The more I use our airplane’s new technology the more I appreciate what it gives us, but I have also discovered some areas that, so far, the technology appears to have missed. One skill that I fear may be lost is chart reading. There is a big difference between a chart and a map. The new technology provides moving maps — not moving charts.
CHARTS, NOT MAPS — WHY IT MATTERS
- Maps illustrate the earth and its landmarks on a flat plane.
- Charts depict the Earth’s true contour complete with hills and plateaus, mountains and river valleys.
The difference between a map and a chart is topography. A map becomes a chart when terrain elevation is added. Even though the chart is printed on flat paper the skilled chart reader can “see” the terrain in relief or three-dimensions. Figure 1 illustrates how the elevations of the Earth’s terrain can be depicted on a flat surface. This illustration shows a river valley between two mountains along the seacoast. The contour lines tell the story. The closer the lines, the steeper the change in elevation.
READING THE CHART — WHAT IT MEANS
Contour lines and color codes: Sectional charts illustrate the terrain elevation using Contour Lines and Color codes. At approximately 1,000-foot intervals there is a contour line, plus a color change. Figure 2 is taken from the Las Vegas Sectional Chart. It shows all the different colors for terrain elevation that can be found on that chart. In this case, it ranges all the way from 282 below sea level up to 13,063 above sea level. The colors between those extremes represent the various ground elevations starting low with greens, then yellows, and finally the highest elevations use brown colors.
ROAD MAP VS. SECTIONAL CHART
Now compare the highway map (Figure 3a) with the sectional chart (Figure 3b) Both illustrate the same location. The highway map (3a) shows Interstate 24 coming in from the northwest corner of the picture. The highway is straight until reaching Monteagle where the road starts to twist and turn. The road map gives no information about why the road twists and turns. The sectional chart (3b) also shows Interstate 24 coming in from the northwest. The Interstate is shown straight as an arrow, but then the road approached contour lines that indicate rapidly rising terrain. The road twists and turns in order to work its way up the side of the mountain indicated by the contour lines.
Beyond the obvious: Look closely at the sectional chart (3b) and you will see the chart symbol for cliffs or bluffs. The cliffs are shown as black lines with shorter perpendicular lines — they look almost like eyelashes. Also you will see the words “Caution – Rapidly Rising Terrain” printed nearby. An automobile driver can get away with the map because the road will take them up and over the mountain, but a pilot must know about rapidly rising terrain ahead on their flight path. The normal GPS moving map gives to pilots only the information available to car drivers – and this could be a problem.
THE MINDSET
If you get used to maps that do not have the information that charts provide, you could train your brain for a 2-D, instead of a 3-D, perception of the environment we fly in. Will it happen someday that a pilot following the GPS moving map at night will simply fly into a mountain because the map did not show the rising terrain? Flying with a 2-D mindset in a 3-D world would be dangerous. Will the widespread use of GPS equipment invoke the ‘law of unintended consequences‘ and turn chart reading and the 3-D realization that it provides into a Lost Art?
COMPETING COLORS
On the horizon are in-cockpit ground warning systems that will couple with moving map technology, but getting a last-minute warning that you are too low is a sad replacement for a good pilot perception of the environment around them. Of course the moving maps could incorporate contour lines and color coding like sectional charts — the technology is already available for experimental aircraft — but that technology could also produce complications.
Looking Closely: Blending displays with weather radar and moving maps will create “competing color codes.” Currently, yellow is used on sectional charts to depict terrain elevation of between 3,000 and 5,000 feet, but yellow is also used on radar screens to depict moderate precipitation. Both colors clearly could not be used simultaneously and safely on the same display — we would not know if a mountain or a rain shower were ahead when yellow was shown on the display screen. I have flown IFR through areas depicted by radar as yellow, but you can’t fly at 3,000 feet in an area where terrain is higher than 3,000 feet as is depicted with the color yellow.
THE BOTTOM LINE: Technology can do many things better, faster, and smarter than we can. So far, chart reading is not one of them. Don’t let chart reading to become a Lost Art. Right now, your safety depends on it.
