My information might be well out of date, but I believe WACs are still produced from film. It's like an acrylic sheet negative, the same size as a WAC and has been in its original form for donkey's years. Every change is made by hand directly onto the film, which is then projected onto a plate and printed. Many years ago, the VNC's were introduced using digital data stored in the supplier's database. The intention was to expand VNC, but the funding dried up and I suppose market justification for expansion was impossible. Initially the supplier's data for the VNC's were no where near as good as the information stored in hard copy on the WAC film. It has become better over time as more discrepancies have been discovered and included/amended. As most would be aware, the big advantage of digital data (VTCs and VNCs) was that it allowed for relatively simple inclusion of other data stored in digital format: airspace, frequencies, etc. with subsequent manipulation for positioning. This was the stuff that couldn't go on WACs because all the hand amendments would wipe out much of the underlying topograhical information in hard copy on the original film.
Another issue with the WAC is that the scale is so small that to print all the information that pilots would like on one chart would mean compromises on the integrity of the topographical information shown. For example, a road or river shown on a scale of 1:500,000 might have to be drawn 1/4 mile wide to be readable on the chart. No biggie in most situations. The same road or river on a scale of 1:1,000,000 might have to be 1/2 mile wide. Combined with an airspace boundary that might have to be shown another 1/2 mile wide and text that might need to occupy 2 miles; the chart gets crowded very quickly and some topographical features have to be sacrificed.
The WAC film is living on borrowed time. It has had information amended and amended so many times, the film has to be handled with care. Why hasn't this information been digitised yet???? Like other things, it relates to money: payback, market, budgets, funding. It's not cheap. Finding the initial outlay is difficult when government departments are supposed to run at a profit. There wouldn't be much change left over from a couple of million dollars. And then how many sales would have to be made before the investment was recouped?
Time is another factor. Possibly the better part of 2 months to get the information digitised for all WACs and then another two or three years going over the data with a fine-toothed comb to make sure nothing is missed prior to release. Meanwhile still amending and producing WACs in the traditional way. While taking the information from the WACs, digitising it and checking it, someone else has to be entering amended information at the same time both on the original film and on the digital data. It wouldn't be a small operation. It would be doubling, or in some cases, tripling the required staff for a period of several years.
Geographical features change. Want something included? Submit notification. It takes time to make it onto a printed WAC, but if it's geographically important, it eventually gets on.
Last edited by Lodown; 8th Jun 2010 at 05:35.