Broken Arrow (Peak 5146* in Arrow Range)

Harlan W. S.
Sat., Dec 03, 2005

This is the same peak as described by Jim Boone here. "Broken Arrow" is the sharp peak in the left distance, in this photo taken from Arrow Peak. I would guess this was originally a Sierra Club hike a la Lee S, Dave H., Howard B. or Ed F.

This peak is located NE of Las Vegas, Nevada. From the intersection of us95 and i15 in Vegas, drive about 21 miles NE on i15. At this point, us93 diverges from i15; take route 93 N for an additional 23.3 miles. Park your car well off the shoulder of route 93, near mile marker 75, to start the hike. The hike came to ~7.4 miles by GPS. This route is trailless, and would be fatally hot from May through October. See bottom of page for GPS files.

We started hiking about 9AM, and returned to the car at ~3:35 PM. Our speed was limited by a strained Achilles' tendon and a mashed toe (be bold, be bold, but not too bold). But this is not the sort of terrain one can travel quickly, anyway.

The one 30' dryfall, described by Jim Boone, is on the dotted route in the first map. We went up this way; but on the way down, we cut south up the ridge and took an easy 2nd class bypass (Ali figured this out). The dryfall is fun to climb (look on south side of dryfall), but as there is no good place to anchor a rope, it is probably best to avoid the dryfall on the way down.

Technically, this route may be 4th class, because there are a few places where a fall could be fatal. However, the rock is so frictional, the route feels like moderate 3rd class at best (especially if you avoid the dryfall downclimb).

There are lots of fossils on this route, many somewhat obliterated by metasomatism. However, Pierre found some nice fossils of Maclurites (an Ordovician snail).




Looking E as we start up the wash ~10AM.





The 30' dryfall, view down.



Midway up the "3rd-class chute", view SW. Believe it or not, Ali is lurking in the shadows.






The top of the 3rd-class chute, view SW, as we start the traverse to the saddle.

Traverse to the saddle, view NW. The highpoint in the distance is Hayford Peak.





View W; this is the hidden gully near Jim Boone's waypoint 12b.


I am at the top of the "4th class" chute on the summit block, looking SSW and down at Pierre and Ali.


Pierre comes up the last "4th Class" chute. Note he is using pressure perpendicular to large rock faces for grip; this is a good idea, as the rock is very frictional, but small ledges or protuberances often break under weight of a foot.





View S from near top, with Pierre for scale. Hidden Peak is at top of sunlit bowl. The main Arrow Range is to the right.


Ali on South summit. View SSW, with Arrow to left of Ali.






Ram Peak to NW.



View NE. Moapa Peak is the sharp summit just right of Ali's head, on skyline; Mormon Peak is behind Pierre.





Coming back down the "4th Class chute" on summit block. View N.


View N; Ali is at the base of 4th-class gully.


Nearly down 3rd-class gully; note tan fault gouge.





View NE.


View NNE. This traverse avoids the dryfalls.


View E. The ascent route goes up the "V" at far left, to the light gray rock just above the dark gray.





Peak 5146 is at left. View W.

Ali's pics -- near bottom of dryfall, view slightly up. Go to the right, then cut back left halfway up the face.


Bottom of dryfall, view up.





What is the elevation of peak 5146?

Perhaps this may seem like a stupid question, but the answer is not that obvious. The elevation marked on top of peak 5146 is just a spot elevation, and this topo sheet is just a provisional map. Furthermore, the elevation mark on the USGS map is near the north peaklet; but when on top, the south peaklet looks higher.

Nowadays, spot elevations are usually NOT checked by an actual field survey, either at the elevation point or afar. The spot elevations are usually determined by a more-rigorous-than-average photogrammetric analysis, and are mainly used for checking residuals on digital elevation models. These spots are supposed to be points that are readily identifiable on aerial photos and on the ground - typically, sharply defined rocky crags or lakes, not necessarily summits.

The aerial for the summit of "Peak 5146" is blurry, streaked and featureless at the position of the south peak; those traits may be why the north peak was picked for a checkpoint. Or, the map could be inaccurate on the exact placement of the spot elevation.

But couldn't you just check the elevation of each peak with a GPS? Not with sufficient accuracy, unless you had a commercial grade GPS with two receivers or a ground station. Yes, some personal GPS can report an EPE ("accuracy") of +/- 7 feet when WAAS is active; but that is the horizontal "accuracy". When the elevation is determined by satellite, the vertical EPE is typically at least twice as great. If you plot the record of elevation vs. time when your GPS is just sitting at the summit (you must use the unaveraged, full-recorded track, to avoid observer bias), you will typically see +/- 10-20' variation, if you wait more than a few minutes. Barometric-aided GPS altitudes may be better, but I've still seen up to +/- 10 feet variation in tracks from barometric-aided GPS.

Here's my GPS log of elevation, vs. time, for my trek over the summits and back. The GPS was reporting +/- 7' horizontal EPE. At first I went rather quickly over the south summit, and recorded a max of ~5140' +/- 14'. Without stopping, I went to the north summit, and walked around a bit with my pack on. Then I took my pack off; the GPS sensed it wasn't moving, and began to time-average the points. Unfortunately, my pack fell over slightly, so that was probably not the best orientation. Then I put my pack back on, time-averaging ceased, and we went back to the south summit to eat lunch. I immediately took my pack off again, this time keeping it upright on a boulder, and the GPS began to time-average, to yield about 5148' +/- 14' on the south summit -- but the elevation "fell" by about 8' when I put on my pack to leave.

So, the obvious question: if I just left my GPS on top for a long time, wouldn't averaging eventually lessen the error? Yes, it would (see this discussion, which is now a bit dated). The error does tend to improve with averaging; it drops off rather quickly, by perhaps 25%, in the first 10 minutes. Then further improvements come quite slowly, so you might have to leave your GPS on top for several hours to see the error improve 50%.



Please, please, please NOTE these files are relative to WGS84 datum. These are deep canyons, and you may lose satellite lock several times in a trip, at which point you must depend on your common sense. Please display the EPE "accuracy" on your GPS, and consult that indicator often, to know when the GPS should be doubted.

This is a 300-point txf-format (text) track file of our descent, in decimal degrees.

This is a waypoint file, gpx format. It contains waypoints inspired by Jim Boone, with two important exceptions: 1) the points are in decimal degrees relative to WGS84; 2) I've added two waypoints, Avoid-dryfall and Cut-north, if you want to bypass the 30' dryfall. Avoid-dryfall is the point where you should leave the streambed on ascent, cut slightly right, and go up a shallow gully in the ridge. This ridge runs SW to NE, but is south of the wash. Cut-north is the point on ascent where you should cut north (left on ascent) to the top of the ridge, and look for a safe descent route across the wash, as you aim for the Chute waypoint.

If you have a Windows PC and GPS connection, you can upload these files directly to your GPS with the free program G7toWin. The gpx file can be read in many programs, such as ExpertGPS, and the txf file can be imported into many programs. But G7toWin can also convert among a vast variety of formats. If you use any program to upload the files, be sure that the program is using a datum consistent with your GPS and the data files.