ENTERPRISE – With help from a friend, and the ability to borrow some very good equipment from his old employer in Alaska, a professional surveyor who recently retired to Enterprise has settled a long-simmering dispute concerning our highest peaks in the Wallowa Mountains.
Henceforth, let it be known that Sacajawea, and not the Matterhorn, is the Wallowas’ highest peak. Surveyor Eric Stahlke does allow, however, that Sacajawea’s claim doesn’t appear all that secure going forward through geologic time.
Before Stahlke settled the argument over which of the two peaks is highest, a few other facts about Sacajawea and the Matterhorn were beyond dispute: In addition to being the two highest mountain peaks in the Wallowa Mountains, they are the sixth and seventh highest mountain peaks in Oregon, as well as the two highest non-volcanic mountain peaks in the state.
According to Stahlke, the Wallowa Mountains are unique in the sense that they are one of the few mountain ranges in the United States that have never been accurately surveyed. The first elevation measurements were based on barometer readings which pegged Sacajawea and the Matterhorn with nearly equal heights at slightly over 10,000 feet. For much of the latter 20th century many maps listed the Matterhorn as the highest peak at 9,845 feet. This elevation is cited by Fred Barstad in his book “Hiking Oregon’s Eagle Cap Wilderness.”
However, in 1990, a newly issued USGS provisional quad map turned the tables and listed Sacajawea Peak as the highest, at 9,838 feet, with the Matterhorn shown 12 feet lower at 9,826 feet.
The 1990 USGS elevation listing, though accepted as Gospel by many, was disputed by others. The reason for doubt is that USGS spot elevations depicted on quad maps have been traditionally measured by photogrammetric methods utilizing high altitude imagery. This method results in estimated elevations which can be fairly close to the truth, depending on circumstances. However, uncontrolled photography, such as exists in the Wallowa Mountains, must be bridged by multiple photographs across long distances, thus accuracy is reduced and can be as much as 10 or 20 feet off.
This state of affairs impressed Stahlke, who, with his wife Laurel, moved to Enterprise from their home in Alaska in 2012. While the move was intended to coincide with his retirement from the profession, Stahlke has continued to work for his longtime employer, Tanana Chiefs Conference, a non-profit Tribal Corporation in Fairbanks, helping TCC cope with heavier-than-expected workloads.
As survey manager, Stahlke supervises three field crews working in the Alaska bush in performance of boundary surveys mandated by the Alaska Native Claims Settlement Act (ANCSA). He stays in touch with his bush crews by satellite phone while he works on computations and platting from a home office in Enterprise.
The Alaska surveying season is very short due to the extreme cold and darkness of sub-arctic winters. Much of the expensive and sophisticated GPS survey equipment used to perform this work remains idle during the long off-season. When the crews returned to Fairbanks in mid-September of this year, it occurred to Stahlke to make use of some of this idle survey equipment to settle the Matterhorn-Sacajawea elevation dispute.
A crate packed with high-precision Leica dual frequency GPS receivers was soon on its way to Enterprise. Stahlke nevertheless was able to summit the Matterhorn with the survey equipment on Sept. 19, where he collected data from U.S. and Russian navigation satellites for a period of 2.5 hours. Networking with NGS CORS stations (continuously operating precision GPS receivers used to monitor movement of Earth’s tectonic plates), and checking the result with simultaneous measurement from a second Leica receiver operating in his driveway in Enterprise, a new elevation of the Matterhorn was computed with a mathematical precision of less than two centimeters. The result was 9,834.8 feet, almost nine feet higher than estimated by USGS.
The measurement of Sacajawea Peak would have to wait, though, because the following day nearly two feet of heavy snow fell on the upper elevations of the Wallowas. Deep snow makes packing the survey equipment to the summit a difficult proposition in the limited daylight of approaching winter. It looked like the measurement would have to wait till the fall of 2014.
A month of relatively warm weather followed, however, averting the feared year-long delay. Much of the snowpack that was exposed to the sun had melted, so the pair of climbers decided to give it another try. Setting up a base camp in Thorp Basin, Stahlke and Bottman were able to climb to the summit of Sacajawea on Oct. 26 and collect the required two hours of data needed for a precise elevation measurement.
The result after processing the data: Sacajawea is indeed the highest mountain in the Wallowas, measuring 9,843.7 feet, six feet higher than previously thought, but only nine feet higher than the Matterhorn. “Probably a temporary distinction,” says Stahlke. “The summit of Sacajawea is pretty fragile, composed of loose talus and fractured bedrock, and likely to erode much faster than the Matterhorn, whose summit is as solid as the Rock of Gibraltar.”
There are 29 other peaks over 9,000 feet in the Wallowas. None of these have been accurately surveyed for elevation. “I’m looking for new hobbies,” says Stahlke, “and for a retired surveyor who enjoys hiking, and who has fallen in love with the Wallowa Mountains, this is very tempting.”