GPS Coordinates: How Many Decimal Places do You Need?

GPS Coordinates

James R. Schmidt, Jr., BSME, Collision Reconstruction Engineer ::::
As reconstruction engineers, we generally quantify vehicles speeds from physical evidence in whole numbers (i.e. 50 mph), and in ranges (i.e. 45 to 55 mph), but rarely in fractions of a mile per hour (i.e. 50.3 mph) and certainly never beyond one decimal place. Physical evidence does NOT allow for the precise determination of vehicle speed down to the hundredth of a mile per hour. It just doesn’t. Anyone who quantifies it as such has NO basis in doing so, nor the understanding of the limitations of an analysis based on input parameters that typically have ranges themselves.
So, that same thought process must then apply to GPS coordinates too, right? Whole numbers only? No decimal places? The answer is a resounding NO!
When it comes to GPS coordinates, the more decimal places, the better. Here’s an example:
A known point in the parking lot of the old DJS offices (before being newly re-built a few years ago) is identified in an aerial photograph.
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