Does Sharp66's reply make this any clearer? The N900 doesn't have a viewfinder, so you can't use that to project the image onto the paper. So what Sharp66 wants is the transparent image layer on top of the image seen by the N900 so that it can actually be traced. If you just hold the N900 next to the paper and try to copy it, you will get an approximation while if you can somehow use a projection, you can do a proper trace, resulting in a very high-quality trace of the original.