There has been an increase in queries regarding the import of coordinate values from spreadsheets into ArcGIS Desktop and ArcGIS Pro. With that in mind, find a checklist that hopefully will encourage, when dealing with this type of data, the understanding of coordinate values, their implications of how they are managed and the relationship to coordinate reference systems in ArcGIS software.
Check coordinates are in the order you expect (e.g. Lat/Long or Long/Lat or X, Y; Y, X and W, E; -X, -Y etc)
Check there are no NULLs or other errors
Check for NULLS, text not number, unrealistic precision, outliers…
Confirm the coordinates make sense (e.g. if you are working with Arctic DMS coordinates a negative latitude value should be a red flag for you)
Check you know the units
Latitude and Longitude are angles therefore = Geographic Coordinate System
XY coordinates (e.g. meters) are linear measurements therefore = Projected Coordinate System
Convert the data you have into a workable format (e.g. DMS to DD = D + (m/60) + (s/3600) with additional formulae including the consideration of negation per hemisphere)
Check you know the correct coordinate reference system
Find a reference for the data that explicitly says the CRS
If you can't find one then beare in mind the following:
Commonly but not always, global datasets are in WGS84 (possibly because GPS utilises WGS84)
Typically but not always, linear units will be in a UTM projection
If you really do not know the correct CRS
Try not to guess – there’s a lot of CRS out there
Go back to source they might know but didn’t include the relevant information in the data
Based on the coordinate values try to place the data in a region/country and look for the most relevant CRS for that region
If you had to make an educated guess say so in any metadata so no one is fooled and makes an important decision on the information later
Loading data to a map (ArcGIS Pro or ArcMap)
Make sure Map Document data frame for ArcMap is blank (in ArcGIS Pro map properties the default is Web Mercator Auxiliary Sphere)
Assign the correct CRS to Map Document/Map
Add data to Map Document/Map
Check against base map and data where location is known
This blog has not accounted for additional items like transformations but it should act as a checklist of things to look out for when bringing data in from a spreadsheet.
Geologist, Geospatial Expert and TAP Certified GIS Trainer working as an Independant Consultant.
I have special interests in Geology, Exploration, Coordinate Reference Systems, Geodesy and Natural Science.