6.3. Setting the coordinate system and adding data to ArcMap
Upon opening ArcMap, first close the pop-up to open a blank map. It is good practice to set the coordinate system to match the data which will be added, but this step is not required as ArcMap will take on the same coordinate system as the first layer that is added. All subsequent data will be projected “on-the-fly” to the coordinate system specified in the first layer. This will become more apparent later.