Support for crossing the date line (anti-meridian) for polylines and polygons

[schloerke]

Original reference from #550

Leaflet.Antimeridian

See this plugin that could be used with leaflet: https://github.com/briannaAndCo/Leaflet.Antimeridian

Normal leaflet (from plugin README)

With anti-meridian plugin: (from plugin README)

While this is typically something that would be better for leaflet.extras, I believe this is a VERY common situation and should be apart of the core leaflet R package.

Bad Example

The polygon should be over the Atlantic ocean, not all of Eurasia.

library(leaflet)
leaflet() %>% 
  addTiles() %>% 
  addPolygons(c(140.0, -120.0, 170.0), c(20, 50, 70))

[tim-salabim]

Without having had a look at the plugin, does it also work for raster images? See the first ever mapview issue r-spatial/mapview#6

[schloerke]

I don't believe so.

It should be possible to adjust the raster to have longitudes larger than +- 180. This is Leaflet.js's suggested method (The requirement of true is no longer needed.)

Doing the adjustment with polyline...

library(leaflet); 
leaflet() %>% 
  addTiles() %>% 
  addPolygons(c(140.0, -120.0 + 360, 170.0), c(20, 50, 70))

This R package implements adjusting a raster to wrap from [0, 360] instead of [-180, 180]. (Even with a comment to an existing issue!)

@tim-salabim, Would either of these work?

[tim-salabim]

@schloerke thanks for the quick reply. Unfortunately, the suggested adjustment does not work with rasterImages. The solution with crop and shift is close, but not optimal. I'll have a closer look again... Sorry to hijack this!

[schloerke]

Np! I've seen this "feature" issue multiple times now. Thought I'd formalize it into an issue.

Would be interesting to try an treat it as a "set-able" line for polyline and polygons. Would not need to force the wrapping to occur at -180 or at 0. Could easily be done with any other value, like 42, which would cause the range to be [42, 42 + 360].

[jmlondon]

Thanks for keeping this topic moving forward. For those of us who regularly work in the Pacific, it will be great to have a straightforward workflow in place. Down the line, I would be happy to contribute a vignette with example code and workflow best practices when dealing with the anti-meridian issue.

[schloerke]

Linking to raster issue: #225

[rjwicks]

Original reference from #550

Leaflet.Antimeridian

See this plugin that could be used with leaflet: https://github.com/briannaAndCo/Leaflet.Antimeridian

Normal leaflet (from plugin README)

With anti-meridian plugin: (from plugin README)

While this is typically something that would be better for leaflet.extras, I believe this is a VERY common situation and should be apart of the core leaflet R package.

Bad Example

The polygon should be over the Atlantic ocean, not all of Eurasia.

library(leaflet)
leaflet() %>% 
  addTiles() %>% 
  addPolygons(c(140.0, -120.0, 170.0), c(20, 50, 70))

Thanks for keeping this topic moving forward. For those of us who regularly work in the Pacific, it will be great to have a straightforward workflow in place. Down the line, I would be happy to contribute a vignette with example code and workflow best practices when dealing with the anti-meridian issue.

My team is running into this issue. Are you aware of any effort to fix it and integrate it with the core leaflet R package.