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How to use the Network Earth Rotation Service

There are three levels of using the NERS:

Level 1: using your browser

 

Advantage of using NERS with a browser: you see what you get.

Disadvantage of using NERS client library: usually you need the Earth orientation parameters for computations.

Level 2: using at as Internet service

An Internet service is a request to a HTTP server with parameters. The server returns the answer upon receiving the request. Although An Internet service works with any browser, normally it used with a non-interactive client such as wget. Here are supported services:

UTC minus TAI: wget -q -O - 'https://earthrotation.smce.nasa.gov/cgi-bin/eop_online.py?req_date=now&param=utcmtai'
UT1 minus TAI: wget -q -O - 'https://earthrotation.smce.nasa.gov/cgi-bin/eop_online.py?req_date=now&param=ut1mtai'
X pole coordinate: wget -q -O - 'https://earthrotation.smce.nasa.gov/cgi-bin/eop_online.py?req_date=now&param=xpol'
Y pole coordinate: wget -q -O - 'https://earthrotation.smce.nasa.gov/cgi-bin/eop_online.py?req_date=now&param=ypol'
Δψ nutation angle: wget -q -O - 'https://earthrotation.smce.nasa.gov/cgi-bin/eop_online.py?req_date=now&param=dpsi'
Δε nutation angle: wget -q -O - 'https://earthrotation.smce.nasa.gov/cgi-bin/eop_online.py?req_date=now&param=deps'
UT1 rate: wget -q -O - 'https://earthrotation.smce.nasa.gov/cgi-bin/eop_online.py?req_date=now&param=ut1rat'
X pole rate: wget -q -O - 'https://earthrotation.smce.nasa.gov/cgi-bin/eop_online.py?req_date=now&param=xpolr'
Y pole rate: wget -q -O - 'https://earthrotation.smce.nasa.gov/cgi-bin/eop_online.py?req_date=now&param=ypolr'
Length of day: wget -q -O - 'https://earthrotation.smce.nasa.gov/cgi-bin/eop_online.py?req_date=now&param=lod'
Euler angle axis 1: wget -q -O - 'https://earthrotation.smce.nasa.gov/cgi-bin/eop_online.py?req_date=now&param=e1'
Euler angle axis 2: wget -q -O - 'https://earthrotation.smce.nasa.gov/cgi-bin/eop_online.py?req_date=now&param=e2'
Euler angle axis 3: wget -q -O - 'https://earthrotation.smce.nasa.gov/cgi-bin/eop_online.py?req_date=now&param=e3'
Rotation matrix: wget -q -O - 'https://earthrotation.smce.nasa.gov/cgi-bin/eop_online.py?req_date=now&param=mat'
Rotation matrix rate: wget -q -O - 'https://earthrotation.smce.nasa.gov/cgi-bin/eop_online.py?req_date=now&param=matr'
Rotation matrix accl: wget -q -O - 'https://earthrotation.smce.nasa.gov/cgi-bin/eop_online.py?req_date=now&param=matrr'

Value of parameter req_date can be replaced to the date string that is ISO 8601 compatible, i.e. in format YYYY.mm.ddTHH:MM:SS.SSSSS, for instance 20110.04.19T08:19:15.545

Advantage of using NERS as an Internet Service: you can include calls to internet service in your program

Disadvantage of using NERS as an Internet Service: Internet service is rather slow.

Level 3: using the client library NERS

Download and install NERS client library.

You nerd insert three calls to your program

  1. ners_init ( config_file, ners, time_tai_start, time_tai_stop, iuer ) — initialization of the ners object using configuration parameters from the config file, start and stop time.

  2. ners_get_eop ( ners, time_tai, cpar, m_par, l_par, pars, iuer ) — return an array of Earth orientation parameters cpar on the specified time.

  3. ners_quit ( code, ners ) — release dynamic memory allocated by ners.

Advantage of using NERS client library: it is very fast serve in your program.

Disadvantage of using NERS client library: you need to know how to program.

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Last update: 2025.10.01_14:26:28