/ AIS-AIMSG/2-Flimsy 1
13/11/2009

AERONAUTICAL INFORMATION SERVICES TO AERONAUTICAL INFORMATION MANAGEMENT STUDY GROUP (AIS-AIMSG)

SECOND MEETING

Montréal, 10-13 November 2009

Agenda Item / 9.3: / World Geodetic System — 1984 (WGS-84) Manual (Doc9674)

Flimsy

Presented by the Secretary

SUMMARY
Following the discussions on Study Note No. 16, this flimsy proposes revised draft text for inclusion in Amendment No. 1 of Doc 9674.

1.  USE OF TRANSFORMATION

Once WGS-84 coordinates have been obtained through a transformation established by the local geodetic specialist, it is recommended that the use of transformation to other local reference frames be avoided.

Note: Guidance on WGS-84 calculations are contained in The Quality Assurance Manual for Flight Procedure Design — Volume 3 (Doc 9906).

2.  COORDINATES RESOLUTION

The charting and data publication resolution ranges from the highest resolution requirement of 1/100 sec to the lowest resolution requirement of 1 min (i.e. 1/100 sec, 1/10 sec, sec and min).

Applications or messages processing or transmitting coordinates may have lower different resolution requirements (e.g. flight plan, coordinate entry in FMS by the pilot) however, a resolution of 1/10 min must not be used.

3.  DECIMAL DEGREES

When For applications process processing coordinates in decimal degrees, the resolution is expressed in terms of the number of significant digits of decimal degrees as specified in Table 2-8. For example, a coordinate published in degree, minutes and seconds when transformed converted into decimal degrees will have a resolution value of 4 (e.g. a latitude of 355418N is transformed into a decimal of 35.9050).

1 min = 1/60 degree = 0.166666… is converted into 0.02

2 min = 2/60 degree = 0.033333… is converted into 0.03

3 min = 3/60 degree = 0.05 is converted into 0.05

etc.

1 sec = 1/3600 degree = 0.000277… is converted into 0.0003 2 sec = 2/3600 degree = 0.000555… is converted into 0.0005

3 sec = 3/3600 degree = 0.0008333.. is converted into 0.0008

etc.

Note that when calculations are done on decimal values and depending on the rounding process (single final application or intermediate applications), end results may differ slightly.

. . .

Insert a new table as follows:

Table 2-8Resolution equivalence in decimal degrees.

decimals
Degrees / 0
Minutes / 2
Seconds / 4
1/10 seconds / 5
1/100 seconds / 6