Projection Class Activity

Challenge

Let’s try to make a reprojection of our task map we just created so that is feels more honest or at least asthetically pleasing.

Tools Background

• Here is a nice list of some standard examples (http://www.radicalcartography.net/?projectionref).
• We can see the set of projection types (http://www.progonos.com/furuti/MapProj/Normal/ProjTbl/projTbl.html)
• Then we can look up the projection type (http://spatialreference.org/ref/)
  • to get proj4string.
  • The proj4 format information can be helpfull¹².
    
• There are many online examples³ of using R for spatial as well.

Note the use of +lat_0=45 and +lon_0=-115 and what they do your map.

my_proj <- "+proj=robin +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs"
my_proj <- "+proj=moll +lat_0=45 +lon_0=-115 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs"

states_tr <- states %>% st_transform( crs = my_proj)
idaho_tr <- idaho %>% st_transform( crs = my_proj)

ggplot() +
  geom_sf(data = states_tr, inherit.aes = FALSE) +
  geom_sf(data = idaho_tr, inherit.aes = FALSE)

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1. http://proj4.org/projections/index.html↩︎

2. http://proj4.org/parameters.html↩︎

3. https://earthdatascience.org/courses/earth-analytics/spatial-data-r/understand-epsg-wkt-and-other-crs-definition-file-types/↩︎