Last month the New York Times covered a subject that you’d expect to be too technical for the general reader: NOAA’s efforts to recalibrate elevation data as part of its update to the National Spatial Reference System, expected in 2022 or 2023. The height modernization program corrects local elevation data—which was last updated in 1988—by using GPS and gravity mapping. The Times article looks at the real-world implications of this effort, which will have the greatest impact the further west and north you go (see map above), from bragging rights about mountain elevation to whether your community is in a floodplain. [MAPS-L]

Previously: NATRF2022 Datum Coming to North America in 2022.

Little is publicly known about the true scope of the information that Hough and his team captured, or the ingenuity they displayed in securing it, because their mission was conducted in secret, and the technical material they seized circulated only among military intelligence experts and academics. But it was a vast scientific treasure—likely the largest cache of geographic data the United States ever obtained from an enemy power in wartime.

The data seized by Hough’s team went on to form the basis of the ED50 geodetic datum, which in turn led to the Universal Tranverse Mercator system.

Basically, the discrepancy comes from the fact that GPS is based on the Earth’s core rather than any point on the surface, whereas local coordinates are based on a geodetic datum—in Australia’s case, GDA94 (North America uses NAD83)—that is based on a fixed point on the surface. But with plate tectonics, points are not fixed: Australia moves northward at seven centimetres a year.

On 1 January 2017 Australia will shift its coordinates north by 1.8 metres, overshooting things a bit so that the continent and GPS will be in sync by 2020, with plans to keep the datum continually updated after that.