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Old 12-21-2014, 12:10 PM   #55
Richard W
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When you look at the entire process from data measurement and acquisition to recording and calculations to rendering from recorded data, not just at the data acquisition step, it is about both, accuracy and precision. I will refer you to the link already provided for the explanation.

The problem of mismatch between low data accuracy and too precise calculation and rendering discussed here is not new. It goes back as far as the invention of digital calculators and computers. Engineering students in the 70's who used the new then digital calculators were failing the exams by simply using mindlessly very precise calculators.

Example, if the data is provided with the accuracy of two decimal points and one uses calculator with a precision of eight decimal points and does not mitigate the intermediary calculations, the end result although seemingly very precise contains unmitigated error introduced by the too high level of calculation precision. The error could be avoided by rounding and limiting the intermediary calculations to three decimal points, and rounding the final result back to two decimal points.

Something similar is happening with old chart data, captured with relatively low accuracy, when converted to vector format and interpreted (mindlessly) by very precise rendering devices.

The example of superimposed charts above shows this ... the vector chart locates navaids in (seemingly) very precise points while the original raster chart shows fuzzy areas where they could be located.
Best ... Richard
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