To kick off the first installment, I'll be covering the "basics" we all should have with us when out in the field. Of course the first item that every Field Investigator should have on them at all times is a compass. More valuable than determining direction, it can be a first indicator of the presence of a magnetic field. If you are at the site of a suspected landing, one of the first things one should do is check for any kind of residual field before approaching the area in question, and the easiest way to quickly check is to pull out your compass and see if it is behaving in an erratic fashion. Do not assume that because your compass is acting normal, there is no cause for concern...A compass will only detect a magnetic field, not radiation! The compass is a good first indicator, but keep in mind that more sensitive readings will be necessary. That brings me to the next two items that I feel are mandatory in every field bag; a geiger counter and a TriField Meter.
The next item I would recommend is a quality TriField Meter. My personal choice is the TriField Meter Model 100XE. It does an outstanding job of measuring magnetic fields from 0 - 100 milligauss, electric fields up to 1,000 volts/meter, and radio/microwave fields (mW/cm squared - into front of box). Make sure to always write down not only how strong the field is, but also how far the measurement was taken from either object or area. You also want to be sure to make the proper notations on your diagrams of the scene. Determining where the differences in field strength are will help to map out the site.
With the proper training all three of these instruments can be your first line of inquiry in an on-site investigation. What the data from these instruments provide to YOU the Field Investigator can determine how you proceed in the first moments on the scene. Remember: Whenever in doubt about any situation NEVER hesitate to call your SSD or even your SD if you have questions!