I don't know any MUG GPS SIGs, but here is what you can do on your own.
On a mac, you can enter GPS coordinates as metadata on any jpg file including actual photos, or dummy photos. Then by loading these into iphoto and making a book of them, you can create a map in the book with a map of these points.
Here is an article on tagging existing photos or dummy jpg files:
When you import those photos or dummy jpg files, iPhoto drops a marker pin for that spot on your map in Places.
If you want, iPhoto can also use the GPS coordinates to look up the location in its database. The location, such as a city name, appears with the marker pin on your Places map.
To use GPS coordinates to identify location names:
• With iPhoto open, choose iPhoto > Preferences from the menu.
• Click Advanced.
• Choose an option from the “Look Up Places” pop-up menu:
Automatically: iPhoto looks up all GPS coordinates to find location names.
You can have iPhoto rescan photos for GPS information. To do so, select one or more photos, hold down the Control key while clicking the photos, and then choose Rescan Photo Location from the shortcut menu. iPhoto rescans the selected photos, which then appear on your Places map.
You can enter GPS coordinates as x and y data in the spreadsheet (excel, numbers, whatever). Then you can plot these points. By adding some known references, you can get relative positions.
If the GPS coordinates are THETAns (for the north-south angle, north is positive and south is negative) and THETAew (for the east-west angle, east is positive and west is negative) the approximate formula for position is:
x= 69.171 cos(THETAns) THETAew(in decimal degrees) miles
y=69.055 THETAns(in decimal degrees) miles
Thus if (x,y) is (0,0) you are on the equator on the primer meridian.
(x,y) is (0, 6,000 miles) at the north pole
(x,y) is (0, -6,000 miles) at the south pole
You may have to convert THETAns and THETAew to decimal degrees, from degrees, minutes and seconds depending on the units your spreadsheet will accept for trig functions.
Decimal Degrees = Degrees + (Minutes + Seconds/60)/60)
Radians = Degrees * PI / 180
Thus in a spreadsheet, if A1 is THETAns (in degrees) and B1 is THETAew (in degrees)
A1 =52+(10+54.64/60)/60 or 52.8181444 degrees (north of the equator)
B1 =-10-(12+27.21/60)/60 or -10.207558 degrees (east of the prime meridian) (the - sign means it is actually west)
Since spreadsheets usually use radians rather than degrees, cos(THETAns) is COS(A1*PI()/180)
Thus the (x,y) of this is (69.171*B1*COS(A1*PI()/180)) , 69.055*A1) or ( -432.93 miles, 3,603.42 miles)
The pythagorean theorem gives you distance between any two points that aren't too far apart since the earth is not flat.