If you have a duplication job at hand, you may wonder if one method is better than other. Here are some factors to help you decide for your individual copying requirement:

Longevity--If you know that users will need to access this data over a decade, Replication is recommended.

Readability--Pre-manufactured discs are used in Duplication process, and although blank discs appear to be "generic," track arrangement can vary slightly from one manufacturer to another. This sometimes results in an inability to read data. Replicated discs do not exhibit this problem.

Data Access Speed--When you perform a search you expect data to be retrieved from proper place on CD-ROM--and fast. There is no measurable difference between Duplication and Replication.

Cost--An order of 1,000 or fewer copies tends to be cheaper to produce by Duplication. This is mainly due to fact that no stamping master is required. If you only need a few dozen copies, Duplication is a whole lot cheaper. On other hand, when economies of scale come into play--you need thousands of copies--Replication is your better choice. Copies made from a master disc get much cheaper as you spread out initial cost over a larger quantity of discs. For example, if you order 100 copies, each would cost about $4.40, whereas same disc would only cost about .80 a copy if you ordered 1,000.

Whatever your choice of copying methods, keep in mind that CDs are not immortal. The thin aluminum layer that reflects light of player's laser, is susceptible to oxidation which causes discs to "rot." Never use off-the-shelf markers or ball point pens to write on discs or labels. Most markers contain chemicals which create oxidation, allows air to penetrate aluminum, which is then eaten up--much like iron rusting in open air. There are special media pens currently on market. Search those out.

Whether you choose to do-it-yourself or outsource your next duplication project, take a few minutes to research what software and technology is currently available--it is improving all time. With a little effort, you can create "perfect" project that will make both you and your boss quite proud of finished product.

Figure 2) On-roof IR image.

The next day, thermographer goes back on roof(s) to take matching visual photographs of marked areas that contain subsurface moisture. The problem with on-roof infrared is that when one is standing on roof, eye-level is at best six feet over surface. Even with best hand-held infrared camera available, there is virtually no way to get large areas (800 sq. ft. blobs or 100’ long striations) of moisture contamination on screen in one infrared shot. Taking multiple shots is labor-intensive and makes report confusing. When performing on-roof surveys, many times “you can’t see forest for trees.” Marking roof is fairly easy, but it is very difficult/time-consuming to produce accurate drawings of wet areas from painted lines on a roof. Often drawing supplied by owner is outdated, incorrect or even non-existent.

AERIAL INFRARED ROOF SURVEYING

There is never a time when on-roof imagery is better than aerial imagery. While best IR imagery of a roof is taken from air, same laws of physics apply to both aerial IR and on-roof IR…like a dry roof, low winds and no rain on night of survey. Also, "window" when roof is radiating heat differently from wet and dry areas is longer with aerial infrared because slight nuances of temperatures over large areas are distinguishable. The high angle of view allows aerial thermographer to produce more usable imagery and therefore accurate CAD drawings. The cameras that are used for on-roof surveys are not of sufficient spatial resolution to obtain good imagery from flight altitudes of 1,200 – 1,500 feet above roof, so high-resolution, large format IR cameras (See Figure 3) are required.

Figure 3) Large format infrared imager, fixed-mounted in a light aircraft.

Once aircraft is over a building, very little time (five minutes per 200,000 square feet, about 25 minutes for two million square feet) is required to fly over making multiple passes. The imagery is recorded on digital videotape. Visual photographs are taken earlier in day or next day. After returning to office, photos are printed and thermographs are saved on computer. The raw video imagery, thermographs and photographs are used to make an edited videotape copy of passes over building. Both visual and infrared images are used to do analysis by overlaying CAD drawing of roof ‘over’ digitized photographs and thermographs. The drawings always need to be corrected, because rooftop equipment has been removed, moved or added since last update of drawings. Then, areas of suspected moisture contamination are drawn on CAD file. The result is a report where visual, infrared and CAD components (printed and video) are well matched and lined-up. The report is given to a roof consultant who verifies wet insulation during day, while making other condition notes on roof.

Fixed-wing aerial infrared imaging provides many advantages over on-roof infrared imaging:

·Access to multiple levels of roof is not a problem. ·High-angle, straight down infrared images lessen reflection problems. ·High-resolution images capture large areas at once, making report writing easier and less expensive to produce. ·Plan-view imaging allows for infrared images, visual images and AutoCAD drawings to be reconciled closely. As a result, report is clear, concise and easy to understand (See Figure 4a, 4b, 4c). ·Plan view imaging allows accurate marking of areas of suspect roof moisture contamination. ·The printed CAD drawings can be used on roof to paint areas of moisture contamination directly on roof (after verification), if desired.

Figure 4a) Photograph of a roof.

Figure 4b) Thermograph of a roof.

Figure 4c) Scaled CAD drawing of a roof.

·The aerial infrared thermographer can wait for a good night for imaging, surveying many roofs under good conditions. ·The trending of roof moisture becomes possible. ·An aircrew of two can easily survey many millions of square feet in a single night. ·Processing data is done in office, not on roof. ·Report components can be purchased as needed. Aerial IR allows building owner to buy only report he needs at that time.

The biggest advantage of aerial infrared is on roofs that are most difficult to image from any distance or angle. Roofs that, for instance, have a lot of ballast, are covered with reflective coatings or for whatever reason are impossible to image while standing on roof. With high-resolution, plan view aerial imagery, slight nuances of temperature can be seen from far enough away to actually see pattern of heat and make a determination of where problems are.

CONCLUSIONS

Every day millions of square feet of perfectly good roofing materials are disposed of in our landfills. Why? Because roofs are often replaced because know one knows where exactly roof is damaged until it is too late. If you want your roof to last, it must be regularly maintained by professionals. Infrared roof moisture surveying is best method of non-destructive testing on roofs, and aerial infrared is best platform for performing infrared roof moisture surveys. Improvements in IR cameras and flight methodology, aerial infrared thermography and aerial infrared reports are getting better and more useable everyday.