Table of Contents
Great Circle Hypotheis
Compass Bearings Hypothesis
Suns' Azimuth Hypothesis
Always Advance Hypothesis
Never Go Back Hypothesis
How To Determine the Co-ordinates
of the Exact Location of your Field Site
Where to find Altitude, Latitude, and Longitude
Altitude, Latitude, and Longitude of the field site need to be recorded only once
and can be added to the data forms at any time. Coordinates for Latitude and Longitude are
required to calculate Great Circle routes form the field site to the overwintering sites,
and are also usually required when look up magnetic declination and magnetic inclination
These data can be obtained in variety of ways.
- VISIT THE LIBRARY. Topographic Maps that show latitude,
longitude, and an average value for magnetic declination (variation) are available in map
section of most libraries.
- GO SHOPPING. Topographic maps for your area will usually be available at stores
specializing in equipping hikers, backpackers, birders, hunters, and other outdoors types.
- GO TO THE AIRPORT. Pilot and aviation supply stores are found at, or near airports
and carry Aeronautical Charts. These charts are particularly useful
because they plot latitude, longitude, altitude, and lines of magnetic declination
- MEASURE IT YOURSELF. Handheld GPS receivers can quickly
provide you with the altitude, latitude, and longitude of a site. I expect GPS receivers
to become increasingly common in the field as they continue to drop in price.