3 ms·
Many countries (I know for certain Sweden, Norway and the US) use Transversal Mercator for local maps. The UTM zoning system makes the error as small as possibl
by widforss 6y ago
Many countries (I know for certain Sweden, Norway and the US) use Transversal Mercator for local maps. The UTM zoning system makes the error as small as possible in the local area.
- azepoi 6y agoSome use a local Lambert conformal conic projection.
- widforss 6y agoInteresting! I guess it is preferable for countries stretching in the east-west direction, instead of north-south?
- legerdemain 6y agoEvery US state consists of one or more zones that use specific map projections for best representation. The choice goes significantly further than just the choice of projection family. You can find resources for the State Plane Coordinate System online.[1] For example, the transverse Mercator projection intuitively maps from a sphere onto a cylinder oriented east-west (rather than pole to pole). But since we can vary the relative position of the sphere (such as which longitude is closest to the line perpendicular to the surface of the cylinder), we actually define a family of projections. Another variable is the model of the Earth's surface used for the mapping. For example, the web Mercator projection maps from an ideal sphere, but that is not sufficient for many more precise applications. See geoid[2] and datum.[3] Geodesy and geomatics are pretty huge areas of applied science that go far beyond the scope of a blog post. [1] https://www.edc.uri.edu/nrs/classes/NRS409509/Lectures/4MapBasics/StatePlaneCoordinateSystem.htm https://www.edc.uri.edu/nrs/classes/NRS409509/Lectures/4MapB... [2] https://en.wikipedia.org/wiki/Geoid https://en.wikipedia.org/wiki/Geoid [3] https://en.wikipedia.org/wiki/Geodetic_datum https://en.wikipedia.org/wiki/Geodetic_datum