st_length

[CheFusi]

There may be an error with the 'meters' column of bike boulevard.

{r}
bart_lines$len_mi <- units::set_units(st_length(bart_lines), mi)
bart_lines$len_km <- units::set_units(st_length(bart_lines), km)
bart_lines$len_m <- units::set_units(st_length(bart_lines), m)

bart_lines$len_m <- units::set_units(st_length(bart_lines), m)

head(bart_lines)

When you calculate the lengths by transforming to various CRS'

bart_lines$len_NAD83 <- units::set_units(st_length(st_transform(bart_lines,26910)), m)
bart_lines$len_WebMarc <- units::set_units(st_length(st_transform(bart_lines,3857)), m)
bart_lines$len_WGS84 <- units::set_units(st_length(st_transform(bart_lines,4326)), m)

you see that Web Marc outputs the closest length to the 'meters' column. The transformation to WGS84 is redundant and was done just to verify how the st_length function is working. So in theory both these outputs should be the same as the 'meters' column.

Caused some confusion during the workshop.