Big Kangaroo Theodolite Survey – New WA Top 100 Peak

Big Kangaroo Theodolite Survey

June 14/17, 2023

Summary of results: Elevation 8,326ft +/-2ft, now 95th tallest peak in WA and new top 100 peak

I’ve recently been interested in discovering which peaks are truly the 100 highest peaks in Washington. This is significant because many climbers in Washington work on climbing the top 100 peaks after finishing the Bulgers list. The Bulgers list is approximately the 100 highest peaks in WA with at least 400ft of prominence, but the climbers making the list made a few exceptions. They included seven named peaks with less than 400ft of prominence (Blackcap, Seven Fingered Jack, Rahm, Little Annapurna, Dark, Sahale, and Horseshoe). This was partially to include some important named peaks that happened to not be prominent, partially to exclude a few volcanic sub peaks, and in one case because of a contour line error on the quad.

This means an additional seven peaks must be climbed in addition to the Bulgers to officially climb the 100 highest peaks in Washington. Traditionally, based on existing measurements, these extra peaks were considered to be Liberty Cap, Ballard, Luna, Castle, Sherman, Colfax, and Lincoln. However, as I’ve discovered, there still exist peaks in Washington that have never been accurately surveyed and that may in fact be among the 100 highest.

I used to think that satellite surveys (SRTM) and plane-based surveys (LiDar) would have measured all peaks by now in Washington with enough accuracy to determine the hundred highest. But this is actually not true. SRTM indeed covers all of Washington, but the error can be very high for sharp peaks. LiDar has smaller error, but surveys have only been done over part of the state. And errors can still be significant for sharp peaks if the measurement doesn’t hit the exact summit.

The quads indeed cover all the mountains, but not all peaks were directly surveyed. Significant peaks and locations were surveyed with ground surveys using theodolites, and topo lines at 40ft intervals were drawn approximately in between these surveyed points. This means for some peaks that may be tall enough to qualify for the WA top 100 list, only approximate topo lines are given. Thus, any peak that is close to being tall enough with enough prominence for list inclusion but has never been directly surveyed could potentially be a WA top 100 peak. Only a ground survey using  a theodolite or very accurate GPS unit could determine this for sure.

Last year I purchased a theodolite, taught myself how to use it, and started bringing it into the mountains to survey peaks. A theodolite is a very accurate mechanical device for measuring angles. This is what the original surveyors used to find elevations. If you measure angles between peaks and know distances between them you can use trigonometry to calculate relative heights. If I bring the theodolite to a previously surveyed location and measure an elevation angle to a peak of interest I can calculate its height. This is not a common piece of equipment you’ll see with hikers and climbers. The whole setup is about 50 lbs with the tripod and the sturdy pelican case, so it’s not necessarily easy to haul it up a peak.

In early October 2022 I hiked in to Buckner Mountain with Talon and Steven helping haul in gear. At that time it was unknown whether the SW or NE peak was the true highpoint. We surveyed that the SW summit of Buckner is in fact 1.5ft taller than the NE summit. This means climbers completing the top 100 and Bulgers can skip the NE summit.

Later that month I ventured into the remote Picket Range with Talon and Nick helping haul in the survey equipment. This area is remote enough that some areas of it hadn’t previously been surveyed. I discovered that East Fury, previously thought to be approximately 8,280ft tall, is actually 8,356ft tall. This qualified it to be a WA top 100 peak and meant that Castle Peak got kicked off the list.

As of early 2023 the lowest peak on the WA top 100 list was Luna Peak. It has been surveyed to have a height of 8,311ft. The closest topo lines above and below this elevation are the 8,280ft line and the 8,320ft line. A handful of peaks exist that have not been directly surveyed, but lie between the 8,280ft and 8,320ft contour lines on the quad and have well over 400ft of prominence. This means any of these peaks could potentially be taller than 8,311ft, but nobody knows since they’ve never been surveyed.

I was suspicious about one of these peaks in particular – Big Kangaroo. This is the tallest point on Kangaroo Ridge near Washington Pass. Nick and I climbed it last September and it has a very unique summit. It looks like a pedestal with a sharp pointy boulder balanced on top. The relevant quad (Silver Star Mountain O48120e5 1:24,000) shows the summit as within the 8,280ft contour but not the 8,320ft contour. Thus, it is generally only assigned the conservative elevation of 8,280ft. But the pointy boulder is actually quite tall. We belayed it as its own pitch to the summit. The summit was sharp enough that only one climber could sit there at a time with legs straddling the sides of the rock.

I suspected the top of the boulder might poke into the 8,320ft contour line, but it is so sharp that didn’t make it onto the quad. And the surveyers just didn’t point their theodolite to that point so its elevation wasn’t exactly known. (Peaks that are important to peakbaggers aren’t necessarily important for surveying). With a summit that sharp, satellite and plane-based surveys wouldn’t be accuract enough. SRTM errors can be hundreds of feet since it is difficult to sample the summit. Even LiDar would be untrustworthy. At a standard 1m sampling interval the summit could still be missed and the vertical error could easily be 10ft. But I couldn’t find any LiDar measurements of this area (source: https://apps.nationalmap.gov/lidar-explorer/#/).

The only survey that could measure the summit elevation accurately enough to determine if it is a WA top 100 peak would be ground surveys. I know of two options for accurate-enough ground surveys. The first is to bring a high-end dual frequency survey-grade GNSS unit placed on the peak for at least an hour. This can theoretically get 1-inch vertical accuracy.  I’ve used these before, surveying peaks to find the true country highpoints of Saudi Arabia, Togo, Ghana, Benin Guinea, Guinea-Bissau, Ivory Coast, and Gambia (using a Trimble GeoXR with Zephyr 2 antenna from Compass Data), but I don’t currently have access to one and they are expensive to rent or buy. Alternatively, a theodolite can be used to very accurately measure angular declination or inclination. High-end electronic theodolites can get 1 arcsecond angular resolution but are very expensive. However, my old-fashioned mechanical theodolite can get 20 arcsecond angular resolution which is still very good and perfectly sufficient for this application.

Unfortunately, standard handheld GPS units like my Garmin 62s are not accurate enough for this kind of survey. I’ve measured that standard unit can have absolute vertical error up to 50ft – way too much for this application. Phone GPS units are even less accurate.

So I decided to conduct a theodolite survey of Big Kangaroo. My plan was to bring the theodolite to a location that had been surveyed as shown on the quad. I would then measure the angular inclination or declination to Big Kangaroo. I could find the horizontal distance between my point and the summit using Google Earth with the coordinates of the two points, then use trigonometry to find the summit elevation. To increase confidence in results I planned to survey from multiple locations and hopefully I would get the same elevation results. Though, in theory one careful measurement from one location should suffice.

The most accurate measurement would be if I could put the theodolite exactly on the surveyed point before taking a measurement. Thus it was important that the point not be a technical spire. Ideally it would be somewhat flat. Also, the measurement would be more accurate if the surveyed point was close to Big Kangaroo. An angular measurement error would translate into a larger elevation measurement error the farther away I was (we call this Abbe error in mechanical engineering, my field of expertise).

The closest surveyed points to Big Kangaroo are Pt 8183 and Pt 7736. These are rock spires along Kangaroo Ridge. But based on pictures and reports these looked technical and thus difficult to haul survey equipment up. The next closest are Pt 7705 to the NE of Big Kangaroo and Wallaby Peak to the south. I had previously climbed Wallaby and it was non-technical with a flat summit. I had skied near Pt 7705 and recalled it being non-technical.

I decided to take my first measurement from Pt 7705 (aka Snagaroo) because it was closest. Interestingly, there was also a surveyed point at the WA Pass overlook. This was farther away but access was very easy, just a 2 minute walk from the parking lot. I would have that be my second point to take a measurement from. If I really wanted to be thorough I could also get a third measurement. But if the first two measurements from different locations matched that would probably make me confident enough in the results.

I had recently been climbing 8000m peaks in Nepal this spring (Everest no-O2 attempt to 8500m and Kangchenjunga successful climb with O2) and by mid June was finally recovered enough after a two-week rest to head back out to the mountains. The forecast was partly sunny Wednesday, improving throughout the day, and I assumed this would be sufficient for some measurements.

Tuesday evening June 13th I drove up to Washington Pass and spent the night. I got up at sunrise, but it was snowing and socked in with clouds. No surrounding peaks were visible. I wanted to get the WA Pass measurement done first, but would have to wait. So I slept another few hours. By 7am the peaks were still socked in. So I decided to bushwhack in to Pt 7709 first. Maybe by the time I got in there things would clear out.

My plan was to bushwhack up Willow Creek. I’d previously gone in that way to climb Big Snagtooth in 2018, and I recalled the forest was mostly open. I’d also gone in there in February 2021 to make the first known winter ascent of Big Snagtooth. On that trip we’d taken a non-standard approach to avoid avy terrain that had brought us along the ridge near the base of Pt 7709. I planned to take that exact same route.

I parked off the side of Highway 20, loaded up my 50 lb pack of survey equipment, and started down around 7:30am. I followed a climbers trail down to a log crossing of Early Winters Creek, then followed the blue-flagged but abandoned Early Winters Trail up creek a little ways. At Willow Creek I started bushwhacking up.

In general the trees were nice and open as I recalled. A few hours later, though, I think I stayed a little too close to the creek. The brush got very dense around 5500ft and I backtracked and went uphill. It cleared out again and I continued up, skirting the 5900ft cliff band on the left. There I diverged from the standard Big Snagtooth approach and cut right above the cliffs. I hiked up through patchy snow to the edge of treeline.

Unfortunately all the peaks were still socked in the clouds and it was flurrying. I layered up and continued to the ridge, then ditched the crampons at the ridgecrest when it was clear I wouldn’t need them. Pt 7709 was going in and out of the clouds but I optimistically headed over. I followed the ridge to the base of the big summit block, then hiked around the right side. I ditched my pack there and made the short but fun scramble to the surprisingly-level summit.

Clouds had lifted just above me by then, but Big Kangaroo was solidly socked in. I hung out in the wind and flurries for a while, but then descended to my pack. I waited there for a while in a sheltered cove, but the clouds weren’t receding at all. In fact, they seemed to be getting lower and denser. It appeared the forecast had been wrong. Partly sunny seemed to mean snowing and socked in with clouds.

By 12:30pm I made the call to head down. I could potentially wait hours there with no change. The clouds were supposed to clear in the morning but that hadn’t happened. It was a tough decision but at least I got a new peakbagger dot (my previous trip I had skirted around the summit and not officially tagged it).

As I dropped off the ridge the clouds briefly rose, only covering the very top of the summit. I turned around and dashed back up. But after only a minute the whole peak was socked in again. This seemed random and not any larger sign of clearing. All surrounding peaks were still thoroughly socked in. So I turned back around and continued down.

I made better time bushwhacking down, this time staying farther uphill from Willow Creek. By 3:30pm I arrived back at the truck. By then the skies were kind of starting to clear. I loaded up and drove back up to Washington Pass. Finally the clouds cleared enough that I could see the summit of Big Kangaroo. But nearby peaks like Silverstar were still socked in. I guess I could have waited at Pt 7709 for three hours, but there was no guarantee Big Kangaroo would have cleared since surrounding peaks did not.

I quickly put my pack back on and walked the short paved trail to the overlook. On the quad there is an X-tic survey point on the edge of the plateau at 5620ft. I expected to find a survey marker, but couldn’t find one anywhere. So I just went to exactly where the X was as confirmed with my GPS. This is on the upper ledge at the logical place to take a measurement. There is a lower ledge with a fence that is much lower than the X mark, and a slightly higher ledge that is significantly farther back than the X mark. So even without the marker I was pretty confident I was in the correct spot, assuming the X is drawn correctly.

Before setting up any equipment I did the most important procedure – donning my orange vest. I’ve found if I’m doing a survey in an area where a bunch of people are walking around the vest imparts instant credibility. People will just assume I’m doing some sort of official duty when I wear the vest and won’t hastle me that I shouldn’t be there. It’s like a force field of protection. I just have an old vest a construction worker gave me in Romania from a bike tour years ago, but it looks official.

With the vest safely on I set up the tripod exactly at the X location, then mounted the theodolite. A few people passed by and I overheard a mother saying to a child, “Look, that’s a surveyor!” I carefully leveled it with the lower dials and the bubble levels, then pointed the scope at Big Kangaroo. The summit was obvious – the highest point on the ridge with a sharp rock spire sticking up. And with my 30x magnification zoom I could easily line up the cross hairs exactly on the top. I was able to recognize the climbing route I had taken up last year.

I measured the angle on the C and D dials and took zoomed-in pictures of the readings for more accurate analysis. I then flipped the scope 180 degrees and rotated the bottom disk, then pointed it at the peak and read off the angle on the dials again. This gave four separate measurements. The final measurement is then the average of these four. This accounts for slight errors in leveling the theodolite, which are hard to avoid (at least for an amateur like me).

One lady passed by and asked what I was measuring. I pointed up to the peak and told her I was finding the height of that peak up there. She asked how high it was, but unfortunately I didn’t know yet so couldn’t say. I could only tell her an angular inclination of 19.36 degrees, which wasn’t super interesting. I still needed to do some processing of the results and a bit of trigonometry to calculate that. I would need to do that back at home.

I soon packed up, loaded up the truck, and drove back home. I intended to return, though, for another measurement, hopefully when the weather was better.

That night back at home I calculated that Big Kangaroo was 8,327ft +/-1ft based on that measurement. That meant it was in fact a WA top 100 peak. It was 16ft taller than Luna Peak, the peak currently thought to be the lowest of the top 100 at 8,311ft.

I still wanted at least one more measurement to increase my confidence in the results, though. I didn’t like the fact that there wasn’t a survey marker at the WA Pass overlook and I had been relying on the X drawn accurately on the map. A result as significant as finding a new WA top 100 peak deserved extra scrutiny.

The weather forecast looked ok for Saturday but then bad for the following week in the WA Pass area. So I decided to return Saturday. By Friday morning the forecast looked like a clear window Saturday morning but low clouds building by mid afternoon. Ideally I wanted to survey from both Wallaby and Pt 7709, but that forecast really only gave time for one of those points. I really didn’t like the prospect of exactly repeating my failed attempt from Wednesday again on Pt 7709.

Wallaby Peak was a very similar distance from Big Kangaroo as Pt 7709. It had the advantage that it was taller (7,995ft), meaning I would be more likely to sight the absolute highest point on Big Kangaroo from Wallaby. I had previously climbed Wallaby and recalled there was no bushwhacking and in fact it had some fun scrambling near the top. So I decided to survey from just Wallaby Saturday. I would start early enough that I could wait around on the summit for hours if needed to wait for good weather.

Friday night I drove back to WA pass to sleep. By 5:30am I was packed up and hiking up from the hairpin. Unfortunately the summit of Big Kangaroo was again socked in the clouds, but I knew this was forecast to clear in the next few hours. I’d been up this valley several times before, but always on skis. This spring it seems the snow melted really quickly while I was away in Nepal, and it was already mostly gone.

I followed a climbers trail, signed in at the register (the first sign in this year) and continued up. I followed the trail up to the pass SW of Wallaby, then continued up the SW ridge. I started directly up the ridge crest and made a few fun scrambling moves. Up higher I traversed right onto the south face following cairns and a faint climbers trail. I then walked up some treadmill scree and eventually reached the summit around 7:30am.

Amazingly Big Kangaroo was cloud free! I quickly set up my tripod on the summit and mounted the theodolite. There was no telling how long the clearing would last. Nearby peaks were still socked in. I leveled the unit, pointed the scope at Big K, and took pictures of the C and D dials. I then flipped the setup around and took more pictures of the angular measurements.

The weather kept clearing so I spent about an hour up there admiring the view and taking pictures. I would still need to process the data, so I wasn’t sure yet if it would match my previous measurement. I soon packed up and started down.

Just below the summit I checked the peakbagger app on my phone and noticed a peak called “The Tomb” just down on the ridge. It looked like a fun scramble so I ditched my pack and headed over. I crossed a scree slope to a col then scrambled up the ridge. I followed the class 2 ridge to the base of the summit block, then made one quick 4th class move to pull myself up to the summit. I found a small cairn there but no register.

I soon returned to my pack, then scree surfed and scrambled back down the ridge. I then hiked down the trail and made it back to the truck by 11am. I considered going over to Pt 7709, but it was still too risky. Last time it had taken me 5 hours to bushwhack up there. So best case I’d probably get there at 4 or 5pm. But by then it was forecast to get cloudy ahead of an approaching storm. If that came a little early (which seems common in the mountains) then I’d yet again have bushwhacked all the way in there and not gotten measurements.

If my two measurements matched that would be pretty solid evidence anyways, so the third measurement wasn’t really needed. It was pretty early to just drive home, though, so I decided to just hike a nearby peak without the heavy survey equipment. I hadn’t made any plans, but saw a peak behind washington pass that looked fun. On my map I saw it was called Hinkhouse Peak. It looked to me like I could just march straight up from the WA Pass parking lot and make an easy scramble to the summit.

So I drove back to WA Pass and started up at noon. I had no beta but I just bushwhacked straight north from the parking lot and aimed for the ridge on the right. There was a cliff band betwee 5800ft-6000ft and I managed to find a fun 3rd class cleft cutting through it. I got through the cliff band, then followed the ridge to Pt 7371. In hindsight I suppose that could have been another good survey point, but it was even

farther away from Big Kangaroo than WA Pass, so would give slighty less accurate results anyways.

I followed the ridge crest left and reached a point just to the east of the summit of Hinkhouse. I’d call this the false summit. Beyond that it looked like an exposed 4th class downclimb to a notch before a scramble to the summit. I guess this was the risk of not doing research beforehand on the route. I descended south down scree slopes then scrambled skiers right to gain a slabby gully. I then scrambled up the gully, making a few exposed moves, and gained the notch. From the notch it was a fun exposed 3rd class scramble up the ridge to the summit.

I took a break and signed in the register. I did not want to down climb that slabby sketchy gully, but it seemed like my only option. I downclimbed the ridge, but then back at the notch I noticed an alternative route. I followed an easy class 2/3 ledge around to the north side of the false summit, then scrambled a 3rd class ridge to the false summit. From there I was able to return via my ascent route.

It was a bit tricky to find the 3rd class cleft at the 6000ft cliff but I’d recorded my track on my GPS watch so I nailed it. I soon downclimbed and bushwhacked back to the truck by 2pm. I then made the drive back to Seattle.

At home I processed the results. I used the measured angles along with the horizontal distance as calculated by google earth and some trigonometry. The formula is H = z + h + d*tan(theta) where H is the Big Kangaroo elevation, z is the survey point elevation, h is the height of the theodolite scope above the surveyed point, d is the horizontal distance between the surveyed point and Big Kangaroo, and theta is the measured inclination angle. See figure to the below.

From Wallaby Peak I measured Big Kangaroo 8,325ft +/-1ft. This was almost exactly the same result as from WA Pass (8,327ft +/-1ft). In fact, the measurements are within the error bounds of each other, as they should be. The errors I’m quoting are due to slight leveling errors in the theodolite, which is tough to avoid (for an amateur like me). I’m assuming there are no errors in the USGS quad surveyed elevations and no errors in the google earth horizontal distances. I’m also rounding all measurements to the nearest foot.

If I average the two measurements and take the most conservative error bounds, my final result is Big Kangaroo has an elevation of 8,326ft +/-2ft. This means Big Kangaroo is now on the WA 100 highest peaks list at #94. Luna peak (8,311ft), previously #100, is now #101 and is no longer on the top 100 list.

For reference I’ve included my raw measurements and calculations in this google doc: https://docs.google.com/spreadsheets/d/1px8TbuUUhSG4OZlf0hbt5w8GJD-zAjaMS8-GvDix8i0/edit?usp=sharing

As a triple check , Greg Slayden performed pixel analysis on a picture taken from the summit of Wallaby looking at Big Kangaroo. He used software written by Edward Earl that analyzes locations and elevations of multiple peaks in the background. By knowing the elevations and locations of all these peaks, the location of Big Kangaroo, the elevation and location of the camera, and knowing the pixel location of the peaks in the image, an estimate can be made for the height of Big Kangaroo. The estimated height was 8,327ft – 8,337ft. This is consistent with the theodolite measurements that Big Kangaroo is taller than Luna and thus a WA top 100 peak.

If you want to support gas money for future surveys you can click the button below. (I’m just doing these surveys for fun, not part of any job and not paid.)

 

© 2023, egilbert@alum.mit.edu. All rights reserved.