Same projected and geographical co-ordinate system, different extents.

[Ashley_Rabot]

Hi All, 

I'm just struggling to align these co-ordinate systems up in ArcMap.

One is the ITN Network Dataset all prepared which is on a British National Grid Projection.

The other is a CSV with lat/long coordinates which is also imported using the XY Data and projected it as a British National Grid Projection.

They simply won't line up and I have tried exporting it as a .shp file, reimporting and then reprojecting as well as using the "Define Projection" tool.

One thing I have noticed is the extents are hundreds of thousands of meters off, however I've been trying to google stuff and haven't come to much luck. 

I don't know if anyone has a suggestion but I thought i'd ask just in case. 

Excel Files are attached. Unfortunetly the ITN network file is over the allowance. The pictures show the locaiton of the cycle points (small red dot) and the ITN map (green dots) Hopefully you can access these if you do want to see my issue.

Thanks in Advance,

Kind Regards
Ashley

[DanPatterson_Retired]

couldn't help but notice that your latitudes put you at the equator -.23 to 0.02 something degrees.  51.4 - 51.5 degrees? and this is supposed to be in Britain (no....)

What ever this file is, if the Define Projection was used, Define it back to what it was because I would venture that those numbers probably aren't long/lat and certainly look sketchy for meters unless you are working with a really really small study area.  

Where is it supposed by be? either in decimal degrees or using coordinates for your preferred coordinate system.  Then maybe 7.png can be figures out.  77.png looks like a projected coordinate system

[JosephCarter]

Hey, Ashley. I looked at your CVS data and your Lat/Long fields need switched. I often help folks land xy data and I have them do this: Open a blank ArcMap/Convert your data to decimal degrees (you have)/Create a default geodatabase for this project//set your map's projection to "WGS_1984_World_Mercator"/add your table and right click to Display XY Data/make sure your x field is your longitude and y is latitude(your field names need switched)/next while in this dialog box click Edit (on the bottom)/choose Geographic, World, WGS 1984, OK. Your points will land correctly and you should then export to your geodatabase and accept the feature class in your map.

Remember, it is best to do this in a blank ArcMap, nothing in it but the table.

Good luck!

Joe

[ChrisDonohue__GISP]

If the above doesn't work, one aspect you may want to evaluate is whether the Datum has been incorrectly assigned to one of the data files.  What you are running into sounds a lot like a common issue encountered here in the United States, where two popular datums are used:  North American Datum 1927 (NAD 1927) and North American Datum 1983.  When one dataset is assigned the wrong datum (say it was assigned NAD 1983 when it really is NAD 1927), this manifests itself when the data is brought into ArcMap as one dataset being off from the other by several hundred feet.  After seeing this often one often instantly recognizes the issue, as their is a distinct directional shift (here in California things shift between the two on a East-North-East and West-South-West orientation).

Chris Donohue, GISP