Shortly after sending my request about CA charts I finally composed a google search that got me the result I was looking for. Comparing the current CD list of charts to the one I got from JARogers they are an exact match. So now my question becomes: Does Maptech make any changes or enhancements to the age old raster charts that have been unchanged in dozens of years? Some of these charts are marked as No Datum in Coastal Explorer, requiring you to select them for use, acknowledging the datum isn't there. Could Maptech go into those charts and update the Datum? I don't know enough about how the raster images is updated to know if it's even possible. Again, I have no problem paying Maptech $500 for replacement cartography, but only if they have done something to earn my money. I'd feel like a chump if I sent them the money to find they are identical. Oh, I guess the better question is when they convert them to BSB4 did they do anything to revalidate the charts? Perhaps there is a chart update index someplace on their web site I can consult? Thanks, Scott Bulger, Alanui, N40II, Seattle WA

> -----Original Message----- > From: Scott E. Bulger > Does Maptech make any changes or enhancements to the age old raster charts > that have been unchanged in dozens of years? Some of these charts are > marked as No Datum in Coastal Explorer, requiring you to select them for > use, acknowledging the datum isn't there. Could Maptech go into those > charts and update the Datum? REPLY Scott; its highly unlikely Maptech would do such a thing. Too much liability would be incurred. The old paper charts were made to be accurate on a relative basis, referenced to bench marks within the boundary of the chart. In other words, bearings and distances measured on the chart corresponded to the actual locality. Over a limited distance, this still permitted safe navigation. Some areas were surveyed to NAD 27 but the bench marks used for position accuracy have subsequently been lost. Now it becomes an "unknown" datum because the original data cannot be verified. It has to be resurveyed. In addition I know of at least one US chart for the Great Lakes which was a composite from three different surveys done at different times. There is no possible way to upgrade such a chart to be accurate with electronic navigation systems. regards Arild