Generic Atmospheric Correction Online Service for InSAR (GACOS)

Submit GACOS Request

Please define a rectangle area, with minimum latitude (S, botom), maximum latitude (N, top), minimum longitude (W, left) and maximum longitude (E, right). You can also draw from the map above. Latitude: -90 to 90. Longitude: -180 to 180. Unit in degree.

Please select the time of the day, with hour (0-23, leftside box) and minitue (0-59, rightside box). All time in UTC.


Please input the date list. One date per line with the format of YYYYMMDD. You can input maximum 20 dates.

Please select the output format. We provide binary grid (little endian 4 byte float block binary) and geotiff. We recommond geotiff as it has a smaller filesize.


Note, we have recovered part of the service affected by the Data Handling System move of ECMWF, and requests after 01 August 2022 can now be submitted as normal. But requests before 2014 may still be affected. We will review the progress every 3-5 days. 

System description

Welcome to our Generic Atmospheric Correction Online Service for InSAR (GACOS).

GACOS utilises the Iterative Tropospheric Decomposition (ITD) model (Yu et al., 2017) to separate stratified and turbulent signals from tropospheric total delays, and generate high spatial resolution zenith total delay maps to be used for correcting InSAR measurements and other applications. GACOS has the following key features: (i) globally available; (ii) operational in a near real time mode; (iii) easy to implement; and (iv) users to be informed how the model performs and whether the correction is recommended.

Datasets used in GACOS include:

  • High Resolution ECMWF weather model at 0.1-degree and 6-hour resolutions;
  • SRTM DEM (90m,S60-N60);
  • ASTER GDEM (90m,N60-N83,S60-S83);

GACOS tropospheric delay maps are given in a grid binary format (4-byte float little endian, naming convention YYYYMMDD.ztd). A ReadMe file is provided to demonstrate how to use GACOS tropospheric correction maps. MATLAB codes (for binary grid format) and MATLAB codes (for geotiff format) are also available to help apply GACOS corrections and view the results instantly.There are also a collection of programs/scripts which can be found at here .The website has restricted the submitted job to be maximum 10 by 10 degrees for up to 20 dates.

Whenever using the GACOS products, please cite the following references:

  • Yu, C., Li, Z., Penna, N. T., & Crippa, P. (2018). Generic atmospheric correction model for Interferometric Synthetic Aperture Radar observations. Journal of Geophysical Research: Solid Earth, 123(10), 9202-9222. [link]
  • Yu, C., Li, Z., & Penna, N. T. (2018). Interferometric synthetic aperture radar atmospheric correction using a GPS-based iterative tropospheric decomposition model. Remote Sensing of Environment, 204, 109-121. [link]
  • Yu, C., Penna, N. T., & Li, Z. (2017). Generation of real‐time mode high‐resolution water vapor fields from GPS observations. Journal of Geophysical Research: Atmospheres, 122(3), 2008-2025. [link]

Details of how GACOS can be used in InSAR time series analysis:

  • Yu, C., Li, Z., & Penna, N. T. (2020). Triggered afterslip on the southern Hikurangi subduction interface following the 2016 Kaikōura earthquake from InSAR time series with atmospheric corrections. Remote Sensing of Environment, 251, 112097. [link]

GACOS is supported by NERC through the centre for seismic, volcanic and tectonic observation and modeling (comet, Ref.: come30001) and LICs (Ref. Ne / k010794 / 1) and esa-most dragon-4 (Ref. 32244). We recognize the European Centre for medium range weather forecasts (ECMWF) for its high-resolution tropospheric products.

Users are free to share, copy and redistribute the data in any medium or format, provided that they give appropriate credit to the author (e.g., citing the above-mentioned papers). However, please do not use the data for commercial purposes.


Chen Yu ( Personal page
Zhenhong Li (
School of Engineering, Newcastle University, Newcastle upon Tyne, UK.
College of Geological Engineering and Geomatics, Chang’an University, Xi’an, China.
Centre for the Observation and Modelling of Earthquakes Volcanoes and Tectonics (COMET).