KeyJ's Geotracker is a web application similar to the discontinued Google Latitude, but much simpler. It allows users to post their current geographic location so that other users can have a look at where they are and where they have been in the last week.
To view someone else's location, just visit an URL like this:
https://tracker.emphy.de/USERNAME
USERNAME is the name of the user you want to know the location of. Note that there is no public user list – the person you want to watch needs to tell you its user name by some other means.
The map displayed is centered around the most recently logged location. In addition, blue lines are drawn where the user has been during the last seven days. Older data will not be displayed by principle; as a result, it's not possible to view a user's location if he/she didn't update it for one week or longer.
To post your current location, load an URL like the following:
https://tracker.emphy.de/YOURNAME?lat=LATITUDE&long=LONGITUDE&key=KEY
Plase take not that it is important to write »lat«, »long« and »key« in lower-case letters.
YOURNAME is the user name under which your location will be posted. It can be any combination of latin characters, digits, dashes and underscores.
There is no user registration – if someone posts his/her location under a specific user name, this user name will be created and stays valid. A minimum authentication method is provided by the KEY parameter: If someone creates an account under a specific user name with a specific key (by posting his/her first location), that account can only be updated with exactly this key in the future. Keys are checked case-sensitively and expire one year after the last use.
LATITUDE and LONGITUDE are the (WGS84) geographical latitude and longitude in degrees as single numbers using a dot as the decimal separator. Positive latitudes are north of the Equator, negative latitudes are south. Positive longitudes are east of Greenwich, negative longitudes are west of Greenwich. This is the standard notion used e.g. in Google Maps. Sexagesimal notation (degrees/minutes/seconds) is not supported.
For example, the following URL puts a user called Pierre directly at the Eiffel Tower in Paris:
https://tracker.emphy.de/Pierre?lat=48.858247&long=2.2945&key=TopSecret
If somebody wants to know where Pierre is and was, he/she uses the following URL:
https://tracker.emphy.de/Pierre
The location data can also be downloaded in GPX or KML (Google Earth) formats like this:
https://tracker.emphy.de/USERNAME.gpx
https://tracker.emphy.de/USERNAME.kml
The API of this service should be trivial enough to use in own projects or third-party clients. If an Android phone is to be used for logging, this can be automatic with the excellent (and free) GPSLogger for Android by Mendhak. Note that I'm not affiliated with the author in any way – it's just that I use his application myself and are very happy with it; YMMV.
Anyway, if you use this application, here's what to set up:
In the menu, go to the submenu »Logging details« and enable »Log to custom URL«. When this option is activated, the application asks for a URL to log to. Here, the following needs to be entered:
https://tracker.emphy.de/YOURNAME?lat=%LAT&long=%LON&key=KEY
In this URL, the YOURNAME and KEY values are exactly as described in the section above, but for the latitude and longitude, »%LAT« and »%LON« need to be written verbatim – in all-uppercase letters and including the percentage sign!
If you only want to post your location manually, this is all you need to set up – you can return to the application's start screen and press the button with the number »1« to get a GPS fix and post it to the site.
If you want to automatically log your position over a longer period of time, go to the submenu »Performance«. There's an option »Time before logging« which sets up the logging interval in seconds. It's recommended to use a rather low value here, in the range of a few minutes (e.g. 300 seconds = 5 minutes), to save battery power.