There are two factors that matter when it comes to the detail of a print map: the data resolution and the print resolution.
To make the world's most detailed maps, we only make maps when our data resolution exceeds that of our printed resolution and we print our maps using the highest resolution mediums available.
Over the last 10 years, the availability of elevation data from new LiDAR sensors offers a resolution improvement of 10 to 20 times over historical elevation models.
Traditional digital elevation models are derived from sensors in space. Satellites can be used for photogrammetry, which uses images from different perspectives to derive elevation with around 10-meters of vertical resolution. Additionally, the space shuttle Endeavor used radar to generate an elevation model of most of the world during a mission in 2000, though at a lower resolution.
Today's higher resolution elevation models are derived from LiDAR sensors. These sensors are flown in planes over an area and use lasers to measure the distance between the plane and the ground, allowing for resolutions smaller than half a meter, which is up to a 20x improvement over the traditional space-generated elevation data.
Check out the difference between the two in this shot of Mount Olympus. You can slide between a LiDAR generated image and a traditional space-derived one. In the LiDAR image you can see glacier crevasses and even individual trees. Pretty cool, eh?
Not every map we make uses LiDAR, though. When we make maps of larger areas like our Contiguous US map, it's not possible make a print big enough that would fit in a home that shows the detail LiDAR provides.
Anytime we're showing a mountain, a small national park, or an area that would benefit from LiDAR, we use it.
None of this awesome data does any good unless we're also printing at high resolution. Fortunately printers have been pushing the envelope long before we started making maps.
Our highest resolution options are inkjet prints on metallic photographic paper. They have a printed resolution at about 300 dots per inch (dpi) and incredible contrast, particularly our face-mounted acrylic print, shown here:
When well lit, you can see the light reflecting off of the terrain as you move around one of our prints. Because we design our maps with this effect in mind, it gives them a distinct impression of dimensionality, despite being flat, 2D prints.
There's no sense printing at a higher resolution than humans are able to perceive. For print, 300 dpi is the gold standard.
The amount of detail you're able to see depends on your eyesight and the distance at which you're viewing. For someone with 20/20 vision at a normal viewing distance (say 5 feet) they can discern detail to about 60 dpi, at around a foot they can discern detail to around 300 dpi. I've got laser-corrected 20/15 vision and can't see the limit to the detail on our face-mounted acrylic or wood mounted prints at any distance.
Our aluminum prints are printed at a slightly lower resolution — around 200 dpi. From a normal viewing distance you can't see any difference but once you get within a foot of the print you can start to see some fuzziness.
To print our maps at 300 dpi we need to consider the sizes that we're printing at. Our widest map is 48" wide. To print a 48" map at 300 dpi, we need:
Now dots are not the same as pixels (dots are the base unit of a print, pixels are the base unit of a monitor) but we want at least 1 pixel per dot so that it is the print, not the data that is the limiting factor. So for our 48" wide map, we want our source image to be at least 14,400 pixels wide.
So there you have it, to make the world's most detailed maps we print at the limit of human perception and make sure our source images exceed that resolution!
If you've read this far you should check out our available maps. I'm really proud of how our images look on our website but I promise, they are even more incredible on the wall!