Coordinate Systems and Spatial Data Models
It is common for GI Scientists who are taking on large projects to have conflicting aligned referenced spatial data. If this happens, the shape, distance, and other important features may get distorted. It is better to fix your alignment issues prior to doing anything else with compiled data for your GIS analysis.
Step 1 : Open ArcCatalog and select each data file for preview. This will allow you to distinguish the file that is not within the same spatial reference as the others.
Step 2 : Right click the data file >> click the XY Tab to confirm its coordinate system, projection, and datum.
Step 3 : Use the projection-on-the-fly (POTF) technique to conform all data files to the same projection coordinate system. You can do this by right clicking the data frame >> properties >> XY tab.
POTF is by far the most practical and accessible method for aligning projection systems. ArcToolbox Project and transformation commands arrive you at the same destination, however, for general use POTF seems to be the favorite among most since it is very straightforward and not very involved to execute.
On the Landsat Program
There are many benefits to using Landsat data for GIS and Remote Sensing Analyses. These tools are exceptionally useful for those in the applied ecological sciences such as forestry, agriculture, hydrology for measuring and visually portraying environmental impact. It is by far one of the most powerful tools I have learned in GIS because the changes occurring to our planet become visible -and it is striking to witness.
I think Landsat programs will be even more prevalent in the near future, as many islands in Polynesia and the Caribbean, where populations live, will be noticeably receding.