First thing that comes to mind is to ask: Do you really need that high a resolution? Are people really going to be looking at actual print detail from just a few meters away on a project that's nearly 200 meters wide? In other words, are you actually creating fine image detail that matters at the 60 ppi scale?
The second thing that occurs to me is that a typical computer with just 16GB of RAM doesn't seem a good fit for working on gargantuan images. You've avoided doing the math that matters for the readers here, so I'll do it:
- 60 pixels/inch * 39.37 inches/meter * 180 meters == 425196 pixels width
Assuming your full length print will also be 2.5 meters:
- 60 pixels/inch * 39.37 inches/meter * 2.5 meters == 5906 pixels height
So your proposed image at this scale will be 425195 x 5906 pixels == 2.5 gigapixels. Assuming you're using 8 bits/channel mode RGB, that's 7.5 gigabytes to store the image exactly once in RAM.
Keeping in mind you'll need to actually WORK on this image in Photoshop, you'll need at least 10x that RAM (for History states, room to run various tools, etc.) and a LOT of super fast disk storage to be able to swap data to the scratch file. Numbers like 96 GB of RAM and several TB of SSD array storage space come to mind to even begin to think about working on such a huge image.
Any image that takes 7.5 gigabytes in RAM is going to be slow to work on no matter what computer you have today. And if you're hoping to work on an even taller image than 5906 pixels, then you start to get into the realm of computers that haven't been invented yet.
Third thing I'm thinking of is that you may have to divide it into smaller chunks and deal with manually aligning things you want to match up.
You could start working at a MUCH smaller scale, lay the groundwork for the layout using things (e.g., paths/shapes) that scale up nicely, then divide the image up for the finish work.
-Noel
