Hi All,
My name is Kris Netchy and I'm currently a graduate student working on marine invertebrate biogeography.  I'm doing my research at the Florida Fish and Wildlife Research Institute in St.Petersburg, Florida.  Here, we have a specimen collection of about 90,000 lots of marine invertebrates.  I'm planning to utilize these records to look at spatial patterns, but the first step is to go through the database and georeference all of the location data.  A lot of these records are very old and the geographic coordinates are not very accurate.  I'm a beginner at this and most of what I'm doing is self-taught, so I often have questions.  My main question is about estimating error of these coordinates.
Can someone help me with this, by any chance?
Here is one example question I have: 
One record has the locality description:  4 miles NW of Carysfort Reef Lighthouse.  I have the coordinates for the lighthouse and I can use a ruler to determine a point about 4miles North of that point, but it's not going to be very accurate.  I read that it would have about 22.5 degrees of directional uncertainty...but what does this mean in terms of distance?  I'd like to quantify the error in terms of distance, so I can make a buffered point or polygon in ArcGIS.
Any insight you have would be wonderful!  Thank you!
Kris
actinopyga@gmail.com [2]