Latitude measures how far north or south of the equator a place is located. The equator is situated at 0°, the North Pole at 90° north (or 90°, because a positive latitude implies north), and the South Pole at 90° south (or –90°). Latitude measurements range from 0° to (+/–)90°.
Longitude measures how far east or west of the prime meridian a place is located. The prime meridian runs through Greenwich, England. Longitude measurements range from 0° to (+/–)180°.
Well-known text (WKT) is a text markup language for representing vector geometry objects on a map
POINT(Longitude Latitude )
1- Create a table in sql server database to store all of your landmarks latitudes and longitudes.
2- Create a web API/Service that gets the position (latitude and longitude) and returns back the list of land marks closest to the point – it’s configurable to set number of expected landmark and radius of search)
3- Implement UI