This document describes the HydrOffice QC Tools 2 application (2.7). For the project page, go here.

2.2.6. Scan Designated

2.2.6.1. How To Use?

Scans grids to ensure the validity of any soundings designated. Currently, only Single-Resolution BAG files are supported.

• Select the Scan Designated tab (Fig. 2.21) on the bottom of the QC Tools interface.

• In Parameters:

  • Turn the knob to select the applicable year as pertaining to required NOAA NOS Hydrographic Survey Specifications and Deliverables (HSSD).
  • Enter the Survey scale. Any designated soundings that have a more shoal designated sounding within 2mm at survey scale will be flagged as invalid.
  • Check the box Evaluate neighborhood as an estimate of designated sounding height 1 meter off the seafloor. Note this is a subjective check to be overrided by the hydrographer’s discretion.

• In Execution, click Designated Scan v2.

Fig. 2.21 The Scan Designated tab.

• After computing, the output window opens automatically.

• From the output window, drag-and-drop the output into the processing software to guide the review.

• The output names adopt the following convention:

  • [grid filename].[s57 filename].DESIGNATED_SCAN_v2.[HSSD year]

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2.2.6.2. How Does It Work?

The grid is scanned to ensure the validity of designated soundings per NOAA NOS HSSD. The three requirements for validity are:

1. Height of the sounding above the grid that is more than:

   • half the allowable TVU (in depths < 20 meters) or the full allowable TVU (in depths >= 20 meters) [2016].
   • the full allowable TVU [2017].

The grid nodes are scanned and any node with a depth adjusted by designated sounding is checked to ensure that the difference between the original depth and the new depth (i.e. the designated depth) meet the requirement as related to TVU.

As shown in the example in Fig. 2.22, the vertical distance between the grid and the designated sounding (0.134 m) is less than half the allowable TVU for this depth (0.269 m based on HSSD 2016), thus designation of this sounding was not necessary.

Fig. 2.22 First example of unnecessary designation.

2. No sounding designated within 2mm at survey scale that is more shoal.

As shown in the example in Fig. 2.23, at the survey scale of 1:20,000, there is a more shoal sounding designated (51 feet) approximately 31 meters away, which is within 2mm at survey scale (40 meters), thus the designated sounding of 53 feet is not necesssary.

Fig. 2.23 Second example of unnecessary designation.

3. A height of 1 meter or more off the seafloor.

As shown in the example in Fig. 2.24, the designated sounding appears less than 1 meter off the seafloor when viewed in both sounding and grid data. This check is not definitive, however, and should only be used if useful. The hydrographer’s discretion may override the output.

Fig. 2.24 Example of possible unnecessary designation.

Finally, a designated sounding is valid if a feature exists within 1 grid node and that feature has a VALSOU value within 1 centimeter of difference from the designated sounding depth.