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mapper.tools

GeoJSON viewer and KML, GPX converter

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GeoJSON, KML and GPX are recognized by themselves.

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Up to 20 MB. Read in your browser, never uploaded.

WGS 84 · geodesic · Guide, examples and sources below

How do I view a GeoJSON, KML or GPX file on a map?

Paste text or drop a GeoJSON, KML or GPX file to see it on the map, read the elevation profile of a GPX track and download it as any of the three. The file is read in your browser and is never uploaded.

Drop the file onto the panel, choose it with the file button, or paste its text into the box. The tool recognizes the format by itself, draws every point, line and polygon on the map, zooms to fit them, and shows how many of each it found, with the total length of the lines and the area of the polygons. If the file is not valid, you get a sentence that says what is wrong and where, rather than a blank map.

To convert, press the button of the format you want: you can download the file or copy the text. A GPX file from a hike becomes GeoJSON for a web page; a GeoJSON export from a database becomes KML to open in an earth browser; a KML route becomes GPX for a GPS device.

How do I read the elevation profile of a GPX track?

Paste or drop a GPX file that holds a track or a route. When its points carry an altitude, the panel draws the profile: the distance along the line runs across the chart and the altitude runs up the side. The slider, or a press and drag on the chart, reads any point: its distance, its altitude and its coordinates. The highest and lowest points are the extremes of the file.

Altitude is optional in GPX, and many apps leave it out. A file without altitude gets a message in place of a profile. A line whose points all share one altitude is shown as flat and labelled as such. A file with several tracks or routes lists them, and the one you pick is the one drawn.

The gain and the loss add up every rise and fall between neighbouring points that both have an altitude, with no smoothing. A point without an altitude breaks the sum, so a climb across a stretch with no altitude is not counted. Altitude readings vary from one point to the next, and a track with more points adds up more of that variation, so its gain can read higher than the climb you made. Compare two recordings only when they come from the same device and settings.

The numbers come from the file alone. The page does not fetch altitudes from a map service, because that would send your route to another server. The GPX format stores altitude in metres (GPX 1.1, Topografix), and the tool shows metres or feet.

What is the difference between GeoJSON, KML and GPX?

The three formats side by side
GeoJSONKMLGPX
Made ofJSON textXML textXML text
Coordinate orderlongitude, latitude (WGS 84)longitude,latitude,altitudelat and lon as attributes
Shapespoints, lines, polygons and their multi versionspoints, lines, polygons, styles, folderswaypoints, routes and tracks; no polygons
Typical useweb maps and databasesearth browsers and presentationGPS devices and recorded trips
StandardRFC 7946 (IETF, August 2016)OGC KML 2.2 and 2.3GPX 1.1 (Topografix, 2004)

Because GPX has no polygons, a polygon converted to GPX becomes a closed track: the outline survives but the fill and the holes do not. The tool tells you when that happens. KML styles (colors, icons) are not carried over, because GeoJSON has no standard place for them.

Why do my points appear in the wrong place?

The most common cause is swapped coordinates. GeoJSON puts longitude first, so a point written as [40.7128, -74.0060] lands in the Indian Ocean instead of New York. If your data came from a spreadsheet with a latitude column first, swap the two numbers. The second cause is coordinates in meters: files from a surveying or GIS system are often in a projected grid (UTM, a state plane) and not in degrees. The tool detects values outside −180…180 and −90…90 and warns you; convert them to WGS 84 first.

The GeoJSON standard also says polygon outer rings go counter-clockwise (the right-hand rule) and that the first and last position of a ring are the same. Most readers, including this one, accept the opposite order, but a strict validator may not. A declared “crs” member is ignored, since RFC 7946 allows only WGS 84.

Does my file leave my browser?

The content of the file does not. It is read with your browser’s own file and XML functions, drawn on the page, and converted there. This site has no server that receives it, there are no accounts, and an automated test checks that loading a file triggers no request that carries its content.

One thing does travel, and it is honest to say it: the base map. To draw the background, your browser requests map tiles from OpenFreeMap for the area on screen. Those requests contain tile numbers and your IP address, so the provider can tell roughly which area you are looking at, but not what is in your file. If that matters, zoom out before loading, or use a file whose location is not sensitive.

Questions about GeoJSON, KML and GPX

Is my GeoJSON, KML or GPX uploaded anywhere?

No. The file is read and converted in your browser. The only network requests are for the map background tiles, which reveal roughly which area you view but nothing about the content of the file.

How large a file can I open?

Up to 20 MB. Bigger files are refused with a message because the browser would struggle to draw them. Split the file or simplify its geometry first.

How do I convert KML to GeoJSON?

Open the KML file or paste its text, check that the map shows what you expect, then choose GeoJSON to download or copy it. The placemark names are kept as the name property.

How do I convert GeoJSON to GPX?

Open the GeoJSON, then choose GPX. Points become waypoints and lines become tracks. Polygons have no GPX equivalent, so their outlines become closed tracks and the tool says so.

What does “not valid” mean?

The text could not be parsed. For JSON it is usually a missing comma or bracket; for KML and GPX, a tag that is not closed. The message names what the parser found so you can fix it.

Are the colors and icons of my KML kept?

No. Geometry, names and descriptions are kept; styling is not, because GeoJSON has no standard place for it and GPX has none either.

Which coordinate system does it expect?

WGS 84 longitude and latitude in degrees, as GeoJSON requires. Files in a projected system (coordinates in meters) are flagged, and need to be converted first.

Does the elevation profile need an internet connection?

No. The altitudes are the ones already in your GPX file, and the profile is drawn in your browser. Nothing about the route is sent anywhere.

Why does my GPX file show no elevation profile?

Either none of its points has an altitude, or the file holds only waypoints, which draw no line. Altitude is optional in GPX. The tool does not add altitudes from a map service, because that would send your route to another server.

Sources and limits

These are calculation aids, not survey instruments. They measure on a mathematical model of the Earth (WGS 84); for a legal boundary, engineering or navigation, use a licensed surveyor or the official chart. Nothing you type or load leaves your browser.

Other map tools

More ways to measure and convert on a map.