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Fledermaus 7

How-to FMMidwater - Work with Dual Head datasets

Step 1. Open FM Midwater and Create project

  1. Using the  icon on the desktop (if available) or the program files list launch FM Midwater. 
  2. Use the File Menu and select Create Project...
  3. Give the project a name and save it in an appropriate location. 




  4. Click OK  

Step 2. Add Raw data. 

  1. Use the File menu to select Add Sonar Files and add any of the supported Raw sonar files (see: InsertLink for more information)  



  2. Set the co-ordinate system that the raw data is in and click finish. 
  3. If the raw files require navigation files add the corresponding files using the File> Add Navigation Files

Step 3. Convert transducer 1

  1. Use the Tools drop down menu and select Convert Sonar Data... option 
  2. Make sure all your files are loaded and click Next
  3. Check that the Navigation is all matching up. If required use the Navigation Options to add external navigation (if you have one navigation file for multiple MBES files)
  4. Also add a vertical offset here if required. Click Next



  5. Make sure that the Downsample factor is set to None. 
  6. Set the Transducer Selection to 1. 
  7. If required then turn on the concatenation and the Dual Swath Compensation (For more information see insert link ) 



  8. Click Finish. This, once it has finished processing will give you the data for the first transducer head. 

Step 4. Convert transducer 2

  1. Repeat points 1-5 in Step 3. 
  2. Make sure that the Transducer Selection this time is set to 2. 



  3. Click Finish. After Processing you will then have a second gwc file with the data from the second Transducer heads data in it. 

Step 5. Process files 

  1. Using the Beam View Options, the Signal Options and the lasso tool, filter out the background noise until you have selected the features. Where the object overlaps in both transducers make sure to process the noise in both. 
  2. When complete you should have something that looks a little like the image below.



  3. You need to reduce the background noise to ensure that the points you export visible. 

Step 6. Export Data. 

  1. When exporting points there are several options depending on your file format and requirements. 
    1. The first option is SD points, which are just for visualisation. 
    2. If you want to further clean your points then you will need to export ASCII points. Here you also have two options
      1. ASCII 
      2. Refracted points (these are currently only available for Kongsberg systems) 
  2. All of the exports can be reached through the File Menu. 



  3. From here the points can be saved and displayed as point cloud in Fledermaus, Qimera or, if using the ASCII method can also be imported and cleaned either in the Dynamic Surface or in the PFM.