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    "info": {
        "author": "Mingye Wang",
        "author_email": "arthur200126@gmail.com",
        "bugtrack_url": null,
        "classifiers": [
            "Development Status :: 5 - Production/Stable",
            "License :: CC0 1.0 Universal (CC0 1.0) Public Domain Dedication",
            "Operating System :: OS Independent",
            "Programming Language :: Python :: 2",
            "Programming Language :: Python :: 3",
            "Topic :: Scientific/Engineering :: GIS"
        ],
        "description": "PRCoords\n========\n\nPeople's Rectified Coordinates (PRCoords) is a cross-language implementation of \"public secret\" Chinese coordinate obfuscation methods including GCJ-02 and BD-09, along with general deobfuscation methods previously established in [ChinaMapShift][], [eviltransform][], and [geoChina][]. (Referring to the process of replacing straight lines with wavy ones as a \"transform\" is euphemism overdone.)\n\n[ChinaMapShift]: https://gist.github.com/anonymous/e7c6f67555099180ce1ae8da4ba2c513\n[geoChina]: https://github.com/caijun/geoChina/blob/master/R/cst.R\n[eviltransform]: https://github.com/googollee/eviltransform\n\nLanguages\n---------\n\n- [x] JavaScript ([`npm install prcoords`](https://www.npmjs.com/package/prcoords))\n  * Web demo: https://artoria2e5.github.io/PRCoords/demo\n- [x] Python ([`pip install prcoords`](https://pypi.org/project/prcoords/))\n- [x] \\(Obj-\\)C/C++ (C structs)\n  * [ ] Makefile with `install`\n- [ ] Ruby\n- [ ] Swift\n- [ ] C#\n- [x] Haskell (GCJ only; data structure incomplete)\n  * need to move googollee/eviltransform#54 here sometime.\n- [ ] Java\n- [ ] Matlab/Octave\n  * too lazy to split the files. also expand \"caijun\"\n- [x] PGSQL\n- [ ] Typed Racket\n  * is it done?\n\n(should I split them into submodules?)\n\nFor languages not yet supported, we recommend you to check for [eviltransform][] (MIT) or [geoChina][] (GPLv3, R) instead.\n\nAPI\n---\n\nPRCoord's APIs operate on, and returns, dedicated structures for coordinates. In API names, we generally refer to WGS-84 as `wgs`, GCJ-02 as `gcj`, and BD-09 (lat-lon) as `bd`. \n\n### Inverse functions\n\nThe obfuscations generally have these properties to maintain basic usefulness:\n\n1. `obfs(coord)` is sort of close to `coord`.\n2. `obfs(a) - obfs(b)` is usually close to `a - b`. (The closer `a` and `b` are\n   to each other, the better it works.)\n\nIn general two approaches of inverting the \"forward\" obfuscations, or working from\n`obfs(coord)` to `coord`, are implemented:\n\n* _Run it backwards_: `obfs(coord)` is never too far from `coord`, so just use\n \u00a0`obfs(obfs(coord)) - obfs(coord)` to estimate `obfs(coord) - coord`.\n* _Iterate a bit_: Get a rough `guess` somehow, and just use property 2 to estimate\n  the remaining error as `obfs(guess) - obfs(coord)` and correct the `guess`.\n\nYou can read on the demo page about how well these methods work from the `\u0394Roundtrip`\nentry. Unless you are doing archival work, you generally don't have to iterate.\n\n### The \"in China\" sanity check\n\nTypically PRCoords is only supposed to be ran on obfuscated input data, which\nare primarily Chinese coordinates. For this reason, initial implementations\ninclude this [very very rough](https://news.ycombinator.com/item?id=10965506)\nsanity check that spans a rectangular region on a mercator-projected map.\nThis check can be overridden by passing a boolean value, or may be not at all\nimplemented in certain languages if I am not in the right mood for doing\nsilly things.\n\nThere is an \"insane\" sanity check intended to approximate the range of Google\nand Baidu's distortion, intended for use by [IITC](https://iitc.me):\n[`js/insane_is_in_china.js`](https://github.com/Artoria2e5/PRCoords/blob/master/js/insane_is_in_china.js).\nIt is basically a ray-casting polygon check with 70 vertices. You, as the\ncaller, should still be responsible for telling whether a point is part of the\ngov-screwed Chinese data.\n\nWhy another wheel?\n------------------\n\n* Public Domain\n* Clean API based on pairs of coordinates\n* Need to find a place for this sarcastic name\n\nPhysical PRCoords\n-----------------\n\nYou can print out a minimal copy of PRCoords with [this PDF file](https://commons.wikimedia.org/wiki/File:PRcoords_Cheatsheet.pdf). I am working on some better options [in issue #2](https://github.com/Artoria2e5/PRCoords/issues/2). A fairly simple tote bag with an older version of the PDF is [available from Teespring](https://teespring.com/miniprcoords-tote-v1).\n\nFeel free to print and sell t-shirts with the PDF file! It is put in the Public Domain, so you don't have to pay me for that. You can always fund my subversive activities on [Patreon](https://www.patreon.com/artoria2e5) though.\n\nLicense\n-------\n\nUnless otherwise mentioned, all files in this package, including this README file,\nare dual-licensed under:\n\n* [CC0 1.0 Public Domain Dedication](https://creativecommons.org/publicdomain/zero/1.0/)\n* [GNU General Public License (version 3 or up)](https://gnu.org/licenses/gpl.html)\n\nGPL is only included for fun here.\n\nSources\n-------\n\n* [Algorithm.Coords.Converter](https://archive.is/20130815104734/emq.googlecode.com/svn/emq/src/Algorithm/Coords/Converter.java) from [EMQ](https://code.google.com/archive/p/emq/) ([GitHub mirror](https://github.com/richardyu-au/emq)) is probably *the* GCJ leak. It is a JSP project \"for demonstrating GIS systems\", probably done by some government contractor.\n  * There is some randomness in the GCJ deltas on both axes: one `sin` invocation and one LCG. Each add a maximum of 1 meter of error.\n* [on4wp7](https://archive.is/20150702191259/https://on4wp7.codeplex.com/SourceControl/changeset/view/21483%23353936) (2013) is the earliest rationalized GCJ (forward) implementation. No randomness is attempted.\n* [ChinaMapShift][] (2014) figured out the quick iterative inverse for GCJ. I learned about it via geoChina first and generalized it here.\n* BD-09 is not very well sourced, but [pycoordtrans](https://github.com/zxteloiv/pycoordtrans) (2014) seems to have it.\n\nSee also\n--------\n\n* [Restrictions on geographic data in China](https://en.wikipedia.org/wiki/Restrictions_on_geographic_data_in_China#Coordinate_systems): this Wikipedia article outlines impacts and the \"common secret\" deobfuscation approach.\n  * Chinese readers: see [\u4e2d\u534e\u4eba\u6c11\u5171\u548c\u56fd\u6d4b\u7ed8\u9650\u5236](https://zh.wikipedia.org/wiki/\u4e2d\u534e\u4eba\u6c11\u5171\u548c\u56fd\u6d4b\u7ed8\u9650\u5236).\n* [eviltransform][] is among the most popular cross-language soltions to the problem. It borrows its name directly from [EvilTransform.cs](https://github.com/Leask/EvilTransform/blob/master/EvilTransform.cs), an early refactored version of a raw-flesh Java implementation found in \"[emq](https://code.google.com/archive/p/emq/)\", some sort of government contractor GIS demo project.\n  * Since June 2016, eviltransform contains numerous parameter errors that compromise its output, especially for BD-09. See googollee/eviltransform[#43](https://github.com/googollee/eviltransform/issues/43), [#53](https://github.com/googollee/eviltransform/pull/53) and [#44](https://github.com/googollee/eviltransform/issues/44) for corrections. As of June 2019 these problems are not fixed.\n* [geoChina][] by caijun is a clear, concise implementation written in R. It features the iterative method from ChinaMapShift.\n* I am planning on moving some of the comments on the algorithm found in [my initial JavaScript implementation](https://zh.wikipedia.org/wiki/User:Artoria2e5/PRCoords.js) to the [GitHub Wiki](https://github.com/Artoria2e5/PRCoords/wiki). I don't think anyone is going to be interested in copying comments on these idiocy when translating my implementation to other languages.\n** If you are doing a translation, consider only using the comments from the PDF.\n\nOh, and finally, here is an official [news report](https://archive.fo/20110804185923/http://cxzy.people.com.cn/GB/196034/14908095.html) on that particular *\\[bleep\\]* who came up with GCJ-02.\n\n\n<a href=\"https://artoria2e5.github.io/PRCoords/demo\">\n  <img src=\"https://Artoria2e5.github.io/PRCoords/Globe%2C_distorted_China.svg\" width=\"100%\" height=\"100\">\n</a>",
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