Having worked in cold weather for a long time, including the Arctic, this seemingly 'unimportant' little correction has become the demise of a few aviatiors and their passengers over the years. Yes it is important and Yes, there is a procdure and Yes there are charts for it.
Take for instance, KMSP (Minneapolis-St. Paul). They get their fair share of cool temperatures as well. (I don't have the ANC Chart at the moment).
ILS 12 L
The MDA is 1039 (200ft)
ATIS giving temperature of -30C
So, what to do? Well, for starters it's important to understand why this altimeter error occurs in the first place. No matter what type of aircraft we fly, be it a small single engine Cessna or a modern state of the art transport category airliner, the pressure altimeters are all sensitive to non-standard temperatures. With temperatures less than standard (15C) the colder it gets, the larger the errors become. This is all because the air molecules become more dense at colder temperatures and by virtue of the density it takes a smaller climb or descent in colder temperatures to affect a large reading on the altimeter in the airplane.
First off, where do we get the correct information? Well, there are several places. Jeppesen provides a nice chart on Page 244, Air Traffic Control. Transport Canada's AIP also has a chart and there are others as well.
There is a rule of thumb that can be applied to surface temperatures of above -15 C, and that is a correction of 4% height increase for every 10C below standard. The charts are more accurate.
Now back to our problem...KMSP....
The 'additives' are always made on the height above the ground, which means to say, the supposed actual true height above the ground, not the altitude with respect to MSL. This can be a source of confusion at times.
The MDA for this ILS is 1039 MSL or 200ft AGL and it is the 200 ft AGL that we want to correct.....so, into the Jepp Chart we find that at a temperature of -30C and at a height of 200 ft, the correction is 40 feet.
We now complete the calculation by adding the 40 feet to the MDA, which is:
1039
plus 40
---------
1079 MSL
Therefore, the corrected MDA for this approach becomes: 1079 ft. If we had NOT made the correction for this approach and we were flying down to limits because of poor weather, we would actually have descended BELOW the legal height limit for this approach by 40 feet and with respect to regulations, broken limits.
In a radar envioronment, corrections for maneuvering is made by ATC, although their numbers need to be checked every now and then. Take for instance, if we were maneuvering in the KMSP area, with no radar and there happened to be a procedure turn of 5000 feet MSL which is close to 4200 AGL....using the same temperature of -30C, the correction becomes important...using the chart again...the correction becomes significant. A correction of 798 feet is actually required at this height.
So.... 5000
plus 798
--------
5798 MSL
Some airline operators provide their crews with 'tailor made' charts that have corrections for all heights found on approach charts, a few being DH/MDA, Fix Crossings, MAP altitudes, transitions to approaches, Circling minima and MSAs.
This procedure is often over looked and those who have operated in cold weather operations and have never made the correction, have technically been descending below legal minima. Unless the rules have been changed recently, failure to apply the corrections, either on a simulator ride or a line check during cold weather operations in Canada, results in a FAILURE of the ride.