Users of the OTL Provider
Geospatial Information
Authority of Japan
Authority of Japan
The periodic deformation of the Earth's surface due to the ocean tides reaches several centimetres and must be corrected for in GNSS, VLBI, DORIS and SLR analyses. This API delivers OTL corrections for any station on Earth in milliseconds — no queue, no waiting.
As the ocean tides rise and fall, the varying weight of water flexes the solid Earth beneath — a phenomenon known as Ocean Tide Loading (OTL). The resulting deformation of the Earth's surface produces periodic displacements of several millimetres to centimetres in both the vertical and horizontal directions, with periods ranging from hours (semi-diurnal, diurnal) to weeks and months (long-period tides).
At the precision that modern space geodesy achieves, these displacements are far too large to ignore. OTL corrections are required for the accurate analysis of GNSS, VLBI, DORIS, and SLR measurements — whether computing precise station coordinates, monitoring crustal motion, or determining Earth-orientation parameters.
OTL corrections are computed by convolving an ocean tide model — which describes the amplitude and phase of each tidal constituent across the world's oceans — with a set of load Green's functions that characterise how the elastic Earth responds to a surface load.
Techniques requiring OTL corrections
Precomputed global maps make every request instant — no job queue, no waiting for results.
Results are interpolated from precomputed global grids. Any station, any location on Earth, returned in under a second.
M₂ S₂ N₂ K₂ K₁ O₁ P₁ Q₁ Mf Mm Ssa — amplitude and phase for vertical, north, and east displacement.
JSON or BLQ output, Bearer token authentication. Integrate into any geodetic processing pipeline with a single HTTP call.
The OTL Provider has been operated since 2002 by Hans-Georg Scherneck of the Onsala Space Observatory, Chalmers University of Technology, Sweden, and Machiel Bos of TeroMovigo, Portugal.
Over more than two decades the email-based service has processed over 130,000 station computations for more than 1,000 researchers worldwide — from graduate students checking a single field site to commercial survey companies processing thousands of stations in automated pipelines.
The service supports four ocean tide models — FES2014b, FES2022b, GOT5.5, and TPXO10_atlas_v2 — convolved with load Green's functions for four Earth structure models: PREM, PREM_disp, STW105, and STW105_disp (the anelastic variants include frequency-dependent dispersion). FES2014b and FES2022b are recommended in the IERS Technical Conventions for high-precision geodetic analysis.
The original email service at Chalmers remains available for manual, more interactive requests. This REST API is for researchers and developers who need speed, automation, and programmatic access at scale.
This service would not be possible without the work of the teams behind each ocean tide model.
Lyard, F. H., Allain, D. J., Cancet, M., Carrère, L., and Picot, N.: FES2014 global ocean tide atlas: design and performance. Ocean Science, 17(3), 615–649, 2021. doi:10.5194/os-17-615-2021
Lyard, F., Carrere, L., Fouchet, E., Cancet, M., Greenberg, D., Dibarboure, G., and Picot, N.:
FES2022 a step towards a SWOT-compliant tidal correction.
J. Geophys. Res., in review, 2025.
Produced by LEGOS, NOVELTIS and CLS Ocean & Climate Division; funded by CNES.
Distributed by AVISO with support from CNES
(aviso.altimetry.fr).
Ray, R. D. (2025). Documentation for Goddard Ocean Tide Solution GOT5: Global Tides from Multi-mission Satellite Altimetry. NASA TM-20250002085. Goddard Space Flight Center, Greenbelt, Maryland.
Egbert, G. D., and Erofeeva, S. Y. (2002). Efficient inverse modeling of
barotropic ocean tides. J. Atmos. Oceanic Technol., 19(2), 183–204.
doi:10.1175/1520-0426
Model data distributed via tpxo.net.
Register once, verify your email, then call the API from anywhere.
Create a free account with your email address. You'll receive a verification link immediately.
Click the link in the email. Your API key is shown on the page — keep it safe, it authenticates all your requests.
POST station coordinates with a Bearer token. Receive BLQ or JSON results in milliseconds.
# 1 — Register (free, no credit card, no password)
curl -s -X POST https://otl.teromovigo.com/v1/auth/register \
-H "Content-Type: application/json" \
-d '{"email": "you@example.com"}'
# 2 — Check your inbox and click the verification link.
# Your API key is shown on the page. Copy it, then store it:
API_KEY="otl_your_api_key_here"
# Lost your key? Have it re-sent to your email address:
curl -s -X POST https://otl.teromovigo.com/v1/auth/recover \
-H "Content-Type: application/json" \
-d '{"email": "you@example.com"}'
# 3 — Compute OTL for one or more stations (JSON output)
curl -s -X POST https://otl.teromovigo.com/v1/compute/ \
-H "Authorization: Bearer $API_KEY" \
-H "Content-Type: application/json" \
-d '{
"stations": [{"name": "BRST", "lat": 48.3803, "lon": -4.4956, "h": 29.3},
{"name": "LISB", "lat": 38.7083, "lon": -9.1364}],
"tide_model": "FES2014b",
"earth_model": "STW105_disp",
"cmc": true,
"format": "json"
}'
# h: ellipsoidal height in metres — optional with lat/lon; derived automatically from X/Y/Z
# tide_model: "FES2014b" (default) | "FES2022b" | "GOT5.5" | "TPXO10_atlas_v2"
# earth_model: "PREM" | "PREM_disp" | "STW105" | "STW105_disp" (default)
# cmc: Centre of Mass Correction — true (default) | false
# format: "json" | "blq" (BLQ is the standard geodetic format)