SWORD Version Differences

River reach and node IDs are defined by the SWOT River Database (SWORD). Version C/2.0 and Version D of the SWOT RiverSP data products were produced using different versions of SWORD:

What changed in SWORD v17b¶

SWORD v17b introduced the following changes relative to v16:

• “Type” classification updated for approximately 1,662 reaches and their associated nodes globally

• Updates to reach and node lengths

• Correction of a bug in node length calculation (affecting less than 2% of reaches)

Impact on Hydrocron queries¶

Because reach and node definitions changed between SWORD versions, a small number of feature IDs differ between Version C/2.0 and Version D data. Users querying the same geographic location across both versions should be aware that results may not align exactly.

The SWORD version used for a given observation can be returned by including sword_version in the fields : string, required: yes parameter.

Example: Node ID 43210100080371¶

The following example demonstrates how node ID 43210100080371 resolves to different geographic locations depending on which collection version is queried. This node is one of the approximately 1,662 nodes affected by the SWORD v16 → v17b update.

Version 2.0 request:

GET /timeseries?feature=Node&feature_id=43210100080371&collection_name=SWOT_L2_HR_RiverSP_2.0&output=csv&start_time=2025-01-01T00:00:00Z&end_time=2025-01-31T23:59:59Z&fields=time_str,wse,lat,lon,sword_version

time_str,wse,lat,lon,sword_version,wse_units,lat_units,lon_units
2025-01-10T10:49:10Z,8.9169,37.5212176,118.3068612,16,m,degrees_north,degrees_east
2025-01-30T18:20:39Z,9.12682,37.52121762,118.3058295,16,m,degrees_north,degrees_east
2025-01-31T07:34:15Z,9.26057,37.52126843,118.3069193,16,m,degrees_north,degrees_east

Version D request (Default):

GET /timeseries?feature=Node&feature_id=43210100080371&output=csv&start_time=2025-01-01T00:00:00Z&end_time=2025-01-31T23:59:59Z&fields=time_str,wse,lat,lon,sword_version

time_str,wse,lat,lon,sword_version,wse_units,lat_units,lon_units
2025-01-10T10:49:26Z,9.96666,37.44975457,118.2463678,7b,m,degrees_north,degrees_east
2025-01-30T18:20:50Z,10.09558,37.44958043,118.2461186,7b,m,degrees_north,degrees_east
2025-01-31T07:34:31Z,10.16265,37.44973246,118.246709,7b,m,degrees_north,degrees_east

The Version 2.0 response places the node at approximately 37.521°N, 118.307°E, while the Version D response places the same node ID at approximately 37.450°N, 118.246°E — a difference of roughly 9 km. These are physically distinct locations on the river network. The discrepancy is a direct result of the SWORD v16 → v17b update, which reclassified this reach type and reassigned its node geometry.