Metadata is data about data. It is a summary document providing content, quality, type, creation, and spatial information about a dataset. Let’s take an example. You visit a car dealership to purchase a car. On the window of each car is a sticker giving you very specific information about the vehicle including manufacturer, make, model, size of engine, transmission type, miles per gallon, accessories, etc. This is metadata about the characteristics of a specific vehicle. It is the information you use to make an informed decision when comparing and purchasing a vehicle. Without this information, you know nothing about the vehicle and your decision to purchase becomes confusing at best. This is also true for GIS data. If you don’t know what it represents, what it covers, who made it or what quality it is, then only the originator of the data would be able to find and use it. If you do find it and use it, it may be totally inappropriate for your project and give you erroneous results.
Metadata can make clear to users the quality of a dataset or service and what it contains. Based on the metadata, you can then decide whether a dataset or service is useful or not, or whether you need to collect additional data. If the data has a metadata file, the knowledge about the data and services does not disappear if the originator of the data is no longer associated with the data.
It is not necessary for metadata to always give access to the dataset or service; however, it must always indicate where the dataset or service can be obtained.
Official standards organizations define metadata standards. By adhering to common metadata standards, organizations can readily share data. Two organizations set metadata standards. They are the International Organization for Standardization (ISO), and, in the United States, the Federal Geographic Information Committee (FGDC). The FGDC first published the Content Standard for Digital Geospatial Metadata in 1998, and it is the standard used by governmental agencies in the United States.
OK, so now you know something about metadata, where do you find it? Let’s look at an example.