Spatial data information:
It is important when using GIS to ensure that the layers are using the same Coordinate system and Datum, so that the different layers of spatial information will align accurately and thus reduce the amount of distortion on the map. Before you start designing a map, you will have to first ensure that all the spatial data obtained have the relevant (metadata) information from its source. We can do this by using ArcCatalog or ArcMap to check each layer of data for its coordinate system (projected or geographic), unit of measurement, the datum used, etc. The type of projection that you choose to use is important as well, as different types of projection will result in different types of distortion. For example, a Mercator projection may distort the area of local area but preserve its shape. An equal-area projection on the other hand may distort shape but retains the area of land. Therefore if different layers of data are using a different set of projection, it will result in minor misalignment or inaccuracy.
Remote Sensing data:
The improvement in remote sensing technology have resulted in the availability of spatial data for geographical analysis. Landsat data is a source of remote sensing data which can be used for many types of geographic analysis, especially for remote areas that have limited access such as the polar regions. One example for the use of Landsat data is to compare and analyse the amount of polar ice melt in the north pole over a period of time (e.g. 20 years). Using the image analysis tool in GIS, we can then see the difference in polar ice cover in time over a specific area.
