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Thread: WEBINAR: Testing Accuracy of tablet digitizer using MovAlyzeR

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    Aug 2009

    WEBINAR: Testing Accuracy of tablet digitizer using MovAlyzeR

    - The following demonstration is for the determination of the accuracy of the Wacom Intuos4 pen tablet using NeuroScript’s MovAlyzeR® software.
    - This test is accomplished through linearity testing, as it calculates the accuracy of the tablet by evaluating the spatial, temporal and proximity errors. This test can be applied to any pen tablet.
    - To begin, prepare your pen tablet by placing a non-conducting ruler on the tablet at a 45-degree angle. For larger tablets, you might need a longer implement to ensure the 45-degree angle.
    - Next, start the MovAlyzeR software from either your desktop or the start menu.
    - After it opens, ensure that the tablet is selected as the input device.
    - You can use a simple experiment with one condition using the default settings. Right-click on an empty subject and click “Run Experiment”.
    - With the pen in a vertical position, draw a diagonal line along the ruler as fluently as possible, ensuring a consistent movement throughout. Repeat for the second recording.
    - Upon the completion of the experiment recordings, the Analysis Chart might be displayed. If so, simply close the chart.
    - Right-click on the first recording and select “Test Linearity”.
    - The Raw Data Chart will be displayed, initially, with the X/Y graph of the recording. Use the down arrow next to the Chart type to navigate to the “Device Units vs. Sample Number” graph.
    - This graph pertains to spatial errors and reflects the straightness and smoothness of the curve.
    - The Departure from Straight Line shows whether the drawn line was sufficiently straight. Slight oscillations are OK, but a slow wave should not be present.
    - The Distance between Samples reflects the movement speed of the pen and indicates whether the movement was sufficiently smooth. The RMS value of this curve is used to estimate the spatial accuracy.
    - Move down to the next chart, Missing Samples vs. Sample Number, to gauge the temporal accuracy. This curve is derived from the quotient of inter-sample distance and its running average. Values around 1 imply isochronous sampling, which is best for digital data processing. Consistent values above 1.5 (which are missed samples) and below 1.0 (which are extra samples) reflect reduced abilities of the device or driver.

    - Close the Raw Data Chart to view the test results in the results window. You can view more of the report by expanding the size of the window with the slider.
    - Scroll up to the top of the report, where you can find such information as the device resolution, sampling rate and minimum pen pressure of the connected tablet. Some additional statistics that are presented are initial and final coordinates, X-, Y- and absolute lengths of the recording, and average velocity.
    - In the SPATIAL ERROR section, the accuracy of the device for this particular recording was calculated at 0.00653 cm (or 65.3 micrometers), which is actually better than the accuracy specified by the tablet manufacturer, of ±0.25 cm.
    - In the TEMPORAL ERROR section, we observe no reports of missing or extra samples, which was also observed in the Missing Samples vs. Sample Number graph with Y-coordinate values above 1.0 and below 1.5.
    - Although not presented in this demonstration, it is ideal to run multiple tests to ensure the results reflect a legitimate representation on the accuracy of the tablet.
    - In conclusion, we have demonstrated a test using MovAlyzeR to determine the accuracy of a Wacom Intuos4 pen tablet. Although these tests do not simulate typical usage, they do, however, provide a solid measurement of the accuracy of pen tablets.

    - Follow this webinar on the following given link.
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    Last edited by Ameya; 2010-01-05 at 13:33.

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