"Robert M. Gary" wrote in message
ps.com...

Are you going to leave us in suspense? What is the MIA based on?


MIAs are established in accordance with FAA Order 7210.37 En Route Minimum
IFR Altitude Sector Charts:



1. PURPOSE. Establishes amended procedures and criteria to develop MIA
sector charts for en route air traffic facilities.

2. DISTRIBUTION. Distributed to offices in Washington and Regional
headquarters, FAA Technical Center, Mike Monroney Aeronautical Center, air
traffic facilities, and Flight Inspection Field Offices.

3. CANCELLATION. Order 7210. 37A, dated March 7, 1980, is canceled. Joint
AFO-700/AAT-300 letter dated May 18, 1981, subject: En Route IFR Altitude
Sector Charts is canceled.

4. ACTION. Each air route traffic control center shall develop and
implement MIA sector charts using these procedures/criteria. Use Appendix 1
for facility status accounting and FIFO chart data review and approval.

5. MIA SECTOR CHARTS. MIA sector charts provide minimum IFR altitude
information for off-airway operations. MIA charts and associated clearance
altitudes are established without respect to normal radar coverage within
the area concerned. It is the controllers responsibility to determine if a
target return is adequate for radar control.

6. MIA SECTOR CHARTING CRITERIA. Establish MIA's with respect to all
surface
areas in delegated airspace as well as adjacent areas where control
responsibility is assumed because of early handoff or track initiation.
Divide the MIA charts into areas (referred to as MIA areas) as required to
accommodate different MIA's without respect to sector or facility
boundaries, as follows:

a. Establish the lateral boundaries of MIA areas:

(1) Using sectional aeronautical charts. The Maximum Elevation
Figures (MEF)
located in sectional quads may be used as a guide to establishing the MIA.

(2) Using geographical points defined by latitude and longitude to
the nearest second.

(3) Addressing operational requirements (i.e., normal traffic
flows, minimum en route altitudes (MEA) where lower than MIA), where
possible.

(4) A minimum of 5 nautical miles (NM) from the terrain/obstruction
used to establish the MIA for each MIA area, except where such
terrain/obstruction is located within 5NM of the lateral limits of an
airway, (or Part 95 direct route or documented non-Part 95 off-airway
route). For the latter, the limits of the airway (or route) will serve as
the associated MIA area boundary.

b. Establish the MIA for each area:

(1) By applying the appropriate mountainous or nonmountainous
obstruction
clearance criteria per Orders 8260.19 and 8260.3. Round the altitudes to
the nearest 100-foot increment.

(2) Within controlled airspace, by ensuring that the depicted MIA
is at least 300 feet above the floor of controlled airspace.

(3) Within uncontrolled airspace, by applying the appropriate
mountainous/nonmountainous clearance criteria without respect to overlying
controlled airspace in paragraph 6.b.(2) above.

Note. - The existence of a MIA in uncontrolled airspace relates to
terrain/obstruction clearance only, it does not constitute authority to
conduct IFR operations within uncontrolled airspace.

Reference. - 7110.65 - Uncontrolled Airspace and Application (Vectoring).

(4) Where an airway MEA is below an adjacent MIA area altitude, it
may be necessary to adapt the airway or an appropriate block of airspace
containing the airway as a separate MIA area to preclude E-MSAW nuisance
alerts. MEA's shall be obtained from en route low altitude charts and thus
become the adopted E-MSAW alerting altitude for an MIA area that defines an
airway. Since radar vectoring along an airway, or radial thereof, requires
greater lateral obstruction/terrain clearance than would normally be imposed
on a flight that has been specifically cleared via the airway, an
independent
check must be made to ensure that vectoring within an MIA defined airway
would not result in reduction of the appropriate clearance criteria.

c. Where small contiguous MIA areas with different altitudes do not
serve an operational need, combine them using the highest applicable MIA.

d. To avoid a large MIA area with an excessively high altitude due to
an isolated prominent obstruction, enclose the obstruction within its own
MIA area. When the isolated obstruction is terrain, evaluate related slopes
or ridge lines to ensure appropriate obstruction clearance criteria is
applied.

e. Each MIA area shall have the terrain/obstruction that constitutes
the basis for the MIA, in addition to its elevation, highlighted in such a
manner that would allow it to be easily found by a controller, but not
clutter the MIA chart. Large MIA areas with irregular or precipitous or
multiple obstructions may have more than one elevation highlighted.

f. MIA areas should be labeled with respect to the E-MSAW area
identification criteria. The identifier has three letters and two digits
(LLLdd), to identify areas relative to significant geographical points or
fixes.

7. MIA SECTOR CHART DISPLAY. Applicable portions of the facility's MIA
chart shall be displayed at each low altitude sector. This MIA sector chart
shall accommodate operational requirements. Air traffic managers shall
determine the appropriate method of displaying this information at the
sector. MIA's shall be displayed with each associated MIA area. For an
airway adapted as a MIA area, (reference paragraph 6.b.(4)):

a. If the MEA is sufficient for vectoring, the MIA and the MEA shall be
depicted as one altitude for that area.

b. If a higher altitude is required for vectoring, then both the
adopted E-MSAW alerting altitude (MEA) and the vectoring altitude shall be
displayed on the MIA sector chart, associated with the proper area, and
separated by a slash (i.e., 90/70). Each sector chart or facility directive
shall contain an explanation of these split altitudes to the effect that:

(1) The higher altitude on the left of the slash is the appropriate
altitude for off-airway operations (radar vectoring).

(2) The lower altitude to the right of the slash is the adopted
E-MSAW alerting altitude.

8. MIA SECTOR CHART PROCESSING. Process MIA charts and altitude reduction
requests per Order 8260.3 criteria as follows:

a. Draw MIA sector charts directly on current sectional charts.

b. Prepare MIA sector chart and chart data record in duplicate.
Indicate amount of obstacle clearance reduction in ALT ADJ (altitude
adjustment) column. This column is also used to document the difference in
required altitude and round-off altitude. Use REMARKS column for
explanation.

c. Forward charts and chart data records to the FIFO for certification
and annual review. One copy of each chart and chart data record with the
FIFO manager's signature will be returned to the facility.

d. Monitor available sources including the weekly National Flight Data
Digest (NFDD) pertaining to construction notices that may affect specific
MIA areas. When needed, revise the affected charts.

e. Verify that the altitude information adapted in the NAS E-MSAW
polygons agree with the MIA sector charts.




I'm not a controller so I don't know what you call it but I know that
when Lemoore approach is open I can fly over Harris Ranch IFR at 2,000
feet but when they close and Oakland center takes over the min is 8000
feet (quite a difference).


That may not be due to the MIA. What's your route? If you're operating
off-airways and beyond normal usable navaid limits radar monitoring must be
provided. If 8000 is required to remain within radar contact with Oakland
then 8000 becomes the minimum altitude even if the MIA is significantly
lower.