Columbia Point Survey – Off CO Centennials List

Columbia Point Survey

Eric Gilbertson¹, Elijah Gendron, Ben Loftin

1. Seattle University

Abstract

Columbia Point is a mountain in South Central Colorado commonly considered to be a Centennial Peak (one of the highest hundred peaks in Colorado with at least 300ft of prominence). Light Detection and Ranging (LiDAR) measurements in 2018-2019 found the prominence of Columbia Point within error bounds of 300ft. Knowledge of which peaks are Cenennial Peaks is important for tourism and mountaineering, as climbing the Centennials is a popular peakbagging objective in Colorado. For this study, ground surveys were conducted with professional surveying equipment including multiple dGNSS (differential Global Navigation Satellite System) units and an Abney level to accurately determine the prominence of Columbia Point. The promince was measured to be 299.6ft, with greater than 99% confidence that the prominence is less than 300ft. Columbia Point is 13,985.9ft+/-0.1ft and the Columbia Point Key Col is 13,686.3ft+/-0.2ft, with prominence 299.6ft +/-0.2ft, 95% confidence interval errors, (NAD83(2011)(Epoch 2025.7), NAVD88 using GEOID18, international feet). Thus, Columbia Point has less than 300ft prominence and is not a Centennial Peak. It is instead a sub-peak of Kit Carson Mountain.

Introduction

Climbing the Colorado Centennials is a popular peakbagging objective that was first completed by Spencer Swanger in 1977 (Swanger 2010). By 2025 several hundred people had completed the entire list (CMC 2025). In recent years speed completions of the list have become popular. In 2017 Justin Simoni set the self-powered completion record in 60 days, biking between trailheads (Moore 2017). In 2020 Eric Gilbertson set the self-supported completion record in 33 days, doing a combination of biking and driving between trailheads, with no support crew and no pacers (Hamilton 2021, Gilbertson(1) 2020, Gilbertson(2) 2020). In 2021 Andrew Hamilton set the supported completion record in 22 days, using a large support crew and pacers and being driven between trailheads (Hamilton 2021, McKee 2021). Note: some sources such as FKT erroneously list the 2020 completion as “supported”, though even Andrew Hamilton recognizes it as self-supported (Hamilton 2021).

The list has evolved over time as more accurate elevation and prominence measurements have been performed. In 1977 the list was based on the most updated USGS quadrangles, which relied on theodolite- and photogrammetry-based measurements. The USGS quad-based centennial list included Columbia Point (Fig. 1) because it had over 300ft prominence based on the topo lines on the quads (USGS 1967).

Between 2018 – 2019 airplane-based LiDAR measurements were taken of the highest mountains of Colorado. For these surveys, the airplane’s elevation and coordinates are known with high accuracy (horizontal one sigma errors 5-15cm, vertical 7.5-22.5cm, May 2007) from onboard GNSS units and inertial measurement units. The plane sends a pulse of light to the ground and measures the time of return to the plane. This time of light travel can be used to calculate the distance from the plane to the ground, which can then be used with the plane’s known position to calculate the elevation and latitude and longitude coordinates of the sampled location on the ground.

Sampled points in a LiDAR survey have nominal horizontal spacing 1.1ft (USGS 2025). However, in practice we have found horizontal spacing can be up to 10ft in mountainous terrain (Gilbertson et al, in review). Locations between samples are unmeasured.

These measurements resulted in several peaks being removed from the Centennials list and several added. Dallas Peak and Teakettle Mountain were removed and Arrow and Trinity added based on elevation. The true summit of Mt Buckskin was found to be several hundred feet away along a ridge from the point previously considered the summit.

Columbia Point was surveyed for the USGS quads to have a prominence of approximately 360ft using theodolite and photogrammetry methods (USGS 1967). It was later surveyed in 2018-2019 by airplane-based LiDAR (Colorado 2020) (Fig. 2). The point cloud data was analyzed manually in 2021. This found the highest return on the summit of 13,985.7ft, and the return closest to the saddle as 13,685.8ft. This meant the LiDAR-measured prominence was 299.9ft.

Because points between LiDAR measurements are unsampled, there is uncertainty in the elevation of the summit of a mountain or of a col based on LiDAR point cloud data. If the summit is sharp, LiDAR samples are likely to miss the summit and measure a lower point on the mountain, resulting in an underestimate of the summit height. The authors have previously measured over 177 peaks with dGNSS units and compared measured summit heights to LiDAR-derived summit heights. We found vertical accuracies of summit elevations derived from manually-processed LiDAR point cloud data for open rocky summits is +/-1.7 ft (95% confidence interval) (Gilbertson et al. in review). We did not specifically study saddles, though it is likely that similar error bounds apply.

Thus, the LiDAR – measured prominence was within the error bounds of the 300ft threshold for list inclusion. With this study we aimed to measure Columbia Point and the Columbia Point Key Col with sufficient vertical accuracy to determine whether the prominence is high enough for inclusion in the Centennials List.

Methodology

Author EG performed static surveys on the summit and at the key col using a Trimble DA2 differential GNSS unit capable of 0.1ft vertical accuracy. On October 4 the DA2 was mounted at the key col, which was identified using an Abney level (Fig. 3). Static survey data was logged for one hour between 9:15am – 10:15am, and an antenna rod height of 0.46ft was measured with a tape measure. The unit was then moved to the summit, with location identified using the Abney level. Static survey data was again logged for one hour between 10:45am -11:45am, and antenna rod height of 0.58ft was measured using a tape measure (Fig. 3). Simultaneous measurements were planned, but were not possible due to a hardware issue with the secondary receiver. Measurement times were thus limited to one-hour each due to an an approaching snow storm.

Results

We processed data with three different software tools – TrimbleRTX Centerpoint (Centerpoint 2025), TrimbleRTX Surveytools (Surveytools 2025), and CSRS-PPP (CSRS-PPP 2025). We also intended to use OPUS (OPUS 2025), the standard processing tool in the US, but it was not available due to the government shutdown.

The three available methods are standard tools for processing differential GNSS measurements and correct for errors such as atmospheric distortion using nearby base stations. We submitted the raw t04 measurement files to each site. We used VDatum (Vdatum 2025) and TRX (TRX 2025) to convert all results to the common horiztonal datum NAD83(2011)(Epoch 2025.7) and orthometric height in NAVD88 (GEOID18) vertical datum. These are currentely the most accurate horizontal and vertical datums in this region.

We calculated prominence by taking the difference between the summit elevation and the key col elevation. All methods were in agreement that the prominence is less than 300ft, with greater than 93% confidence. The CSRS-PPP method found the prominence less than 300ft with greater than 99% confidence. Resulting elevations, sigmas, and prominences can be found in Table 1.

Table 1: Elevation measurement results for each peak for each processing method.

Peak/Method	Elevation NAVD88 Geoid18 (ft)	Sigma (ft)	Lat	Long (W)
TrimbleRTX Centerpoint (NAD83(2011) Epoch 2025.7)
Summit	13985.98	0.13	37.9790250925	105.598165111
Key Col	13686.42	0.24	37.9792956008	105.599505794
Prominence	299.56	0.27
TrimbleRTX Surveytools (NAD83(2011) Epoch 2025.7)
Summit	13985.99	0.13	37.9790250870	105.598165106
Key Col	13686.40	0.24	37.9792955814	105.599505847
Prominence	299.59	0.27
CSRS-PPP (NAD83(2011) Epoch 2025.7)
Summit	13985.89	0.07	37.97902521	105.5981655
Key Col	13686.30	0.09	37.97929576	105.5995062
Prominence	299.59	0.12

Normalized normal distribution plots for each prominence measurement are shown in Figure 4. This data can also be visualized in a box-and-whisker plot in Figure 5.

All three processing methods found, to the nearest 0.1ft, the prominence of Columbia Point is 299.6ft, with 95% confidence interval error bounds +/-0.2ft for CSRS-PPP, and +/-0.5ft for TrimbleRTX Centerpoint and TrimbleRTX Surveytools.

To calculate the probability that the prominence is less than 300ft, we assumed normal distributions for each set of measurements and found the probability that P(300-S-C)>0, where S represents a random summit measurement and C represents a random col measurement. We calculated the sigma of the 300-S-C distribution by using the formula

σ=√(σ_S^2+σ_C^2 )

where σ_S is the sigma for the Summit distribution and σ_C is the sigma for the Key Col distribution. We then calculated the cumulative density function where P(300-S-C)>0 for this sigma value. The final results for the mean prominence and confidence that prominence is less than 300 are shown in Table 2.

Table 2: Mean measured prominence and confidence prominence is less than 300.0ft.

Method	Prominence	Confidence Prominence <300.0ft, percent
TrimbleRTX Centerpoint	299.56	94.75
TrimbleRTX Surveytools	299.59	93.39
CSRS-PPP	299.59	99.98

The processing method with the highest confidence is CSRS-PPP. This measured the prominence is 299.59ft, and the prominence is less than 300.0ft with greater than 99.9% confidence.

Discussion

Columbia Point has less than 300ft of prominence, thus it does not qualify as a Centennial Peak. It is in fact a sub peak of Kit Carson Mountain. The final elevation of the summit is 13,985.9ft +/-0.1ft, and key col 13,686.3ft +/-0.2ft (NAVD88 vertical datum using GEOID18, NAD83(2011) Epoch 2025.7 horizontal datum), with prominence 299.6ft +/-0.2ft.

LiDAR under-measured the summit by 0.2ft because it missed the very top of the boulder on the summit. LiDAR under-measured the key col elevation by 0.5ft because it hit a point below the col and not the exact location of the col. Both of these results are within the +/-1.7ft 95% confidence interval of LiDAR summit elevations reported previously (Gilbertson et. al. in review). These LiDAR measurements resulted in the LiDAR – derived prominence being 0.3ft too high.

The CSRS-PPP method resulted in a more precise result with lower sigma values than the TrimbleRTX methods. One possible reason for this is that TrimbleRTX uses estimated satellite positions, while CSRS-PPP uses reported positions, which are generally more accurate.

Columbia Point should be removed from the Colorado Centennials list. This means Niagara Peak, formerly considered the 101st tallest peak in Colorado based on LiDAR, should be added to the Centennials list. The current order of peaks near the cutoff for inclusion by elevation based on LiDAR-derived summit elevations is now Peak 13820 (#97, 13,820ft), Arrow Peak (#98 13,817ft), Trinity Peak (#99 [tie], 13,816ft), Niagara Peak (#99 [tie], 13,816ft), Teakettle Mountain (#101, 13,815ft), American Peak (#102, 13,814ft), Dallas Peak (#103 [tie], 13,812ft), Obstruction Peak (#103 [tie], 13,812ft).

Given that we have previously measured errors up to 3.1ft in LiDAR-derived summit elevations for above-treeline peaks in Colorado (for Crestone Peak, Gilbertson et al. in review), a conservative error bound would be +/-4ft on any of these elevations. This means all eight of these peaks are edge-case peaks. Only four of these eight are true Centennials, and the other four are too short to qualify. Future work includes surveying each of these edge case peaks with dGNSS surveys. Until that is completed, it will not be known for certain which are Centennial Peaks. Accuracy-minded mountaineers could climb all eight to be certain to have completed the list.

Data Availability

Raw measurement files (t04 format) can be accessed at https://github.com/ericgilbertson1/ColumbiaPoint

References

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© 2025, egilbert@alum.mit.edu. All rights reserved.