ORS (Spire Measure) Home Page

Welcome! This part of the peaklist.org site is dedicated to peak lists based on omnidirectional relief and steepness (ORS), formerly known as spire measure, which measures a peak by height and steepness above local terrain, and lists based on reduced ORS (RORS), formerly known as reduced spire measure, which also includes a measure of the independence of a peak from higher-ranking peaks. These measures provide ways of measuring and ranking mountains which are different from both height and prominence. They also lead to an interesting measure of the ruggedness of a mountain region, called domain relief and steepness (DRS).

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Nomenclature alert!

We have recently changed from using the term "spire measure" (SM) to the more prosaic, but hopefully less misleading, "omnidirectional relief and steepness" (ORS). The term "reduced spire measure" (RSM) has become "reduced ORS" or simply "RORS". Some, but not all, of the pages on this site have been changed to reflect the new terminology.

ORS (Spire Measure) in Brief

Omnidirectional relief and steepness (ORS) is a purely objective mountain measure which takes into account how high the peak rises above local terrain, and how steeply. Since it is a local measure it does not take absolute elevation into account, only the relative height of the peak above its surroundings. So for example a lot of the Colorado Fourteeners get low ratings, since many of them are not very steep and rise from high bases.

Also, it is an omnidirectional measure, so it averages out how steep a peak is in all directions. Hence something like El Cap gets a pretty decent rating, but not as much as if it were a spire which was sheer in all directions. Hence the old name "spire measure"; while something does not have to look like a spire to get a decent spire measure, the more a peak is shaped like a big, steep pointy spire, the higher its spire measure will be. However ORS measures any landscape feature, not just spires; hence the new name.

ORS thus roughly measures the visual "impressiveness" of a peak, since peaks which rise high and steeply above their surroundings tend to be the most visually impressive. ORS also acts as a very rough measure of how difficult a peak is to climb, since it factors in steepness and height. However there are many other factors which determine how impressive a peak looks (a subjective notion, after all) and how hard a peak is to climb. It is important that ORS is not claimed to match any particular person's notion of impressiveness or climbing desirability. Click here for a detailed explanation of ORS.

RORS (reduced spire measure) in brief

There is another related measure called reduced ORS (RORS), formerly reduced spire measure (RSM), which combines ORS data (local relief and steepness) with the peak's degree of independence from nearby better peaks. Roughly, it takes the spire measure of the peak in question and subtracts off a piece for each nearby better peak, based on how close together they are.

What "close together" means depends on the characteristic scale of the peaks in question. For example, Denali and Foraker are about 20km apart, but on the scale of these peaks, that is not very far. Hence Foraker's RORS is significantly lower than its (unreduced) ORS.

The main reason for introducing RORS is to make "Top N" lists like the ones on this site. As mentioned on the prominence sections of this website, in a purely height-based list one has to introduce some cutoff to disallow subpeaks. One can do the same for a purely ORS-based list. However RORS has the property that an insignificant subpeak will automatically get a very low RORS value. So it makes sense to list peaks by RORS, with no arbitrary cutoff whatsoever.

Most of the lists on this site include both RORS (reduced spire measure, RSM) and ORS (spire measure, SM), and are ranked by RORS. You may prefer to concentrate on the "ORS/SM" column if you do not value a peak's independence very much. This is a personal preference which varies widely. However both ORS/SM and RORS/RSM are (necessarily approximate) meaningful measures, and good ways of describing interesting peaks.


ORS (spire measure) and RORS (reduced spire measure) were developed jointly by David Metzler and Edward Earl, with significant inspiration and prodding from Bob Bolton, and feedback from various members of the prominence@yahoogroups.com discussion group, notably Andy Martin and Steve Gruhn.
(More about the history of spire measure.)

The author and maintainer of the ORS (spire measure) section of peaklist.org is David Metzler. All calculations are by David Metzler. Acknowledgements of source data and notes can be found on the individual list pages.

Any comments or questions are very welcome:

metzler (at) aa (dot) edu

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