- Degree, minutes, seconds
- Degree, decimal minutes
- Decimal degrees.
# Command Name -- convert
# Original Author -- Emmanuel Frecon - emmanuel@sics.se
#
# This command converts a longitude or latitude expressed in one of
# the ISO 6709:1983 formats into a (D)DDMMSS.SS string. It generates
# error if the string does not comply to the standard.
#
# Arguments:
# ll - Longitude or latitude.
proc convert { ll } {
# see
# http://ioc.unesco.org/oceanteacher/OceanTeacher2/06_OcDtaMgtProc/01_DataOps/06_OcDtaForm/01_OcDtaFormFunda/02_Geography/01_Locations/ISOLatLonStd.htm
# and http://maps2.nris.state.mt.us/topofinder1/LatLong.asp for
# more practical explanations.
if { [regexp {(\+|-)?\d+:\d+:\d+(\.\d+)?} $ll] } {
# (D)DD:MM:SS.SSSSSSSS
set l [split $ll ":"]
set deg [lindex $l 0]
set min [lindex $l 1]
set sec [lindex $l 2]
} elseif { [regexp {(\+|-)?\d+\.\d+} $ll] } {
set li [expr int($ll)]
set ld [expr $ll - $li]
set len [string length [expr abs($li)]]
if { $len >= 1 && $len <= 3 } {
# (D)DD.DDD
set deg $li
set dmin [expr $ld * 60]
set min [expr int($dmin)]
set sec [expr ($dmin - $min) * 60]
} elseif { $len >= 4 && $len <= 5 } {
# (D)DDMM.MMMM
set deg [string range $li 0 end-2]
set min [string range $li end-1 end]
set sec [expr $ld * 60]
} elseif { $len >= 6 && $len <= 7 } {
# (D)DDMMSS.SSSS
set sec [string range $li end-1 end]
set sec [expr $sec + $ld]
set min [string range $li end-3 end-2]
set deg [string range $li 0 end-4]
} else {
return -code error "$ll is not in ISO 6709:1983 format!"
}
} else {
return -code error "$ll is not a recognised ISO longitude/latitude"
}
if { [string length $deg] == 1 } {
set deg "0${deg}"
}
if { [string length $min] == 1 } {
set min "0${min}"
}
if { [string length [expr int($sec)]] == 1 } {
set sec "0${sec}"
}
return "${deg}${min}${sec}"
}AMG: This may be a little bit off topic, but I'd like a utility to calculate great circle distances between pairs of latitude/longitude coordinates. This would be quite useful here at work (COMPANY: L-3 Communications, Titan Group, except I have never heard of the Titan Group; I'm in Link Simulation & Training). I wrote such a thing in MS Excel but it only gives rough approximations.(Later.) Ah, geodesy gives the solution. Thanks!
