Back to Stories

HOW FAR IS IT?

Story and Photos By R. E."Bob" Lochbaum

How far is it? That's a question I pondered many times while hiking the various trails in the Smoky Mountains. It is also a question I was asked many times by hikers I met while using a calibrated wheel to measure these trails. That question is not easy to answer since it requires a careful definition of where "it" is; i.e., from where to where. Another question I have been asked is why did I measure them and how was it done? That question is easier to answer. The desire to measure the trails in the Smoky Mountains evolved naturally from my hiking activities. Walking has long been a favorite leisure time activity for me. Upon early retirement in 1991 the existence of free time allowed me to pursue some serious hiking. Joining the Smoky Mountains Hiking Club was a step in that direction. As with many members of the club, hiking every trail in the park soon became an objective. I teamed up with member John Sloan, who had a similar hiking appetite and we completed all of the trails on August 8, 1993.

Completion of this goal did not end our desire for continued hiking and we mutually agreed that having an objective made planning hikes easier. To this end we set a new goal to do every trail again in less than a year. We had noted during the first time through that several of the published trail distances, on maps and signs, didn't seem right; therefore, I decided to collect information on these distances during this second time through.

I set up a data base for accumulating distance data. Using the 1994 edition of the "Great Smoky Mountains Trail Map" as the reference, I defined trail segments as the distance between trail intersections or between trailhead and an intersection. Each trail segment and intersection was assigned a unique designation. I planned to accurately measure the time to do each segment. With apologies for the lack of humility, I have a steady and quite predictable pace which permits reasonable distance estimates by measuring elapsed time. John provided me with an alternate backup measurement by using a pedometer. This instrument had shown good results in places where the distance was already known. In order to compare these measured distances with those on the trail signs, a data base was created to record the contents of each sign. I noted elapsed times, pedometer readings, and the information on every trail sign with a tape recorder. All of the trail segments were measured in this manner in nine months; thus, we met our "less than a year" original objective. A review of the resulting data bases did in fact reveal there were a number of trail distances which appeared to be at odds with trail signs and/or map data. My fetish for detail which may result from my German heritage required a more precise evaluation. Coupled with the fact we wanted a new objective for hike planning, we decided to do each trail again. This time I planned to measure each trail segment with a calibrated wheel.

The data base for collecting wheel data already existed. A measuring wheel was fashioned using a rejected bicycle front fork obtained from a local bicycle shop and the front wheel from my bicycle. A handle was made using PVC piping and fittings. A counter was mounted for counting wheel revolutions. About this time I become acquainted with Steve Kemp of the National History Association who is the motivator behind the little brown trails book Hiking Trails of The Smokies, published by that organization. He acknowledged several of the trail profiles in the book were lacking and new measurements would be appreciated. To accommodate this an altimeter was mounted on the wheel assembly. This setup, which would also go through some evolution, was the device for starting a more detailed trail measurement. As an Adopt-a-Trail Volunteer in the Park (VIP program), I learned that backcountry camp pictures were lacking so I added photographing each to the agenda.

The first step in collecting the wheel measurements was to calibrate the wheel. I was aware of survey markings on the Little River Road extending from Sugarland Visitors center to Townsend "Wye". These included an accurately placed mark every hundred feet. (Historical Notation: These were lost when the road was washed out by the flood and subsequently repaved in 1994). In my opinion the longer the calibration measurement the better the accuracy; therefore, I ran the wheel over several miles of the marks and recorded the distance and number of turns. This also provided a shake down for the wheel assembly. Dividing the distance by the number of turns gave the initial distance per turn calibration. I used this value for the initial segment measurements.

After twenty hikes using the initial setup, the need for adjustment became apparent. I used the wheel from my bicycle with an inflation pressure of 60 psi. This was fine for a trail with good tread (Hannah Mountain), but became difficult on rough and rocky trails (Clingman's Dome Bypass). The high pressure caused the tire to have a resilience somewhere between a super ball and a golf ball. The wheel was hard to control because of its tendency to bounce. To solve this problem I lowered the pressure to the point where it was firm enough to hold its shape but not so firm as to be bouncy. As a result of this change I needed a new calibration procedure. At the high pressure the tire is stretched against its structural cords. A change in pressure resulted in no noticeable change in circumference since above the pressure it was fully expanded. At low pressure a change in pressure did affect circumference. To deal with this, a fine piece of twine was tied around the tire cross section to use as an index. It was rolled over a smooth flat surface for three turns and carefully measured to within a 1/16th inch; thus, for a single turn it was calibrated to 1/48th inch. The scientific basis for using three turns was that's all that would fit in my garage! After the first hike using the low pressure configuration, I decided it would be better to have the same circumference each time out rather than have it vary. A parametric study was run to plot wheel circumference, or turns per mile, versus tire pressure. This led to the selection of a value that resulted in an even number of turns per mile. Since the pressure could not be accurately determined, the wheel was calibrated using the three turn measurement to 1/16th inch method before each hike. The next wheel change occurred when Steve Kemp gave me a second wheel. This allowed me to put my bicycle back together again! This second wheel was a nominal 27 inch wheel compared to the original 26 inch one. A new turns per mile versus tire pressure parametric plot was developed for it and the three turn calibration before each hike was continued. The final wheel variation resulted in an even number of turns per 500 feet instead of the even number for a mile. Since an altimeter reading was being taken every 500 feet, this simplified data collection. The majority (78%) of the trail mileage was measured using this final setup.

During the early phase of this project the need for an indication of precision was recognized. To this end I decided to measure each trail segment twice and to be acceptable, the two measurements would have to be within 1/2 % of each other, which is 26 feet per mile. In cases where this standard was not met, the segment would be remeasured until it was. Careful attention was given to defining the end points of individual segments so that the same length was being measured each time. Although the spacing of the wheels spokes permitted recording measurements in the realm of an inch, to be practical distances were recorded to one half turn of the wheel or about 3 1/2 feet.

To obtain consistent altimeter readings it was necessary to eliminate errors caused by parallax. This phenomenon is the result of getting slightly different readings by looking at the instrument from slightly different angles. This can be mitigated by assuring that it is consistently viewed from the same angle. To accomplish this. a system analogous to the open sights on a rifle was added to the rig. Altimeter readings were nominally recorded every 500 feet along the trail. With unique topography such as a prominent peak or dip, intermediate recordings were made. On fairly level or very gentle grades where changes in elevation were slight, readings could be extended to longer intervals.

A typical data collecting hike included the aforementioned distance measurements as well as the altimeter readings for profile development. The data was compiled using a small tape recorder. In addition to trail segment distances, the distances to significant landmarks were recorded. These included stream crossings, notable artifact features, prominent geographical features, etc. Each numbered backcountry camp and shelter was photographed. Usually each site was photographed from three different angles. Each trail sign was checked and where necessary previously recorded information was revised and updated. The data thus amassed was accumulated into several different data bases. After 179 hikes which resulted in measurements totaling 3271.4 miles, sufficient data had been collected. Data evaluation and manipulation was an on going activity.

In analyzing the distance measurement, the 1/48th inch calibration tolerance was checked. This resulted in a maximum error of 15 inches per mile or 0.025%. Since the wheel circumference was sensitive to tire pressure, two sources of pressure change were examined; namely, elevation and temperature changes. Since there were significant elevation changes on many trails and since ambient air pressure varied with altitude these effectively changed the tire pressure. The results of this evaluation indicated that there was a 5 inch per mile change in distance measured for a 1000 foot change in elevation. Increase in tire temperature caused an increase in tire pressure. If the ambient air temperature increased during a hike and it was assumed the tire experienced the same change, there would also be a change in circumference. From an analysis of this effect it was determined that a 10 degree change in temperature results in a 4 inch per mile change in distance measurement. Another source of error was running over obstacles in the trail. Three categories were examined; namely, a round object such as a limb laying on the trail, a round object such as a water bar half buried across the trail, and finally a step - such as a large flat rock. From the equations for each case a series of parametric curves were plotted. Three variations of the round objects were examined. First was the case where the wheel was rolled over the obstacle. In the second case, the wheel was rolled up to contact the obstacle and then picked up and set on the other side and in contact with the obstacle. Finally, the wheel was rolled up to contact the obstacle and then picked up and set on top of the obstacle. These curves were not linear but typical examples for an eight inch obstacle gave various results. For a flat rock step, about a three inch increment was added to the distance measured. Rolling over an eight inch round object, resulted in a 5 1/2 inch increase while lifting the wheel over it resulted in a one inch decrease in measurement. For the half buried round object, the effects were a two inch increase and a 3 1/2 inch decrease respectively. In summary, the elevation and temperature changes resulted in distance measured being less than the actual, while the obstacles generally result in increases; thus, their effects would tend to work against each other. Furthermore, their effects were less than a 1/10 % so it was concluded there was not a significant degradation of accuracy.

Elevation accuracy was evaluated indirectly since I had no means to calibrate the altimeter. The difference in elevation measured between ends of a trail was compared to the difference for that segment derived from the topographic map. The ratio of these two values provided an insight to the quality of the elevation measurement.. Also since each segment was wheeled at least twice the comparison of the two profiles provided a further check. Repeatability of these profiles when plotted on top of each other proved to be quite good. Also, the ratio of the elevation differences measured versus the differences derived from the topographic maps for each segment were generally within 5%. Each profile was adjusted such that its end points were in agreement with the topographic map. This was done in a manner that maintained the integrity of the profile. Since there were ups and downs along many trail segments, the difference between their end points did not generally give an accurate indication of the actual gross elevation gained when traversing the segment. To obtain the gross elevation gain for a trail segment a computer program was developed which sums all of the upward increments encountered in proceeding along the segment. The program was run for each trail segment to provide the gross elevation gain in both directions.

To wrap this project up a computer program was developed to use these results for planning hikes. By inputting the trail segments to be hiked it accesses the different data bases to print out an itinerary which includes the trail segments in sequence with the length of each, the starting and ending elevation of each and the gross elevation gain for each. The length and gross elevation gain are summed. A list of landmarks to be encountered along the planned route is also provided. A printout of each trail sign on the route presents the information as shown on the sign with the correct information in parenthesis as necessary. A plot of the profile of each of the planned segments is usually printed on back of the itinerary. (See attachments 1 through 6.)

As a conclusion the distances reported by the trail map and the trail signs are in general quite good; however, there are differences and the following are some interesting examples. By dwelling on these differences the impression may be created that there are major discrepancies. There are many discrepancies but few are major and usually measure about a tenth of a mile. For instance, on the map there are less than two dozen cases where the difference is more than a tenth of a mile and greater than a 10% error. Also there have been revisions to signs and map. About one third of the mileages listed on the 1999 edition of the map have been revised since the 1994 reference map. Approximately one quarter of the segments shown on the map do not have their distances shown. One principle discrepancy on the map is that the legend states distances are between intersections while several are clearly the cumulative length of several segments. There are several cases where the map and signs give different lengths for a segment. The sign at the intersection of Forney Creek and Jonas Creek trails would be a candidate for the least informative or most disinformative. In addition to every item on it being incorrect it also has one of the largest absolute errors in reporting the distance up to Forney Ridge as being 6.1 miles when it is 7.4 miles. The mileage for a segment being different on different signs occurs. The Hatcher Mountain Trail is an example. The sign at its junction with Cooper Road says its 2.8 miles to Little Bottoms Trail while the sign at Little Bottoms end says it 2.6 miles up to Cooper Road. The signs along Deep Creek, Forney Creek, and in the area of the tunnel to "no where" seem to have the most discrepancies. To reiterate, overall the signs and map are reasonable.

A frequently asked question is what is the total length of the park trails? To give a precise response it is necessary to be specific as to exactly what is included. For example since selecting the 1994 revision of the trail map as the reference several changes have been made. There have been deletions (Hughes Ridge lower end, Blanket Mountain, etc.), additions (first segment of Little River), and rerouting of some segments (AT along Mollies Ridge). There are also some ambiguities as to just what route segments take; for example, the Wet Bottoms Trail has a variety of courses. Mindful of this, the approximate answer is about 810 miles. Several other trivial facts can be extracted by manipulating these data bases; for example, there are 392 trail signs in that collection which includes some enroute navigationally informative signs. There are 348 trail segments in the basic reference and thirty additional if the Wet Bottoms variations and Cherokee Orchard area horse trails are included. These were measured separately. The longest segment is Lakeshore from Hazel Creek to Forney Creek at 21.030 miles. The shortest segment is the first part of the Old Sugarlands Trail from the trailhead to the horse trail intersection at 141 feet. Three of the steepest sections are Hyatt Ridge, Low Gap, and Mount Sterling all at over 800 feet per mile. There are 310 photographs of 106 campsites in the album. Five mini hand held tape recorders were used - three being totally used up. Two and one half million revolutions of the wheel were registered by the clicks of the counter that led to over 26,000 data elements being recorded. The 0.5% precision objective was met with the overall average for the over 800 miles of trails being 0.17% or less than 9 feet per mile. As a follow up action since the completion of this project, the photographs have been scanned into digital format.

During a meeting with park personnel a comprehensive review of the data collected was presented. All data including an album of the photographs plus a second set of serial numbered and indexed photographs was volunteered. It is my understanding that the distance and profile data will be used in a future revision of the Natural History Association's Hiking Trails of The Smokies.

Also, it was established that my hiking activities with John Sloan would definitely continue toward our goal of completing every trail ten times. As an adjunct to this the park's Resource Management and Science Organization offered me the opportunity to use a sophisticated Global Positioning System (GPS) to map the trails. This is proceeding and as of December 1999 is over half completed. Under good conditions the equipment is capable of accuracies of a meter or less. While the desirable conditions do not always prevail, I believe accuracies of less than ten meters are being attained with three meters or less being most common. To put this in perspective, on a topographic 7 1/2 minute map with a scale of 1:24000, a line with the thickness of a piece of copy paper is seven and a half feet (2.3 meter) wide. The accuracy achieved meets or exceeds the USGS mapping standards for mapping with scales of 1:24000 or 1:12000. The instrument is set to record a position every five seconds. The data provides a three-dimensional position for each point. In addition to horizontal positions for mapping, the opportunity exists to use the elevation data to revisit the profiles generated with the wheel project data. This will be, time permitting, a future data reduction exercise.

How far is it? As I said - it depends where "it" is. While I have a good grasp of the distance for each of the elements to get "there", I don't really expect to ever reach the terminus of my hiding adventures.

-------------------------------------------------------------------------------------

Check out these 6 Sample Documents

1    2    3    4    5    6