BIPM Time Department API Web Service

Overview

To answer the need of providing machine readable data, the BIPM Time Department started providing access to machine readable data through automatized process.

Results are still available using FTP protocol, this remains unchanged. In addition to the historical FTP access, it is proposed an application programming interface (API) using GET method which gives access to machine readable data regarding various time scales. The method to access these data is using HTTP/HTTPS protocol: This can be done using utilities to transfer data from a server (such as cURL, wget or any programming languages supporting HTTP protocol). Data are provided in standard exchange format, such as JSON, CSV and text.

Execution documentation

Changes between versions 1.0 and 0.2-beta

• generated files format remains unchanged wrt previous version, only additional field have been introduced
• new feature to get the list of existing laboratories using argument 'list'
• results are now provided for Galileo and Beidou
• prediction of UTC broadcast by GNSS
• uncertainties have been added
• arguments are now case-insensitive

Custom requests syntax and arguments

The API using GET method uses URL general syntax below :
https://webtai.bipm.org/api/v1.0/get-data.html?arg1=xxxx&arg2=yyyy ...
Using as many arguments as needed by your query.

• customized period
  To get only a subset of available data between given two MJDs, following URLs should be completed with:
  &mjd1=59000&mjd2=59200 (example for request between MJD 59000 and 59200)

• customized output file format
  Ouput format can be JSON (default, if not specified), Comma-Separated Values (CSV) or Text.
  To define output format of the request, use following arguments in the URL:
  &outfile=json
&outfile=csv
&outfile=txt

• laboratory name selection
  In this document labo refers to the laboratory acronym as used in Circular T (up to 4-characters).
  &lab=labo
  The list of available laboratories can be generated passing argument 'list' :
  list&outfile=[json|csv|txt]

• time scale selection Results from several time scales are available, the examples in the following section.

Get values [Scale-local realizations of UTC]

Get values [UTC-GNSS time scales ]

Get values [UTC-prediction of UTC broadcast by GNSS]

HTTP utilities / examples

It is required to use utilities supporting HTTP protocol to get the data, such as cURL (https://curl.se/) , wget (https://www.gnu.org/software/wget/) or other programming languages such as Python, Perl, etc.

Below you can find examples of commands:

Using wget

wget -O utc-utc_aos.json "https://webtai.bipm.org/api/v1.0/get-data.html?scale=utc&lab=AOS"

Using cURL

curl -k --url "https://webtai.bipm.org/api/v1.0/get-data.html?scale=utc&lab=AOS" > utc-utc_aos.json

Using Perl

#!/usr/bin/perl

use LWP::UserAgent;
my $ua = LWP::UserAgent->new;
my $response = $ua->get("https://webtai.bipm.org/api/v1.0/get-data.html?scale=utc&lab=AOS") ;
if ($response->is_success) { print $response->decoded_content; }

Using Python

import requests
r = requests.get("https://webtai.bipm.org/api/v1.0/get-data.html?scale=utc&lab=AOS")
print(r.text)

Using Matlab

(Example contributed by A. Wallin, VTT)

clear all
close all
data = webread("https://webtai.bipm.org/api/v1.0/get-data.html?scale=utc&lab=MIKE")
mjd = data.data.x;
phase_ns = data.data.y;
figure()
plot(mjd,phase_ns,'o')

Ouput files format

txt file format

The format of txt is in fixed format. Since version 1.0, txt files are formatted as :
- %6d %10.1f %10.1f\r\n for a single scale request ( MJD, value, uncertainty )
- %6d %10s %10s\r\n for a 2-scales request ( MJD scale1, scale2)
- # character is used to identify comments/headers which are not data to be processed.

Additional metadata

Since version 0.2, for each data serie, additional metadata are available in the JSON files to facilitate the use of data

Execution error codes

In version 0.2, error codes have been reinforced, with messages to provide details on the issue.

Final status of execution are reported using specific keys :

In TXT and CSV output files, these keys are reported only in case of failure of the process, line starting with a #.
In JSON files they are always available.
Always ensure that your query syntax is valid and that data have been published, then contact BIPM to report observed troubles.

Change log

Historical changes