What is Metadata?
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.
Where is Metadata found?
OK, so now you know something about metadata, where do you find it? Let’s look at an example.
- Navigate to U.S. Department of Agriculture Geospatial Data Gateway where you can obtain soils data for a specific state and county.
- At the landing page, click on the large green DATA button at the top right of the page.
- This brings you to a screen where you should see five tabs in the left sidebar.
- Click on 1-Where Tab. In the center panel, enter your state and county (move county to right pane using>>), then click 'Submit Selected Counties'.
- This takes you to 2-What: Scroll down the center pane until you come to 'Soils', Check the box next to US General Soils Map (STATSGO2), then click 'Continue'.
- You are now on 3-How: Click on 'Continue'.
- You are now on 4-Who: Complete the form and click on 'Continue'.
- You are now on 5-Review: Review the information and click on ' PLACE ORDER' in left sidebar.
- Your data will now be emailed to the address you included on the order form.
- Open the email, look for Ordered Items and click on the link having a .zip file.
- Navigate to where this file has been downloaded to and extract it.
- I believe you will have a file named 'Soils'. There may be a second file to extract. If so, extract this to the 'Soils' file.
- Open the soils file again, and click on a file that has the state abbreviation followed by the date in parentheses (Example: wss_gsmsoil_NC_[2006-07-06])
- Open the soil_metadata_us.txt file.
- What you will see next is the metadata for the specific county soils data you selected. You will now see the metadata including: Identification Information, Data Quality Information, Spatial Data Organization Information, Spatial Reference Information, Entity and Attribute Information, Distribution Information, and Metadata Reference Information. Explore each of these links and familiarize yourself with the information in the various categories. You will get an opportunity to practice using metadata in the class activity that follows.