Author
Marko Visic
Geospatial writer & editor, Open Map Lab
Marko Visic writes and edits Open Map Lab's guides on maps, coordinates, time zones and US geography.
Marko Visic on LinkedInPosts by Marko Visic
How to Find Out What County You Live In (and What County an Address Is In)
Updated ·10 min read
The fastest way to find out what county you live in is to look up your exact location or street address against county boundaries, not your ZIP code. This guide compares the methods (GPS, address lookup, the Census Bureau geocoder and official records), explains why ZIP codes and mailing cities mislead, and covers county equivalents and addresses near a county line.
What Is a ZCTA? ZIP Code vs ZCTA and How ZIP Codes Are Assigned
Updated ·10 min read
A ZCTA (ZIP Code Tabulation Area) is the Census Bureau’s polygon version of a ZIP code, built from census blocks so that statistics can be mapped by ZIP. The Postal Service itself assigns ZIP codes to delivery routes and post offices and publishes no boundaries. This guide explains how ZIP codes are assigned, how ZCTAs are built, where the two disagree and which one to use for a given job.
How GPS Location Accuracy Works in Web Browsers & Smartphones
Updated ·6 min read
When you click "Find My Location" in a browser, the device chooses among satellite positioning (GPS, Galileo and other GNSS), Wi-Fi positioning, cell towers and, as a last resort, IP address geolocation. Which one answers explains why accuracy can range from a few meters to many miles. This guide explains each method, what the accuracy number means, what degrades it, and how to get a better fix before relying on a location-based lookup.
How Time Zone Boundaries Work: Political Law vs Solar Longitude
Updated ·6 min read
In pure geometry, Earth turns 15 degrees of longitude every hour, so 24 neat stripes would make sense. In reality time zones are political and commercial boundaries set by law, bent around cities, counties and countries. This guide explains who sets U.S. time zone boundaries, why they wander, how daylight saving time and IANA zone IDs fit in, how this site determines your zone, and the mistakes that most often cause missed meetings.
What Is Sea Level? Elevation vs Altitude vs GPS Height Explained
Updated ·8 min read
Sea level, as used for elevations, is mean sea level: the average height of the ocean surface measured at tide stations over a 19-year epoch, extended under the land as the geoid. This guide explains tidal datums, the difference between elevation and altitude, why GPS height is measured from a different surface, how elevation models such as Copernicus GLO-90 work, and why different sources disagree.
Latitude vs Longitude: The Difference and How to Read Them
Updated ·9 min read
Latitude tells you how far north or south of the Equator a place is (0° to 90°), and longitude tells you how far east or west of the Prime Meridian it is (0° to 180°). This guide compares the two side by side, shows how to read coordinates in decimal and degrees-minutes-seconds form and off a map, gives memory tricks, and explains precision, sign conventions and datums.
As the Crow Flies Meaning: Straight-Line vs Driving Distance
Updated ·7 min read
"As the crow flies" means the straight-line distance between two places: the shortest path over Earth's curved surface, ignoring roads. Driving distance follows the road network around rivers, mountains and one-way streets. This guide explains how geodesic distance is computed, how to calculate and interpret the detour factor, how this site estimates road distance, and why contracts and tax rules care which one you use.
Coordinate Formats Explained: DD vs DMS vs DMM vs UTM, With Worked Conversions
Updated ·9 min read
The same spot on Earth can be written as decimal degrees (DD), degrees-minutes-seconds (DMS), degrees and decimal minutes (DMM), UTM or MGRS. This guide shows how to recognize each format at a glance, converts one real location through all of them by hand, explains how UTM eastings and northings are built, and lists the mistakes that most often send a point to the wrong place.
How to Find Coordinates on Google Maps (Desktop, Android, iPhone)
Updated ·8 min read
On a computer, right-click any spot in Google Maps and the latitude and longitude appear at the top of the menu; click them to copy. On a phone, touch and hold the map to drop a pin and read the coordinates from the search box or the place sheet. This guide covers each platform, the formats Google accepts when you paste coordinates back in, and the mistakes that put pins in the wrong hemisphere.
How to Find Elevation on Google Maps (and Better Ways to Get It)
Updated ·8 min read
Google Maps has no elevation readout for a clicked point. Its Terrain layer draws contour lines with gray height labels in hilly areas, Google Earth Pro reports the elevation under the cursor and draws profiles along a path, and cycling directions can show the climb on a route. This guide covers each method, how to read contour lines, their limits, and quicker ways to look up the elevation of any point.
Marko Visic is also credited as the editor of the map tools. How content is checked and corrected is described in the editorial policy and on the about page.