Optical technology as an alternative to RFID
For years, the material handling and logistics communities have looked toward RFID  for solutions to track movable assets indoors. RFID has always presented great customer appeal, with its promise of reliable and consistent data capture, and a wide variety of end-uses and operating environments. RFID projects have produced well documented results for unit load identification, carton and item identification, and more recently, real-time location systems (RTLS ).
So long as customers research the technology, gain formal training, identify key engineering issues, and carefully procure or develop applications, actual results will fall in line with expectations. But RFID systems often represent major investments, and sometimes technical details regarding imperfect read rates, variability of environmental factors, and questionable data accuracy are smoothed over, and by project end, results do not match expectations.
Specifically, buyer’s remorse can be felt in critical moments post-installation, when small technical problems and hidden challenges are suddenly revealed. As a case in point, RF transponders that function well on pallet loads of paper products may be unreadable on steel drums. Radio waves traveling between the transceivers and tags can reflect or attenuate due to the nearby materials. This can result in imperfect read rates, which may distort or degrade the data collection process.
In a second case, consider RFID-based RTLS systems, where RF tags placed on vehicles are monitored for their position within a facility by an array of transceivers and antennas. Accuracies can be good up to 20 feet under ideal conditions, but due to the same effects mentioned above, building contents can have a negative impact on accuracy and reliability.
Steel racking, which interferes with radio waves, and the multitude of warehoused goods can cause significant degradation. For instance, a warehouse full of televisions will create a very different set of challenges than a warehouse full of marshmallows. Consequently, inventory variability can lead to unexpected data collection errors, less than perfect capture data accuracy, and costly reconfiguration.
After working with RFID for several years, the founders of Sky-Trax  offered up a different solution, one based on optics  instead of radio. From that mindset came the Sky-Trax System, utilizing indoor position sensing (IPS) technology.
IPS is designed to use optical position markers (OPMs), which are installed on the facility ceiling.
A sensor is then mounted on each forklift, to track its exact location and feed the information back to a server that keeps a “what/where/when” database, and displays a real-time animation of all vehicles in the facility. Where RFID has claimed accuracy within several feet, IPS measures accuracy in inches, often within an inch.
The advantages of real-time inch-accurate data are plentiful, and still being uncovered. Perhaps the biggest advantage is the new level of driver accountability, and operations visibility. With IPS, the movement of all fork trucks is tracked in real-time, via the ‘Ops Man’ feature, which allows managers to view warehouse operations live on a screen. They see the location of each truck and constantly monitor its activity. They see if vehicles are moving or stopped, how fast they are going, which direction they are traveling, how close to other trucks are they traveling, and so on.
Reports summarize activity for periods of hours, days, and months. In the event that a critical event occurs, such as an unfortunate collision, the manager can replay the animation for the period of time in question. This way, management can witness events leading up to the collision and take preventive measures.
This new element of driver accountability has enormous advantages. Real-time inch-accurate tracking affords real fleet optimization.The standard reporting package provides accurate data to help identify driver performance, operational practices, safety issues and event recording. It clearly shows routing issues, congestion areas, and productivity problems.
Two Forms Of ID
For unit load identification, we have found the same story to hold true. Radio interference, building structures, and load content can degrade RFID tag reading. Bar code read rates have historically been higher under even less than ideal conditions, with accuracy problems more often owed to operator error; for example, when the operator scans the wrong barcode.
The development and widespread acceptance of two-dimensional (2-D “matrix”) barcodes have brought about another alternative. Matrix scanners  are able to read 2-D barcodes with accuracies equal to linear barcode scanners, but with an important additional benefit: label placement, orientation, size, and print quality variations can be accommodated much better by 2-D scanners.
Sky-Trax has developed a label reader that is able to find and decode a 2-D unit load barcode within its field of view in a few milliseconds. Data redundancy designed into the barcode makes the label readable even when partially obscured or damaged. By fitting 2-D label reading sensors to the forklifts, manual label scanning is obviated, saving a major fraction of the labor cost and improving data collection accuracy.
For more information on Sky-Trax, visit www.Sky-Trax.com .