# LidarValidate1

Keywords: lidar, validation

## Summary

This is a LIDAR verification/validation demonstration. An Excel spreadsheet is included which shows a hand-computed, "expected" result which can be compared against the DIRSIG output.

## Details

The conditions for the validation case are summarized in the table below:

    128        Number of pixel elements per side of array (e.g. 128 x 128)
    1.064E-06  Wavelength [m]
    1.500E-04  Pulse energy [J]
    2.000E-09  Pulse length (rectangular/uniform pulse profile) [s]
    1.000E+04  Pulse repetition rate (PRF) [Hz]
    4.000E-01  Focal length [m]
    0.10       Receiver radius [m]
    8.000E-03  Beam divergence half angle @ 1s [radians]
    5.000E-05  Size of pixel elements (lenslet size) [m]
    0.10       Nominal target reflectivity (Lambertian assumption)
    0.50       Optics throughput
    2000.00    Range [m]

## Important Files

The parameters summarized previously are spread across the various input files. The `demo.scene` file defines a flat plate scene with a 10% reflectance. The `demo.platform` file includes all the transmitter and receiver parameters. The `demo.ppd` file places the instrument the appropriate distance from the scene.

### Excel Calculation

The point of a validation is to compare the model output to an accepted value. In this case, an analytical computation was performed to produce the accepted value. This was accomplished in an Excel worksheet (see `validate.xls`) that includes all the input parameters and then does a step by step computation of the number of photons expected to arrive on the focal plane.

Figure 1. Screenshot of the Excel worksheet to compute the expected value.

## Setup

To run the simulation, perform the following steps:

1. Run the DIRSIG `demo.sim` file

This produces the file `demo.bin`.

## Results

The expected value computed in the `validate.xls` file is 7.34537. This can be compared to the value output by the BIN Analysis Tool when run on the `demo.bin` file, which is:

    $ bin_analyze demo.bin
    ...
    [header info deleted for documentation purposes]
    ...
    Pulse #1:
        Minimum total photons in a pixel = 7.34517
        Maximum total photons in a pixel = 7.34517
        Pixels with zero total photons = 0/1 (0%)
        Average background photons per pixel = 1.09663e-05
        Average total photons per pixel = 7.34517

    Complete!