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  • 1.  TPU...All things TPU!!!

    Posted 05-31-2024 10:32 AM

    Post any thoughts, comments, concerns, and or needs related to bathy lidar and TPU. Chris Parrish will be hosting an extended TPU talk for bathy lidar mid July and you have the chance to shape the talk and Q&A following. 

    Thanks for your support!



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    Nicholas Johnson
    Physical Scientist
    USACE
    Kiln MS
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  • 2.  RE: TPU...All things TPU!!!

    Posted 06-21-2024 01:21 PM
    Edited by Danial Mariampillai 06-21-2024 01:21 PM

    Hi everyone,

    I'm really looking forward to Chris Parrish's talk on TPU for bathy LiDAR in July! I have a few questions and thoughts that I'd love to get a better perspective on:

    Data Validation and TPU:

    1. Understanding TPU:

    • Could we discuss TPU in the context of bathymetric LiDAR and why it's so critical for validating our data? I'm particularly interested in understanding the key factors that contribute to TPU.

    2. Validation Techniques:

    • What are the best practices for validating bathy LiDAR data against ground truth measurements or other high-accuracy sources? I'd love to hear about any cross-validation techniques with other datasets like sonar or satellite-derived bathymetry, and how TPU plays a part in this.

    3. Contractor Requirements:

    • When working with contractors, what specific data and documentation should we be asking for to ensure their bathy LiDAR data meets our quality and accuracy standards? Are there standard protocols or guidelines they should follow, especially regarding TPU information?

    4. Evaluating Data Without Specialized Software:

    • For those of us who don't have access to specialized software (like CARIS), what alternative methods can we use to evaluate the quality and accuracy of bathymetric LiDAR data? Are there any open-source tools or software recommendations?

    5. Documenting and Addressing Discrepancies:

    • How can we systematically document and address any TPU-related discrepancies or errors we find during the validation process? Specifically, what methods or workflows are recommended for tracking these issues, reporting them, and ensuring they are resolved effectively?

    6. Role of Metadata:

    • How important is metadata in the validation and utilization of bathymetric LiDAR data? Could we discuss examples of critical metadata elements that help us assess the reliability and accuracy of the data we collect?

    Looking forward to hearing your thoughts and insights on these topics!

    Best regards,

    Danial



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    Danial Mariampillai
    Victoria BC
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    Original Message


  • 3.  RE: TPU...All things TPU!!!

    Posted 06-23-2024 10:08 AM

    ALL:  Yes, I have been giving a lot of thought to TPU validation and would like to hear others thoughts on the matter.  I have been thinking of some type of Discrete Event Simulation (DES/Monte Carlo simulation) following some type of test-range.  Any thoughts?



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    Alvan Karlin
    University Of Tampa
    Tampa FL
    (813) 972-3531
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    Original Message


  • 4.  RE: TPU...All things TPU!!!

    Posted 06-21-2024 03:36 PM

    I understand TPU doesn't include systematic biases but how do we account for things like empirical derived depth correction uncertainty? Is this a ridiculous question? What should I be asking?
    With post-flight navigation strip adjustment processes almost being a standard practice, where do we account for this if the process is not integrated in the  navigation processing?



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    Nicholas Johnson
    Physical Scientist
    USACE
    Kiln MS
    ------------------------------

    Original Message


  • 5.  RE: TPU...All things TPU!!!

    Posted 06-24-2024 09:53 AM

    One issue I have faced is dealing with submerged aquatic vegetation (SAV) in the bathymetry survey.  I have several questions about what Total Propagated Uncertainty (TPU) can do about it or with it. 

    Over multiple years, can the TPU help find 'bare earth bottom' under the SAV?  In the spirit of 'when life give you lemons make lemonade', can TPU be used to quantify canopy height?

    When the bottom is more of a fluffy, soft density gradient than a surface, does TPU help in choosing a 'surface' elevation? 

    I can see that SAV penetration might be about finding the lowest elevation in a region that penetrates the canopy and that soft bottom sounding might be about capturing the highest or first return from the bottom surface. 



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    Edward Carter
    St. Johns River Water Managerment District
    Palatka FL
    (352) 514-7665
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    Original Message


  • 6.  RE: TPU...All things TPU!!!

    Posted 06-24-2024 03:23 PM
    I don't see TPU helping with classification but this topic is an interesting one for sure for the industry as it can be difficult when you mix SAV and turbid waters. I think reflectance or a few other return signal metrics might help with what you are looking to do but still I think you'd want support from people who specialize in SAV for a region. I am interested in Parrish's response as he does a little of all things. Attenuated -scattered signals, varying bottom slope/roughness/reflectance, and a range of optimized sensors for different purposes makes this fun!
     



    Original Message


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