[Gvsig_english] BIG problems with reprojecting AGD66 to GDA94

[Juan Lucas Dominguez Rubio]

Hello, Simon.
 
I have done a test with a view in EPSG:4202 and two shapefiles (a target shapefile in EPSG:4202 and a source shapefile in EPSG:4283) extracted from your DBF. After adding the target shapefile (same projection as the view) I have added the source shp trying a variety of transformations. When you add it to the view, gvSIG lets you choose among eleven available "EPSG transformations" between those two EPSG codes. The one that gives me the best result is the first one:
 
Transformation code: 1278
Name: AGD66 to GDA94 (1)
(we are actually doing the inverse transformation (GDA94 to AGD66) but the algorithm seems to be aware of this and does it well)
 
I have measured the distance between the obtained coordinates (transformed source shp) and the expected coordinates (target shp)  for 5 random points and I get these errors:
 
1.2 m
0.9 m
1.57 m
0.88 m
0.96 m
 
I have also looked into some pdf files and I have found these parameters (AGD66 to GDA94) for Victoria and NSW:
 
http://www.icsm.gov.au/icsm/gda/gdatm/gdav2.3.pdf
 
Dx = -119.353
Dy = -48.301
Dz = 139.484
Rx = -0.415
Ry = -0.26
Rx = -0.437
Sc = -0.613
 
Since we are doing the inverse transfomation, we should reverse the sign for each parameter, but I don't get good results.
 
I have also read somewhere that in Australia and the US, the rotation parameters have the inverse meaning than in Europe (big ???), so I tried these parameters (reversing the ones above except for the rotation parameters):
 
Dx = 119.353
Dy = 48.301
Dz = -139.484
Rx = -0.415
Ry = -0.26
Rx = -0.437
Sc = 0.613
 
And indeed, I get significantly smaller errors for those 5 points:
 
0.7 m
0.15 m
0.75 m
0.8 m
0.25 m
 
Those 7 parameters can be entered with the "manual transformation" option. I didn't get the grid to work either, sorry, although the format seems to be one supported by gvSIG. And I have not done any tests with non-geographical SRS.
 
Regards,
 
Juan Lucas Domínguez Rubio
---
Prodevelop SL, Valencia (España)
Tlf.: 96.351.06.12 -- Fax: 96.351.09.68
http://www.prodevelop.es <http://www.prodevelop.es/> 
---

________________________________

De: gvsig_internacional-bounces at listserv.gva.es en nombre de Simon Cropper (Botanicus Australia Pty Ltd)
Enviado el: sáb 28/11/2009 7:36
Para: Users and Developers mailing list
Asunto: [Gvsig_english] BIG problems with reprojecting AGD66 to GDA94



Hi Guys,

I am having problems getting the reproject tool to work as expected with
Australian Projections/Datums.

If I create a shapefile in AGD66 then reproject the file to GDA94 using
the reproject tool, the points are moved but only ~20m rather than 204
metres northeast of the original position. If I use the resulting GDA94
file in the AGD66 View and tell the program, it reprojects on the fly
and the points overlap.

This shows (a) that the reproject on the fly facility works, and (b) I
appear to have chosen the wrong projection.

The problem is I have tried reprojecting northing-eastings,
latitude-longitude, in EPSG and ESRI format but can't get the correct
reprojection. I have been using EPSG:4202 for AGD66 geographicals,
EPSG:4283 for GDA94 geographicals, EPSG:20255 for AGD/ AMG zone 55 and
EPSG:28355 for GDA94/MGA zone 55. I have also tried ESRI: 28355 and
ESRI:20255 with no luck.

I have even downloaded the transformation grid but not been able to get
this to work either.

Can anyone help?

Attached is a list of points in a table that are released by the local
government apparently created by FME. This has the comparable
coordinates in 4 commonly used projections for 160 distinct points
across Victoria.

Can anyone get the correct setting and procedure to get these points to
superimpose when reprojecting on the fly and for the reproject facility
to work correctly?

I have also included some useful links to help the more industrious and
knowledgeable to figure out what is wrong.

http://www.land.vic.gov.au/Land/lcnlc2.nsf/LinkView/9B33746B3D77040F4A256A250008E70A5B923E73477D6D65CA256E5F0013D73B

http://www.icsm.gov.au/icsm/gda/gdatm/

http://www.icsm.gov.au/icsm/gda/gdatm/gdav2.3.pdf

Any help would be appreciated as I am trying to tick this off my list of
things gvSIG can do, and was surprised to see when resulting reprojected
files were compared to external reference documents they did not align.

Any help would be greatly appreciated.
--

Cheers Simon

Simon Cropper
Botanicus Australia Pty Ltd
PO Box 160, Sunshine, Victoria 3020.
P: 9311 5822. M: 041 830 3437.
mailto: scropper at botanicusaustralia.com.au
<mailto:scropper at botanicusaustralia.com.au>
web: www.botanicusaustralia.com.au <http://www.botanicusaustralia.com.au <http://www.botanicusaustralia.com.au/> >



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