How maximum elevation figures are calculated for a Joint Operations Graphic

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The Calculate Maximum Elevation Figures tool computes the maximum elevation figures for a Joint Operations Graphic (JOG) based on the type of the highest vertical obstruction in a quadrangle. Two obstruction types influence the calculation: man-made and natural terrain. The calculation differs if one type is higher than the other.

Man-made vertical obstruction

When within a designated quadrangle, a man-made vertical obstruction is higher than the highest natural terrain feature plus an allowance of 46 meters (150 feet) for nonrepresented man-made obstructions, the Calculate Maximum Elevation Figures tool follows this process:

1. Determine the elevation of the top of the obstruction above sea level.
2. Add the vertical error of the source material to the above figure.
3. Round the resultant figure up to the next higher hundred-foot level, if necessary, to achieve a complete value in even hundreds of feet. This final figure is the MEF.

Example

Elevation of obstruction top (above mean sea level)    =  2424
Possible vertical error                                = + 250
Sum Vertical error + obstruction top elevation         =  2674
Raise to next higher 100-foot level                    =  2700
Maximum Elevation Figure (MEF)                         =    27

Natural terrain feature vertical obstruction

If at least one of the following conditions exist within a designated quadrangle:

• A man-made vertical obstruction is lower than the highest natural terrain feature plus an allowance of 46 meters (150 feet) for nonrepresented man-made obstructions.
• A natural terrain feature is the highest point.

The Calculate Maximum Elevation Figures tool will compute maximum elevation figures following this process:

1. Determine the elevation of the feature.
2. Add the possible vertical error (one contour interval) of the source to the above figure.
3. Add a 46-meter (150 foot) allowance for natural or man-made obstructions that are not portrayed because they are below the maximum height at which the specification requires their portrayal by an obstruction symbol.
4. Round the resultant figure up to the next higher hundred-foot level, if necessary, to achieve a complete value in even hundreds of feet. This final figure is the MEF.

Example

Highest Terrain Elevation                              =  3440
Possible vertical error                                =   250
Allowance                                              = + 200 
Sum highest elevation, vertical error, and allowance   =  3890
Raise to the next higher 100-foot level                =  3900
Maximum Elevation Figure (MEF)                         =    39