I have a .dat file with x,y having this projection description:

A polyconic projection is used. The WGS84 datum system, which is based on the GRS80 ellipsoid, is used as the geodetic reference system. The origin of the projection is 36 degrees north latitude and 136 degrees east longitude.

An example of the data:

1249500.0      -     1278500.0    
1249000.0      -     1278500.0    
1248500.0      -     1278500.0

When I convert the file to .xls and plot it into ArcGIS the data locate somewhere else Japan.

How to display these data in ArcGIS with this projection? Or how to transform this projection to UTM or to geographic coordinate sysyem?

  • First off, don't convert a perfectly good flat file to a spreadsheet. Spreadsheets are not databases and should not be used as such. Next, you need to make a .prj file. Unfortunately, doing so is a larger topic than our focused Q&A allows. Then you have to determine if the - in your file is a negative or just a placeholder, because it may make conversion a nightmare. If you can get the file as coordinates in the source projection, convert it to a file geodatabase table. At that point it will be easy to reproject to GCS_WGS_1984 or UTM.
    – Vince
    Jan 24, 2017 at 12:07
  • Please research each of these steps, and if you have difficulty, edit this question to contain 4-5 full sample rows and the projection file contents you have generated so far, then describe the exact difficulty.
    – Vince
    Jan 24, 2017 at 12:12

2 Answers 2


When you add your data to ArcMap, perhaps as an XY event layer, you need to associate/define its current coordinate reference system.

I'm very familiar with this area of ArcGIS (I work at Esri), and so I grabbed an existing prj file that uses WGS84 and polyconic, updated the name and the projection parameters, and it should be ready to go. The well-known text string is:


The string has been reformatted into multiple lines for display.

Create a new text/ASCII file (using Notepad) and copy/paste the string into it. Remove the line breaks so you the string is in a single line. Save it. When you add the XY Event layer, use the import option to browse to this file and use it for the data's coordinate system.

I did not bother to modify the existing geographic coordinate reference system, WGS84. The difference between using the WGS84 ellipsoid and the GRS80 ellipsoid when the GeoCRS/datum is WGS84 is minor (like sub-cm).


Create a new custom coordinate system. Select "D_GRS_1980" as your datum and set the prime meridian. after that you can import the data to ArcGIS using your custom coordinate system.

enter image description here

Then you can project your map to all other projection systems.

  • Doing this means that there are no existing transformations available. WGS84 (on WGS84 ellipsoid) and WGS84 (on GRS80) are practically identical unless you're doing geodetic survey work. OP also needs a custom projected CRS using polyconic.
    – mkennedy
    Jan 24, 2017 at 20:26

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