NorthStar 961 Reference Manual page 138

Chapter 5 - Understanding Position Coordinates
About loran's
absolute accuracy
Page 5-8
Loran isn't as proficient as GPS in absolute accuracy; that is,
when you're visiting a spot for the first time. Because loran
transmits at a relatively low frequency (100 kHz—similar to
that of an AM radio), your ability to obtain an accurate
position fix is related to several factors:
• your distance from the loran transmitters, and their power
• line geometry from the loran transmitters
• weather conditions between you and the transmitters
In these areas, GPS consistently excels when it comes to
absolute accuracy. GPS provides an absolute accuracy of
better than 100 feet, almost everywhere in the world, under
virtually all conditions—far surpassing the 600-foot absolute
accuracy of a good loran receiver under ideal conditions.
If you're used to relying on a loran receiver's repeatable
accuracy to return you to within one vessel's length of a
lobster trap or buoy time after time, you won't necessarily see
this same performance with non-differential GPS: You could
be as far as 200 feet away from your expected position.
This is especially apparent when using the CHART screen,
where you may see your vessel's plotted position appear to
wander within an area up to 200 feet in diameter. See Figure 4,
"Position variances with uncorrected GPS," below. When using
the 1/8-nm chart scale, this 200-foot area covers almost the
full screen.
961/962 Operations and Reference Manual, Rev. A