| Line Parent Definition The line parent of a given peak is the nearest higher peak on the prominence line. Table of Contents
In defining "Line Parent" I assume you have already been introduced to Mountain Prominence, and know that every mountain has exactly one "key saddle" joining it to higher terrain. A loose definition of "line parent" is that it is the first higher peak you come to as you travel the steepest uphill path from the key saddle. In almost all cases, the "line parent" is the first higher peak on the highest ridge leading away from a given peak. The discussion in this document is more technical, because it deals with database stability issues with regard to line parent data. The simple minded rule is that the line parent is the first higher peak that is in the database". But that rule is unstable if the database is continually expanding. What we want is a rule that allows us to "skip over" low prominence bumps when filling in distant line parent data. This will be much more stable as the database is expanded. If we don't have a "skip over" rule, then we have a major database stability problem, because every time you add a new subpeak you need to fix dozens of distant peaks. Eg: As soon as you add Lunette Peak (prominence 28 meters), then all the peaks south of Assiniboine should technically have Lunette as their LineParent. The situation is never stable, because there is always demand to put new subpeaks into the database, to correspond with particular trip reports or climbs. So our first "stability enhancement" is to ignore low prominence subpeaks when setting the line parent for a distant peak. Specifically, ignore any peak less than P300 if a given peak is a long way away. So peaks in the same massive should be properly linked to their technical subparent, no matter how small the prominence, but distant peaks can just refer to the main peak. So Joffre can just refer to Assiniboine directly, and skip over Lunette. The definition of "a long way away" is defined as a ratio. If the remote peak is more than ten times the subpeak distance, then it is "far away". Eg: The subpeak separation of Lunette is 1 km, so any peak more than 10 km away should just skip over Lunette and use Assiniboine as a parent.
(Just go down the list of direct dependants for Assiniboine, and decide which should truly be linked directly to it). In the above, Joffre goes to Assiniboine directly, and skips over Lunette, because it is more than 10 km away. Mount Seymour This is an example where there are numerous low prominence subpeaks in a local area, and all of them are linked to their technical line parent, and no peaks are skipped. This example works perfectly with our rule. No peak is more than ten times the subpeak distance. Ulysses and Fairweather Example This is the case of several unnamed peaks between a given peak and a distant well known peak. Ulysses is about 800km away from Fairweather, and between them is Mount Root and also three nnamed subpeaks, all higher than Ulysses:
So one temptation is to just put Fairweather as the parent of Ulysses. Or at least Root. The way it is on the database as of 5.102 is that the lineparent chain shows every peak above P300, regardless of distance. (the rule is never to ignore P300 peaks). If this proves to be REALLY undesirable, then I suppose we could raise the threshold from P300 to P500 if the distance is more than 100 km. (Or a ratio, like if distance is 800 km, then threshold is 800m, if distance is 600 km, then threshold is 600m. (With this rule, Ulysses could be "wired" directly to Root (P918), and we could jump over the obscure Root N7, Root N6, etc. But of course once someone has done the more detailed work, no-one should "undo" that work unless there was some other bug or confusion and you were redoing the whole thing. Murray Peak, Mull Peak Initially the database had Murray S2 linked directly to Mull. By the ratio rules, this is clearly a mistake, because Murray is too close. Therefore the line parent was changed to Murray Peak. Readers of this Page
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