Finding your latitude and longitude
Latitude and longitude give the place of birth. Latitude is the distance north or south of the equator, and longitude is the distance east or west of the Greenwich meridian.
What it is
Positive latitude is north and negative is south. Positive longitude is east and negative is west. Indian cities are north of the equator and east of Greenwich, so their values are positive, as in Mumbai at about 19.08 north and 72.88 east.
How it is worked out or read
The tools include a list of cities with their coordinates. For a town not on the list, use a map or a gazetteer, and enter the coordinates to two or three decimal places. The difference from the exact value is small compared with the time error.
Where it appears on this site
The coordinates are in each tool, and a city list fills them. The panchang uses the same fields.
What the numbers mean
Latitude measures how far north or south of the equator a place lies, from 0 degrees at the equator to 90 at the poles. Longitude measures how far east or west it lies from the meridian through Greenwich, from 0 to 180 degrees each way. The birth chart tool on this site takes both as decimal degrees, with north latitudes and east longitudes positive. Delhi, for example, is about 28.61 north and 77.21 east; New York is about 40.71 north and 74.01 west, entered as -74.01.
Converting degrees and minutes
Older records and atlases often give coordinates in degrees and minutes, such as 19 degrees 4 minutes north. To convert, divide the minutes by 60 and add: 19 degrees 4 minutes becomes 19 plus 4 divided by 60, or about 19.067. If seconds are given, divide them by 3600 and add as well. Mixing up minutes and decimals is a common error: 19 degrees 30 minutes is 19.5, not 19.3.
How precise they need to be
Longitude affects the Lagna directly: one degree of longitude shifts local sidereal time by four minutes, which typically moves the Lagna by about a degree. Latitude affects the Lagna less directly, through the rising times of the signs. For most purposes, two decimal places, about one kilometre, are more than enough. Using the coordinates of the birth town rather than the exact hospital is fine.
Finding coordinates
For a city in the list on the chart page, the coordinates are filled in automatically. For other places, any reliable map service or atlas gives latitude and longitude: search for the town, and read the coordinates from the map's information panel. Check the signs: places in India are always north and east, so both numbers should be positive.
A common pitfall
A frequent mistake is to enter the longitude of the birthplace but the time zone of the place where the person lives now, or vice versa. The longitude, latitude and UTC offset must all belong to the birthplace and the moment of birth. After making the chart, the quick check of the Sun's house against the time of day, described in the time zone article, catches most such errors.