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For NGS Databases - Version 1.7

NGS United States Benchmark Viewer FAQ

Questions:

1. What is A Benchmark?
2. About the Viewer
3. What do the Letters and Colors of the Icons mean?
4. Why can I only view 100 markers at a time?
5. What happens when I click on a marker?

What is a Benchmark:

A benchmark is a point whose position is known to a high degree of accuracy and is normally marked in some way. The marker is often a metal disk made for this purpose, but it can also be a church spire, a radio tower, a mark chiseled into stone, or a metal rod driven into the ground. One of the Best FAQ's on Benchmarks is found on the Geocaching.com Web Site.

About the Viewer:

This benchmark viewer is populated with NGS Benchmarks gathered from the Archived ShapeFiles Retrieval Page on the NGS Web Site. Most ShapeFiles collected have a "Data Date" assigned to them. What does this mean? Well, it means that the data being plotted here may actually be out of date. According to the NGS:

"Archived ShapeFiles were created from NGS Yearly Archives datasheets. Whenever a new Yearly Archives region is retrieved a new Archived Shapefile is created for each state in the region. Archived ShapeFiles are static and may be out of date, as opposed to those retrieved from the shapefile retrieval page."

View the Software Version page to see what date the benchmarks in the database were updated..

What Do The Icons Mean?

Good question. I have coded the markers with a color and a symbol. The Letter A or S refers to the Positional Source of the GPS Coordinates. A mark of A signifies the horizontal coordinates are Adjusted, and therefore, more Accurate (See, the both start with A - Adjusted = Accurate, its handy to remember them that way). Adjusted coordinates are more precise than your handheld GPSr can read. They will take you right to the benchmark.

A mark with an S on it signifies that the horizontal coordinates are Scaled. Scaled coordinates can be off more than a quarter mile. They are determined by someone reading the description on the benchmark page and then plotting where they think it will be on a map.

A mark with a C on it means it is a Cluster of Marks. The viewer is only efficient when displaying 100-200 marks. Closer to 100 the better. So when over 100 marks are visible in an area, I have written software to average the marks together. The averaged benchmarks are displayed in a Yellow marker with a C on it. By zooming in you can view the marks that are clustered into the one C cluster.

The marks themselves can be white, green red, or yellow. White Markers are benchmarks that have only been Monumented. This means they may have only been found one time (at the time they were first placed), so their current status is an unknown. Green Markers are benchmarks who's most recent recovery was in "GOOD" condition. Marks that are Red in color are everything else. The marks may be Not Found, or a reference to See Description in the Data Sheet. I would not make the leap that these marks are destroyed. That would be erroneous. It simply means the last recovery may not have been successful.

This mark is Adjusted, and found in Good Condition

This mark is Scaled, and found in Good Condition

This mark is Ajusted, and found in one of the following conditions: Monumented, Not Found, or Other

This mark is Scaled, and found in one of the following conditions: Monumented, Not Found, or Other

This mark is Adjusted, and has been Monumented.

This mark is Scaled, and has been Monumented.

This icon represents a cluster of marks. It is an average of at least 2 marks in the nearby vicinity.

Why Can I only view 100 Markers?

If you were allowed to view more, your internet browser would slow down to a snail's pace. I set the limit to 100 because that is a number recommended by the Google Maps API for stable marker viewing. If you are zoomed out far enough that over 100 marks are viewable, the marks will be clustered together into one mark that averages nearby marks.

What Happens When I Click A Marker?

When you click your mouse pointer on a marker, additional information about that marker will be displayed to the user. The PID, Benchmark Name, If the Location is Scaled or Adjusted, Last Activity (Was it Found, When, and by Whom), a link to the NGS Data Sheet will be provided in a popup window, as well as a link to the Geocaching Web Site benchmark page (if one exists).