Yes you are absolutly right, i did’nt look so far to I/LG-325.
May be i will plan a walk to this Col (as i live near the french/Italian border) and bring my GPS to check
the height properly…
73 and thanks for info. Gerald
Not so - it only needs to be done once!
When I was preparing the data for YU association, I used 1:25.000 scale topo maps. In my country these maps are available for anyone who pays for them.
I have found that google maps are very inaccurate, i.e. unusable for final height measurements.
As Gerald F6HBI suggests, maybe a simple handheld GPS, properly calibrated, would be fine to check the height of the col - of course, if SOTA Summits team finds that those measurements are reliable. If the col height is really critical, then a professional grade instrument (as on your photo) would be the only choice. As far as I know, some new SOTA summits in G association have been recently resurveyed with these instruments.
That’s correct Fric. There is a group in the UK who maintain the Marilyn summit list who used surveying grade GPS to check summits which they think have a measurement uncertainty.
What this long thread shows is how very difficult it is to get a definitive list of summits. In this thread we have seen a mountain listed as 1245m and 1248m. I looked and on Open Topo Maps it is shown at 1250m. Which is correct? The summits team spend a lot of time and effort locating definitive mapping. I’m not sure the source used in Italy’s case but it will have been something more accurate than the RADAR and SRTM data used by Google.
So everyone can see how much effort can go into checking a summit is P150. When you can see the prominence is much more than P150 it is easy to be sure. But when it nears 150m (140-150) then you have to do lots and lots of work to be sure. The summits team have a number of software packages to help with the task. But in the end someone has to look at the maps.
All of this discussion about 1 summit. There are another 3663 in Italy. This should make the scale of the work done by the summits team clearer to everybody involved.
I should clarify about proper topo maps, since Gab IZ1KSW asked specifically about this
(I guess this might be of interest for anyone who calculates summit prominences and uses topo maps).
I consider the maps with smallest contour interval to be the best, since almost all col heights, and some summit heights, are calculated from the contour lines.
1:25.000 scale topo maps I used, have contour interval of 10 meters. On some areas on the map (but not all), there are 5 m and 2.5 m subdivisions. Still, there are summits where a 1:25.000 map can not give a yes-or-no answer if the prominence is P150, so those summits are discarded, left to be checked with better maps or with GPS some day.
Larger scale maps (1:10.000, etc) are clearly much better. Those who have access to them are really lucky!
1:50.000 scale maps look fine at the first glance, but if the contour interval is 20 meters (as it is in my country), these maps are not the best choice.
73 Fric YU1WC
Thaks for the info Fric.
I think the “official” topo maps for Italy are from the Military Geographic Institute (I.G.M.) and despite being quite expensive are generally outdated. But it’s definitely worth having a look.
73s IZ1KSW - Gab
This varies from country to country, Fric. Sometimes it varies even within one country at a given scale, with some areas having a much finer contour interval than others.
What you describe when you say you can demonstrate by the contour lines that a summit has the required prominence is what we call the “clean” (or “clear”) prominence. It does indeed get more difficult to be sure when you want to go beyond that.
However, just because a map has more contour lines doesn’t mean it’s more accurate! For instance, Open Street Map looks just fine, but with SRTM-based contours it doesn’t really tell us anything we didn’t already know and is not particularly accurate. I’ve seen examples of a massive lump in elevation in the middle of a lake for example. I don’t mean an island - I mean the water coming up out of the page!!
I have access to 1:5.000 topo maps with contours. Contours have interval of 5 meters. This should be fine for the job.
Unfortunately, are Liguria (LG) only.
Caucaso summit is over 1245m, while the col is under 1085. A GPS survey may help, but I believe in the paper.
I would consider to check up all the LG summits with new accurate maps, using the 3d models to pick up faster the most probable cols. It seem like a job for retired…
When I shared my thoughts with the local Wikimedia manager, he clearly told me that OSM is far from being accurate by the heights but someone is working on it…
the Col to validate Caucaso is there at 1085m. 44.28’22.40’‘N, 9.13’49.36’'E
There is a plate to commemorate a death during the war.
(Dal Passo del Gabba Confluenza su AV) Marcia 40 minuti
Dal Passo del Gabba, quota 1108 metri, si continua a sinistra sulla strada principale, percorrendo un lungo
tratto pianeggiante, comodo e largo, segnato con quadro e triangolo rossi e pieni. Arrivati ad un intaglio
roccioso con lapidi che ricordano un delitto in tempo di guerra, la strada scende con pendenza elevata fino
ad un fosso a quota 1075 metri. Subito dopo inizia una salita tortuosa e sempre sotto la faggeta. Si transita
davanti alle sorgenti dell’Aveto e si contorna il Monte Larnaia, arrivando al culmine della salita. In
seguito il percorso scende leggermente, incontrando una sbarra che impedisce l’accesso alle auto e
confluendo sull’Alta Via in prossimità di un cippo marmoreo. Siamo a quota 1125 metri, dopo tre ore e
10 minuti di marcia dal Passo della Scoglina.
Ciao da F6HBI
Maybe more than one of them is “correct”. What vertical datum is each of them referenced to? The figures don’t mean much unless you specify that.
Actually the figures also don’t mean much unless we have some idea of the accuracy of the determinations - error bars would be a help!
To be clear about the process I have written a blog entry giving more information on the methodology and data sources used for the update of the Italian summits list. You can find it here:
Simon, G4TJC - Summits Team
thanks for the post, it’s really interesting and informative. Having this grade of transparency on the process of referencing the summits really helps to understand the validation process.
Looking forward to helping fixing the possible errors and inaccuracy that inevitably happens in a such huge work.
73s IZ1KSW - Gab
That’s exactly what it needs. Some local people who can validate marginal hills to be either in or out of the SOTA programme.