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Spotter Data Modes

Team Sofar

Spotter Data Modes

Your Spotter has three (4) remotely configurable modes (Waves: Standard, Waves: Partition, Waves: Spectrum, and Track). In Waves: Standard and Waves: Spectrum modes, you can set a range of update rates to tailor your Spotter’s behavior to your specific application needs. These changes are achieved via your Spotter’s 2-way satellite communications interface, and can be changed at any time from your Dashboard regardless of where your Spotter is in the world.

Waves: Standard

  1. (Recommended for standard marine monitoring applications)

In this mode your Spotter calculates wave statistics based on a 30-minute sample period, and transmits bulk wave statistics through the satellite network (see the technical manual for more specifics on the on-board calculations of wave bulk statistics). You can select a satellite update rate of 30 minutes or 60 minutes (default). In the default setting, Spotter will include two 30-minute samples in its hourly update. The 30-minute update option can be selected if more real-time updates are required for your application, but will incur higher data usage costs.

Note: The timestamp returned on dashboard and in the API will correspond to the end of the sampling interval.

Sofar Spotter Data Subscription and Storage
Sofar Spotter Data Subscription and Storage

Figure 1: The Waves: Standard mode uses 30-minute sampling periods to calculate wave statistics. You can select either 30-minute (top) or 60-minute (bottom, default) update intervals. If the 60-minute update rate is selected, two sample periods are included in a single update to the Dashboard, which saves data transfer costs. If data updates are required faster, you can set your Spotter to send updates every 30 minutes.

Waves: Partition

(Recommended as a balance between Standard and Spectrum modes.)

In the Waves: Partition mode your Spotter calculates wave statistics based on a 1-hour sample period instead of the 30-minute sample period in the Waves: Standard mode.

In addition to the standard bulk parameters (Waves: Standard), Spotter can provide the same parameters over two ‘sea’ and ‘swell’ wave partitions (Waves: Partition).

Effectively, this means that we break up the total sea state, which is the superposition of all the waves in the wave field, in a part that is primarily forced by the local wind (the ‘sea’) and a part that is primarily decoupled from the local wind (the ‘swell’). The standard Spotter bulk parameters are calculated for the complete sea state (or the complete wave spectrum). The partitioned bulk parameters are calculated for their respective parts of the wave spectrum. We define all waves with a period shorter than 8s (.127Hz) to be part of the sea partition, and all waves with periods longer than 8s to be part of the swell partition. This is a common threshold for sea/swell separation, but admittedly somewhat arbitrary. 

(Note: Currently, this is fixed, however, we plan to provide user-adjustable and self-tracking thresholds in the near future.)

The separating out of sea and swell partitions provides better insight in the nature of the sea state than an average parameter for the whole sea state. For instance, the sea roughness (or choppiness) is primarily dictated by the energy in the sea partition. Whereas nearshore shoaling and refraction effects are stronger for the longer waves in the swell partition. 

(Note: The total significant wave height is not a simple sum of the sea and swell height combined.)

Waves: Spectrum (Full)

(Recommended for deeper analysis, modeling, and science applications)

If Waves: Spectrum mode is activated, your Spotter transmits the variance density spectrum and directional moments (a­1, b1, a2, b2) as a function of frequency (for further details, see the technical manual). In this mode, the system uses a 60-minute sample period to improve the statistical estimate of spectrum and directional moments. The user can select an update rate of between 1 and 6 hours. Update rates faster than 6 hours will incur higher data usage costs than Waves:Standard mode due to the increase in amount of data transmitted.

Note: The timestamp returned on dashboard and in the API will correspond to the end of the sampling interval.

Figure 2 In Waves: Spectrum mode, Spotter uses a 60-minute sampling period to compute wave statistics. The user can select update intervals between 1 and 6 hours. Example for 1-hour (top) and 2-hour (bottom) update intervals shown in figure.

Track

In this mode, Spotter transmits five samples of its position (lat/lon) separated by 3 minutes, every 15 minutes. Measurement resolution is 1/100,000th minute of arc. This mode is designed to provide high-resolution location track data for retrieval or surface current tracking. Based on the location data, the Dashboard continuously calculates and provides a 15-minute forecast of Spotter position (to aid retrieval) and estimates surface drift rates based on differential position.

Details on Wind and Sea Surface Temperature (SST)

  • - In Standard, Partition and Spectrum: A single SST measurement per report (An averaged sample over the latest 10 seconds prior to upload).
  • - In Standard, Partition and Spectrum: A wind sample for each wave sample.
  • - In Track: No SST and Wind data provided.

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