Woo, wellcome, howlawood! I just start geotagging, and I came across a problem. Most of the time, my GPS devoice works well that receive satellite fast and accurate. While, last Friday at noon, I found it was hard to fix, it continued several minutes, then turned normal. These days, it works well. Is that normal?
There are normally several times during each day in ever location on earth when the GPS satellite constellation (that’s what it’s called, for some reason) has only 1-2 satellites “visible” to the receiver. At that time you will either get no fix or a fix that is wildly inaccurate (sometimes by several miles). Wait for a few minutes and the problem goes away as the receiver acquires additional satellites.
This also occurs:
1. In areas with obscured line of sight to the horizon (in all directions) such as in a deep valley or in a large municipality, as your ability to receive “line of sight” timing signals simultaneously from multiple satellites is impaired. In these cases your ability to get a good fix (normally considered at least 4 satellites) may be non-existant, or it may be limited to only a few minutes at a specific time each day.
2. On specified dates and times in a rather large (4+ million acres) area centered on White Sands Missile Range (actually, Holloman AFB), which is the designated test area for GPS “spoofing” systems. Normally, these are listed on the latest pertinent FAA data links and notices to aviators, and only last a short time.
With your Easytagger, remember that your heading (line of sight bearing) is based on a magnetic compass in the unit and it will be off, sometimes significantly, depending on the local magnetic deviation (for instance, at Yellowstone National Park the MD from true North is 11.5 degrees, which isn’t exactly a trivial amount).
