PhotoModeler Coded Targets and Automation
How to automate some measurement tasks
Automation of 3D point extraction and/or the project setup (initial marking, referencing, and orientation of photos) can be done in two ways. In both PhotoModeler products, the Coded Target feature provides one form of automation. Coded Targets are described below. The SmartMatch feature carries out a similar function with non-targeted points.
A coded target is a high-contrast dot with a pattern around it that is placed in the scene before photography. The targets are identified automatically by the program from the images. There are two forms of coding – the RAD target, and the non-ringed coded target.
The RAD target (pictured to the right) is more robust and recommended for most new projects. These targets are printed easily on your own printer at the required size and quantity from within PhotoModeler. If you need a more permanent configuration you can send postscript files to a sign shop for production in vinyl, or visit one of the 3rd party manufacturers listed below.
The offset coded target provides an automated method for obtaining the location of a point where a target cannot be placed (such as in a corner or under a lip). These can also be printed on your own printer. Each offset pair has two RAD targets and a 3rd offset point that gets measured automatically:
The Coded Target capabilities in PhotoModeler include:
- printing of targets to a Windows printer or to a Postscript file
- high accuracy sub-pixel marking of coded target dots
- manual marking with automatic referencing of coded targets
- automated marking and referencing of coded targets in a region, whole photo, or multiple photos
- fully automated point-based projects using coded targets
- ability to mark targets in natural environments with ‘noisy’ backgrounds
- naturally lit targets (no flash required) (although reflective targets with a flash can be used too)
- Up to 999 unique target codes are available (with new RAD targets available in version 6.3+). 8, 10 and 12bit unringed coded targets have fewer codes.
- Offset target system which provides an automated method of obtaining a 3rd 3D point that would not normally be accessible by using two other coded targets
Coded Targets can assist with virtually any project (optimal with scene/object sizes from 50cm (19in) up to 30m (100ft)). Most PhotoModeler projects require the basic geometry of the camera stations to be solved (called orientation) and coded targets provide a very quick way of doing this.
Target sizes w/ Nikon D90 and 20mm lens
Approx. target size
50cm / 1.64ft
8mm / 0.31″
2m / 6.6ft
32mm / 1.26″
10.5m / 34.5ft
168mm / 6.6″ ‡
14m / 46ft
223mm / 8.8″
|† scenes can be larger – this is typical ‘ground’ coverage for each photo.
‡ largest RAD target that can print on a 8.5″x11″ sheet.
Target dots are used (along with PhotoModeler’s subpixel marker) in any application where high-accuracy 3D points are needed. In these applications, you can further automate and speed up these projects by using Coded Targets
Fully automated measurement of a manufactured part
Automated Offset Target measurement of a stair case
Coded Targets used to automate project setup in Scanner
3rd Party Target Manufacturers
The companies listed below sell dot targets for general photogrammetric use, and several also make coded targets for specific use with PhotoModeler. Targets can be printed from within PhotoModeler on your printer but in situations where greater robustness is needed the products below may be what you need. Note that these companies are not related to or supported by PhotoModeler Technologies. Please contact them directly for information on availability and pricing.
- WNBC in LA – retroreflective dot targets of various sizes, backings, and configurations. Custom targets are also available.
- DCM Technical Services – PhotoModeler specific RAD targets in strips, individual, and on rods – all on hard plastic.
- HUBBS – high precision photogrammetric targets.
- Brunson – high precision photogrammetric scale bars.