Chart Legend
--Tint colors range from light green to brown. The top color gives highest elevation. All shading is based on lighting from the northwest. Contours are basic at 500’ apart with intermediate contours down to every 50 feet.
--Boldface dot and number gives critical highest elevation. Other elevations are not boldface. An x marking an elevation is only approximate.

Jeppesen IFR Chart Legend (Right Click To Download)

Highlight the Approach Plates:
--Main NAV frequency
--Final approach heading
--First part of missed approach
--Minimum descent altitude/decision altitude
--Time
--Missed approach fix

Approach Plates
--10mile distance rings are not limitation unless stated as a limitation.
--Only data within the reference circle is drawn to scale.
--Other dashed circles used to give information but not to scale
--When distance is stated as "remain within" it is a critical safety altitude and distance.
--Primary area gives 1000 feet of clearance
--Secondary area gives 500 feet at innermost edge tapering to zero at the outer edge.

IFR Charts
The top heading boxes contain the frequencies most likely to be required in the order of common use. If multiple frequencies exist they will appear on other charts. An asterisk means part-time use and CTAF appears. Approach charts are diagramed and listed under the assumption that they will be used for arrival. Airport diagram charts have frequencies listed as for departure.

Chart NOTAMs
These change with every new issue of Jepp charts. En route charts are listed first then terminal charts. These highlight things that did not arrive in time for inclusion in the new charts issued. these must always be updated by requesting NOTAMs from the FSS prior to flight.

The Mean Level of the Sea
Water level measurements at primary tide stations show that the problem is somewhat more complex than that. For one thing, mean sea level measured relative to the land - is changing.

Today, global sea level rise is occurring everywhere due to increases in water volume in the world's oceans. But the chief reason for the difference in trend shown above lies within the earth's crust.

Along with most of the U.S. East Coast, falls within a region where the crust is sinking – adding to the effect of a global rise in sea level. However, in many parts of the U.S. West Coast, and especially in Alaska, the crust is actually emerging faster than the global sea level rise rate.

Tidal Factors
Nothing is going to prevent sea level from changing in response to these and other factors. However, we can take sea level averages over several years to obtain a tidal datum - a vertical reference based on some phase of the tide - to slow the process if only temporarily. This is a workable idea because, in addition to sinking crusts and melting ice, tidal variations also have their effect on sea level.

One such effect is the 18.6-year cycle of the lunar nodes – a cycle accompanied by variations in tidal range. Another force for change is the annual variation in solar declination that modulates solar heating and density of ocean waters.

To account for both, a 19-year period of water level averaging – the National Tidal Datum Epoch (NTDE) – has been established in the United States. NTDEs have included the years 1924-1942, 1941-1959, 1960-1978, and most recently, 1983-2001. NTDEs thus are being updated roughly every twenty years.

1) Why nineteen years and not twenty?
"We can take sea level averages over several years to obtain a tidal datum - a vertical reference based on some phase of the tide - to slow the process if only temporarily. This is a workable idea because, in addition to sinking crusts and melting ice, tidal variations also have their effect on sea level.

One such effect is the 18.6-year cycle of the lunar nodes – a cycle accompanied by variations in tidal range. Another force for change is the annual variation in solar declination that modulates solar heating and density of ocean waters.

Basic definitions commonly used in the U.S. and its territories:
Mean Sea Level (MSL) Arithmetic mean of hourly water levels observed during current NTDE.
Mean Higher High Water (MHHW) – Mean of higher high water heights during current NTDE.
Mean High Water (MHW) – Mean of all high water heights observed during current NTDE.
Mean Low Water (MLW) – Mean of all low water heights observed during current NTDE.
Mean Lower Low Water (MLLW) – Mean of lower low water heights during current NTDE.
Mean Tide Level (MTL) – A datum located midway between MHW and MLW
All tidal datums have elevations above some arbitrary but well-protected reference – usually the station datum or staff zero

Tidal Datum Transfers
1) Tidal datum elevations vary from place to place as dictated by tide wave hydrodynamics
2) Establishing the datum by direct means (19-year series every 20 years) is an exacting and expensive operation conducted at a relatively small number of primary tide stations. Fortunately, there's an easier way called simultaneous comparisons.:

At a primary tide station, get the NOS tidal datum elevations for the current NTDE.
--Obtain a month of tidal observations at station B matched by simultaneous readings at station A.
--Calculate monthly mean tide level at both stations
--Calculate the monthly mean range and the range ratio between the stations
--If stations A and B are connected by a tidal waterway and we assume that both experience similar monthly deviations from mean tide level.

There are 175 stations all over the world. Here's a link that allows you to see each station:
http://co-ops.nos.noaa.gov/usmap.html
http://co-ops.nos.noaa.gov is a very cool web site! Check it out!

Altimeter Setting:
Any altimeter setting more than five miles from the ARP affects the landing minimums. No remote setting can be used beyond 75-miles or different than 6000 feet.

Minimum Sector Altitudes
MSA give 1000' obstruction clearance within 25 NM including mountains. MSA is measured from markers on ILS approaches, the NDB on NDB approaches and runway threshold on GPSs. MSA does not apply in mountains, which require 2000' obstacle clearance.

Minimum Safe Altitude
The Minimum Safe Altitude (MSA) circle has nothing to do with the approach or the initial approach altitude or the approach segments or the procedure. The MSA is for emergency purposes only. Minimum vector altitudes (MVA)are usually below the MSA. The required obstacle clearance (ROC)of the TERPS procedures for making an instrument approach procedure also set that the ROC of the MSA must be 1000’ higher than any obstacle within the circle. The MSA circle may be divided into sectors for any approach except for the GPS approaches. The MSA is essentially a non-functional part of the approach plate.

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