Coordinate system transformation given only differences as parameters

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04-08-2018 12:13 AM
RonMan
by
New Contributor III

Hi,

This is a question regarding coordinate system transformation of WGS84 or latlong to KosovoRef.  I am using ArcMap 10.3.1.

I am given the attached excel file given the parameter as differences (-2.37349693011492 and- 1415.26511242054).

I have done an excercise to test this in ArcGIS project tool using the  only kosovo coordinate system available but unfortunately i am getting a difference between the excel file and the transformed coordinates.

If given only parameter differences (-2.37349693011492 and- 1415.26511242054) can i input this in ArcMap to do the transformation for points and shapefiles?

My aim is to have ArcGIS transform/project as per the excel file.  How do i achieve this?

I hope someone could spare time to help me on this.

Regards,

Ron

UAE

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11 Replies
AbdullahAnter
Regular Contributor II
MelitaKennedy
Esri Notable Contributor

Hi Ron, 

This is very interesting. I only found a little bit of information on KOSREF except that another name maybe KOSOVAREF and that the projected coordinate reference system is the same as EPSG's 3909, MGI 1901 / Balkans 7. The projection parameters are:

Central meridian: 21.0

Latitude of origin: 0.0

Scale factor: 0.9999

False easting: 7500000.0

False northing: 0.0

I assume that the geographic coordinate reference system is MGI AKA MGI 1901, but the offsets between your KOSREF and WGS84 "GK zone 7" coordinates are too small compared to when I convert between MGI and WGS84 using any of the geographic/datum transformations. 

I haven't been able to confirm whether KOSREF is on MGI (which uses Bessel 1841 ellipsoid) or not. 

Because your offsets are between two projected coordinate reference systems, there isn't a direct way to model the differences. You might be able to do this by creating two projected CRS, and modifying the false easting and false northing parameters of one to incorporate the offsets.

Another method could be to use the Create Custom Geographic Transformation tool. There is a Geographic 2D Offset method. The offsets are in arc-seconds. I unprojected both datasets, assuming that the KOSREF is on MGI 1901.

                

WGS84 longitudeWGS84 latitudeKOSREF longitudeKOSREF latitudelongitude difference in secondslatitude difference in seconds
20.997329210022942.540392604834620.997357063958642.55741210537650.1002741685141561.2702019508362
20.996574528235842.537709656140820.996602084949142.55472887070770.0992041678756661.2691724408421
20.994857969121442.537790620038020.994884852450842.55480984362730.0967799858301561.2692049214587
20.994918628164342.540401526413420.994945536344042.55742102845670.0968694469278861.2702073558950

The offsets aren't as uniform as the projected versions (which seem suspicious to me actually). You could average these and use them. 

Melita

MelitaKennedy
Esri Notable Contributor

I hunted around a bit more and found some documents from 2005, which state that the geodetic reference net is based on ETRS89. If the KOSREF projected coordinates are based on ETRS89, they still don't make sense to me, because they shouldn't be that different from WGS84 coordinates.

RonMan
by
New Contributor III

Thank you Abdullah for the link.

Thank you Melita for your valuable input and time and prompt response.

I really needed an expert help on this since i do not have background on coordinate system projections.

I have attached a pdf i have found online that could give additional info.

I still have to digest on your response.  I'll respond back as soon as my task at hand finishes.

Thank you Melita.

Regards,

Ron

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MelitaKennedy
Esri Notable Contributor

The attachment didn't make it. If I remember correctly, you have to upload it and then attach it to the post.

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RonMan
by
New Contributor III

Hi Melita,

Here is the link where i got the pdf.

https://www.fig.net/resources/proceedings/fig_proceedings/fig2009/papers/ts04c/ts04c_idrizi_bajrami_... 

When i got the coordinates in WGS84 i searched for which UTM zone.  Is WGS84 "GK zone 7" the same with WGS84 UTM 30N?

The only Kosovo system i see in  ArcMap is ETRS89.  Were you able to verify my values from ArcGIS in the excel file?  My differences are not the same with the differences in the original table(left).

Thanks

Regards,

Ron

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MelitaKennedy
Esri Notable Contributor

The one I found is very similar. 

RonMan
by
New Contributor III

I do have a follow up question on this which is now about vertical transformation between ETRS89 and WGS84.

I am using ArcMap 10.3.1 which does not have the vertical transformation. Are any of the newer versions of ArcMap supports the transformation between the two Coordinate Reference System?

Is there a big difference in the elevations if i don't do any vertical transformation vs the vertically transformed elevations?

Since i have 10.3 is there any other ways i can do vertical transformation?

Thank you.

Regards,

Ron

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MelitaKennedy
Esri Notable Contributor

Between ellipsoidal heights relative to ETRS89 and WGS84, there shouldn't be too much difference. Between EVRF89 and WGS84 geoidal heights (AKA sometimes called EGM96 or EGM2008 heights), or mixing the two like WGS84 ellipsoidal heights and EVRF89 elevations, possibly larger offsets. Ellipsoidal heights and gravity-related heights using a geoid model can differ by up to a 100 m, but it depends on the location.

Project Tool started supporting some vertical transformations in 10.4. It's using a look-up table. You have to install a separate ArcGIS Desktop Coordinate Systems Data setup. We supported world geoid model, EGM2008, a bunch of US ones, some other vertical transformations. We don't have a geoid model for Europe. At 10.6, we have geoid models for Japan, New Zealand, USA. ArcGIS Pro is about a release or so behind Desktop. 

If a transformation uses a grid file, some customers have converted the grid file into a supported raster format and then used raster tools to do the transformation.