Where to begin? The first step is to understand your project and its properties. If the end goal is to create a display or map that looks different than the original dataset, than projecting-on-the-fly is the way to go. However if you need to analyze and do calculations, than you need to manually make sure that all data is in the same coordinate system to ensure proper and trustworthy results.
To accomplish this you use the project tool in ArcToolbox to change it to your project areas projection. Here are a few tips that I learned in class when starting a new project:
- It is always a good idea to preview the data with ArcCatalog before starting on your analysis.
- Check whether layers have coordinate system information, and fix the ones lacking that data.
- Find out what the official/common projections are for the area of study. Many regions have official or recommended coordinate systems for analysts to use.
- Before setting out with your GIS analysis, convert all your layers into the common projection for the area of interest. This will make calculations run more smoothly.
- Keep in mind that ArcGIS will use a layer’s default projection when performing calculations. For example, if the layer uses feet as the linear unit, any area calculations for that layer will be done in square feet by default.
Landsat data An Afterthought
Landsat measures light reflected by the Earth from the sun and can show us great detail about earth’s surface. Different surfaces reflect light in various ways allowing Landsat data to show much more than is visible to the eye. Landsat data is extremely useful to compare land use change over time. Using Landsat data for geographic analysis can powerfully visualize how our world is changing and provide evidence of pertinent issues such loss of albedo in glaciers and sea level rise.