Yes, I know the pixels per inch is really resolution. I thought that was
not relevant though. But, here it becomes related to scale because of
the lack of image info in the beginning and the default behavior of PSE.
What do mean by "tagged to conform to geographic position"? I always
thought that when they say their maps are 1:24000 scale, that would
always translate to exactly 2000 FPI on the printed map. Of course that
is neglecting plane projection error, which should be negligible for
BTW, the downloaded maps do not have a grid. On the topo maps I have,
the 1000m grid is shown as small blue ticks on the outside border of the
map. There are what appear to be partial latitude and longitude ticks
around the inside of the border. I say partial because some of them
appear to have been left out.
Thinking about this last (longitude and latitude), I guess that the 7.5'
maps, to be constant in scale would have to be different sized (printed
map size) depending on latitude. Maybe this is what you mean by "tagged
Anthony Costello wrote:
It depends! Look up dots per inch in Wiki. Pixels per inch is
to resolution, not scale. Digital USGS maps are rendered as raster, but
the same size image can be rendered at the maximum resolution of the
screen, or anything below. A higher dpi will produce smoother lines.
GIS mapping programs use USGS maps which are tagged to conform to
geographical position, and so scale accurately. Your solution does more
or less the same thing, assuming that the deedmapper projection and the
map's projection are the same, but any difference will not matter on a
small scale. The grid lines on the USGS map will give you the scale -
on the 1:25000 maps they are drawn at 1000m intervals, approximately