Radius Map — Circles, Towns & Postal Codes Inside

About the Radius Map — Circles, Towns & Postal Codes Inside

Draw a circle on the map — tap a centre, search a city, use your location, paste coordinates or open a CSV of centres with a radius column — and see what lies inside: every town and village with its distance and direction from the centre, and the postal codes whose centre falls inside. Add up to ten rings around one centre (2, 5 and 10 km, for example) for delivery bands, and as many centres as you need to compare service areas and see where they overlap.

Each circle is a true geodesic circle on the WGS 84 ellipsoid, its points worked out every 2° with Karney’s method, so a 100 km circle in Norway is as right as one in Kenya; its area and circumference are shown too. The places come from GeoNames (towns and villages of 500 or more people) and the postal codes from GeoNames and, for US ZIP codes, the Census Bureau’s ZCTA gazetteer, all built into the page and searched on your device. Without a pass you get a free preview: your first circle searched, its counts in full and the nearest few of each list (up to five), with the other circles and the files locked.

Common uses

• Planning delivery zones, service areas and sales territories.
• Checking “within X km” rules, such as school admission distances or job and housing radius conditions.
• Finding every town within a commuting distance of a city.
• Listing the postal codes to target with a local campaign.
• Comparing the catchment areas of several branches and where they overlap.

How the circles and lists are worked out

• The circle is every point at the chosen geodesic distance from the centre on the WGS 84 ellipsoid (Karney’s direct method, every 2°); a place is inside when its geodesic distance from the centre is at most the radius.
• Distance and direction are the geodesic distance and the initial bearing from the centre (0° north, 90° east), with the compass point.
• Area and circumference come from the geodesic polygon of the circle’s points, corrected for the slivers between its points.
• Towns and villages are GeoNames’ populated places of 500 or more people; postal codes are placed at the centre of the places GeoNames lists for them, and US ZIP codes at the Census Bureau’s internal point of their ZIP Code Tabulation Area.

Which postal codes are included

Postal codes of about 120 countries from GeoNames, with these differences: Canada, the Netherlands and the United Kingdom have the first part of their codes only, Ireland and Malta their first letters, and Chile and China their first digits; Brazil has its main codes; Portugal is listed by its four-digit areas and Singapore by its postal sectors (the first two digits); the United Arab Emirates has no postal codes. US ZIP codes are the Census Bureau’s ZIP Code Tabulation Areas: not every ZIP code has one, so a few ZIP codes are not listed.

Limitations

• A postal code is counted by its centre point: a large rural code can reach into the circle while its centre is outside, or the other way round.
• Some postal codes share one approximate position in the source data (several codes of an area placed at the same point, as for more than a third of the codes in the source data): their distances are marked ≈ in the list and counted in the files’ shared_position column, and such a code near the edge of a circle can fall on the wrong side of it.
• Only places of 500 or more people are listed; hamlets and single farms are not.
• Searching street addresses is not offered: place a centre by tapping the map, searching a city or pasting its coordinates.
• Very large circles (over a few hundred kilometres) load more of the built-in lists and take longer on a phone; radii up to 2,000 km are searched.
• A map circle is not a legal boundary: for rules that measure by road or by an official map, check with the authority that sets the rule.
• The map shows coasts, water, streets and places but no national or state borders: it is made for measuring, not for showing boundaries.

Privacy

Looks up live data online

Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot. The place and postal-code lists are part of this page and are downloaded from MySmartCoPilot a few files at a time for the area a circle covers. The street map, when you turn it on, loads its squares from OpenFreeMap, which sees your IP address and which part of the map you look at. Your centres stay on your device; your location is asked for only when you press My location.