Discrepancies Between Thirteener Lists

The following discrepancies exist between the Lists of John “California Thirteeners List” (independently developed by John Kirk) and the VRMC California Thirteeners List :

1. Mr. Kirk passes Mt. Muir with an interpolated 331' saddle depth. We measured this saddle depth using several altimeters on 22-July-2000, and it was only 276'. The new 10m DEM data show a 92m (301.83727') saddle depth, whereas the older 30m DEM data showed 98m (321.52231). I never pass up a chance to climb this peak on the way to Mt. Whitney, but it narrowly misses the VRMC ranking criteria.

2. He passes UTM769620 (which he refers to simply as “13720”) with an interpolated 301' saddle depth. RidgeWalker extracted a saddle elevation of 4094m (13,431.759') resulting in a saddle depth of 90m (295'), even when using (as is my convention) the highest DEM summit elevation (4184m), rather than the surveyed summit elevation (4182m) to compute this depth. This peak should certainly be climbed, but it narrowly misses the VRMC ranking criteria.

3. He fails “Twelve Flags Peak” with an interpolated 280' saddle depth (based on interpolating both the summit and saddle elevations). I performed an altimeter measurement on 25-Sep-2004 of 340', and this is consistent with the contour data (summit elevation 13,460'+/-20' less saddle elevation 13,180'+/-20' = saddle depth 280'+/-40'). Although this was only a single altimeter, the easy terrain allowed for a fairly accurate reading. I consider this the best available data, so it narrowly passes the VRMC criteria.

4. He fails the Clyde Spires (West Peak) (which he refers to as “Clyde Spires”) with an interpolated 280' saddle depth. Based on the 13,267' spot elevation on this ridge from the old Mt. Goddard USGS 15' quadrangle, summit photography and climber reports, I believe “Crumbly Spire” is the high point on this ridge, and that it narrowly passes my critiera. For more details, see the Clyde Spires Analysis page.

5. He passes UTM751908 (which he refers to simply as “13264”) with an interpolated saddle depth of 305'. RidgeWalker extracted a saddle elevation of 3954m (13,431.759') resulting in a saddle depth of only 91m (299'), even when using the highest DEM summit elevation (4045m), rather than the surveyed summit elevation (4043m) to compute this depth. This peak should certainly be climbed, but it narrowly misses the VRMC ranking criteria.

6. He fails “Picture Peak” with an interpolated 280' saddle depth (based on interpolating both the summit and saddle elevations). RidgeWalker extracted a summit elevation of 4005m (13,139.764') and a saddle elevation of 3912m (12,834.646'), resulting in a saddle depth of 93m (305.11811'). I’m hardly confident that this does indeed pass, but I’m still going to rank it for now.

7. He passes Ericsson Crag 1 (which he refers to as “Ericsson Crags South”) with an interpolated 328' saddle depth. RidgeWalker extracted a saddle elevation of 3915m (12,844.488'), resulting in a saddle depth of only 85m (279'). This peak should certainly be climbed, but it narrowly misses the VRMC ranking criteria.

8. He passes “Sky Pilot Peak” (which he refers to simply as “13024 A”) with an interpolated 13,024' summit elevation. RidgeWalker extracted a summit elevation of 3962m (12,998.688'). This peak should certainly be climbed, but it narrowly misses the VRMC ranking criteria.

9. Several peaks receive different rankings due to straight interpolation of saddle elevations (as well as some un-surveyed summit elevations) vs. RidgeWalker-extracted elevations from the DEM data. For example, he ranks UTM829540 (which he refers to simply as “13746”) just above 13,741' Mt. Gabb, because his interpolated height of 4190m+/-10m is 4190m (13,746.719'). However, the high point RidgeWalker found in the DEM data is only 4183m (13,723.753'), and this seems consistent with the relatively gradual slope in the summit area and the relatively small area bounded by the 4180m contour line. Thus, I think it’s more likely that Mt. Gabb is actually higher than UTM829540.

Why I Favor Using Digital Elevation Model (DEM) Data

Mr. Kirk uses straight interpolation of USGS contour data to calculate summit and saddle elevations which have not been surveyed. This is a perfectly reasonable approach. Using the USGS Digital Elevation Models certainly adds more precision to my results. The open question is whether doing so also increases their accuracy. A few clarifying points:

1. As I understand it, nearly all of the DEM data originated from raw contour data. Thus, one could argue that any additional “precision” in the DEM data is really just noise. However, I believe the algorithms used to construct the DEM data from the contour data may actually do a better job of modeling the surface than is possible through simple “jagged model” interpolation. For example, in the DEM data the partial derivatives of height with respect to northing and easting can be made more continuous functions.

   If you graph elevation on the Y-axis, and longitude along the X-axis for any east-west path through a USGS quadrangle, the straight interpolation model assumes that the graph will be a sequence of straight lines connecting points where the path intersects contour lines. In contrast, the DEM construction algorithm would ideally try to smooth out the data so that the DEM points (several between each pair of contour lines) all fell along a curve that was a continuous function intersecting the contour lines. There may be even better models that might statistically give closer approximations based on typical surface feature characters, even region-specific ones (though it’s probably unlikely that the USGS approach was that sophisticated).

   I have sent numerous emails to the USGS attempting to get more details on the methods used to construct the DEM data, some metadata that would give location-specific error bars, etc. Unfortunately, my requests have not yet reached anyone who both knows the answers and is willing to take the time to respond.

2. In some instances I have found gross errors in the DEM data (e.g., a couple of ridiculous data points that I had to remove by hand from the DEM data). The Colorado DEMs had more such problems than did the California DEMs, by the way. In my view, these do not necessarily indicate more serious problems (e.g., local elevation bias, at least when compared to the contour data).

   I have also reported these problems to the USGS, and I hope that they resolve the errors, though it seems unlikely that my feedback has made its way to anyone who could do so.

3. I do expect the DEM data to improve in the future. As it does so, I intend to run RidgeWalker over these updates to provide revisions to my list (as I did when the 10m DEMs replaced the 30m DEMs). This is consistent with my desire to use the best available data for my list (e.g., field altimeter measurements) and to continue updating the list as more data become available.

4. Finally, I do not believe that I have reported any summit or saddle data originating from DEM data that is in conflict with the contour data, though it will nearly always be in conflict with a simple interpolation of the elevation as the value halfway between the contours. Again, I also have (slightly) more confidence in reasonable field altimeter checks than I do in contour data, as long as they are in near agreement.

In summary, I favor spot elevations, then contour data, then field altimeter measurements, then DEM data (in that order). For more details, please see my Methodology page.

Methodology Criticisms

I have the following minor citicisms of the Lists of John methodology:

1. Mr. Kirk apparently truncates his meter to foot conversions, rather than rounding them. For example, he lists the summit elevation of UTM829540 (see above) as 13,746', even though his interpolated summit elevation of 4190m would be 13,746.719' (which I would round to 13,747'). Similarly, he lists the height of UTM690535 (which he refers to as “Kern Ridge West”) as 13,185', even though the surveyed summit elevation of 4019m would be 13,185.696' (which I would round to 13,186').

2. He ranks peaks with summit elevations surveyed at 4113m below peaks with summit elevations surveyed at 13,494', even though 4113m is 13,494.094'. For example, he ranks Mt. Thompson above Mt. Hale (just because Mt. Thompson has a deeper saddle). This is another consequence of the truncation he performs when converting to feet.

3. He ignores survey data from previous editions of USGS quadrangles, even when these data are consistent with (less specific) contour data on newer editions of USGS quadrangles. For example, Mt. Versteeg was surveyed at 13,470' on the old Mt. Williamson USGS 7.5' quadrangle. This is consistent with the contour data on the new Mt. Williamson USGS 7.5' quadrangle, which has no surveyed summit elevation but which puts the summit at an elevation of 4110m+/-10m (13,451.444 to 13,517.06). I also note that the highest summit elevation RidgeWalker found in the DEM data was 4107m, and (once again) the 4100m summit contour bounds a relatively small area. Accordingly, my official elevation of 13,470' puts Mt. Versteeg below Mt. Pickering (official elevation 4107m, or 13,474.409').

4. He doesn’t even list cases where the maximum possible saddle depth is just below 300'. For example, UTM884436 has a surveyed summit elevation of 4151m and a saddle elevation supposedly guaranteed to be above the 4060m contour. However, if the saddle was truly at the 4060m level, UTM884436 would have a saddle depth of 91m (298.55644'), less than 18 inches from his minimum saddle depth. I think this warrants listing among the peaks that were close to meeting his criteria.

5. He doesn’t even list cases where the maximum possible summit elevation is just below 13,000'. For example, UTM447207 has a summit elevation supposedly guaranteed to be below the 13,000' contour, but that 13,960' contour sure encloses a large area. I think this warrants listing among the peaks that were close to meeting his criteria.

6. He doesn’t even list cases where the surveyed summit elevation is just below 13,000'. For example, Vennacher Needle has a surveyed summit elevation of 3961m (12,995.407'), less than 5' from his minimum summit elevation. I think this warrants listing among the peaks that were close to meeting his criteria.

Presentation Issues

I have the following minor criticisms of the presentation of the peak lists on Lists of John:

1. Peaks with interpolated elevations are not identified explicitly in his tables. For example, he lists the summit elevation of UTM829540 (see above) simply as “13,746'”, indistinguishable in form from the summit elevation of Mt. Gabb, which he lists as “13,741'”. In fact, the Mt. Gabb summit elevation has been surveyed at 13,741', whereas the UTM829540 summit elevation has been interpolated from 4190m+/-10m.

2. I obviously prefer referring to unnamed peaks using a method that is both unique and stable (e.g., UTM designation), rather than simply by their (often interpolated and, in my view, inappropriately truncated) summit elevations.