Hi
I am new to GIS and am a bit confused about how geographic coordinate systems and projected coordinate systems work together. I understand conceptually what they both are, i.e. one is based on a 3d model of the world and the other is for 2d surfaces. My question though is about what happens or what should you do when importing coordinates taken in a GCS.
For example, I wish to measure the area of a region of Africa I have been working in and the distance between seem points. I have been out with my garmin GPS which is set to WGS_84 and taken a bunch of coordinates, some of them form an outline of an area which i want to calculate and some i just want to know the distance between. I import these coordinates into ArcGIS and the coordinate system says it is in WGS_84. But since these are now being displayed on my 2D computer screen surely it is now in a projected coordinate system? Why is it using a GCS on my 2D computer screen? and why when I go to data frame properties can I change the the projection to other GCS's surely now that my data is being represented on the screen I have to use a projected coordinate system?
So what I would really like to know is should I be setting the map properties to a projected coordinate system, or can I just leave it set to the WGS_84 coordinate system and start using ArcGIS to measure area and distance?
Does anyone understand my confusion? I get the conceptual differences but i dont understand why i would change it from wgs_84 to a projected systems if ArcGIS understands it in that format, these are small areas too as in 10km squared so is distortion going to be an issue?
Thanks in advance
I am new to GIS and am a bit confused about how geographic coordinate systems and projected coordinate systems work together. I understand conceptually what they both are, i.e. one is based on a 3d model of the world and the other is for 2d surfaces. My question though is about what happens or what should you do when importing coordinates taken in a GCS.
For example, I wish to measure the area of a region of Africa I have been working in and the distance between seem points. I have been out with my garmin GPS which is set to WGS_84 and taken a bunch of coordinates, some of them form an outline of an area which i want to calculate and some i just want to know the distance between. I import these coordinates into ArcGIS and the coordinate system says it is in WGS_84. But since these are now being displayed on my 2D computer screen surely it is now in a projected coordinate system? Why is it using a GCS on my 2D computer screen? and why when I go to data frame properties can I change the the projection to other GCS's surely now that my data is being represented on the screen I have to use a projected coordinate system?
So what I would really like to know is should I be setting the map properties to a projected coordinate system, or can I just leave it set to the WGS_84 coordinate system and start using ArcGIS to measure area and distance?
Does anyone understand my confusion? I get the conceptual differences but i dont understand why i would change it from wgs_84 to a projected systems if ArcGIS understands it in that format, these are small areas too as in 10km squared so is distortion going to be an issue?
Thanks in advance