I have an address that I converted to Lon/Lat. Now, I want to go 500 feet South and 3960 feet West, and make new points. How do you convert -93.84756 to feet?
This is the name of an Excel Add-in that contains various functions related to geography. You can find this free excel add-in with Ask.com
To find the lat, long of your new point, C. I would first do some simply triangle geometry. Think of a right triangle ABC (you need to ignore the periods, if the periods are not there, the triangle is collapsed to the left margin and I cannot prevent it without the periods):
Point A is your known lat, long. Point B is 500 ft to the south and Point C is 3960 ft west of Point B.
The distance From A to C is the hypotenuse of the right triangle which is 3991.4 (a^2 + b^2 = c^2).
To find Angle A you need some trig. In Excel, use ASIN(3960/3991.4) - the arc sine of the adjacent side / hypotenuse is in radians. To convert to degrees, divide the radians by (2*PI/360) which is 7.19 degrees. So the bearing from A to C is 180 (due south) + 7.19.
Next, find the lat and long of point C by using these two functions from geofunc.xla:
NewPosLat(Lat1, Lon1, Bearing, Distance)
NewPosLon(Lat1, Lon1, Bearing, Distance)
And there you have it.
Keep in mind that it is slightly complicated by the fact that the earth is round.
One degree of latitude is the same length (69 miles) everywhere on the globe, but the length of one degree on longitude varies depending upon where you are. One degree of longitude will vary from 0 feet at the poles to 69 miles at the equator.
Since a degree of latitude is approximately 69 miles, and a minute of latitude is approximately 1.15 miles. A second of latitude is approximately 0.02 miles, or just over 100 feet.
The longitude will vary by the cosine of the latitude.
Rigel and MM's answer helped me in this particular case, and I thank you. Now for my next question. Is there somewhere that explains, for example, for Latitude, going south, does the number grow bigger or smaller, and for Latitude, going East and West, does it grow or shrink? What I am needing, I guess is a "Crash Course" in Cartography. Maybe someone on this Forum has some suggestions.
Alleghany - I'd suggest looking up Latitude and Longitude in either Wikipedia or TotallyExplained (many times the text is identical). They have a good, brief summary of the concepts.
You might also be interested in "great circle", "rhumb line", and many other interesting navigational topics at the bottom of the Wikipedia pages.
If you need more than what is there - let us know and we'll help you look for more information.
As rigel said, check out Wikipedia.
Picture a globe.
Latitude 0 (zero) is at the equator and 90 is at the poles (-90 for the South pole). The lines of latitude are all the same distance between each other. Picture rings parallel with the equator. Or layers on a spherical cake. The layers are all the same width.
Longitude rings run through the poles. The lines are furthest apart at the equator and closest together (touching) at the poles. Picture the sections of an orange.
Longitude 0 (zero) is at the Prime Meridan which is also where GMT is in England. It goes +180 degrees to the east and -180 to the west. The line that is directly opposite GMT (0) is the International Date Line (180).
So in the northern hemisphere, going North the latitude INCREASES.
And in the Western hemisphere, going West the longitude INCREASES.
I found this link that contains a calculator and also the formula
I hope is helpful
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