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Identify the prime meridian convention from longitude values

Source: R/nctools_spatial.R
findPrimeMeridian.Rd

Infers whether a longitude vector is expressed using the `[-180, 180]` convention or the `[0, 360]` convention.

Usage

findPrimeMeridian(x)

Arguments

x

Numeric vector of longitude values.

Value

A character string, either `"center"` or `"left"`, or `NULL` if the convention cannot be determined.

Details

The function returns `"center"` if any longitude is negative, and `"left"` if any longitude is greater than `180`. If neither condition is met, the convention cannot be determined unambiguously and the function returns `NULL` with a warning.

See also

[checkLongitude()]

Examples

if (FALSE) { # \dontrun{
findPrimeMeridian(c(-10, 0, 20))
findPrimeMeridian(c(10, 180, 350))
} # }