Suitable projection for a map of Japan

Question

I'm making a map of Japan in QGIS which will span UTM zones 54 and a small part of zone 53 (central and North Honshu). I'm using Natural Earth raster and shapefile datasets with some WGS84 based location points plotted on, but would like to set a projection that represents the distances between points relatively accurately across the whole map (also giving an accurate scale bar).

Would just using Japan UTM zone 54 for the project CRS be suitable, or would someone be able to direct me towards a more suitable projection and how to implement this in QGIS?

Answer 1

The official JGD2000 Japan Plane rectangular CS is the most precise CRS, but it needs 18 different zones.

So I think that UTM 54N is the best choice to draw a map of whole Japan. You can store your data in WGS84 as well, and select one of the 18 zones as project CRS for printing local maps.

I would not recommend Google Mercator, because this has correct metres as units only at the equator.

Answer 2

UTM 54 N is a good first choice, because it fits your area of interest quite well (so the scale error is reasonably small) and because it's simple to use: It's already included in the standard projection of QGIS.

Depending on the purpose of the map, you might want to consider using a projection with custom parameter values. You could, for example, use an equidistant conic projection with the central meridian 138°E and the standard parallels 34°N and 40°N:

Compared to the UTM 54N projection, this has two advantages:

1. Not only one meridian is standard, but all of them are (though that's not really an issue for an extent as small as this)
2. More importantly, the meridian at the center of the map is vertical (notice how the UTM 54N map is slightly tilted)

To use this projection in QGIS, you'll have to define a custom CRS with the following proj4 string:

+proj=eqdc +lat_0=0 +lon_0=138 +lat_1=34 +lat_2=40 +x_0=0 +y_0=0 +ellps=WGS84 +units=m +no_defs