Can't identify coordinate system

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05-16-2019 11:23 AM
BrendanDwyer
Occasional Contributor

I have some geospatial data in a text file but I can't identify the coordinate system it is using.  Coordinates were in a format like this: xxxxNx, xxxxxEx, where the x's are integers.  I think it might be a naval or military format, but I'm not sure.

It would look something like this: "3506N8 13922E5"*

Any help would be appreciated.

*not a real example, may not be plottable.

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BrendanDwyer
Occasional Contributor

Figured it out. It's a format used by OTH-Gold, as described in Appendix C here:

https://apps.dtic.mil/dtic/tr/fulltext/u2/a405953.pdf 

Enter the position of the report in its original format and precision if possible. Use one of the alternate field contents provided below. Enter the designated field descriptor followed by the data. Data can be expressed in:
Coordinate  System    Field Descriptor
LL:                               Latitude/Longitude
UT:                               UTM (Universal Transverse Mercator)
GR:                              GEOREF (World Geographic Reference System)
The precision reported in this field should reflect the original known precision. The only boundary or restriction placed on the reported precision of data in this field is the field length range. An optional floating decimal is allowed as  appropriate, e.g., LL:304055.55N7-1304055.55E8, UT:45FDK0474, GR:DIQA

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RobertBorchert
Frequent Contributor II

Shoot a real example.

The example you used is in the Alabama?

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RobertBorchert
Frequent Contributor II

I think it might be a County Coordinate system. 

it would then be specific to a particular county.

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RobertBorchert
Frequent Contributor II

Possibly in the Tampa Area

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BrendanDwyer
Occasional Contributor

I'm sure it's not a local system like state plane.

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RobertBorchert
Frequent Contributor II

County Coordinate systems are more local then State Plane and not formatted the same as state plane.

And were genera rally created by

The numbers you show are too small to represent a system as large as UTM or State Plane.

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BrendanDwyer
Occasional Contributor

Thanks for the reply.  I found that the coordinates are preceded by what looks like a reference to a grid system, which could explain the low precision.   But I know for certain this is a global system.  That's about the only thing I know for sure.

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DanPatterson_Retired
MVP Esteemed Contributor

Melita Kennedy‌ flagged

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MelitaKennedy
Esri Notable Contributor

The format doesn't look familiar to me. Can you tell us approximately where the data is supposed to be? 

I'm assuming E = easting and N = northing but the trailing number is odd. It wouldn't be unusual if the numbers were, for example, 

1392250 or 139225 or 13922500

350680 or 3506800

I've seen 13 million eastings in state plane zones, particularly if in feet, but that's unlikely for military-based numbers. They don't match georef or GARS. I guess if you're working with military data, you could try contacting NGA, the Coordinate System Analysis group, https://www.nga.mil/ProductsServices/GeodesyandGeophysics/Pages/CoordinateSystemAnalysis.aspx

Melita

note: edited 5:15 p.m. PDT to fix a number because I'd repeated one of them.

BrendanDwyer
Occasional Contributor

Melita, thanks for the reply.

Unfortunately, I can't post an actual coordinate b/c the data is sensitive.  But I do have more information to go by. First off, the coordinates are preceded by a two letter code, for example LL:3521N1-12429E8.  That's got to be some sort of grid reference, I'd guess.

Also, a colleague figured something out: The trailing number after the northing and easting is actually a checksum.  You add up the integers preceding the N or E and take the least significant digit.  For example:

3521N1-12429E8

3+5+2+1 = 11 and 1+2+4+2+9 = 18

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