number of targets positionned on the cube : 40 (8 per face)
Size of targets : 17.80x10mm (HERMA Removable Label Ref : 4343)
We take 17 shots of this cube, rebuild the scene, then draw Plane Surfaces through the points of each face ("_PlaneThroughPt" Rhino command).
Results :
Max Error Distance on Plane surfaces : 0.038mm (3.8/10000).
Mean Error Distance on Plane Surfaces : 0.013mm (1.3/10000).
Standard deviation : 0.009mm : (0.9/10000).
How many targets can I use in a single project ?
The number of coded target is limited by the coding :
The standard version uses 14 bit coded targets.
Theoretically, a 14 bits coding give 16384 possibilities but as our softwares reads target in any positions, this give 1167 different targets for a 14 bits coding.
Targets can be coded from 8 bits to 17 bits.
This give at Maximum :
- 35 different Targets for 8 bit coding
- 59 different Targets for 9 bit coding
- 107 different Targets for 10 bit coding
- 187 different Targets for 11 bit coding
- 351 different Targets for 12 bit coding
- 631 different Targets for 13 bit coding
- 1167 different Targets for 14 bit coding
- 2191 different Targets for 15 bit coding
Notes :
- Higher the number of bit coding is, more difficult it is to decode, eg : A 15 bit coding is more difficult to read than a 12 bits and will require bigger targets on the photo
- The uncoded target number is unlimited
Is there a limitation to the number of photos ?
No, theoretically no, but you can be limited by the memory of your PC.
We have made tests with 200 photos on a PC with Win XP - 2Gb RAM.