Attachment 11
COMPASS CALIBRATION PAD (CCP) MAGNETIC SURVEY
A11.1. Contents. This Attachment describes the procedures for performing a magnetic survey for new or
existing CCP by a state registered land surveyor. These surveys will determine the following:
A11.1.1. Suitability of a particular site for use as a CCP.
A11.1.2. Variations of the magnetic field within the surveyed area.
A11.1.3. Magnetic declination of the area at the time of the survey.
A11.2. Air Force, Navy, and Marine Corps Requirements. This Attachment does not apply to the
Navy and Marine Corps other than to provide applicable Navy publications where additional information
may be found. USAF designers may use these criteria or the criteria given in Appendix 4 of FAA
Advisory Circular 150/5300-13, Airport Design (see paragraph 6.11.1).
A11.3. Accuracy Requirements. For the purpose of this survey, final calculations should be reported to
the nearest one minute (1') of arc with an accuracy of 10 minutes (10'). Typically, magnetic variations
can be determined to the nearest 30 minutes (30') of arc by using a conventional transit with a compass.
The finer precision needed for these surveys may be obtained by taking a minimum of three readings at
each site and then reporting their average. All azimuths must be established by the Global Positioning
System (GPS) or Second Order Class II conventional control survey referenced to known positions within
the North American Datum of 1983 (NAD83) adjustment network, or convert host nation datum to World
Geodetic System 1984 (WGS-84).
A11.4. Preliminary Survey Requirements. Preliminary surveys are conducted for proposed sites to
assure that the areas are magnetically quiet and thus suitable for a CCP. They are also used to determine if
newly constructed items within the influence zone (see paragraph A11.6) of an existing CCP are causing
magnetic interference. When siting a new CCP, the location should be chosen such that all separation
distances, as defined in paragraph A11.6, are allowed for to the greatest extent practical. A preliminary
magnetic survey will then be conducted to determine if the area is magnetically quiet with no natural or
manmade magnetic disturbances. When conducting the preliminary survey, the surveyor must
immediately notify the agency requesting the survey of any areas they find that are causing magnetic
interferences so they can try to identify and remove the interference and they can also determine if the
survey should continue any further at that time. The location of the anomaly can be pinpointed by taking
readings at additional points around the disturbed area and finding the location with the highest
disturbance. If the magnet anomaly cannot be removed and the site made magnetically quiet, then a new
site will need to be chosen. One of the following methods is suggested for a preliminary survey.
A11.4.1. Proton Magnetometer Method. A proton magnetometer can be used by walking over the
area and making observations approximately every 6 meters (20 feet.) in a grid pattern covering the
site. If the values measured do not vary from any other reading by more than 25 gammas for the whole
area, then the site can be considered magnetically quiet.
A11.4.2. Distant Object Method. A distant landmark is selected for siting from the various points, 6
meter [20 foot] grid pattern, of the area being checked. A second distant object at approximately 90
degrees (90) can also be chosen to increase accuracy. The further away the distant object is, the wider
an area of points that can be compared to each other and still obtain the accuracy needed. An 8
kilometer (5 mile) distant object will allow a comparison of magnetic declinations of points that are
within a 24 meter (80 foot) wide path in the direction of the distant object; while a 24 kilometer (15
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