Co-Ordinate System in ArcGIS

[SaadIbrahim]

I am taking a course in ArcGIS, I have a question regarding co-ordiante systems. In the course it specifies to select a specific co-ordinate system for the Data Frame, but when it comes to specific data sets (Layers) under that data frame, it specifies me to select different co-ordinate systems for it. Shouldn`t both be same?

E.g, For my data set my co-odrinate system is ( North_America_Albers_Equal_Area_Conic
WKID: 102008 Authority: Esri ) but for my  data set (Layer) it is (WGS 1984) why is that so ?

I don`t understand the concept behind this.#

[JoeBorgione]

Just a guess but I think what they are trying to get you to see is how different coordinate systems/projections effect the view of your data.  

Here are a couple of links your instructor should have included:

Coordinate systems, map projections, and geographic (datum) transformations 

What are projected coordinate systems?—Help | ArcGIS for Desktop 

And what I consider a classic and must read for anyone interested in geo-sciences:

https://books.google.com/books/about/Understanding_Map_Projections.html?id=sr0sAQAAMAAJ 

[SaadIbrahim]

Thank you! this helped a lot.

[MelitaKennedy]

What Joe said! 

The module may also be trying to demonstrate that you can have data layers using one or more coordinate reference systems, and the data frame (map) use the same or a different coordinate reference system. 

This is possible because the data frame will project "on-the-fly" the features of any vector layers or the raster layers from their native coordinate reference systems to the coordinate reference system of the data frame.

Melita

[SaadIbrahim]

Thanks, this makes a lot of sense to me.

[curtvprice]

If you have more questions, I suggest posting to the https://community.esri.com/groups/coordinate-reference-systems?sr=search&searchId=fe9baa70-e55e-4321...‌ space. 

(Hi Melita, and thank you!)