PROJ4 Issues The case of Romania: increasing transformation - - PowerPoint PPT Presentation

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PROJ4 Issues The case of Romania: increasing transformation - - PowerPoint PPT Presentation

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PROJ4 Issues The case of Romania: increasing transformation accuracy through grid shift files Daniel Urd 17.07.2014 Outline National Reference System of Romania Reference transformation: TransDatRo Current implementations

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PROJ4 Issues The case of Romania: increasing transformation accuracy through grid shift files

Daniel Urdă 17.07.2014

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Outline

  • National Reference System of Romania
  • Reference transformation: TransDatRo
  • Current implementations
  • Open source software
  • Proprietary software
  • Towards increased precision (in FOSS)
  • Conclusion

2 PROJ4 Issues - The case of Romania

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Romanian National Projection System

1

3 PROJ4 Issues - The case of Romania

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Romanian National Projection System

  • S-42 National Reference System – “Stereo70”
  • Characteristics:
  • Krasovski 1940 ellipsoid
  • Stereographic projection “1970”

4 PROJ4 Issues - The case of Romania

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Transformation issues

  • No simple mathematical formula
  • Existing attempts produce inconsistent errors, with

accuracy depending on actual location of the dataset

  • Reprojection

to/from

  • ther

systems result in topological errors

5 PROJ4 Issues - The case of Romania

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Why bother with it

  • De jure standard for topo-geodesic measurements
  • Large existing database of geographic information

using the projection (both classical maps and GIS systems)

  • Regulation No. 1089/2010 (EU) on the implementation
  • f the INSPIRE directive as regards interoperability of

geodatasets and services recommends using ETRS89

6 PROJ4 Issues - The case of Romania

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Reference transformation: TransDatRo

2

7 PROJ4 Issues - The case of Romania

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  • “Dumb” application provided by

the Romanian Cadaster Agency (ANCPI)

  • Reprojects

from/to ETRS89 (LAEA and Transverse Mercator projections available)

  • Declared planimetric precision:

±10+15 cm

TransDatRO

8 PROJ4 Issues - The case of Romania

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SLIDE 9
  • 1. Convert ETRS89 ellipsoidal coordinates to Cartesian coordinates

in the oblique stereographic projection

  • 2. Convert GRS80 coordinates to Stereo70 coordinates
  • 3. Interpolate geometric correction based on a table of datum shifts
  • 4. Interpolate quasigeoid anomalies to account for the Black Sea

reference altitude (Marea Neagră 1975 system)

Algorithm

9 PROJ4 Issues - The case of Romania

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TransDat v.1.02 absolute horizontal datum shifts

10 PROJ4 Issues - The case of Romania

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  • MS Windows only
  • “Experimental” source code for version 1.0
  • Accepted input format:
  • ESRI Shapefile (v1.0)
  • Text files (v4)
  • Cumbersome UI

Limitations

11 PROJ4 Issues - The case of Romania

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Alternative transformations: Open Source Software

3

12 PROJ4 Issues - The case of Romania

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  • FOSS library available for most major OSs
  • A large database of global, national and

local projection systems

  • WGS84 as intermediary projection system
  • Used for reprojecting in a large part of

higher-level open-source GIS software

PROJ.4

13 PROJ4 Issues - The case of Romania

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  • No standard EPSG code
  • Several potentially applicable codes

(originally from the GeoTIFF library)

  • EPSG:31700
  • EPSG:3844
  • EPSG:4284
  • EPSG:4178
  • Standard transformation parameters

Stereo70 ?!?

14 PROJ4 Issues - The case of Romania

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+proj=sterea +lat_0=46 +lon_0=25 +k=0.99975 +x_0=500000 +y_0=500000 +ellps=krass +towgs84=28,-121,-77,0,0,0,0 +units=m +no_defs

EPSG:31700 Dealul Piscului 1970 / Stereo 70

15 PROJ4 Issues - The case of Romania

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EPSG:3844 Pulkovo 1942(58) / Stereo70

+proj=sterea +lat_0=46 +lon_0=25 +k=0.99975 +x_0=500000 +y_0=500000 +ellps=krass +towgs84=33.4,-146.6,-76.3,-0.359,-0.053,0.844,-0.84 +units=m +no_defs

16 PROJ4 Issues - The case of Romania

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EPSG:4284 Pulkovo 1942 + Stereo70

+proj=sterea +lat_0=46 +lon_0=25 +k=0.99975 +x_0=500000 +y_0=500000 +ellps=krass +towgs84=23.92,-141.27,-80.9,-0,0.35,0.82,-0.12 +units=m +no_defs

17 PROJ4 Issues - The case of Romania

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EPSG:4178 Pulkovo 1942(83) + Stereo70

+proj=sterea +lat_0=46 +lon_0=25 +k=0.99975 +x_0=500000 +y_0=500000 +ellps=krass +towgs84=33.4,-146.6,-76.3,-0.359,-0.053,0.844,-0.84 +units=m +no_defs

18 PROJ4 Issues - The case of Romania

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  • Romanian Cadastre Agency:
  • 7-parameter “Helmert” transformation between “Sistem 42” and

ETRS89

  • Issues:
  • WGS84 and ETRS89 postulated identical (default PROJ4 behaviour)
  • “Wrong” sign for the rotation parameters (EPSG:9607 apparently used

instead of the ISO 19111 recommended EPSG:9606, used by PROJ4)

User-defined parameters

19 PROJ4 Issues - The case of Romania

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User-defined parameters – ANCPI

+proj=sterea +lat_0=46 +lon_0=25 +k=0.99975 +x_0=500000 +y_0=500000 +ellps=krass +towgs84=2.3283,-147.0416,-92.0802,-0.30924979,0.32482188, 0.49730012,5.68907711

20 PROJ4 Issues - The case of Romania

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Alternative transformations: proprietary software

4

21 PROJ4 Issues - The case of Romania

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  • Potentially

applicable reference systems:

  • S-42 (Pulkovo 1942)
  • S-42 Romania
  • Dealul Piscului 1970

Global Mapper (v.14)

22 PROJ4 Issues - The case of Romania

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Stereo70 / S-42 Romania

23 PROJ4 Issues - The case of Romania

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Stereo70 / Dealul Piscului 1970

24 PROJ4 Issues - The case of Romania

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Stereo70 / S-42 (Pulkovo 1942)

25 PROJ4 Issues - The case of Romania

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  • Potentially

applicable pre-defined transformations:

  • Dealul_Piscului_1970_to_WGS_1984_1
  • Dealul_Piscului_1970_to_WGS_1984_2
  • Pulkovo_1942_Adj_1958_To_ETRS_1989_4

ESRI ArcGIS (v10.2)

26 PROJ4 Issues - The case of Romania

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Dealul_Piscului_1970_to_WGS_1984_1

27 PROJ4 Issues - The case of Romania

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Dealul_Piscului_1970_to_WGS_1984_2

28 PROJ4 Issues - The case of Romania

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Pulkovo_1942_Adj_1958_To_ETRS_1989_4

29 PROJ4 Issues - The case of Romania

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Improving precision in FOSS

5

30 PROJ4 Issues - The case of Romania

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PROJ.4 – alternative algorithm

  • 1. Convert

ETRS89 ellipsoidal coordinated to rectangular coordinates in the oblique stereographic projection

  • 2. Convert coordinates based on GRS80 ellipsoid to ones based
  • n the Krasovski 1940 ellipsoid
  • 3. Interpolate geometric corrections based on a grid of datum shifts

31 PROJ4 Issues - The case of Romania

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Grid shift files – NTV2

  • Binary format developed in Canada and Australia
  • De facto standard (official grid shift files published by

Brazil, Germany, New Zealand, United States, South Africa, etc.)

  • Used by PROJ4 for high precision transformations

32 PROJ4 Issues - The case of Romania

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Building a NTv2 file for Romania

  • Issues:
  • NTv2 – grid points in geographical projection
  • ANCPI – grid points in stereographic projection

33 PROJ4 Issues - The case of Romania

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Building a NTv2 file for Romania

  • Algorithm:
  • Generate a custom regular grid in geographical projection (35 sec latitude,

50 sec longitude) covering the territory of Romania

  • Convert grid to “Sistem 42” using TransDatRO
  • Convert back to WGS84 using PROJ4, ignoring datum transformations
  • Compute shifts between the points of the original grid and that of the

reprojected one

  • Generate NTv2 binary file using the above shifts

https://github.com/danieluct/ntv2generator (Work in progress)

34 PROJ4 Issues - The case of Romania

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Transformation using grid shifts file

+proj=sterea +lat_0=46 +lon_0=25 +k=0.99975 +x_0=500000 +y_0=500000 +ellps=krass +nadgrids=stereo70_etrs89A.gsb +units=m +no_defs

35 PROJ4 Issues - The case of Romania

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Conclusion

6

36 PROJ4 Issues - The case of Romania

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Comparing transformation accuracy

No Transformation Minimum error (m) Maximum error (m) Mean error (m) Standard deviation (m) 1 PROJ.4 Generated grid shift file 0,000 0,029 0,007 0,003 2 PROJ.4 ANCPI parameters + Stereo70 0,000 1,463 0,339 0,219 3 ArcGIS 10.2 Pulkovo_1942_Adj_1958_To_ETRS_1989_4 0,000 1,464 0,339 0,219 4 Global Mapper 14.0 Stereo70 / S-42 Romania 0,000 1,718 0,416 0,250 5 Global Mapper 14.0 Stereo70 / S-42 (Pulkovo 1942) 0,000 1,949 0,488 0,325 6 PROJ.4 EPSG:3844 Pulkovo 1942(58) / Stereo70 0,001 2,976 1,290 0,647 37 PROJ4 Issues - The case of Romania

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No Transformation Minimum error (m) Maximum error (m) Mean error (m) Standard deviation (m) 7 ArcGIS 10.2 Dealul_Piscului_1970_to_WGS_1984_2 0,004 3,587 1,640 0,774 8 Global Mapper 14.0 Stereo70 / Dealul Piscului 1970 0,001 3,593 1,650 0,776 9 PROJ.4 EPSG:31700 Dealul Piscului 1970 / Stereo 70 0,004 3,587 1,648 0,774 10 PROJ.4 EPSG:4178 Pulkovo 1942(83) + Stereo70 1,195 4,918 3,124 0,619 11 ArcGIS 10.2 Dealul_Piscului_1970_to_WGS_1984_1 1,690 8,312 4,698 1,495 12 PROJ.4 EPSG:4284 Pulkovo 1942 + Stereo70 3,731 7,304 5,686 0,498 38 PROJ4 Issues - The case of Romania

Comparing transformation accuracy

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Further work

  • Modify EPSG:3844 to use parameters published by the Romanian

Cadastre Agency

  • Official endorsement of the NTv2 grid shift file / Publication of a

ANCPI-generated grid shift file based on latest measurements

  • OGR/GDAL support for vertical grid shift files

39 PROJ4 Issues - The case of Romania

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Questions?

7

40 PROJ4 Issues - The case of Romania

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Thank you!