Q. TINモデルにおけるフィラデルフィア法体積計算(Implementing of Philadelphia Post-dredge Method in TIN Model)[英語]


Overview: Over the last couple of years, the use of multibeam echosounders for dredge payment surveys has become more common. Users have requested the ability of using all of the multibeam sounding data when computing volumes over an area.

Late last year, Lazar Pevac adapted the TIN MODEL program of HYPACK® MAX to be able to compute the volumes of a survey surface versus the template information in a planned line file (*.LNW). The Philadelphia District of the U.S. Army Corps of Engineers funded this work. The advantage of this method over previous methods was that it provided volume quantities for both dredge and overdredge templates and provided quantities for each pair of lines, breaking it down into left slope (or box), left of channel, right of channel, right slope (or box).

The last step of this development project was to be able to perform a pre-dredge versus post-dredge calculation in the TIN MODEL. Lazar has just completed this task and it is now available for interested users. It was not done in time for the 00.5 release CD, but is available from customer support. A description of the method is shown below.

Start-up: There is nothing really new on starting the TIN MODEL program. When you are asked to enter your file information, you can specify a single file for a pre-dredge computation or two files for a pre-dredge versus post-dredge computation.

The figure (shown upper right) shows the layout for a single data file to be used in a pre-dredge computation. The figure (shown lower right) shows the layout for two data files and will result in a pre-dredge versus postdredge computation.

In both cases, we have included a planned line file (*.LNW: created in CHANNEL DESIGN). This planned line file will be used to determine the location of the lines and the dredge templates for each line.

In both cases we have checked the "Invert Value of Z" box. You want to do this if you are entering XYZ data. If I were using single beam data, I would not check this box. TIN MODEL will then correctly interpret the data.

You need to have the Tin to Tin method checked in the lower left hand corner in order to enter the Second File (Post-Dredge survey data).

If you are doing a Pre-dredge versus Post-Dredge computation, you should enter the filename with your Pre-Dredge data as your "Input File" and the filename with your Post-Dredge data as your "Second File".

Once you click the OK button, the TIN MODEL program will start with the first file and create the surface model. It will immediately go to the second file and create a surface model. Control will then be returned to the operator.

Set Method: The user should next go to the Calculate - Set Method menu item. There have been a couple of minor changes to the window.

The Planned Line file (*.LNW) specified during the initial window will appear as the "Section" file. This can be changed at any time before computing the volumes.

Under the "Calc Mode" frame, there is now just a Philadelphia choice. If you have specified only a single input data file, the program will provide a pre-dredge computation. If you have specified two input data files, the program will provide a pre-dredge versus post-dredge report. There is no way to over-ride this.

The type of Philadelphia computation can be either a Box or Slope. This check box has been moved into the "Philadelphia Setting" frame. If the user selects "Box", they must then enter the depth of the overdredge template beneath the design template, along with the extension distances for the box on the left and right sides.

If the user selects "Slope", all they have to specify is the depth of the overdredge template beneath the design template.

Once you have entered your settings, click OK to return to the main menu. Then click Calculate - Volumes to start the computation.

Computation Sequence: The TIN MODEL program is going to go through three computation stages:

  • Compute Philly Volumes for Input File and Second Files .
  • Generate a 3rd Surface that is the Differences Between Surfaces. 
  • Compute a Tin to Tin volume on the New Surface.

The image to the left shows the program after the first stage. It has computed the Philly volume information for each data set. The image on the right shows the program at the end of phase 2. It has computed a new surface by determining the separation between the original two surfaces.

In the figure to the right, the program has completed phase 3. This is the TIN-to-TIN computation. It is used to determine the total amount of material removed (regardless of the template) and the total of material "infilled" during the dredging process. These are areas where the bottom in the Post-Dredge data is shoaler than the Pre-Dredge data.

Before performing the TIN-to-TIN computation, the program "clips" the data to the borders of the Planned Line File (*.LNW). This is to prevent it from including material outside the area of interest in this computation.

The Pre-Dredge versus Post-Dredge report is then generated and can be viewed or printed from the Export menu. The report lists the quantities for each pair of survey lines. It shows the amount of material available after the pre-dredge survey, the amount of material remaining after the post-dredge survey and takes the difference between the two to obtain the material removed. 

The summary for the computation is shown in the figure right. A description of each item is provided below.

Total Removed to Project Depth: This is the total material above the dredge template from the pre-dredge survey minus the total material above the dredge template from the post-dredge survey.

Total Pay Removed in the Overdepth: This is the total material available in the overdredge template area from the pre-dredge survey minus the total material available in the overdredge template from the post-dredge survey.

Total Pay Removed: This is the sum of the above two items.

Total Removed: This is the total material removed between the pre-dredge and post-dredge surveys, without respect to the templates. It would include any material removed beneath the overdredge template that would not be included in the Total Pay Removed quantity.

Total Remaining Above Project Depth: This is the amount of material computed from the Post-Dredge survey that is above the design template. The pre-dredge survey is not used when computing this number.

Total Overdredged Material: This is the Total Removed less the Total Pay Removed.

Total Infill Material: This is the volume of material where the depth of the Post-dredge survey is shoaler than the Pre-dredge survey.

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