This is a library to determine the timezone for a given GPS coordinate. The library uses the combined-with-oceans.json file found at Timezone Boundary Builder. This file is processed by the code in the GeoJson directory to produce the per timezone files found in the SDCard/TimeZoneJson directory. All the timezone JSON files total over 230 Megabytes and an SD card or other large storage is required for all timezones, but a subset of the files can be supported by the flash filesystem.

An ESPGPSTimeZone object is first created specifying the filesystem and the path to the timezone JSON files. findTZ can then be called to lookup the timezone for a given coordinate. If the lookup is successful the timezone name, posix timezone specification, and radius are available. Radius can be used to check if a new coordinate is in the same timezone without having to process any timezone JSON files.

ESPGPSTimeZone objectName(fs::FS& fileSys, const char* path);

• fileSys - the file system for the configFileName (LittleFS, SPIFFS, SD)
• path - the path to the timezone JSON files

bool findTZ(double lat, double longi)

• lat - the latitude of the GPS coordinate
• longi - the longitude of the GPS coordinate

Find the timezone of the GPS coordinate, returning false if the timezone can not be found

bool inCircle(double centerLat, double centerLong,
              double locationLat, double locationLong, double radius)
bool inCircle(std::array<double, 2> center, std::array<double, 2> location,
              double radius)

• centerLat - the latitude of the circle center GPS coordinate
• centerLong - the longitude of the circle center GPS coordinate
• locationLat - the latitude of the location GPS coordinate
• locationLong - the longitude of the location GPS coordinate
• radius - the radius of the circle
• center - the circle center GPS coordinate { longitude, latitude }
• location - the location GPS coordinate { longitude, latitude }

Determine if a given GPS coordinate is within a circle defined by the center coordinate and the radius. This allows a GPS coordinate (center) and radius to be stored and used to determine if a new location is in the same timezone without having to process any timezone JSON files.

const char* tzName()

Get the timezone name.

const char* posix()

Get the timezone posix specification.

double radius()

Get radius of the current lookup. Then a coordinate is successfully looked up the radius value is set so that any point inside the circle defined by the coordinate and radius is guaranteed to be in the same timezone as the coordinate.