Distance, drawn honestly.
What Compass is for.
Compass answers questions about places: how far apart two cities are, which way to face, what the weather is doing, and how to read a coordinate someone sent you. People use it to plan trips, compare flight distances, aim antennas, read GPS positions off old paperwork, and decide whether to take an umbrella.
Three of the five tools do all their work in your browser: the Coordinate Converter, the Unit Converter, and the bearing and declination math in the Compass Heading Calculator. The other two need outside data, because a forecast has to come from a weather service and a road route has to come from a routing service.
Here is what goes to outside data services. Place search in Distance Arc, Compass Weather, and the Heading Calculator checks a built-in city list first and only asks OpenStreetMap’s Nominatim service about places that aren’t on it, like a street address. Compass Weather sends the coordinates of the city you pick to Open-Meteo for the forecast and loads radar images from RainViewer. Distance Arc sends your two points through our server to OpenRouteService to look up driving distance and time. Maps load their tiles from OpenStreetMap-based tile servers.
Which tool to open
Questions people ask.
Why is the straight-line distance shorter than the drive?
Distance Arc draws the great-circle path, the shortest line over the surface of the globe. Roads bend around terrain, water, and borders, so a drive is almost always longer. When a road route is available, the results show driving distance and time. When it isn’t, they show the great-circle distance and an estimated flight time.
What is the difference between true north and magnetic north?
True north points at the geographic North Pole. A compass needle points at magnetic north. The angle between them is the magnetic declination, and it depends on where you stand: about 12.5° west in New York and close to zero in London. The Heading Calculator gives true bearings plus the declination at your starting point, so you can convert for a handheld compass.
Which coordinate format should I use?
Decimal degrees, like 40.7128, -74.0060, for web maps, spreadsheets, and APIs. Degrees, minutes, and seconds for deeds, charts, and older documents. UTM and MGRS for topo maps, search and rescue, and military grids. They all describe the same point on WGS84, the datum GPS uses, and the Coordinate Converter shows all four at once.
How reliable is the weather?
Compass Weather shows Open-Meteo forecasts, which are built from national weather service models. It is still a forecast, so a 10-day outlook is a rough guide past the first few days. Radar images are published in intervals, so they trail real conditions a little. For storm and flood warnings, go to your national weather service.
Does any of this work offline?
The coordinate and unit converters do their math in the page, so they keep working if your connection drops after the page loads. Weather, radar, map tiles, and address search all need a connection.