Crossline Analysis

Owned by Tore Sannes (Unlicensed)
Last updated: Oct 10, 2014
3 min read

In this section:

Introduction

This command is executed from a folder with schema type Multibeam and will analyze the deviations between one or more crosslines (schema Multibeam Survey) and a base surface (schema Structured Points). 

The result of this analysis is a table in the folder from which this command was executed with statistics regarding the errors (deviations) as a function of beam number. 

 


The Crossline Analysis dialog.  

 

The content of the menu

The Crosslines part:

Select which survey lines to compare against the base surface and add to the statistics. 

Base Surface: 

This Structured Points surface is taken as the true depth of the seafloor and any deviations from this from the crosslines is taken as an error. 

The maximum depth of this surface is used to determine the actual IHO Order to compare the points with.

The IHO Orders:

  • Special Order: Areas where under-keel clearance is critical, i.e. the depth is less than 40 meters.
  • Order 1a: Areas shallower than 100 meters where under-keel clearance is less critical, but features of concern to surface shipping may exist.
  • Order 1b: Areas shallower than 100 meters where under-keel clearance is not considered to be an issue for the surface shipping expected to transit the area
  • Order 2: Areas generally deeper than 100 meters where a general description of the sea floor is considered adequate.

 

The Summarize results part:

Per Survey Line: 

The error statistic output is created separately for each file and for the totat of all input files.

 

Number of beams per bin: 

Since the error statistic is a function of beam number and a Multibeam Survey typically contains a large number of beams; beams are typically binned together to make a shorter more readable table. 
E.g. Number of beams per bin = 20 gives us the following bins: beam number: (1->20), (21->30), ... 

 

 

The Results

After executing the Crossline Analysis a dialog will pop up showing the parameters, result and statistics from the calculations. The report itself is saved in the project structure in a folder named Reports under the same folder as the command is executed from. The report itself is named as YYYYMMDD Crossline Analysis (the name of the executed command).

All reports from all runs will be saved in the Reports folder.

A table containing the statistics is saved in the same folder with a Sqlite database entry named CrosslineAnalysis.  Opening this will show a Database Tables folder, and then the Database Table named Statistics appear. 

 

The CrosslineAnalysis Statistics folder.

 

Rightclick the Statistics item and select Export will same the statistics as a .csv file.

 

Rightclick the Statistics item and select Open will make a new tab the area of the 3D graphics window.

Then the text select * from Statistics will appear in the upper part of the window. Above the text the  icon is located. When clicking this icon the table will be created in the lower part of the tab.

 

The Crossline Analysis Statistics table.

 

 

 

 

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