Hanetz and 
shekia (sunrise and sunset times) are influenced by elevation.
                This page allows you to display sunrise and sunset times for
                a specific elevation profile.
                
                Caution: Entering the wrong information will produce incorrect zmanim;
                if there's something you don't know, please leave it blank.
                
                
                
Horizon elevations
                For 
Elevation of east horizon enter the elevation of the point on the eastern horizon where the sun will rise.
                For 
Elevation of west horizon enter the elevation of the point on the western horizon where the sun will set.
                
                
If you do not specify any Horizon Elevation we will assume it is the same as Your Elevation. Whenever Horizon Elevation and Your Elevation are equal, the impact it has on sunrise/sunset times is minimal.
                
                If the 
Horizon elevation is greater than 
Your elevation the zmanim will be calculated
                as if the 
Horizon elevation was the same as 
Your elevation.
                
(שבת קיח: ”יהא חלקי ממכניסי שבת בטבריא“)
                
                If your view of the horizon is blocked by obstructions (such as nearby hills or mountains) determine the point
                where the sun will set 
behind the obstructions and use the elevation of that point as your 
Horizon elevation.
                
(מהרי"ל הל' תפילה ”מכל מקום אחורי ההרים עוד היום גדול“')
                
                How do I find my elevation?
                Among others, a convenient tool for checking elevations is Google Earth
                (
earth.google.com).
                Set 
units of measurement
                to meters (under Tools > Options) and then hover over a location to display
                its elevation at the bottom of the window.
                Measuring your elevation with a GPS (or mobile app such as "GPS Test") is
                also fine provided that the GPS accurately converts 
elevation above
                ellipsoid to 
elevation above sea level. (Note: MyZmanim cannot take
                responsibility for the accuracy of elevation data provided by Google Earth or
                your GPS.)