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The PDF format contains multiple pages, with each page containing one spectrogram. We recommend this format when users would like to scroll through a large amount data looking for events such as whale calls. PDF spectrograms are not normally archived for fast retrieval, so they will be generated on the fly, which will take some time. PDF spectrograms do have the advantage of having higher resolution, approximately 300 dpi for landscape letter sized image, while the PNG spectrograms are 1200 by 900 pixels.
Spectrograms can be produced from WAV files (described above) or from FFT files (described below). Spectrograms generated from FFT files have a fixed and generally lower resolution, but have the advantages of not being affected by military diversion and have wider frequency range (WAV-sourced spectrograms maybe limited in frequency by their multi-point calibration). Here is an example of a spectrogram generated from an FFT file:
Daily or Weekly Collated Spectrograms
The spectrogram collation option allows users to group/collate spectral data into plots and data (MAT) files. For plots, daily and weekly spectrograms are available, while the data files can be daily or unlimited duration collations. Spectral data is data for daily plots and also data files are assembled into 1-minute box car averages (no overlap), accounting for the logarithmic scale of the data. Spectral data for the weekly plots are assembled into 5-minute box car averages (no overlap), accounting for the logarithmic scale of the data. These plots are useful for daily and monthly inspections of data and, as such, will appear on Data Preview. Here's an example where a passing ship can be seen in a daily plot:
Here is an example of a weekly plot:
Oceans 2.0 API filter: extension={png,pdf}
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Oceans 2.0 API filter: extension=oct
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