# Projections for solar eclipse umbral paths

Most projections of the path of totality for the 2017 solar eclipse look like

But there are also maps online using different projections such that the path is a straight line or mostly straight line, as in

I cannot find any CRS for the latter. The ideal CRS for me would produce a straight path (just has to be mostly straight for the part of the path across the US) and in addition the path would be straight up and down with "west" side on the top. I am using QGIS but I am amenable to switching to another open source package if necessary.

@MichaelZeiler said (and I have confirmed) that for this particular eclipse and this part of the run (the US) a standard projection happens to work well enough to produce a satisfyingly straight enough umbral path: EPSG:102003 = USA_Contiguous_Albers_Equal_Area_Conic

+proj=aea +lat_1=29.5 +lat_2=45.5 +lat_0=37.5 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs

Now I am trying to figure out how to transform that into a CRS that produces maps that are rotated 67.560 degrees clockwise relative to the above.

In other words I want to change the CRS so that I get

Notice how all the labels are horizontal. This is an advantage of changing the CRS as opposed to the Canvas and other solutions - labels just work normally for all new layers. I still don't understand how to change the CRS after reading a number of pages.

Xavier Jubier said that a good approximation of a straight line can also be obtained with EPSG:102009 = North_America_Lambert_Conformal_Conic

+proj=lcc +lat_1=20 +lat_2=60 +lat_0=40 +lon_0=-96 +x_0=0 +y_0=0 +datum=NAD83 +units=m +no_defs

I have learned after many searches that there are obscure projections that will give more exact and general astronomy related solutions and anyone wanting to take this more difficult approach will want to know the keyword quincuncial.

• If you want folks to look at your graphics, it's best to include them in the post (properly cited), since link-throughs aren't as common as question links. It would also make a better quality question, since the links tend to fail over time. As a new user, please take the Tour Oct 26, 2016 at 3:35
• The second image appears to be from greatamericaneclipse.com. Have you tried asking them directly? I'm sure they'd be happy to help. Oct 26, 2016 at 8:10
• Actually, Xavier Jubier's site is also referenced here greatamericaneclipse.com/resources. Looks like this is the go-to place for eclipse resources. Oct 26, 2016 at 8:13
• You could use the Space Oblique Mercator or the Oblique Mercator, but it will take a bit of care getting the map right. landsat.gsfc.nasa.gov/?p=8718 Oct 28, 2016 at 19:44

Try Oblique Mecator, e.g. with

"+proj=omerc +lonc=-100 +gamma=90 +alpha=10 +lat_0=30 +ellps=WGS84"

Here's an R example, just to show what I tried. I haven't explored this in any depth.

``````library(rgdal)

prj <- "+proj=omerc +lonc=-100 +gamma=90 +alpha=10 +lat_0=30 +ellps=WGS84"

library(USAboundaries)
us <- us_states()

library(graticule)
g <- graticule(seq(165, 300, by = 15), seq(-30, 85, by = 15), proj = prj)
gl <- graticule_labels(seq(165, 300, by = 15), seq(-30, 85, by = 15), proj = prj, xline = 285, yline = 20)
x <- spTransform(us, prj)
plot(x)