Testing the Waters 2012 - Beach Locations in the United States
The EPA gathers beach locations from state and local officials and provides those data in a central database.
The local or state officials in most cases have provided to the EPA with a "start" latitude/longitude and "end" latitude/longitude for each beach. There is a wide variety in the monitoring protocols for the different beaches, and we are unable to provide any information at present about the location of the monitoring locations. As a consequence, the icons are simply based on the mid-point of the latitudes/longitudes provided.
In some cases, the state officials provided only a single point for the beach (not start and end points). In those situations we simply represented the beach as a single icon with no boundaries denoted.
We implemented fixes to address obvious problems:
- Some of the beaches' locations were missing decimal points, which resulted in impossible locations (e.g. beaches that crossed oceans). Solution: when we added in the correct decimal points, the beaches locations appeared to be correct.
- Some beach locations were missing the negative sign in front of the longitude. As a consequence, American beaches were showing as being located in central Asia. When the negative signs were entered, the beaches showed up in the correct state.
- Repetitive start locations: some beaches were using the same start location as other beaches, even though it was clear that they were distinct beaches. In these situations, we used the end of the previous beach to signal the start of the next beach. The resulting beach locations were consistent with other beaches.
- Incorrect coordinates: Some beaches had coordinates where one end of the beach might be off the coast, or several hundred feet inland. In those situations, we moved the endpoint to the coastline.
We ran a series of checks to try to verify and improve the accuracy of EPA's data:
- We shared the draft map with several state and local beach contacts. In general, they viewed the map as a positive addition to the public knowledge base on beaches. They also identified some beaches that appeared to have incorrect locations. For those, we adjusted the beach locations based on their recommendations. As we receive more feedback from state and local officials, we will continue to improve the beach locations.
- We compared the map generated from EPA's data to several state and local government maps of beaches we found online to see if there was general agreement between our map and these other sources of information. We found that there was good overall agreement between our map based on EPA data and these other sources, and also identified additional beaches to investigate in more detail as we continue to improve the map.
- We did a beach-by-beach review of every sixth beach for Hawaii, the entire West Coast, and from Maine to Delaware, to see whether the beach position was reasonable. We looked to see if the latitude/longitude information placed the beach on the coast and if it caused beaches to overlap with one another. We found that approximately 8% of beaches overlap with another beach, however slightly, and approximately 2% of beaches had locations offshore. We found that the rate of clear errors (ones where the beach was significantly offshore, e.g.) was very low.
We know there are remaining issues with the map:
- Beaches without coordinates: Out of the 6800+ beaches we analyzed, we were unable to find latitude and longitude coordinates for roughly 5%. As the EPA releases updated information for those beaches, we will update that information
- Beach names: With more than 6,500 beaches in the EPA database, there are a variety of names. Some local people might refer to one beach by one name, while others might consider another. In addition, some beaches in the database have names like "Unnamed Beach #4." We hope you will be understanding about the differences in beach names.
- Disagreement between Satellite and Google Maps: Some beaches appear incorrect when viewed with Google Maps' regular view, but appear correct when viewed with the satellite view (e.g. Montgomery). In these situations, we relied on the satellite imagery instead of the Google Maps.
- Bays or Curved Beaches: When officials provide latitude/longitude information about bays, the two points they select might span the area under consideration (for example, Ma'alaea Beach and Hilton Head Island), and the resulting "beach" rectangle covers some part of the bay, or stretches across it. We didn't take corrective action in those situations, but in the future may strive to provide better representations of the beach (instead of the current rectangle).
- Not enough information: In some situations where we suspected the beach's coordinates were incorrect, we were unable to get enough information to correctly identify the correct start or end to a beach. In those situations, we have left the beach representation as it was (with the hope that we will receive additional information from the public or state/local officials).
We are committed to improving the map.
We are anxious to get information that will help us implement improvements to the beach location information. If you notice a problem with a beach, simply click on its icon, then click the "Let us know" link at the bottom of the window. When you submit a report, we are notified about the beach and your feedback. We'll review all submissions we receive, and will work with state coordinators to make needed corrections.
Furthermore, as EPA or state officials provide us with improved information about the beach locations, we plan to evolve the beach location information.
last revised 5/22/2012
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