Projection transformation issues

ChrisBoulter — Tue, 26 Jul 2011 09:45:14 GMT

Hi,

Thanks in advance for the help.

OK, so I am working on data for Ukraine.

I have XY data in GK Pulkovo 1942 that I want to load into my basemap.

My basemap projection is WGS 1984 Zone 35N. This contains a lot of data (georef topo maps, relief, landsat, roads, drainage etc) for the whole of Ukraine.

I have the transformation to get from Pulkovo 1942 to WGS 1984 Zone 36N, but I do not have one for zone 36N to 35N or vice versa.

My question is:

Is there a conversion from 36N to 35N? Unhelpfully, Ukraine is covered by both 35N and 36N, which confuses me a little.

Thanks,

Chris

Re: Projection transformation issues

MelitaKennedy — Tue, 26 Jul 2011 15:35:52 GMT

Hi Chris,

Converting between projected coordinate systems is easy, if the map projection algorithm is supported. In this case, you can either have the data project on-the-fly in ArcMap to the data frame's coordinate system, or create a copy of the data in the base map's coordinate system using the Project Tool (ArcToolbox, Data Management, projections and transformations).

The actual steps that occur internally when converting vector data between two projected coordinate systems are:

1. Coordinates converted from projected x,y to geographic lat,lon.
2. If the input and output geographic coordinate systems are different, do a datum transformation if one is specified. [In ArcMap] If not, treat coordinates as if they're already using the output gcs.
3. Convert coordinates to the output projected coordinate system.

If the input data is using a gcs, start at 2 instead, and so on.

I would use zone 36 North over 35 North, but the area is really too wide for a UTM zone. It would probably be better to map it in a conic projection, but Esri doesn't have any defined already.

Hope this helps,
Melita

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Projection transformation issues

Re: Projection transformation issues