Projected Coordinate System vs. Geographic Coordinate System

Discussion created by sgerhardt on Feb 28, 2011
Latest reply on Nov 9, 2017 by chayze
Hey everyone,

I'm new to the world of GIS so I was somewhat confused when I saw the option of choosing from either a geographic coordinate system or projected coordinate system in arcMap.

My first layer is a Landsat 5 image that reads as being in WGS_84_UTM_zone_15_N, which is a projected coordinate system in arcMap. I am trying to display a shapefile over this Landsat image, but the shapefile is in WGS84 which is a geographic coordinate system in arcMap. The input for the shapefile is in lat/long without regard to projection.

When I load the shapefile layer, arcMap gives me a warning that the coordinate systems differ, but the shape file still appears to be in the correct place.

So my main questions are:

1. What is the difference a geographic coordinate system and a projected coordinate system?

2. The shapefile is in WGS_84 and the Landsat 5 image is in WGS_84_UTM_15. Will this incorrectly affect the placement of the shapefile, or can I simply ignore this warning?

Any help would be greatly appreciated!