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function [leapSecs] = LeapSeconds(utcTime) |
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% leapSecs = LeapSeconds(utcTime) |
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% find the number of leap seconds since the GPS Epoch |
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% |
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% utcTime: [mx6] matrix |
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% utcTime(i,:) = [year,month,day,hours,minutes,seconds] |
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% year must be specified using four digits, e.g. 1994 |
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% year valid range: 1980 <= year <= 2099 |
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% |
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% Output: leapSecs, |
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% leapSecs(i) = number of leap seconds between the GPS Epoch and utcTime(i,:) |
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% |
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% The function looks up the number of leap seconds from a UTC time table |
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% |
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% LATEST LEAP SECOND IN THE TABLE = 31 Dec 2016. |
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% On 1 Jan 2017: GPS-UTC=18s |
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% See IERS Bulletin C, https://hpiers.obspm.fr/iers/bul/bulc/bulletinc.dat |
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% and http://tycho.usno.navy.mil/leapsec.html |
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% |
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% Aren't Leap Seconds a pain? Yes, and very costly. Ban the Leap Second: |
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% Leap seconds occur on average once every two years. |
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% What would happen if we had no leap seconds: |
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% 1) Thousand of engineers would NOT spend several weeks each two years fixing |
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% or planning for leap second bugs. |
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% 2) About seven thousand years from now, solar time would be 1 hour behind UTC |
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% and we would need a 1 hour adjustment - similar to daylight savings time. |
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% 3) GMT (which is solar time) will lose its significance. |
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%Author: Frank van Diggelen |
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%Open Source code for processing Android GNSS Measurements |
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[m,n] = size(utcTime); |
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if n~=6 |
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error('utcTime input must have 6 columns'); |
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end |
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% UTC table contains UTC times (in the form of [year,month,day,hours,mins,secs]) |
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% At each of these times a leap second had just occurred |
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utcTable = [1982 1 1 0 0 0; |
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1982 7 1 0 0 0; |
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1983 7 1 0 0 0; |
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1985 7 1 0 0 0; |
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1988 1 1 0 0 0; |
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1990 1 1 0 0 0; |
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1991 1 1 0 0 0; |
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1992 7 1 0 0 0; |
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1993 7 1 0 0 0; |
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1994 7 1 0 0 0; |
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1996 1 1 0 0 0; |
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1997 7 1 0 0 0; |
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1999 1 1 0 0 0; |
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2006 1 1 0 0 0; |
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2009 1 1 0 0 0; |
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2012 7 1 0 0 0; |
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2015 7 1 0 0 0; |
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2017 1 1 0 0 0 |
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]; |
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%when a new leap second is announced in IERS Bulletin C |
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%update the table with the UTC time right after the new leap second |
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tableJDays = JulianDay(utcTable) - GpsConstants.GPSEPOCHJD; %days since GPS Epoch |
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%tableSeconds = tableJDays*GpsConstants.DAYSEC + utcTable(:,4:6)*[3600;60;1]; |
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%NOTE: JulianDay returns a realed value number, corresponding to days and |
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% fractions thereof, so we multiply it by DAYSEC to get the full time in seconds |
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tableSeconds = tableJDays*GpsConstants.DAYSEC; |
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jDays = JulianDay(utcTime)- GpsConstants.GPSEPOCHJD; %days since GPS Epoch |
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%timeSeconds = jDays*GpsConstants.DAYSEC + utcTime(:,4:6)*[3600;60;1]; |
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timeSeconds = jDays*GpsConstants.DAYSEC; |
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% tableSeconds and timeSeconds now contain number of seconds since the GPS epoch |
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leapSecs=zeros(m,1); |
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for i=1:m |
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%add up the number of leap seconds that have occured by timeSeconds(i) |
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leapSecs(i) = sum(tableSeconds<=timeSeconds(i)); |
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end |
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end %end of function LeapSeconds |
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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% Copyright 2016 Google Inc. |
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% |
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% Licensed under the Apache License, Version 2.0 (the "License"); |
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% you may not use this file except in compliance with the License. |
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% You may obtain a copy of the License at |
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% |
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% http://www.apache.org/licenses/LICENSE-2.0 |
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% |
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% Unless required by applicable law or agreed to in writing, software |
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% distributed under the License is distributed on an "AS IS" BASIS, |
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% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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% See the License for the specific language governing permissions and |
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% limitations under the License. |
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