org.tinfour.gis.las

Class GpsTimeConverter

java.lang.Object

org.tinfour.gis.las.GpsTimeConverter

public final class GpsTimeConverter
extends Object

Provides methods for converting GPS times to Java's internal milliseconds standard based on epoch 1 January 1970. Java is based on the UTC system which depends on the use of leap seconds which are issued by international committees at irregular intervals. The classic Java Date API does not, itself support leap seconds, but assumes that the length of a day is uniformly 86400 seconds. However, the GPS time is a strictly linear time (adjusted for relativistic effects) that is not not affected by leap second rulings. So, in applications where we wish to be able to determine what time the Java would report at a particular GPS time, we need to apply an adjustment for leap seconds.

The GPS to Java time transition is complicated somewhat by the effect that the conversation may actually produce the same Java value for two different GPS times. For example, there was a leap second at the transition from 30 June to 1 July in 2015. Thus the GPS times 1119744016 and 1119744017 both map to 2015-07-01 00:00:00 UTC.

Method Summary

Modifier and Type	Method and Description
static Date	gpsToDate(double gpsTime) Convert a GPS time to a Java Date object which represents time in milliseconds since the Java epoch 1 January 1970.
static long	gpsToMillis(double gpsTime) Convert a GPS time to milliseconds since the Java epoch 1 January 1970.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

gpsToMillis

public static long gpsToMillis(double gpsTime)

Convert a GPS time to milliseconds since the Java epoch 1 January 1970. This value will be the time that would have been presented by a call to the Java System.currentTimeMillis() at the instant indicated by the GPS time.

Note that the GPS time is based on the Epoch 6 January 1980 while the milliseconds system is based on the Epoch 1 January 1970. So a GPS time of zero will have value milliseconds value of 315964800000.

This routine does not handle leap seconds in the period before 1980, thus negative gpsTime values will not be adjusted for leap seconds.

Parameters:

gpsTime - a valid positive number giving a GPS time in seconds measured from the GPS epoch 6 January 1980.

Returns:

a valid Java time in milliseconds

gpsToDate

public static Date gpsToDate(double gpsTime)

Convert a GPS time to a Java Date object which represents time in milliseconds since the Java epoch 1 January 1970. This value will be the time that would have been presented by a call to Java's new Date() constructor at the instant indicated by the GPS time.

Parameters:

gpsTime - a valid positive number giving a GPS time in seconds measured from the GPS epoch 6 January 1980.

Returns:

a valid Java time in milliseconds