# WGS84 geographic vs projected representation in GIS

I'm new at this (studying for a masters of GIS) and trying to understand the WGS84 geographic coordinate system as presented in ArcPro

WGS84 is a datum and reference ellipsoid EPSG 4326 is WGS84 using latitute and longitude as a coordinate system The data is have is being represented in ArcPro in WGS84 with lat/lon coordinates, so really EPSG 4326.

However, WGS84 is an ellipsoid, while the representation I see in ArcPro is flat. So the coordinates are being projected in some way. My lecturer assures me that there is no projection. When I use the "measure distance" tool the line between two points is curved since it's a geographic system. I get that, that part is fine. But the map is still flat, so I keep insisting there has to be some sort of projection. If there was no projection I'd be looking at an ellipsoid. What am I missing?

• There have been similar questions here, e.g. gis.stackexchange.com/questions/387517/… - also search for plate carree projection on this site and see: desktop.arcgis.com/en/arcmap/latest/map/projections/… Mar 18 at 9:15
• From Gabor Farkas: Practical GIS: "Technically, EPSG:4326 is the QGS84 ellipsoid (or datum) alone as a geodetic CRS. However, as every ellipsoid is mapped with a linear projection when used alone, the fact that EPSG:4326 uses a Plate Carrée projection still stands.", see books.google.ch/books?id=Qng5DwAAQBAJ&pg=PA90 Mar 18 at 9:22
• There is no projection, not in the stricter sense of the term; there is no mathematical procedure involved to transform geographic coordinates into a planar reference here; they are literally only put into a coordinate grid where the numbers dictate them to be (which is congruent to the Plate Carrée 'projection'). This is purely presentational, while internally ArcPro is aware you are working on geographic coordinates. Mar 18 at 9:28
• As per comment on answer below I understand that what I'm seeing is a mapping from WGS84 to a rectagular grid, which is equivalent to Plate Caree, but not actually a projection. Mar 18 at 20:59