The BILBY Geotrail
Basic Information for Locating Benchmarks Yourself
BOUNDARY MON INITIAL DE MD
THE GEOTRAIL
The Maryland Society of Surveyors (MSS) welcomes everyone to participate in this statewide trail which showcases the different “Benchmarks” used by surveyors and which geocachers enjoy finding. The BILBY trail will include a total of 20 cache locations with geocoins awarded at different levels of caches found.
To most non-surveyors any brass disk they find is a benchmark, however not all benchmarks are created equal. There are approximately a dozen different types of benchmarks, and this trail will introduce you to 5 of the most common. Azimuth Marks, Triangulation/Horizontal Marks, Reference Marks, Special Marks and Bench Marks also known as Vertical Marks.
One MSS geocoin will be awarded when 3 caches are found from EACH of the five different types of marks (15 total finds). We have a limited amount of National Oceanic and Atmospheric Administration geocoins that will be awarded to anyone finding all 20 BILBY caches. Be sure to record the code word from each cache to qualify for geocoins.
To claim your geocoin(s) use this link to access the decoder. If multiple people share one geocaching username, only single coins will be awarded per user.
First of all, we will refer to all these marks as “Control Stations” since the word benchmark really pertains to just one type of control station. Next, we will use “Bench Mark,” with two words, since that is the way the National Geodetic Survey (NGS) defines it and the NGS is the federal agency that maintains this network of control stations.
While Geocaching.com no longer allows you to find and record these in your geocaching statistics, you can still post your finds on Waymarking.com and the NGS would welcome all finds or DNF’s to be recorded in the Survey Mark Recovery section of their web site. The NGS also has an interactive map located on their Map Page to help you find them.
Here are the five types of Control Stations and locations in the BILBY Geotrail:
HISTORY AND WHY THE NAME BILBY
The first set of Control Stations were placed around 1816 when Thomas Jefferson established the “Survey of the Coast” with the mission to map the eastern coastline of the United States. Since boats were the main method of transportation and how to get goods to the citizens of this new nation, accurate maps were needed to identify rivers, bays, harbors, shoals, light houses and any other navigation aids to keep commerce moving safely.
The only way to make measurements, until GPS was invented over 200 years later, was by direct line of sight. Measuring from hilltop to hilltop was a way to cover large areas quickly, however since the hills and mountains were mostly forested, they needed a way to get above the trees. Lumber was obtained either from the forest itself or purchased at a nearby lumber yard to construct towers. Some towers were constructed over 100 feet tall.
Jasper Bilby (1864-1949), who this trail is named, was a surveyor and geodesist that worked for the U.S. Coast and Geodetic Survey. Jasper (Click Here for more information) saw the enormous amount of manpower and cost to build these towers which were typically left behind, due to the time and manpower to dismantle then transport them to a new location. He noticed the steel windmills used by farmers to pump water and thought he could do something with that. He developed a tower within a tower system, so the survey instrument was on one tower and the operator stood on another. That way as the operator moved around to take readings it did not affect the stability of the instrument. The inner and outer towers were color coordinated and bolting the sections together made assembling and disassembling easier and faster.
THIS STATION
A REFERENCE MARK control station is one that is used to assist the surveyor to find another mark, usually a Triangulation/Horizontal mark. The Reference mark will always have an arrow in the center of the disk pointing to the "true" mark with the accurate coordinates. There are always multiple Reference marks set for the true mark. All stations in the NGS database have a unique two-letter, four-number label known as a permanent identifier or PID as names of stations are frequently repeated. Reference marks typically do not have an accurate horizontal or vertical value, so their PID does not have a separate datasheet. This mark is one that was able to get horizontal coordinates by measurements made in 1992. Clicking the link below, after the station name, will take you to the datasheet of the station which has a lot of information about the mark.
BOUNDARY MON INITIAL DE MD (PID HU1443) is one of four Reference markers set in 1932 for the main station named FENWICK ISLAND (PID HU0377), however the stone in which this disk is placed has much more history. The stone itself was set in 1751 to mark the easternmost end of the boundary between Maryland and Pennsylvania (now Delaware) to settle an 80-year dispute between the Calverts of Maryland and Penns of Pennsylvania.
THE CACHE
The posted coordinates will take you to the Boundary Mon Initial DE MD brass disk as shown in the picture above and the focus for this BILBY cache.
Please take a picture of the disk with a signature item and post with your log. While this is not required, it shows your appreciation to those many volunteers who helped create the BILBY trail.
There were four surveyors involved in placing this Boundary Monument in 1751 as mentioned on a nearby sign. Place their last names, in alphabetical order, in certitude for the final. Use this example for how to list the names "Jefferson-Lincoln-Reagan-Washington" with a dash between the names.
You can validate your puzzle solution with
certitude.