Description Usage Arguments Author(s) References Examples
Compute the length of 1-degree of latitude and longitude
1 2 3 |
lat |
numeric; degrees |
model |
(optional) character; which ellipsoidal correction should be used? |
A.J.Barbour, adapted from degreelen.m
by B.W.Crowell
http://en.wikipedia.org/wiki/World_Geodetic_System
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | ## Not run:
lats <- 30:32
# Lon should be about 111.4 km, and Lat 96 - 94 km
degreelen(lats)
# In most cases there is no discerible effect
# caused by varying the semi-major axis.
# Not much difference according to this machine:
all.equal(degreelen(lats,"IRTF"), degreelen(lats,"WGS84"), tolerance = .Machine$double.eps)
# unless the precision of the input is in micrometers,
# which is essentially impossible to achieve:
options(digits=13)
lats <- 30.1111111123
rbind(degreelen(lats,"IRTF"),degreelen(lats,"WGS84"))
## End(Not run)
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