Homogenisation

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04-27-2017 02:35 AM
TheresaFurness
New Contributor II

Hi,

I am new to ArcGIS.  I am a bit stuck.  I am adding a 2 layers in ArcMap :

ArcGIS coordinate system

*Type Geographic

*Geographic coordinate reference GCS_WGS_1984

and

*Type Projected

*Geographic coordinate reference GCS_MGI

*Projection MGI_Austria_GK_M31

I cannot see the projected layer - when I Define Projection as MGI, they are both there, but very FAR apart.  Is it the Datum that is incorrect?  How can I correct this?

Thanks in advance

Terri

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17 Replies
DanPatterson_Retired
MVP Emeritus

Well given the easting and northing values of the 2nd image, I think it is within the correct latitudinal range.  The only thing to resolve now is what projected coordinate system would give rise to those values, hence my guess of some UTM or transverse Mercator based projection since 45 degrees is 1/2 way between the equator and the pole and the original definition of the metre was 1/10,000,000 of the distance between the equator and the pole... ergo, 5,000,000 metres-ish would be an appropriate northing.  As for the easting, you should be able to figure what UTM zone you are in and whether your longitude falls to the east or west of the central meridian for the utm zone that covers the latitude and longitude range.  

Of course this doesn't rule out any other projections that you might encounter in your studies that are unique or widely used in your area.  Trial and error and/or comparison to a known dataset are your only options to narrow down appropriate candidates.

JayantaPoddar
MVP Esteemed Contributor

Thank you for the mail. The correct projected Coordinate system for LULC_NAWI is WGS_1984_UTM_Zone_33N.

Go to the Shapefile Properties from ArcCatalog > XY Coordinate System Tab. And define WGS_1984_UTM_Zone_33N as the coordinate system.

PCS

The Project_area and LULC_NAWI will then exactly overlay on each other.

overlay



Think Location
TheresaFurness
New Contributor II

Excellent - that worked!

Please could you tell me how you ascertained that correct projected

Coordinate system - I hunted through my list for hours and tried MANY.

There must be an easier way.

Terri

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JayantaPoddar
MVP Esteemed Contributor

UTM is a very common PCS used globally. It was just a hunch.

Check How to calculate the UTM zone using longitude values (Decimal Degrees)



Think Location
DanPatterson_Retired
MVP Emeritus

plus your longitudes are in the appropriate range for that utm

TheresaFurness
New Contributor II

Thanks - a very helpful link. 

Terri

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JoeBorgione
MVP Emeritus

Try this:  add one of the layers to an ArcMap session, right click and Zoom to Layer.  In another ArcMap session do the same thing with the other layer.  If one of them 'dissapears' from your screen, that's the problem child and it has an extent problem.

That should just about do it....
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AnaPavcec
New Contributor

Hi, 

I am also new in GIS.

How do I know name for  the EPSG 31258 projection?

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