FYI:
The FEMA world *.png / *.pnw are in UTM meters and not State Plane, so a simple scaling of meters to feet will not work. Also, it won't work to convert the insertion point in the file to state plane coordinates in feet, either. While it gets close, there is a rotation issue from UTM to SPCS, which could be calculated at the insertion point, but there doesn't seem to be a way to automate it by just editing the world file.
I had emailed help from the FEMA map specialist about what conversion was necessary before I found out what has been stated, and I got back a response " .. We recommend viewing the National Geodetic Survey (NGS) guidelines for making conversions between meters and feet by visiting at http://www.ngs.noaa.gov/faq.shtml#Feet. " There is more to it than that, though, it appears, but it can be done by converting, scaling, and rotating it manually in plain CAD. It would probably be simple in Acad Map.
Thanks to the others who responded.
I use Global Mapper. Bring in PNG as UTM meters (metadata should have Zone). Change to SPC (unit) and export with new world file.
DDSM
Yes, that will work, I didn't think of that.
I have been meaning to buy the latest version.
This would be a good time to do it.
thanks, JT
