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Calculate the MEF for a TPC

Available with Production Mapping license.

The Calculate Max Elevation Figures tool computes the maximum elevation figures for a Tactical Pilotage Chart (TPC) based on the type of the highest vertical obstruction in a quadrangle. Two obstruction types influence the calculation: human-made and natural terrain. The calculation differs if one type is higher than the other or if the obstruction is below sea level.

Human-made vertical obstruction

If the highest vertical obstruction within a quadrangle is a human-made feature, the Calculate Max Elevation Figures tool follows this process:

  1. Determine the elevation of the top of the feature (above mean sea level [MSL]).

  2. Add the vertical error figure (vertical accuracy factor of data/source).

  3. Round the resultant sum to the next higher hundred-foot level for the final figure.

Note:

The resultant figure is not rounded up to the next higher hundred-foot level when it is an even multiple of 100.

Example

Elevation of Vertical Obstruction (top, above mean sea level)  =  6265 ft.
Possible vertical error                                        = + 250 ft.
Sum vertical error and elevation                               =  6715 ft.
Round to next higher 100 ft. level                             =  6800 ft.
Maximum Elevation Figure (MEF)                                 =    6<sup>8</sup>

Natural terrain feature vertical obstruction

If the highest vertical obstruction within a quadrangle is a natural terrain elevation, the Calculate Max Elevation Figures tool follows this process:

  1. Determine the highest natural terrain elevation.

  2. Add an allowance of 61 meters (200 feet) for nonrepresented natural or human-made features.

  3. Add the vertical error figure (vertical accuracy factor of data/source).

  4. Round the resultant sum to the next higher hundred-foot level for the final figure.

Note:

A resultant figure is not rounded up to the next higher hundred-foot level when the addition results in an even multiple of 100.

Example

Highest natural terrain elevation (above mean sea level)       =  10115 ft.
Allowance                                                      =    200 ft.
Possible vertical error                                        =  + 250 ft.
Sum elevation, allowance, vertical error                       =  10565 ft.
Round to next higher 100 ft. level                             =  10600 ft.
Maximum Elevation Figure (MEF)                                 =    10<sup>6</sup>

Highest feature is below sea level

If the highest vertical obstruction within a quadrangle is below sea level (BSL), the Calculate Max Elevation Figures tool follows this process:

  1. Add the BSL value to the 61-meter (200-foot) allowance, for nonrepresented natural or human-made features.

  2. Add the vertical error figure (vertical accuracy factor of data/source).

  3. Round the resultant sum to the next higher hundred-foot level for the final figure.

Note:

A resultant figure is not rounded up to the next higher hundred-foot level when it is an even multiple of 100.

Example

Highest terrain elevation (above mean sea level)               =  - 150 ft.
Allowance                                                      =    200 ft.
Possible vertical error                                        =  + 250 ft.
Sum elevation, allowance, vertical error                       =    300 ft.
(Even hundred - do not round)                                  =    300 ft.
Maximum Elevation Figure (MEF)                                 =     0<sup>3</sup>