Working on finding information on Altimeters, wondering what the relevance is found this bit of information:
NOTICE
U.S. DEPARTMENT OF TRANSPORTATION FEDERAL AVIATION ADMINISTRATION
Air Traffic Organization Policy
N JO 7210.907
1. Purpose of This Notice. This notice revises the requirements for facility altimeter equipment and altimeter comparison checks.
2. Audience. This order applies to all FAA and FAA-contract personnel, FAA Technical Operations, Limited Aviation Weather Reporting Stations (LAWRS) personnel, Non-Federal Observation (NF-OBS) Program personnel, as well as United States Coast Guard (USCG) personnel, as a component of the Department of Homeland Security and engaged in taking and reporting aviation surface observations.
3. Where Can I Find This Notice? This notice is available on the MyFAA employee website at https://employees.faa.gov/tools_resources/orders_notices/ and on the air traffic publications website athttp://www.faa.gov/air_traffic/publications/.
4. Explanation of Policy Change. This change revises the requirements for facility altimeter equipment and altimeter checks.
5. Procedures. FAA Order JO 7210.3. Amend the following paragraphs to read as follows:
1−2−4. ABBREVIATIONS
Title through SWAP, no change
Abbreviation Meaning
SAWS . . . . . . . . . .Stand Alone Weather System
SWAP . . . . . . . . . .Severe weather avoidance plan
SWS . . . . . . . . . .Surface Weather System
2−10−3. ALTIMETER REQUIREMENTS
a. At least two sources of altimeter setting information, or an approved pressure standard, are required in a TRACON, radar approach control (RAPCON), terminal radar approach control in tower cab (TRACAB), combined center/RAPCON (CERAP), radar ATC facility (USN) (RATCF), tower cab, and a FSS that takes weather observations and/or provides Local Airport Advisories (LAA). When two or more facilities are located on the same airport, the requirement may be reduced to one source of altimeter setting information per facility. Aircraft altimeters must not be used in reporting altimeter settings.
b. Each of the following systems is considered to be one (1) source of altimeter setting information for the purposes of this paragraph:
1. Automated Surface Observing System (ASOS)
2. Automated Weather Observing System (AWOS)
3. Stand Alone Weather Sensor (SAWS)
4. Surface Weather System (SWS)
5. Digital Altimeter Setting Indicator (DASI)
6. Altimeter Setting Indicator (ASI)
c. ASOS, AWOS, SAWS, and SWS systems are considered approved pressure standards for the purposes of this paragraph. No further changes to paragraph
https://www.faa.gov/documentLibrary/media/Notice/N_JO_7210.907_Altimeter_Requirements.pdf