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Data (Sounding) Density

Data (Sounding) Density

Definition  

Data density is the average or range of density of source data (e.g. number of accepted points per surface unit).  

Acceptable data density is specified by the minimum threshold of accepted soundings per node (e.g. greater than or equal to five (5) sounding per node). 

Data density requirements should also meet the threshold percentage of nodes within the grid that are required to achieve this density (e.g. at least 95% of all nodes within the grid shall be populated with the minimum required density - IHO S-44 Edition 6.1.0 - section D.3.2 Sample Density).

Data density is dependent on: 

  1. Water depth 

  2. Ping rate 

  3. Swath coverage 

  4. Survey speed 

During the survey data density should always be monitored such as to avoid any data gaps over area of interest (pockmarks, feature detection, shoals, etc.)

Checks 

  1. Check data density. 

Pass Requirements  

  1. Data density: Run the 3-band 32-bit Geotiff through QAX and ensure that the data passes. 

Please note that in some cases the survey will appear not to pass the density check, however if this is an edge effect occurring along the edge of the survey, this will be an exemption.

Examples

Description    20180011S Beagle Marine Park (GA-0364)  Test results    Figure 1: Data density: Failed.  Figure 2: Data density check shows the location where it failed, on the boundary of the survey  Pass   Yes  Explanation    While the density check failed, it was only on the boundary of the survey, hence we determined that it passed. This dataset meets the requirements outlined above and passes checks 1 

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