I have a couple of lat/long points that I have calculated a distance between and would like to confirm it. If someone could see if their calculations agree with mine it would be appreciated.
Pt 1
Lat: N 30 deg 38' 58.65506"
Long: W 87 deg 54' 12.62303"
Pt 2
Lat: N 31 deg 08' 55.14513"
Long: W 87 deg 04' 30.82570"
Distance: 316907 feet, 60.02 miles
I get 96599.3307 Ellipsoidal distance
Geezer
sorry, that is in meters
Using 0 as the ellipsoid height for both points I get an ellipsoid distance of 316926.304' with a forward azimuth of 54 50' 49" and a back azimuth of 235 16' 20". This is the same distance that Geezer posted in meters.
I'm sure this doesn't help, but I got 60.11 miles simply using Google Earth. Plus or minus 0.04', of course.
Varies according to the ellipsoid chosen. GRS80 is the accepted current one. Google Earth uses a spherical Earth model, so it's only approximate. Computing ellipsoidal distances on the GRS80 with NGS software is legally admissible in Federal Court.
I get 316926.3039' in NAD83
Fwd N 54 50 49.1 E
Mean N 55 03 34.8 E
Back S 55 16 20.4 W
I get :
60.001601557864454
using a Earth mean radius of 3958.756
My quandary when I wrote that little program is that I found three other values for the mean radius.
Mean radius is an approximation according to Gauss' equation that is dependent on the ellipsoid chosen and the LATITUDE chosen. The value is infinitely variable between the limits of the Equator and the Pole.
It's the same equation for computing the scale factor correction for "sea level."
Right - I was using GRS80
Using the NGS INVERSE program
Yup, that's the kosher way for Federal Courts.
B9G,
That NGS Inverse Program is cool!
Dave
