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I am trying to import the National Bridge Inventory Lat/Long data into ArcGIS. But when I do it with WGS 1984 Geographic coordinate system, they don't match with the base maps. I don't where I am going wrong. To convert the Lat/Long values I am using the ddMMSSHH concept.

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    Could you please provide a reference to the referred systems. Also WGS 194 - sure you do not mean WGS 1984? – ragnvald Mar 20 '15 at 7:30
  • @ragnvald thanks for the reply. fhwa.dot.gov/bridge/nbi/ascii.cfm i – adr0327 Mar 20 '15 at 7:33
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    There is an edit button beneath your question that you can use to revise it in response to any requests for clarification such as that above. – PolyGeo Mar 20 '15 at 7:44
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    There's no hemisphere information. Probably assuming positive west longitudes. Here's a sample in Alaska: 55074800131341800. Thus latitude = 55 07 48 and longitude = 131 34 18. The trailing zeroes could mean it's DDMMSS.ss and DDDMMSS.ss. – mkennedy Mar 20 '15 at 16:21
  • Mkennedy I figured out that the longitude if negated showed me the locations. They are from new mexico. But in ARCGIS which coordinate system should I select wheb i import this xy data.. Would it be the newmexico UTM zone?? – adr0327 Mar 20 '15 at 16:26
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At the top of the page linked to in the comment and now question is a line "Recording and Coding Guide for the Structure Inventory and Appraisal of the Nations Bridges" with a pdf and doc format link. This document includes the metadata for each field in the data, and it confirms mkennedy's interpretation that it's (D)DDMMSS.ss and assumes positive west longitudes (the specified format doesn't allow for signs). They don't, however, specify a datum reference though they do mention 'for GPS use'. The original WGS84 and NAD83 are extremely similar for North America, depending on your accuracy requirements.

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