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I am trying to convert a shapefile from GCS to PCS to calculate the area of each polygon. I have tried two different methods:

1) "Data Management Tools->Projections and Transformations->Define Projection" and clearing the previous projection. I then go back in and define the new PCS projection ("World_Cylindrical_Equal_Area"). This creates a tiny shapefile centered on 0,0 lat/lon with a miniscule amount of area.

2) "Data Management Tools->Projections and Transformations->Feature->Project" and choosing a new Output Coordinate System ("World_Cylindrical_Equal_Area"). When I run this, an error message comes up that says the table name is invalid and cannot be found.

I am trying to convert from "GCS_Bissel_1841" to "World_Cylindrical_Equal_Area" - any help would definitely be appreciated.

Also, here is a link to the shapefile: https://filestogeaux.lsu.edu/public/download.php?FILE=tjoyne1/71691ctWDJg

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3 Answers

The Define Projection tool updates the coordinate reference system metadata only. It doesn't change the coordinate values. The same thing occurs (metadata only) if you change the coordinate system via the data's property page in ArcCatalog.

In 2), a geographic (datum) transformation is required because the source and target geographic coordinate reference systems are different: Bessel 1841 and WGS 1984. First Bessel 1841 isn't a true geodetic datum (and thus geographic coordinate reference system). Bessel 1841 is an ellipsoid. Someone didn't bother to define the GCS/datum at some point in this data's history. So, ArcGIS has no transformations for Bessel 1841. Looking at the data--it's worldwide, and there are no GCS that work for the world and are on Bessel 1841. I think my updated recommendation is just redefine the data as WGS 1984.

If you can make an educated guess as to its real GCS, you should use the Define Projection tool to update the information and then try projecting it again.

You could also modify the World_Cylindrical_Equal_Area definition to use Bessel 1841 as its GCS so no transformation is required.

Another possibility is to add the data to ArcMap, set the data frame to World_Cylindrical_Equal_Area (change its GCS or not), and export the data by right-clicking the layer and choosing data, export data. In that tool, set it to use the data frame's coordinate system.

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Thank you for your suggestions - I tried them, but still couldn't get the shapefile into the right projection. I think I just found a crude work-around. I clipped this shapefile based on a "countries" shapefile that has the exact same area shape, but is in WGS 1984. After doing this, I reprojected the new clipped shapefile as World_Cylindrical_Equal_Area and it produced a shapefile that I could calculate area from. –  Andrew Mar 12 '13 at 20:19
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Try using Project tools in Data management tools-->Feature-->Project... Use the shape file and enter the required projection in which you want to get. I think it might answer your problem.

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Thank you 'mkennedy'. For anyone struggling, the method that worked best for me was to export the data by right-clicking on the layer and choosing data, export data. In that tool, I set it to use the data frame's coordinate system. It produces an Export-Output layer which should be projected correctly.

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This seems more a comment than an answer? –  Mapperz Mar 27 at 15:49
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