projecting to Swiss national grid

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05-31-2013 02:40 PM
MinaIse
New Contributor
Hello,

I need your advise regarding changing coordinate system for some files.
I had no problems projecting some shapefiles from WGS84 to CH1903.prj. I think it has to do with the fact these layers were already defined, so just changed coordinate system. Also in the process here (Feature - Project) geographic transformation option is available to define the transition from one coordinate system to the other (WGS_1984_To_CH_1903).

I need the same coordinate system for some files which have downloaded from the open source data website http://data.gbif.org, the latitude and longitude are defined in decimal degree format but there is no coordinate system/no projection (as I understand). So now I have to choose Define Projection here instead of Project, which I think is were trouble starts... So I define the same CH_1903.prj BUT the layers won`t match although they have the same projection. Am I right to think it has to do with the fact that decimal degrees will not be converted to meters and that`s why the layers won`t match?

Data Type: Shapefile Feature Class
Geometry Type: Point

Projected Coordinate System: CH1903_LV03
Projection: Hotine_Oblique_Mercator_Azimuth_Center
False_Easting: 600000,00000000
False_Northing: 200000,00000000
Scale_Factor: 1,00000000
Azimuth: 90,00000000
Longitude_Of_Center: 7,43958333
Latitude_Of_Center: 46,95240556
Linear Unit:  Meter

Geographic Coordinate System: GCS_CH1903
Datum:  D_CH1903
Prime Meridian:  Greenwich
Angular Unit:  Degree

and

Data Type: Shapefile Feature Class
Geometry Type: Polygon

Projected Coordinate System: CH1903_LV03
Projection: Hotine_Oblique_Mercator_Azimuth_Center
False_Easting: 600000,00000000
False_Northing: 200000,00000000
Scale_Factor: 1,00000000
Azimuth: 90,00000000
Longitude_Of_Center: 7,43958333
Latitude_Of_Center: 46,95240556
Linear Unit:  Meter

Geographic Coordinate System: GCS_CH1903
Datum:  D_CH1903
Prime Meridian:  Greenwich
Angular Unit:  Degree



I also tried to be clever and change the coordinate system by doubleclicking Layer Properties - Source - Set Data Source and choose the coordinate system from the previously projected layers but unfortunately those layers are the polygon layers and the ones I`m having problems with are observation points, but changing the coordinates in this way also geometry type would change (from point to polygon). 

What am I supposed to do please...

PS! Maybe I should also mention that the unprojected layers matched perfectly with each other (country shapefiles in WGS84 and the observation points with no coordinate system).
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MelitaKennedy
Esri Notable Contributor
Hi,

The adscita mannii shapefile is still in latitude-longitude. When you labeled it as CH1903 LV03 using Define Projection tool or the data's property page in ArcCatalog, you updated the metadata only, not the actual coordinate values. The software then thinks the latitude-longitude values are in CH1903 LV03 meters. When those coordinates are unprojected back to lat-lon, you get values near the equator (because that's where the actual origin of the projected coordinate system is).

I tried assigning CH1903, CH1903+, and ETRS89 to the data. Even after setting a transformation to CH1903 when it's defined as ETRS89, there's one observation falling outside of the administrative region layer. You might want to email one of the contacts listed at GBIF, or GBIF itself and see if they can clarify what coordinate reference system is being used. Switzerland could be CH1903, CH1903+, CHTRF, ETRS89 (once it's available on GBIF), or even WGS84.

Regards,
Melita

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MelitaKennedy
Esri Notable Contributor
Hi,

The adscita mannii shapefile is still in latitude-longitude. When you labeled it as CH1903 LV03 using Define Projection tool or the data's property page in ArcCatalog, you updated the metadata only, not the actual coordinate values. The software then thinks the latitude-longitude values are in CH1903 LV03 meters. When those coordinates are unprojected back to lat-lon, you get values near the equator (because that's where the actual origin of the projected coordinate system is).

I tried assigning CH1903, CH1903+, and ETRS89 to the data. Even after setting a transformation to CH1903 when it's defined as ETRS89, there's one observation falling outside of the administrative region layer. You might want to email one of the contacts listed at GBIF, or GBIF itself and see if they can clarify what coordinate reference system is being used. Switzerland could be CH1903, CH1903+, CHTRF, ETRS89 (once it's available on GBIF), or even WGS84.

Regards,
Melita
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MinaIse
New Contributor
Thank you for the explanation Melita.

I`m sorry but may I ask in detail what exactly I`m supposed to do if I want to project these layers, I`m not that familiar with ArcGis.
Define Projection does not work..
Projection I cannot choose (if unprojected)..

How did you manage to assign these different coordinate systems to the data?
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MelitaKennedy
Esri Notable Contributor
Hello,

Make sure that you have write permissions for the files and the folder that the shapefile is in (that's one reason why Define Projection would not work). Close ArcMap if it's open (we want to make sure that the shapefile isn't locked by being in use somewhere).

Use the Define Projection tool in ArcToolbox. You will probably get a warning that the shapefile already has a coordinate system. You can ignore the warning. Set the coordinate system to the ETRS 1989 geographic coordinate system. It's under geographic coordinate systems, Europe. In ArcCatalog, refresh the folder by selecting it and hitting F5. Now try adding the shapefile to a new ArcMap with your administrative boundaries.

Melita
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MinaIse
New Contributor
Thank you Melita!
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