August 2003Features

View from above

Aerial images of checkpoints and airports can enhance your cross-country flying


During my final dual cross-country training flight, I was inbound to the Hagerstown, Maryland, VOR. It was late November, but there was a layer of haze from the surface to 5,000 feet msl - not unheard of here in the Mid-Atlantic, where an unseasonably warm stretch can produce hazy conditions even in winter - and I was having trouble locating my checkpoints. The haze rendered many details shown on the sectional chart difficult to pick up until we were relatively close. And, much of the detail that was visible through the haze was not depicted on the sectional chart. For example, there were many more roads than were shown on the chart.

Without a more detailed depiction of the area, things I could see through the haze at farther distances were not useful in helping me to get oriented. My CFI talked me through it, and we continued on. Overflying the Hagerstown VOR, I turned to the south on course for Martinsburg, West Virginia, our intended destination.

As I approached Martinsburg from the north, I began scanning for the airport. Eastern West Virginia Regional Airport/Shepherd Field (MRB) is approximately four nautical miles south of the center of Martinsburg. Despite my earlier problems identifying checkpoints along the route, with the city in view and the sectional chart depictions of the area, I was certain that I would quickly locate the airport. But again, I found it difficult to get oriented and pick out the airport through the haze. Finally I spotted it to the east. Having approached from almost due north, this was not a timely discovery. Fortunately, at this point my CFI had planned to have me divert to an alternate airport. Otherwise, this late sighting of the airport would have delayed my descent and placed me closer than desired for an initial call to the tower.

It had now become apparent that translating the depictions on a sectional chart to the visual reality passing below was not simple, even when a position is well-known and there is a good visual reference, like a city. Sectional charts must combine aviation information and ground detail. As a result, the ground detail must be limited, or the clutter would render the charts unreadable. Sectionals are quite useful for planning a cross-country flight. But they are depictions, not photographs. Thus what you see on the charts simply does not look like the view from the aircraft. It's not uncommon to fail to see a particular site or feature or to misidentify a landmark that you do spot.

An ideal solution for pilots - particularly those in the cross-country stage of their training - is to augment the planning and aeronautical-information advantages of sectional charts with aerial photographs that can provide better visual details of critical points on a cross-country route. Fortunately, in this information age, you can quickly and easily obtain aerial photographs of every area of the United States.

The United States Geological Survey (USGS) is constantly updating its maps of the United States, and part of this effort involves the use of photographs from aircraft and satellites. These USGS-generated photographs are in the public domain and may be viewed and downloaded from the Internet free of charge. The Web site used for this was a cooperative effort between Microsoft and the USGS, but the Web site is no longer a Microsoft property.

Key in the name of the desired location into the search field, and the Web site provides a list of any locations containing the text entered. As airports are a common feature identified on USGS topographical maps, entering the name of a public airport will usually provide a listing of topographic maps and aerial photographs covering the area in which the airport is located. If not, searching for a nearby town or city will list photographs of sufficient area to include the airport you seek.

The initial image provided is typically 8-meter resolution, which displays a large area. The particular feature desired might not be immediately apparent. Zooming in, by increasing resolution, and then scanning the more detailed reduced-area image, helps you to identify the landmark you want. If multiple photographs are listed, note the date for each and use the most recent one. It's important to be aware of the image's age, because an older file might omit important details such as new runways or taxiways, new structures adjacent the airport, and the like.

Once you identify the desired site in the image, you can vary both the resolution of the image and the amount of ground area depicted on screen to create an image of the desired detail and area coverage. Download the image by clicking on the "download" button and following the instructions.

When I found this site, I realized how helpful it would have been on previous cross-country flights. An aerial photograph of the region covering the city of Martinsburg and the airport would have made locating the airport much simpler. A composite image created from several downloaded 2-meter resolution images shows details well beyond those found on a sectional chart. Every road, including streets in the city; exact depictions of highway interchanges; shapes of surrounding fields and woods; precise detail of all streams, etc. - all of these are visible in the photograph. This detail, and the fact that this is an actual image of the area - not a graphical depiction - would have made it much easier to put into proper perspective exactly where to look for the airport.

If you want to get extra fancy, try creating a composite image like that shown above - download some higher-resolution images and then combine them to produce a single, higher-resolution image of a larger ground area. (In this case, a single onscreen image that included views of both the city and the airport produced insufficient detail to be useful.) You can create composite images with any software capable of editing graphics files such as those in BMP or JPEG formats.

Another resource for aerial imagery can be found at Carterra Online. High-resolution satellite images of airports and other locations can be purchased and viewed in color or black and white. If you register at the Web site you can access the images but if you wish to download them for future reference, you must purchase them from Carterra Online.

These photographs can be used to aid in planning a flight to an unfamiliar airport. Though airport schematics depicting runways, taxiways, parking areas, and facilities are available, just as with the sectional charts, these depictions are not always as easy to interpret as photographs. A composite of 1-meter-resolution images for Martinsburg (a 1-meter-resolution image covers 3.75 minutes of latitude by 3.75 minutes of longitude) shows far greater detail than a line-based schematic. Get the best of both worlds by printing the photograph and labeling taxiways and facilities using information from your Airport/Facility Directory or airport diagrams obtained from AOPA's Airport Directory Online.

If you like, you can lower the resolution to 2 meters and an area four times greater can be printed in the same space. You'll see a lot of detail of the area surrounding the airport, allowing preliminary selection of pattern reference features before you actually see the field.

Don't limit the use of these photographs to areas near airports. They can provide improved detail of critical checkpoints and also increase the number of locations that you can use as checkpoints. Relatively small towns or minor features with insufficient detail on a sectional chart can be better identified using an aerial photograph of proper resolution, allowing these sites to serve as checkpoints when no other alternatives exist. (Just take care that you are not clipping five, 10, or 15 composite images to your kneeboard that you must reference in flight. Your eyes should be outside the cockpit as much as possible so that you can see and avoid other aircraft. It's best to review this graphic information well in advance so that you need only refer to it briefly - if at all - in flight.

During my second solo cross-country flight, I wanted a visual reference to determine when I was 10 nm from the Reading, Pennsylvania, airport. The town of Robesonia was directly on my course and at the proper distance. However, my CFI noted that Robesonia is depicted on the chart as a small yellow square - similar to others nearby all lying along the same road - and would be difficult to positively identify. So I created a composite 1-meter-resolution aerial image developed from the USGS photographs. While the sectional chart detail is limited to a road, railroad, and power line - all of which run past other nearby towns - the aerial photograph details include the true shape of the town, individual streets, identifiable buildings, parks, and baseball fields.

I am sure that in the future, my cross-country flight preparation will include obtaining aerial images of the area around intended landing sites, detailed images of any unfamiliar airports, and images of any checkpoints that may be relatively poorly defined on a sectional chart. The ease of obtaining these on the Terraserver site makes this a relatively simple additional step in cross-country planning, and it certainly improves the ability to transition from circling checkpoints on the chart to actually identifying them once in the air.

-Vince Pascucci

Vince Pascucci received his private pilot certificate in April 2002, and has 150 total hours. He is secretary of the Thompson Flying Club, which owns a Piper Archer II based in Harrisburg, Pennsylvania.

Surfing for airport pix

If you're planning a flight to a brand-new destination, sometimes a little extra help is all you need to turn jitters into assured flying. If you're unsure whether you'll be able to pick out the airport - particularly if it's located in a dense urban area - an aerial photograph could calm your fears. A number of Web sites now provide such images, taken primarily by pilots who understand that a picture is worth a thousand words. You can read all about it in the Airport/Facilities Directory or AOPA's Airport Directory, but a photo of that 160-foot water tower near the pattern shows you what you're dealing with. (The tower in question is located just 662 feet off the displaced threshold to Runway 2 at Tappahannock Municipal in Tappahannock, Virginia, and you can see a photo at www.dcpilots.org.)

Here are some Web sites that offer aerial images, but please don't use the information provided in these sites to cut corners in your flight planning.

Airstrip America. This online directory uses photos provided by pilots who have landed at the facilities. Not all airports listed have photos, but Airstrip America cordially invites you to fill in the gaps, providing information on how to upload digital images. As of mid-June, the site had more than 3,000 photos in its database, with more coming in every day, according to David A. Soyka, president.

Civil Air Patrol. The national headquarters' Web site has an extensive database of airport photos, helpfully arranged so that you can click on the state and then the airport you want, rather than having to plug identifiers or airport names into a search engine. Photos are not available for every airport, but registered site users can upload images. As a nice touch, the CAP site includes views from north, south, east, and west.

DCpilots. DCpilots is technically a newsgroup for pilots who fly in and around the Washington, D.C. area - when they can, that is - but its administrator, Jeff Cook, also maintains a Web site loaded with additional information, including aerial photographs of airports in nearby Virginia, Maryland, Delaware, and Pennsylvania. Newsgroup participants provide the photos.

-Jill W. Tallman


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