China datums - Revision history

Artoria2e5: /* Datums in China */

2023-05-18T13:46:01Z

Datums in China

Artoria2e5: /* Datums in China */

2023-05-18T13:24:19Z

Datums in China

Artoria2e5: /* Datums in China */

2023-05-18T13:12:13Z

Datums in China

Artoria2e5 at 13:12, 18 May 2023

2023-05-18T13:12:04Z

Artoria2e5: /* Datums in China */

2023-05-17T15:37:51Z

Datums in China

Artoria2e5: /* Datums in China */

2023-05-17T15:35:18Z

Datums in China

Artoria2e5: /* Datums in China */

2023-05-17T15:34:03Z

Datums in China

Artoria2e5: /* Possible Xian 1980 sources */ Collect some open-source (in the "OSINT" sense) information

2023-05-17T15:32:17Z

Possible Xian 1980 sources: Collect some open-source (in the "OSINT" sense) information

Artoria2e5: /* Datums in China */

2023-05-17T14:59:15Z

Datums in China

Artoria2e5: /* Datums in China */ It's all [REDACTED]. Transformation parameters? Uh-oh.

2023-05-17T14:05:54Z

Datums in China: It's all [REDACTED]. Transformation parameters? Uh-oh.

@@ Line 4: / Line 4: @@
 Transformation for PRC datum are only legally acquired from the local government, which should normally be your source for maps made in old datums too.
-* CGCS2000 (EPSG:4490) is the modern datum. For casual use, assume it's close enough to WGS 84. For more precise use, it is referenced to ITRF97 at epoch 2000.0 and you can use that for conversion. There are later, better parameters such as [https://isprs-archives.copernicus.org/articles/XLII-3-W10/535/2020/isprs-archives-XLII-3-W10-535-2020.pdf Wang ''et al.'' (2019), Table 1] and the official recommendation of CPM-CGCS2000, defined in CH/T 2014-2016.
+* CGCS2000 (EPSG:4490) is the modern datum. For casual use, assume it's close enough to WGS 84. For more precise use, it is referenced to ITRF97 at epoch 2000.0 and you can use that for conversion. There are later, better parameters such as [https://isprs-archives.copernicus.org/articles/XLII-3-W10/535/2020/isprs-archives-XLII-3-W10-535-2020.pdf Wang ''et al.'' (2019), Table 1] (frame) and the official recommendation of [https://www.sciencedirect.com/science/article/pii/S2095809920302149 CPM-CGCS2000] (plate) + usual ITRF97 frame, defined in CH/T 2014-2016.
 * Xian 1980 is still commonly used. Papers dealing with its conversion are heavily redacted.
 * For Beijing 1954 (EPSG:4214), the EPSG has a few local transforms to try, centered on some oil-producing areas.

@@ Line 3: / Line 3: @@
 On this page we aim to just supplement the more widely known information.
-If you are doing modern work, you should mostly see CGCS2000 (EPSG:4490), which is close to ITRS and WGS 84 for casual use.
+Transformation for PRC datum are only legally acquired from the local government, which should normally be your source for maps made in old datums too.
-Parameters for precision transforms is not directly available, but you can try your luck with [https://isprs-archives.copernicus.org/articles/XLII-3-W10/535/2020/isprs-archives-XLII-3-W10-535-2020.pdf Wang ''et al.'' (2019), Table 1].
+* CGCS2000 (EPSG:4490) is the modern datum. For casual use, assume it's close enough to WGS 84. For more precise use, it is referenced to ITRF97 at epoch 2000.0 and you can use that for conversion. There are later, better parameters such as [https://isprs-archives.copernicus.org/articles/XLII-3-W10/535/2020/isprs-archives-XLII-3-W10-535-2020.pdf Wang ''et al.'' (2019), Table 1] and the official recommendation of CPM-CGCS2000, defined in CH/T 2014-2016.
-The current official way is CPM-CGCS2000, defined in CH/T 2014-2016.
+* Xian 1980 is still commonly used. Papers dealing with its conversion are heavily redacted.
+* For Beijing 1954 (EPSG:4214), the EPSG has a few local transforms to try, centered on some oil-producing areas.
 === Possible Xian 1980 sources ===

@@ Line 4: / Line 4: @@
 If you are doing modern work, you should mostly see CGCS2000 (EPSG:4490), which is close to ITRS and WGS 84 for casual use.
-Parameters for precision transforms is not publicly available, but you can try your luck with [https://isprs-archives.copernicus.org/articles/XLII-3-W10/535/2020/isprs-archives-XLII-3-W10-535-2020.pdf Wang ''et al.'' (2019), Table 1].
+Parameters for precision transforms is not directly available, but you can try your luck with [https://isprs-archives.copernicus.org/articles/XLII-3-W10/535/2020/isprs-archives-XLII-3-W10-535-2020.pdf Wang ''et al.'' (2019), Table 1].
 The current official way is CPM-CGCS2000, defined in CH/T 2014-2016.

@@ Line 4: / Line 4: @@
 If you are doing modern work, you should mostly see CGCS2000 (EPSG:4490), which is close to ITRS and WGS 84 for casual use.
-Parameters for precision transforms is not officially given, but you can try your luck with [https://isprs-archives.copernicus.org/articles/XLII-3-W10/535/2020/isprs-archives-XLII-3-W10-535-2020.pdf Wang ''et al.'' (2019), Table 1].
+Parameters for precision transforms is not publicly available, but you can try your luck with [https://isprs-archives.copernicus.org/articles/XLII-3-W10/535/2020/isprs-archives-XLII-3-W10-535-2020.pdf Wang ''et al.'' (2019), Table 1].
 Transformation for PRC datum are only legally acquired from the local government, which should normally be your source for maps made in old datums too. For Beijing 1954 (EPSG:4214), the EPSG has a few local transforms to try. All articles dealing with Xian 1980 are heavily redacted.

@@ Line 3: / Line 3: @@
 On this page we aim to just supplement the more widely known information.
-If you are doing modern work, you should only see CGCS2000 (EPSG:4490), which is close to ITRS and WGS 84 for casual use.
+If you are doing modern work, you should mostly see CGCS2000 (EPSG:4490), which is close to ITRS and WGS 84 for casual use.
 Parameters for precision transforms is not officially given, but you can try your luck with [https://isprs-archives.copernicus.org/articles/XLII-3-W10/535/2020/isprs-archives-XLII-3-W10-535-2020.pdf Wang ''et al.'' (2019), Table 1].

@@ Line 6: / Line 6: @@
 Parameters for precision transforms is not officially given, but you can try your luck with [https://isprs-archives.copernicus.org/articles/XLII-3-W10/535/2020/isprs-archives-XLII-3-W10-535-2020.pdf Wang ''et al.'' (2019), Table 1].
-Transformation for PRC datum are only legally acquired from the local government, which should normally be your source for maps made in old datums too. For Beijing 1954 (EPSG:4214), the EPSG has a few local transforms to try. All articles dealing with Xian 1980 are heavily redacted; the screenshots in [https://www.researchgate.net/publication/334379904_GISshujugeshizhuanhuanjizuobiaoxizhuanhuanfangfatantao 10.32629/gmsm.v2i4.291] look promising, until you realize the Bursa-Wolf values look way off and the source data is also redacted.
+Transformation for PRC datum are only legally acquired from the local government, which should normally be your source for maps made in old datums too. For Beijing 1954 (EPSG:4214), the EPSG has a few local transforms to try. All articles dealing with Xian 1980 are heavily redacted.
 === Possible Xian 1980 sources ===
 This section is for those who really want to put a TOWGS84 on Xian 1980 once and for all.
-* The aforementioned publication has three pairs of XYZ points in Xian 1980 and CGCS2000. The redaction is sloppy enough to have the top pixels show through. If anyone wants to try, use the PDF archived at [https://archive.is/iVplB] (click "Download Zip").
+* The publication doi:10.32629/gmsm.v2i4.291 has three pairs of XYZ points in Xian 1980 and CGCS2000. The redaction is sloppy enough to have the top pixels show through. If anyone wants to try, use the PDF archived at [https://archive.is/iVplB] (click "Download Zip").
 * In the GCJ-02 tradition, open-source code often inadvertently leak classified information. [https://github.com/Artoria2e5/GNSSAMS/tree/main/workspace/%E5%9D%90%E6%A0%87%E8%BD%AC%E6%8D%A2%E6%95%B0%E6%8D%AE GitHub: GNSSAMS] (forked for preservation) provides six pairs of XY points in Xian 1980 and Beijing 1953.
 * [https://github.com/Artoria2e5/iDesktop-MainDocs/blob/master/en/tutorial/DataProcessing/Projection/TransformationParaStep.md SuperMap/iDesktop-MainDocs] (also forked) provides a dozen pairs of tightly clustered XYZ in Xian 1980 and CGCS 2000, 3° zone 36.

@@ Line 1: / Line 1: @@
 ==Datums in China==
-Please see e.g., http://www.asprs.org/a/resources/grids/05-2000-china.pdf and https://www.iag-aig.org/doc/5d8dd34ba63c6.pdf.
+Please see e.g., http://www.asprs.org/a/resources/grids/05-2000-china.pdf and https://www.iag-aig.org/doc/5d8dd34ba63c6.pdf (reports #1, #3).
 On this page we aim to just supplement the more widely known information.

@@ Line 8: / Line 8: @@
 Transformation for PRC datum are only legally acquired from the local government, which should normally be your source for maps made in old datums too. For Beijing 1954 (EPSG:4214), the EPSG has a few local transforms to try. All articles dealing with Xian 1980 are heavily redacted; the screenshots in [https://www.researchgate.net/publication/334379904_GISshujugeshizhuanhuanjizuobiaoxizhuanhuanfangfatantao 10.32629/gmsm.v2i4.291] look promising, until you realize the Bursa-Wolf values look way off and the source data is also redacted.
-: Artoria2e5: On a second look, the redacted source numbers actually seem plausible and they are done sloppily enough to maybe recover the original. Although three control points will only give a small useful area (this could also explain the nonsense 7 parameters), it's something. The PDF is archived at [https://archive.is/iVplB] (click "Download Zip") for anyone who wants to try. --[[User:Artoria2e5|Artoria2e5]] ([[User talk:Artoria2e5|talk]]) 07:59, 17 May 2023 (PDT)
+=== Possible Xian 1980 sources ===
 ==Coordinate systems used in China==

← Older revision		Revision as of 14:59, 17 May 2023
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	Transformation for PRC datum are only legally acquired from the local government, which should normally be your source for maps made in old datums too. For Beijing 1954 (EPSG:4214), the EPSG has a few local transforms to try. All articles dealing with Xian 1980 are heavily redacted; the screenshots in [https://www.researchgate.net/publication/334379904_GISshujugeshizhuanhuanjizuobiaoxizhuanhuanfangfatantao 10.32629/gmsm.v2i4.291] look promising, until you realize the Bursa-Wolf values look way off and the source data is also redacted.		Transformation for PRC datum are only legally acquired from the local government, which should normally be your source for maps made in old datums too. For Beijing 1954 (EPSG:4214), the EPSG has a few local transforms to try. All articles dealing with Xian 1980 are heavily redacted; the screenshots in [https://www.researchgate.net/publication/334379904_GISshujugeshizhuanhuanjizuobiaoxizhuanhuanfangfatantao 10.32629/gmsm.v2i4.291] look promising, until you realize the Bursa-Wolf values look way off and the source data is also redacted.
		+
		+	: Artoria2e5: On a second look, the redacted source numbers actually seem plausible and they are done sloppily enough to maybe recover the original. Although three control points will only give a small useful area (this could also explain the nonsense 7 parameters), it's something. The PDF is archived at [https://archive.is/iVplB] (click "Download Zip") for anyone who wants to try. --[[User:Artoria2e5\|Artoria2e5]] ([[User talk:Artoria2e5\|talk]]) 07:59, 17 May 2023 (PDT)

	==Coordinate systems used in China==		==Coordinate systems used in China==