New State Highpoint of Michigan – Mt Curwood

Michigan State Highpoint Survey

New State Highpoint – Mt Curwood

Eric Gilbertson

Oct 26-27, 2024

Summary of results:

Mt Curwood 1979.3 ft, Location (46.703004, -88.239504)
Mt Arvon 1978.9 ft, Location (46.755828, -88.155317)

(NAD83(2011) Epoch 2010 NAVD88 (Geoid18) datum)
First dGNSS survey of Arvon and Curwood.
Mt Curwood is the state highpoint of Michigan. Mt Arvon, previously thought to be the state highpoint, is the second highest peak in Michigan

Results have been recognized by the peer-reviewed scientific journal Progress in Physical Geography: Earth and Environment.

Gilbertson, E., Hensley, R., Kirmse, A., Bretherton, K., Stanchak, K., “LiDAR Accuracy on North American Mountain Summits,” Progress in Physical Geography: Earth and Environment, 2025 Link: https://doi.org/10.1177/03091333251401361 (Link to free version: https://arxiv.org/abs/2511.12341 )

Introduction

Mt Curwood (46.703004, -88.239504) and Mt Arvon (46.755828, -88.155317) are two peaks located in the upper peninsula of Michigan in Baraga County near the town of L’Anse. They are separated by a horizontal distance of roughly 5 miles, and access is via a network of rough logging roads. The first surveys of the peaks were conducted by the USGS in 1954 (Mt Arvon) [1] and 1956 (Mt Curwood) [2]. This showed Mt Curwood was about 3ft taller, and it was considered the state highpoint of Michigan based on these results.

A subsequent USGS survey in 1958 [3][25] using a double-run alidade line showed Curwood 5ft taller. An independent spirit level survey by the “Committee for Michigan’s Highest Point” in 1963 showed Curwood 14ft taller [25][26]. Subsequent USGS quads were updated in 1960 [4], 1961 [5], and 1967 [6], though Curwood and Arvon were not field checked for these quads and results were based on photogrammetry.  In 1982 a field survey conducted by personnel from the Mid-Continent Mapping Center (MCMC) using third-order levels showed Mt Arvon approximately 1ft taller than Mt Curwood. See original 1982 field notes for Arvon [23] and Curwood [24] and the original announcement in the Daily Mining Gazette in Houghton, Michigan [26]. In 1985 the USGS put out a new quad based on photogrammetry using the 1982 field surveys [7]. See Table 1 for results from all surveys 1954-1982.

Since 1982 Mt Arvon has been recognized as the highpoint of Michigan. No subsequent ground surveys have been conducted on these peaks since the 1982 measurement. Neither peak had ever been measured with modern differential GNSS equipment prior to the 2024 survey.

However, in 2015 USGS collected LiDAR (Light Detection and Ranging) data of both peaks (Curwood [8] and Arvon [9]). LiDAR measurements involve a plane flying over the peaks and sending light pulses to the ground. By measuring the time for the pulses to return, and using an accurate elevation of the plane, an elevation of the ground can be calculated.

The LiDAR measurements showed the highest points of Mt Curwood and Mt Arvon within 0.1ft elevation, which is the same height within the accuracy of the measurements. LiDAR has a stated vertical accuracy of +/- 4in (+/- 0.33ft) for measured points [10]. However, LiDAR measurements are taken roughly every 3-10ft horizontal spacing, so locations between these points are unmeasured. Also, LiDAR cannot distinguish between man-made cairns and natural bedrock.

The LiDAR data called into question which of the two peaks is the true state highpoint. It was not known with certainty if LiDAR measured the highest point on each peak, and even if it did the results were within error bounds of each other.

I have surveying equipment capable of measuring elevations more accurately than LiDAR, and I can measure the exact summit of a peak. I’ve surveyed over 60 peaks around the world over the past seven years, and I can generally get elevations to the nearest +/-0.1ft or better.

I’ve previously conducted ground surveys to discover new country highpoints in Saudi Arabia [11], Uzbekistan [12], Gambia [13], Togo [14], and Guinea Bissau [15] (for Gambia, Togo, and Guinea Bissau I collected the field data and CompassData engineers processed the data). I recently conducted surveys and discovered the historic summit of Mt Rainier, Columbia Crest, has melted down 21.8ft revealing a new summit location on a different area of the mountain [16]. After hearing about my Rainier surveys, a lot of state highpointers asked me if I could survey Arvon and Curwood, since they were known to be so close in height. If I could conduct ground surveys of Curwood and Arvon I could potentially figure out which peak is the true state highpoint. I’d previously climbed Mt Arvon on my project to climb all the state highpoints (finishing in 2012). Though, I’d never climbed Mt Curwood.

I studied pictures and videos of the two peaks, and made an intriguing observation. The USGS benchmark on the summit of Mt Arvon is mounted on a concrete pillar that looked to stick up about half a foot above the surrounding ground. The USGS benchmark on Mt Curwood was set at ground level. But near the Curwood benchmark there appeared to be bedrock sticking up over half a foot above ground.

Based on my experience surveying I know the elevation written on the quad for a benchmark location is the elevation of the benchmark. Surveyors measure benchmarks because they provide a location for repeatable measurements at a known location. Peakbaggers might assume the number on the quad is the elevation of the top of the mountain, but that is not always true.

Just like the elevation of the top of a fire tower on a summit is not considered the elevation of the mountain, the elevation of the top of an artificial concrete pillar is not considered the elevation of the top of the mountain. The elevation of the mountain is the elevation of the highest natural ground or rock (or permanent ice, but that’s not relevant for these peaks).

In this case, it appeared that in the 1982 survey Mt Arvon was artificially measured higher than the highest natural point, and Mt Curwood was artificially measured lower than the highest natural point. This was consistent with the LiDAR measurements. The summit of Arvon should actually be the elevation of the ground next to the monument. The elevation of Mt Curwood should actually be the elevation of the top of the highest bedrock sticking up on the summit.

I suspected based on my estimates of monument and bedrock heights that Curwood was likely a few inches taller than Arvon. This would be consistent with the LiDAR data. But in order to be certain I wanted to take ground measurements. So I planned a trip to Michigan to collect some data.

Methodology

I planned to take measurements with two survey-grade differential GNSS units capable of vertical accuracies 0.1ft or better. A differential GNSS unit is much more accurate than a standard handheld GPS or a phone, which can have vertical errors +/-70ft or more [27]. A differential GNSS has access to many more satellites and uses an external antenna to help with multipath errors and sky visibility. It also collects enough data that results can be compared to base stations around the country to correct for atmospheric distortions. Data can also be post-processed by other sophisticated methods like PPP (precise point positioning).

For Mt Arvon I would mount one unit on the monument and one unit on the highest ground or bedrock next to the monument. I would bring 2.0m tall antenna rods to help improve accuracy (generally errors are lower when the GNSS receiver is higher off the ground). For Mt Curwood I would also mount one unit on the monument and one on the highest bedrock. I would identify the highest bedrock with a 10 arcminute 5x Abney level.

I planned to take a 4-hour measurement at each location. This is the twice the standard length of time for surveying benchmarks with differential GNSS units.

From photographs and trip reports I knew each summit was forested with overhead tree cover. This is not great for GNSS measurements since it can add error. The error can be reduced if the leaves are off the overhead branches.

I determined the optimal time of year to survey these peaks was late October. Historically in northern Michigan all the leaves have fallen off the trees in this area by late October, but snow doesn’t typically start until November. I didn’t want to survey with snow on the ground because this would complicate finding the highest point on each summit. Also, access would be difficult without renting a snowmobile for those particular peaks in winter.

I would additionally use a tape measure to measure the height of the Arvon monument pillar above ground and the height of the Curwood bedrock above the monument.

With these measurements I would then get four independent measurements of the elevation of the highest natural point on each mountain. I would have the corrected 1982 USGS measurement, corrected LiDAR measurements, and the two independent GNSS measurements.

For equipment I planned to use a Promark 220 dGNSS with Ashtech antenna and a Trimble DA2 dGNSS. Using two different models of dGNSS would help increase confidence in the final results.

Previous Measurements

I first conducted background research to fully understand all existing measurements of the peaks. This included researching all previous USGS measurements and conducting detailed analysis of existing LiDAR measurements.

USGS

The first USGS quads covering these peaks were published in 1954 [1] for Mt Arvon and 1956 [2] for Mt Curwood. These were broadly based on photogrammetry but were also field checked at specific locations, including Mt Arvon and Mt Curwood. These measurements showed Mt Arvon was 1975 ft and Mt Curwood 1978 ft.

A subsequent USGS survey in 1958 [3][25] using a double-run alidade line showed Curwood 5ft taller, with Curwood 1980ft and Arvon 1975ft.

In 1963 an independent spirit level survey was conducted by the “Committee for Michigan’s Highest Point” composed of chairman Eric Bourdo of the Ford Forestry center, district conservation supervisor Robert Gouin, district game manager Robert Rafferty, and Bruce Deter. This survey found Curwood 14ft taller [25][26], with Curwood at 1993.76ft and Arvon at 1979.69ft. Results were published by the Lion’s Club.

Subsequent USGS quads were updated in 1960 [4], 1961 [5], and 1967 [6], though Curwood and Arvon were not field checked for these quads and results were based on photogrammetry. The 1960 and 1961 quads showed Mt Curwood at 1955ft and Mt Arvon 1975ft. The 1967 quad showed Mt Curwood 1980ft and Mt Arvon 1975ft.

In 1982 a field survey conducted by personnel from the Mid-Continent Mapping Center (MCMC) using third-order levels showed Mt Arvon approximately 1ft taller than Mt Curwood, contrary to previous results that all measured Curwood taller. This measured Mt Curwood 1978.284ft and Mt Arvon 1979.238ft. No error bounds were given for the measurements. The survey was directed by district chief Ryan, with Mt Curwood surveyed by Don King, Chuck Nankervis, and Jack Fish. Mt Arvon was surveyed by Dave Burgeson, Chuck Nankervis, and John Bennett. See original field notes for Arvon [23] and Curwood [24] and the original announcement in the Daily Mining Gazette in Houghton, Michigan [26].

During this survey the current benchmarks on the summits were installed and stamped with elevations rounded to the nearest foot, with Mt Curwood 1978ft and Mt Arvon 1979ft. According to the field notes the Mt Curwood benchmark was set “flush with the ground” and the Mt Arvon benchmark was set “in a concrete post.”

In 1985 the USGS put out a new quad based on photogrammetry and the 1982 field surveys [7]. For the quad the 1982 measurements were converted to meters and rounded to the nearest 0.1 meter. They were given as 603.0m for Mt Curwood and 603.3m for Mt Arvon.

All results for surveys between 1954-1982 are given in NGVD29 vertical datum to be consistent with how they were reported. These results are shown in Table 1.

For my analysis I am using the numbers from the 1982 survey as the most recent and accurate USGS measurements of the peaks.

LiDAR

In late October and early November 2015 LiDAR measurements were taken of each peak [8][9]. I downloaded the raw point cloud data and analyzed it using QGIS [18], a free open-source software package used by surveyors.

I located the highest elevation measured for each peak from the raw point cloud data. Results are given in the results section.

Measurements

On Friday evening, October 25^th I flew to Minneapolis, Minnesota, rented an SUV, and started driving into Wisconsin. I first measured the two contender peaks for the Wisconsin state highpoint (results to be given in another report). By the evening of Saturday, October 26^th I was driving in to Michigan.

I had read that the roads to Mt Curwood were rough, so I was happy to have an SUV. I drove to L’Anse, then continued on deteriorating gravel roads until I reached Mt Curwood just before sunset.

I parked the SUV about 100ft from the summit, and walked the remaining distance with my survey equipment. I was familiar with the summit area based on pictures and videos I had seen.

I quickly identified the highest bedrock, and verified with my Abney level that it was indeed the highest natural point. There was a fire ring nearby, but that had obviously been created by people. The bedrock was obviously natural and would not budge no matter how hard I tried.

The leaves were all off the trees and there was no snow on the ground. Conditions were thus optimal for surveying these peaks. I think the only way more accurate data could be collected is if the area ever gets logged. It’s unclear if this will ever happen, though.

I mounted the DA2 GNSS antenna rod so it exactly touched the top of the bedrock, then started logging data. I mounted the Promark GNSS antenna rod so it exactly touched the top of the monument, which was at ground level.

With my tape measure I measured how far the bedrock stuck up above the ground. I additionally mounted my tape measure vertically next to the monument and sighted it with my Abney level from the top of the bedrock. This gave consistent results for the height of the top of the bedrock above the monument.

I took many pictures, including pictures of the setup looking North, East, South, and West. This is standard procedure for ground surveys. With the data recording started I set a 4-hour timer on my watch, then laid out my sleeping bag on the ground nearby to take a nap.

My alarm went off around 10:30pm, and I quickly packed up and headed out.

Mt Arvon is only about 5 miles line-of-sight from Mt Curwood, but it takes a surprisingly long time to get there. The area contains a network of old logging roads in various degrees of abandonment, and many of the roads I passed on the way in that showed up on my map were impassable. I didn’t really have time to spare reaching a dead end, so I decided to drive out all the way back to L’Anse, then follow the standard approach to Mt Arvon.

I made it out to L’Anse around midnight, then drove north just past the Huron Bay Trading Post. I then followed the standard route in to Mt Arvon from the north via Sawmill Road. It’s a much easier route than the way in to Curwood, and there are even signs at most intersections pointing the way to Mt Arvon.

I arrived at the trailhead around 1am, and quickly walked my equipment 100ft in to the highpoint.

As before, I mounted the Promark antenna rod directly on the monument on the concrete pillar. The ground around the monument was mostly flat but the tip of bedrock stuck up a few feet away from the monument. This was level with the ground at the base of the monument and the highest natural point (as verified with my Abney level). Thus, this was the highest natural point on Mt Arvon.

I mounted the DA2 antenna rod directly on the bedrock and started logging data. Interestingly, I noticed a bunch of rocks piled around the Mt Arvon summit sign. These were obviously put there by people. It appeared these may have been picked up by LiDAR to give an artificially-high reading for the elevation of Arvon.

After taking a bunch of pictures I set another 4-hour timer, then laid out my sleeping bag on the ground next to the tripods to take a nap.

After 4 hours passed around 6am I decided I could really use an additional hour of sleep, and it wouldn’t hurt to get another hour of data. I was a little nervous some other highpointers would come up and get mad at me for having all that equipment set up on the summit. But it wasn’t quite sunrise yet, so I was still good for another hour sleeping on the top.

By 7am I finally woke myself up and packed up. I soon headed out and made the 7hr drive back to Minneapolis. I had just enough time to meet my aunt and uncle for dinner before catching my evening flight back to Seattle.

Results

All elevation results will be reported in NAVD88 vertical datum, because this is the current standard used by surveyors in the US. A vertical datum is essentially a definition for a zero elevation. It can be thought of as mean sea level extended across land. The 1982 measurement was reported in NGVD29 vertical datum (established in 1929), but the current standard in the USA is NAVD88 (established in 1988). This is what LiDAR data is reported in and it is generally considered the most accurate way currently to report elevations in the US. The complete datum specifications for results in this paper are NAD83(2011) Epoch 2010 NAVD88 (Geoid 18). This is currently the standand horizontal and vertical datum for the US.

In practice the NAVD88 and NGVD29 datums only differ by around 0.1ft in this area of Michigan. Thus, historical elevations from the quads that were rounded to the nearest foot would be essentially the same in either datum. But for peaks this close in elevation when updated elevations need to be reported to the nearest 0.1ft or better, this distinction is important. The tool to convert between datums is NCAT [22], provided by NOAA.

USGS

For Mt Curwood I measured that the highest bedrock sticks up 8.5 inches above the monument. This means the corrected USGS elevation of Mt Curwood after converting to NAVD88 and adding 8.5 inches is 1979.25 ft. For Mt Arvon I measured the monument pillar sticks up 7 inches above the surrounding ground and above the bedrock nearby. This means the corrected USGS elevation of Mt Arvon after converting to NAVD88 and subtracting 7 inches is 1978.81ft.

Comparing elevations, this means the 1982 survey measured Mt Curwood 0.38ft taller than Mt Arvon.

No error bounds are given for the 1982 surveyed elevations. I know from other surveys conducted in the 1980s in Washington state on mountain tops a standard error bound was +/-0.2ft (two-sigma error range, 95% confidence interval). I have assumed this same error for the 1982 USGS measurements.

LiDAR

For Mt Curwood I compared the coordinates I measured for the monument and highest bedrock to that of the measured points in the LiDAR point cloud. I discovered the highest LiDAR ground-return measurement was measuring the fire ring near the summit. The highest ground-return measurement not the fire ring was several feet east of the monument at 1978.70ft. One LiDAR measurement hit the side of the tallest bedrock, but not the top. The corrected LiDAR measurement of the top of the bedrock is thus the ground measurement between the monument and the bedrock plus the bedrock height (8.5in). This gives a corrected Lidar elevation of 1979.41 ft.

For Mt Arvon I also compared the coordinates I measured of the monument pillar and the bedrock to those of the LiDAR point cloud data. I discovered the highest LiDAR ground-return point measured the rocks artificially piled up around the summit sign.

The closest ground measurement to the monument was about 1ft away horizontal. Thus, the corrected LiDAR measurement is the elevation of this ground measurement, which was 1978.88ft.

Comparing elevations, this means LiDAR measured Mt Curwood 0.53ft taller than Mt Arvon.

LiDAR stated accuracy is +/-0.33 ft for measured points. I will use this as the two-sigma error bounds (95% confidence interval) for the corrected LiDAR measurements.

DA2

I processed both GNSS measurements with three methods – OPUS [19], CSRS-PPP [20], and TrimbleRTX [21].

OPUS is a free software tool provided by the US government for processing dGNSS data. CSRS-PPP is a service provided by the Canadian government that uses a slightly different processing method. TrimbleRTX is a service provided by Trimble.

I have discovered based on previous surveys that in general all three processing methods give similar accuracy when surveying on open mountain tops with unobstructed sky views. Generally I get 0.1ft vertical accuracy after a one-hour measurement for all methods, and as good as 0.05ft accuracy for a 2hr or longer measurement.

However, OPUS generally has the highest errors when surveying under tree cover. CSRS-PPP generally gives slightly lower errors in trees. TrimbleRTX generally gives the lowest errors in tree cover.

For both Curwood and Arvon I found for all measurements TrimbleRTX gave the smallest errors. Thus, I have given final results using this processing method.

To correct for errors related to overhead tree cover, called cycle slips, the online TrimbleRTX service (accessed via https://surveytools.trimbleaccess.com/gnssprocessor) automatically filters out cycle slips from data from newer dGNSS units, including the DA2. Once the cycle slips are removed, the data is processed with TrimbleRTX.

The DA2 GNSS was mounted exactly on the highest natural point for Curwood and Arvon. Thus no corrections need to be added to these measurements other than accounting for the antenna rod height (2.00m).

For Mt Curwood I measured 1979.39ft +/-0.42ft. For Mt Arvon I measured 1978.90ft +/-0.30ft (two-sigma errors, 95% confidence interval).

Comparing elevations, this means the DA2 measured Mt Curwood 0.49ft taller than Mt Arvon.

Promark

For the Promark measurements, the TrimbleRTX service does not automatically filter out cycle slips. This is related to the Promark being a much older unit (from 2012). For the Promark data, I first processed measurements with Trimble Business Center to manually remove cycle slips before I submitted them to TrimbleRTX for final processing.

For both peaks I mounted the Promark GNSS on the monument, thus corrections need to be added to get the final elevation of the highest natural point.

For Mt Curwood I added 8.5 inches of the bedrock height to the measured monument height. This gave an elevation of 1979.12ft +/-0.16ft. For Mt Arvon I subtracted 7 inches of the monument pillar from the measured monument height. This gave an elevation of 1979.03ft +/-0.08ft (two sigma errors, 95% confidence interval).

Comparing elevations, this means the Promark measured Mt Curwood 0.09ft taller than Mt Arvon.

Overall Results

To compare the different measurements, Figure 1 shows normalized normal distributions of each measurement using the measured mean and one-sigma standard deviation values. These plots assume normal distributions of measurements.  This figure shows that in general the Curwood measurements are higher than the Arvon measurements, and for any pair of measurements Curwood is taller. The vertical lines show the mean elevations for Curwood and Arvon.

I additionally made box plots of the same data in Figure 2. The left curve shows Mt Arvon and the right Mt Curwood. The box is centered at the mean with the edge of the box +/- one sigma and the whiskers +/- two sigma. These results again show that in general the Curwood measurements are higher than the Arvon measurements. Horizontal lines show the mean measured heights for Arvon and Curwood.

Finally, I plotted the elevation difference for each individual measurement method in Figure 3. This allows for fair comparison between measurements. This plot shows the corrected 1982 measurement measured Curwood 0.38ft taller than Arvon, corrected LiDAR measured Curwood 0.53ft taller than Arvon, the DA2 measured Curwood 0.49ft taller than Arvon, and the Promark measured Curwood 0.09ft taller than Arvon. The horizontal line shows the mean height difference of 0.37ft Curwood above Arvon.

To reach a final elevation for each peak I took the mean of the four elevations for each peak and rounded to the nearest 0.1ft. This gave the final result of Mt Curwood 1979.3 ft and Mt Arvon 1978.9ft. This means the final result is Mt Curwood is 0.4ft taller than Mt Arvon and is the true state highpoint of Michigan.

To calculate the probability that Curwood is higher than Arvon, I assumed normal distributions for each set of measurements and found the probability that P(C-A)>0, where C represents a random measurement from the Curwood distribution and A represents a random measurement from the Arvon  distribution. I calculated the sigma of the C-A distribution by using the formula

σ=√(σ_C^2+σ_A^2 )

where σ_C is the sigma for the Curwood distribution and σ_A is the sigma for the Arvon distribution. I then calculated the cumulative density function where P(C-A)>0 for this sigma value. The final results for the mean height differences Curwood above Arvon, and confidence that Curwood is higher than Arvon are shown in Table 2.

Table 2: Confidence that Curwood is taller than Arvon.

Method	Confidence Curwood > Arvon (%)
Corrected USGS	99.6
Corrected LiDAR	98.8
DA2	97.1
Promark	84.8

Discussion

Each of the USGS, LiDAR, DA2, and Promark measurements found Curwood higher than Arvon. These are completely independent measurements using different measurement techniques (third-order levels, LiDAR, and different models of differential GNSS) all giving the same result for which peak is higher. The USGS, LiDAR and DA2 methods all found Curwood taller than Arvon with greater then 95% confidence. The Promark found Curwood taller than Arvon with 84.8% confidence, and this lower confidence is likely related to the unit being much older than the DA2.

Based on these results I can conclude that Mt Curwood is taller than Mt Arvon, and Mt Curwood is the true state highpoint of Michigan. The final elevations are the means of all measurements, with Mt Curwood 1979.3ft and Mt Arvon 1978.9ft.

A separate point of discussion could be what counts as a summit. In general there is broad agreement that the summit is the highest natural point on the mountain, and man-made structures and trees don’t count. This should mean that artificial concrete monuments don’t count towards elevation, and piles of rocks artificially moved by humans don’t count. If these counted, then humans could make a mountain have whatever elevation they wanted.

Under this definition, Mt Curwood is taller than Mt Arvon.

Practically, I would be comfortable saying anyone who climbed Mt Arvon before these results were published should be grandfathered in and given credit for climbing the state highpoint of Michigan. But going forward I would say people should climb Mt Curwood to claim the true state highpoint.

Conclusion

Mt Curwood (46.703004, -88.239504) is the state highpoint of Michigan at 1979.3ft. Mt Arvon (46.755828, -88.155317) is the second highest peak in Michigan at 1978.9ft.

Data Availability

Raw measurement files can be downloaded at https://github.com/ericgilbertson1/michigan

References

1. U.S. Geological Survey: Michigamme quadrangle, Michigan [map]. Photogrammetry 1951-1952. Field checked 1956. 1:62,500. 15 Minute Series. United States Department of the Interior, USGS, 1956

2. U.S. Geological Survey: Skanee quadrangle, Michigan [map]. Photogrammetry 1951 and 1953. Field checked 1954. 1:62,500. 15 Minute Series. United States Department of the Interior, USGS, 1954

3. U.S. Geological Survey: Iron River quadrangle, Michigan [map]. Photogrammetry 1957. Field checked 1958. 1:250,000. United States Department of the Interior, USGS, 1958

4. U.S. Geological Survey: Iron River quadrangle, Michigan [map]. Photogrammetry 1957. Field checked 1958. 1:250,000. United States Department of the Interior, USGS, 1960

5. U.S. Geological Survey: Iron River quadrangle, Michigan [map]. Photogrammetry 1957. Field checked 1958. 1:250,000. United States Department of the Interior, USGS, 1961

6. U.S. Geological Survey: Iron River quadrangle, Michigan [map]. Photogrammetry 1957. Field checked 1958. Limited revision 1967. 1:250,000. United States Department of the Interior, USGS, 1967

7. U.S. Geological Survey: Mt Curwood quadrangle, Michigan [map]. Photogrammetry 1980. Field checked 1982. 1:24,000. 7.5 minute series. United States Department of the Interior, USGS, 1985

8. U.S. Geological Survey, 20221108, USGS Lidar Point Cloud MI_13County_2015_C16 935700: U.S. Geological Survey. Available at https://apps.nationalmap.gov/downloader/

9. U.S. Geological Survey, 20221108, USGS Lidar Point Cloud MI_13County_2015_C16 955720: U.S. Geological Survey. Available at https://apps.nationalmap.gov/downloader/

10. USGS, “What is Lidar and Where Can I Download It?”, https://www.usgs.gov/faqs/what-lidar-data-and-where-can-i-download-it 

11. “Ferwa – The Highest Saudi Peak,” Arriyadiyah, https://arriyadiyah.com/611058 , Aug 28, 2018

12. Gilbertson, E., “Alpomish, First Ascent, New Country Highpoint of Uzbekistan,” The American
Alpine Journal, 2024

13. Gilbertson, Gambia – Sare Firasu Hill, Dec 2021, https://www.countryhighpoints.com/gambia-highpoint/

14. Gilbertson, Togo – Mt Atilakoutse, Dec 2021, https://www.countryhighpoints.com/highpoints-of-ghana-togo-benin/

15. Gilbertson, Guinea-Bissaue Dongol Ronde, Dec 2021, https://www.countryhighpoints.com/guinea-bissau-highpoint/

16. “Mount Rainier is shrinking and now has a new summit,” Conrad Swanson, The Seattle Times, Oct 6, 2024, https://www.seattletimes.com/seattle-news/climate-lab/mount-rainier-is-shrinking-and-now-has-a-new-summit/

17. Dufresne, Jim. “A Summary of Summits.” Ann Arbor News, Oct 31, 1992. Available at https://aadl.org/aa_news_19921031_p03-a_summary_of_summits

18. QGIS.org. QGIS Geographic Information System. QGIS Association. http://www.qgis.org

19. Online Positioning User Service (OPUS), NOAA, https://geodesy.noaa.gov/OPUS/

20. CSRS-PPP Precise Point Positiong processing, https://webapp.csrs-scrs.nrcan-rncan.gc.ca/geod/tools-outils/ppp.php?locale=en&_gl=1*1as3oua*_ga*NTQ2NTE3OTMwLjE3MTQ2NzgzMjU.*_ga_C2N57Y7DX5*MTcyNjA4NjU

21. Trimble Centerpoint RTX Post Processing https://trimblertx.com/UploadForm.aspx

22. NGS Coordinate Conversion and Transformation Tool (NCAT), https://www.ngs.noaa.gov/NCAT/

23. Skanee Quadrangle Benchmark Records, US Department of the Interior Geological Survey, Edition of 2/4/1987. See pdf: SkaneeBenchmarks

24. Michigamme Quadrangle Benchmark Records, US Department of the Interior Geological Survey, Edition of 12/15/1982. See pdf: MichigammeBenchmarks

25. Deter, B. (1963, May 4) Letter from Bruce Deter to USGS Topo Division Central Area. See pdf: MIhighpointletters1963

26. French, Robert. “Mt. Arvon, not Curwood, hightest [sic] point in Michigan,” Daily Mining Gazette, Oct 17, 1983. See pdf: MichiganNewspaper1983

27. Rodriguez, R., Jenkins, D., Leary, J., Nolan, K., Mahnken, B., “Performance Analysis of Consumer Grade GPS Units for Dynamic Aerial Applications,” ASABE Annual International Meeting, 2016, doi:10.13031/aim.20162460946

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