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https://github.com/MaSzyna-EU07/maszyna.git
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bf82c35734
"New map" now asks what is being started. A fictional scenery keeps its own frame, where coordinates mean nothing outside it. A real one pins the scenery's zero to a point picked off a map of Poland, so the plan is drawn in EPSG:2180 - the frame the layout library already works in, and the one Geoportal serves imagery in. The projection is the standard transverse Mercator series for PUWG 1992 on GRS80. Checked against known values: the central meridian comes out at easting 500000 exactly, Warszawa at 637382/486757, Krakow at 567614/244588, Gdansk at 477038/720937. The map behind the picker is a schematic border outline plus the larger cities, projected from geographic coordinates on first use. It is coarse on purpose - it is there to point at a region, not to measure against - and the dialog says so. No network is involved.
74 lines
2.5 KiB
C++
74 lines
2.5 KiB
C++
/*
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This Source Code Form is subject to the
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terms of the Mozilla Public License, v.
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2.0. If a copy of the MPL was not
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distributed with this file, You can
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obtain one at
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http://mozilla.org/MPL/2.0/.
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*/
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#include "stdafx.h"
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#include "editor/puwg1992.h"
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namespace editor
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{
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namespace
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{
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// PUWG 1992: a single transverse Mercator zone over the whole country, on the GRS80 ellipsoid
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double const kSemiMajor = 6378137.0;
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double const kFlattening = 1.0 / 298.257222101;
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double const kCentralMeridian = 19.0; // degrees east
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double const kScaleFactor = 0.9993;
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double const kFalseEasting = 500000.0;
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double const kFalseNorthing = -5300000.0;
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} // namespace
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glm::dvec2 puwg1992(double const Latitude, double const Longitude)
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{
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auto const e2 = 2.0 * kFlattening - kFlattening * kFlattening;
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auto const ep2 = e2 / (1.0 - e2);
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auto const lat = glm::radians(Latitude);
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auto const dlon = glm::radians(Longitude - kCentralMeridian);
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auto const sinlat = std::sin(lat);
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auto const coslat = std::cos(lat);
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auto const tanlat = std::tan(lat);
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// radius of curvature in the prime vertical, and the series terms of the standard
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// transverse Mercator expansion (Snyder); good to millimetres over a zone this size
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auto const n = kSemiMajor / std::sqrt(1.0 - e2 * sinlat * sinlat);
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auto const t = tanlat * tanlat;
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auto const c = ep2 * coslat * coslat;
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auto const a = dlon * coslat;
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// meridional arc from the equator
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auto const m =
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kSemiMajor * ((1.0 - e2 / 4.0 - 3.0 * e2 * e2 / 64.0 - 5.0 * e2 * e2 * e2 / 256.0) * lat -
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(3.0 * e2 / 8.0 + 3.0 * e2 * e2 / 32.0 + 45.0 * e2 * e2 * e2 / 1024.0) * std::sin(2.0 * lat) +
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(15.0 * e2 * e2 / 256.0 + 45.0 * e2 * e2 * e2 / 1024.0) * std::sin(4.0 * lat) -
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(35.0 * e2 * e2 * e2 / 3072.0) * std::sin(6.0 * lat));
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auto const a2 = a * a;
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auto const a3 = a2 * a;
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auto const a4 = a3 * a;
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auto const a5 = a4 * a;
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auto const a6 = a5 * a;
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auto const easting = kFalseEasting + kScaleFactor * n *
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(a + (1.0 - t + c) * a3 / 6.0 +
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(5.0 - 18.0 * t + t * t + 72.0 * c - 58.0 * ep2) * a5 / 120.0);
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auto const northing = kFalseNorthing + kScaleFactor *
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(m + n * tanlat *
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(a2 / 2.0 + (5.0 - t + 9.0 * c + 4.0 * c * c) * a4 / 24.0 +
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(61.0 - 58.0 * t + t * t + 600.0 * c - 330.0 * ep2) * a6 / 720.0));
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return {easting, northing};
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}
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} // namespace editor
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