Geography & Maps

Find the point on Earth diametrically opposite to any latitude/longitude.

Initial and final bearing plus midpoint between two coordinates.

Translate a compass bearing in degrees into 16- or 32-wind cardinal direction names.

Convert wind speed to Beaufort force with sea/land descriptions.

Look up what you can see at each Bortle class (1 = pristine dark, 9 = inner city).

Build a bounding box from points or a center+radius, in every common ordering.

Find the mean (centroid) of a list of lat/lng points on the sphere.

Suggested constellations to look for tonight by season and latitude.

Compute great-circle distances between every pair of lat/lng points.

List the countries bordering any given country.

Look up a country's capital, driving side, area and population.

Approximate geographic centroid for every country by name or ISO code.

Convert a 2-letter ISO country code into its flag emoji.

Estimate total daylight hours for a date at any latitude (CBM analytical model).

Convert latitude / longitude between decimal degrees, decimal minutes and DMS.

Parse decimal, DMS or DM-formatted coordinates into a normalized lat/lon.

Encode a coordinate to a geohash or decode one back to a cell.

Approximate morning and evening golden- and blue-hour windows for a location.

Distance, ascent, descent, duration and average speed of a GPX track.

List N intermediate points along the great-circle route between two coordinates.

Great-circle distance between two latitude / longitude points.

Look up E.164 country calling codes (+1, +44, +81 …).

ISO 3166-2 codes for US states and Canadian provinces.

Convert between calendar UTC, Julian Day Number and Modified Julian Day.

Searchable reference of essential outdoor knots: use, strength rating and category.

Encode and decode amateur-radio Maidenhead grid locators.

Searchable reference for common map projections — what each is good for.

Convert latitude / longitude to a Military Grid Reference (and back).

Compute moon phase, age (days) and approximate illumination for any date.

Encode and decode Open Location Codes (Plus Codes).

Test whether a lat/lon falls inside a polygon (geofence).

Compute the area of a polygon on Earth from lat/lng vertices.

Compute constant-bearing rhumb-line distance and heading between two coordinates.

Compute Greenwich and Local Mean Sidereal Time for any UTC date/time and longitude.

Convert between lat/lng and slippy map tile X/Y/Z.

Sunrise, sunset, solar noon and the three twilight bands for a date and lat/lon.

Convert latitude / longitude to UTM zone, easting and northing (and back).