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MOJ projection engine   Mohammad Ishfaq Jan 24, 2005
Re: MOJ projection engine   Kerry Coffin Feb 11, 2005
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Subject MOJ projection engine 
Author Mohammad Ishfaq 
Date Jan 24, 2005 
Message Hi,
I have a bunch of questions and would appreciate input from any body here. I am providing my supposed answers to each of them in brackets.
* What is projection engine of MapObject for Java Edition (MOJ) based on (...EPSG? if yes then which version?)
* Is it using a projection engine different then the one used in mapobject for windows and arcobjects projection engine? (...Yes?)
* This is a main question now. When I try to convert a sample point from wgs84 to some other projected coordinate system (ED50/UTM30N) and then convert it back to wgs84, it causes a positional error of 0.414m, which in not acceptable in my case. Is there any way we can minimize this error effect so that it is reduced to 0.05m.
* My final question is that by default MOJ uses molodensky method for transformation. What other projection transformation methods we can adopt to get better results.
Regards. 
   
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Subject Re: MOJ projection engine 
Author Kerry Coffin 
Date Feb 11, 2005 
Message The projection engine in MapObjects is different than the projection engine in ArcObjects. It does reference epsg ids.

For your problem, can you send me the data (kcoffin@esri.com) and I'll look at it. I know that the ellipsoidal Transverse Mercator projection was accurate to about 15 degrees both sides of the central meridian, but before I comment on your problem, I'd like to see your data. (It recently was changed from this) (Most/All ellipsoidal TM zones are smaller than this).

Datum Transformations
It also supports Bursa Wolf, Coordinate Frame, NADCON, HARN, Geocentric translation, Geographic Offset. FOr ED50 there are several reference datums with transformations (called a ReferencedDatum) within the resource file GeodeticDB.txt. (com.esri.mo2.res.gdb)
This is where all the predefined geodetic objects are.

ED50,"GDB957","", 8033, MOLODENSKY, -87, -98, -121
ED50-BURSA,"GDB958","", 8237, BURSA, -89.5, -93.8, -123.1, 0, 0, 0.156, 1.2
ED50-WESTERN,"GDB959","", 8034, MOLODENSKY, -87, -96, -120
ED50-IRELAND,"GDB960","", 8038, MOLODENSKY, -86, -96, -120
ED50-UK,"GDB961","", 0, MOLODENSKY, -86, -96, -120
ED50-CYPRUS,"GDB962","", 8036, MOLODENSKY, -104, -101, -140
ED50-EGYPT,"GDB963","", 8037, MOLODENSKY, -130, -117, -151
ED50-MIDDLE EAST,"GDB964","", 8035, MOLODENSKY, -103, -106, -141
ED50-IRAN,"GDB965","", 8041, MOLODENSKY, -117, -132, -164
ED50-IRAN-ED77,"GDB966","", 8492, BURSA, -110.33, -97.73, -119.85, -0.3423, -1.1634, -0.2715, 0.063
ED50-GREECE,"GDB967","", 8040, MOLODENSKY, -84, -95, -130
ED50-GREECE-2,"GDB968","", 8372, MOLODENSKY, -86, -92.2, -127.5
ED50-SARDINIA,"GDB969","", 8042, MOLODENSKY, -97, -103, -120
ED50-SICILY,"GDB970","", 8043, MOLODENSKY, -97, -88, -135
ED50-MALTA,"GDB971","", 8044, MOLODENSKY, -107, -88, -149
ED50-NORWAY/FIN,"GDB972","", 8039, MOLODENSKY, -87, -95, -120
ED50-PORT/SPAIN,"GDB973","", 8045, MOLODENSKY, -84, -107, -120
ED50-TUNISIA,"GDB974","", 8148, MOLODENSKY, -112, -77, -145
ED50-FRANCE,"GDB975","", 8184, MOLODENSKY, -84, -97, -117

The CoordSysTreeframe allows you to select different datums. I enclose some sample code to show how to use it. Also I enclose the sample code the calculator and the projection editor.



Kerry
kcoffin@esri.com 
  Kerry Coffin
Sr. Software Architect, ESRI 
  javasamples.ZIP (opens in new window)