Document ID: chunk:federal_register_of_legislation:F2021L01154:reg:12:p4
Version: federal_register_of_legislation:F2021L01154
Segment Type: reg
Provision Reference: reg 12 (pt 4/4)
Character Range: 24578–26976

the purpose of calculating hs where the latitude or longitude of the radiocommunications transmitter as defined in Schedule 1 corresponds to a DEM-3S cell boundary is provided in the document titled 'Digital Elevation Model Interpretation' available, free of charge, on the ACMA's website at www.acma.gov.au.

Diagram 1 Calculating effective antenna height

Part 2  Average ground height
   1. The average ground height at the mth increment on the nth radial is calculated as follows:
    Step 1: Determine the associated latitude and longitude of the mth increment on the nth radial (lmn, Lmn) as calculated in Part 3 of this Schedule.
    Step 2: Identify the DEM-3S cell represented by (lmn, Lmn).
Note: See item 2 below for identifying the DEM-3S cell in a particular case.
    Step 3: Bound the identified DEM-3S cell with the 8 adjacent DEM-3S cells in a 3 x 3 matrix and obtain each DEM-3S cell height attribute (as shown in Diagram 2).
    Step 4: Determine the average value of the 9 DEM-3S cell heights for each cell in the the 3 x 3 matrix.
Diagram 2 Calculating average ground height
   2. If the seconds component of (lmn, Lmn), plus 1.5, has a modulus of zero when divided by 3, then the corresponding DEM-3S cell, for the purposes Step 2 in item 1, is the adjacent DEM-3S cell with the minimum height.
Note: Additional information for the case where (lmn, Lmn) corresponds to a DEM-3S cell boundary is provided in the document titled 'Digital Elevation Model Interpretation', available, free of charge, from the ACMA's website at www.acma.gov.au.

Part 3  Vincenty's Direct Formulae
Note: This implementation of Vincenty's Direct Formulae uses the parameters from the GRS80 ellipsoid as referenced by GDA94.
   1. In calculating (lmn, Lmn):

lt     is the latitude of the fixed transmitter (decimal radians)

Lt     is the longitude of the fixed transmitter (decimal radians)

α      is the azimuth angle (decimal radians)

d      is the separation distance to required point (m×100 metres)

a      is the semi-major axis with value 6378137 metres

fl     is the flattening of the value 1/298.25722210

b      is the semi-minor axis of (a×(1-fl))

   2. Using an initial value , iterate the following three equations until the change in  is less than 10-12.

   3. Then:

Note: Use the four-quadrant inverse tangent, atan2.

Note: Use the four-quadrant inverse tangent, atan2.