卫星测高数据处理常见问题

1.时间转换

用matlab从jason-2的nc文件中读出的时间（time_20hz）单位，从数据说明中可以看出是以秒为单位，从2000-01-01 00:00:00.0开始：

time_20hz:---------------------------time field[tai_utc_difference] is the difference between TAI and UTC reference time (seconds) for the first measurement of the data set. [leap_second] is the UTC time at which a leap second occurs in the data set, if any. After this UTC time, the [tai_utc_difference] is increased by 1 secondDimensions:   time=3204     meas_ind=20   - _FillValue: 18446744073709552000.000000- calendar: gregorian- leap_second: 0000-00-00 00:00:00- standard_name: time- tai_utc_difference: -33.000000- units: seconds since 2000-01-01 00:00:00.0

如果要还原成日期怎么办？

简单的做法是，直接在excel中处理一下就可以了。

time_20hz （列号：L） 天 (列号：M) (列号：N) (列号：O) 269091209.6 =L2/3600/24=3114.481592 2000/1/1 =M2+N2=2008/7/11 11:33

---

2.作图时横坐标时间刻度问题

先看看这个：matlab作时间相关的图

以jason2为例，jason读取的时间是从2000-01-01 00:00:00.0开始的秒数，所以不能直接将其转换为天数，需要将2000-01-01 00:00:00.0转换为天数后与其相加，再作相应的图，大概用法如下：

time1 = datenum('2000/1/1') + time0;