geolocator (Software defined GPS) final evaluation

Hi everyone,

with this blog post I would like to explain the full Google Summer of Code Project as a final post. For people who haven’t read over the geolocator (Software defined GPS) project before, it might be interesting to read these three blog posts at first:

– geolocator (Software defined GPS) (english)[1] and (german)[2]

– geolocator (Software defined GPS) first evaluation (english)[3] and (german)[4]

– geolocator-software-defined-GPS-second-evaluation (english)[5] and (german)[6]

Otherwise I will give in the following a short overview about the project structure to remind you of it. I structured the Google Summer of Code project into 3 main subprojects:

web backend,

– The web backend named sgps-core is a service, which should give requested clients their geo position.


– The idea of gps-share is to create an udev device, which provides NEMA-formata protocols over tty addicted on information, which is received from the above mentioned backend.

LEDE Package,

– The intention behind this subproject is to develop a new package for LEDE called geolocator, which should provide the geo position of LEDE devices.

Now I would like to give you a full state of each above mentioned subproject. Firstly I will explain about the web backend and finally a peroration including my valediction as a Student by Google Summer of Code.

web backend

Generally the backend service receives over the OpenWLANMap[7] App from mobile phones the mac addresses of surrounding wireless networks linked to GPS positions. This information will be stored into a database. If a device like a WiFi router requests its position, it will send surrounding Wireless mac addresses to the backend and get back a geo position, which is calculated from these information in the database.

The new web backend called sgps-core[8] is an API-core, which should replace the old backend. The old one consists of a collection of different programs in different program languages. sgps-core includes a fully backwards compatibility to the old openwifi API[9] for requesting a position. sgps-core is written in Golang, which processes a lot faster than the old API, which is written in Ruby. sgps-core is more secure because it checks and take only requested strings, which contain only comma separated macaddresses with 12 hex characters.

As a fallback feature, sgps-core is able to receive coordinates from unknown WIFIs by requesting them on Mozilla Location Service (MLS)[10] if there are no db entries for that WIFIs. The position for clients will be returned in form of latitude and longitude. As a quick reminder, here is the schemata from the first post, which represented the the functionality of sgps-core:

The sgps-core solved a problem about calculating the position. The old method counts the average of all latitude values. Analogous for longitude. The new method calls geographic midpoint calculation and needs 4 parameters lat0, lon0, lat1, lon1 (give two take one) which will be explained in detail in following:

deg have to be replace with latitude or longitude value.

rad = deg *π / 180 <- Generally conversion from degrees to radiant.

dlon = (lon1 – lon0) * pi / 180

lat0 = lat0 * π / 180 <- lat0 from degrees to radiant.

lat1 = lat1 * π / 180 <- lat1 from degrees to radiant.

lon0 = lon0 * π / 180 <- lon0 from degrees to radiant.

Converting into Cartesian coordinate system.

Bx = cos(lat1) * cos(dlon)

By = cos(lat1) * sin(dlon)

Calculate new position reference to sphere and Converting back from Cartesian coordinate system into new latitude and longitude:

lat2 = atan2(sin(lat0) + sin(lat1), (cos(lat0) + Bx)² + By²)^(1/2))

lon2 = lon0 + atan2(By, cos(lat0) + Bx)

On this point it is also possible to use a ellipsoid to increase the accuracy of positions. This may be interesting for long distances. For short ones like from seen wireless networks, it is not really relevant.

Converting back to degrees:

deg = rad / pi * 180 <- Generally conversion from radiant to degrees.

lat2 = lat2 / pi * 180 <- lat2 from radiant to degrees .

lon2 = lon2 / pi * 180 <- lon2 from radiant to degrees.

In the last few weeks, I spent a lot of time on discussing with the current server administrator of to deploy the sgps-core on the server for a test environment. But he did not have much time, so we decided to migrate the to our Nordwest Freifunk infrastructure to make the administration more accessible for other people. In my last report I wrote “I will release in the next few days a first version”. This could not be done because of the above mentioned discussion. After the migration I can test that backend on huge databases and compatibility to the DBS. The current code can be found here [11]. For people who want to try the sgps-core please check out the following URL[12].


The Idea at the beginning of GSoC17 was to write a program to provide GPS NEMA-formats over a tty udev device. The information for the GPS NEMA-formats should come from the above mentioned sgps-core. As I told in the first blog post I discussed with some people from the Mozilla Location Service Malinglist and it turned out that something similar was already exist called geoclue. To avoid developing redundant software I decided to drop this idea. Instead of it the new plan was to build support for native GPS in gps-share[13], which is an add-on for geoclue. But during the Google Summer of code I had to focus more on the both other subprojects because they are more important, especially for Freifunk. In my peroration I will tell about the future plans, especially for gps-share.

LEDE Packages

The third subproject was to create some opkg packages for LEDE[14] and similar Frameworks. The main package called geolocator provides the geo position of the device via UCI[15]. Positions should be received from the above explained sgps-core. The 4 other packages are only for Gluon[16], which add the configuration options of the geolocator to the Web-interface.

This month I mainly worked on the LEDE Packeges. At the beginning of the august I sent a merge request to Gluon for integrating the Gluon-geolocator[17]. The containing geolocator program was written in ash shell code. While reviewing and discussing about the merge request, I realized that I had to rewrite the program from shell to lua code because Gluon mainly work with in lua written programs. You can find the shell code here[18] and the Lua version here[19]. At the moment I am waiting here for another review and subsequently merging.

The other packages for the Gluon Web-interface are also already in process. The first idea was to create a detection of installed packages to show related configuration options on the Web-interface. This idea was dropped because I found a better solution. The problem is detecting packages on runtime, which means many extra code on Routers, which only have 4MB Flash for example. So I decided to generate the package with their options on compile time. These packages are:





The main package is gluon-config-mode-geo-location, which is already exist in gluon, but with a difference Web-interface. Each package should either integrate an open street map or the geolocator options. Integrating both are also possible. For communities which would like to stay on the currently variety of functionalities, it is also no problem not integrate any of these extra options.

Here is how the new packages look like:

I wrote some C++ programs, which generate me the Lua code for the Gluon Web-interface, which is written in Lua. Base on preprocessor variables, the amount of options for each package will be included into the Lua output from the C++ program. These preprocessor variables will be set by selecting one of the above packages. Also PO files for the translation will be generated in the same way. A merge request of the above new packages can be found here[20] I am still working on it.

Peroration and Future plans

Now I am coming to my peroration.The last 3 months were really awesome, just like last year as a student on the Google Summer of Code. I would love to recommend this great opportunity for not only students but also for open source organizations. Students can not only learn a lot of new things but also meet new great people, make new friends and take part in many events. For example: at the beginning of august I was on the SHA2017[21] (Still Hacking Anyway) and had a meetup with some Freifunk communities there. We had a great discussion about a lot of technical stuffs and a nice time for socializing. The SHA2017 took place in Netherland nearby Amsterdam. Another example is : this week I flew to Spain to start my exchange semester. Coincidentally a student from Germany who I met at the beginning of the GSoC17 in Berlin on the WCW[22] (Wireless Community Weekend) is also doing an exchange semester in Spain. We have already emailed each other and planned to meet up in the next months, probly in Barcelona or any other places. As I said above, this is my second time as a student on the GSoC, which means this is also my last time and sadly I have to say goodbye to GSoC as a student now. But maybe next year I can work as mentor to support other students in their great opportunities.

Back to the projects, as i said I’m still working on it. I will finish the Integration into Gluon and LEDE and continue developing sgps-core integrate new features and migrate the infrastructure to a better server. I would like to contact Zeeshan Ali, the maintainer of gps-share and try to help on this project as well. Also I am still working on the hoodselector which is my Google Summer of Code project from the last yeah. You can read about it here[23]. The hoodselector should also integrated into Gluon but it requires for sure a few weeks of work to integrate VXLAN on it. A merge request for can be found here[24].

Also I would like to say thank you to my Mentors Clemens John from the Google Summer of code 2016 and Johannes Rudolph from 2017 and especially to Andreas Bräu who works so hard on the Freifunk Org for many years to give students these opportunities to be a part of the Freifunk Community.



























Hi everyone,


I am now taking you over my second evaluation. A German version of this blog post can be found here [0]. For people who did not read over the geolocator (Software defined GPS) project before, here is a link to the project introducing (english)[1] and (german)[2]. The first evaluation from last month can be found here (english)[3] and (german)[4]. First of all I would like to tell you about the web backend:


Web Backend

As I said it in the blogpost before, the new web backend should replace the old one.
The current web backend consists of a collection of different programs in different programlanguages. The new one is written in Golang it has a fully backward compatibility. The new web backend is more secure.  It checks all requested strings at the end of the url that they contain only comma separated macaddresses with 12 hex characters, as a validation check.


Also the new web backend fix an issue by calculating the requested position. The method before just adds all latitude values and devides them over the amount of positions. Same for longitude. The new way is a geographic midpoint calculation. First the lat/lon values will be converted into radius and then the radius will be converted into a Cartesian coordinate system, after that the midpoint calculation will be done and will gave us a lat/lon in the form of radius and the values will be converted back into degrees, that is all.


The web backend has a new feature which should help to enhance the position quality. If there are BSSIDs unknown in the database of, the new backend sends an extra request for the unknown BSSIDs to Moziller location service [5] and brings that information into the calculation of the response.


At the moment the new web backend is being tested. In the next few days a first version of the new web backend will be released. The current code can be found here [6].


LEDE Package

The last project is to build packages for LEDE and send merge requests to Gluon. The idea behind that is, for WiFi routers and other WiFi devices to be able to automatically receive their own position. This could be a nice feature for mobile Freifunk Routers. It could also provide a good alternative instead of setting positions by hand. A first version of that package is here [7].


For the integration in Gluon I plan 4 new packages. The first one is the gluon-geolocator, which depends on gluon-node-info and provides the programme with the capability of receiving geopositions based on surrounding WiFis.


The next 3 packages are just for the Gluon configmode. The configmode is a state that begins at the initial start of a Gluon router and the owner of that router can configure it over a LAN connection.
I would like to integrate the following 3 packages within the gluon-config-mode-geo-location.
They are named:


As their names indicate, the package gluon-config-mode-geo-location-with-geloc-map should integrate the options of the geolocator and an OSM map into the configmode. The other 2 packages, gluon-config-mode-geo-location-with-map and gluon-config-mode-geo-location-with-geloc should either integrate only an OSM map or just the configuration options of the geolocator. Also the package gluon-config-mode-geo-location should be able to and will show the current location interface without any map or geolocator.


A merge request of the above new packages will follow soon. Some of the gluon-config-mode-geo-location extensions are currently not finish yet.


In the next few weeks I would like to finish the integration into Gluon, as well as continuing to develop the new web backend and releasing the first version of it. There are many ToDo points currently open e.g. Multicore functionality, optionally other geographic midpoint calculations. At the beginning of August there is the SHA2017[8], which I will use for a marathon session.


With best wishes
Jan-Tarek Butt


geolocator (Software defined GPS) first evaluation

Hi together,
Now I am coming to my 1 phase: evaluation. An introduction into the geolocator (Software defined GPS) has been already done last month. You can find it here [0]. In the previously mentioned blog post I have told about the 3 main sub-projects: web backend, gps-share, LEDE Package. In this post I will show you what I have done in each sub-project. Beginning with the web backend:

web backend

This sub-project should replace the old web backend of the project. 
The old backend is split into various programs and scripts, grown over years. First of all I started with the part of receiving positions. This program is written in ruby and just parses the URL as a string. So users can simply call
wget -O -,0018E7DC21BB,30FC681F37A6,F81A673626E8,EC086BA8ED18,8416F9A8E2FA,E894F6A230E4,98DED020D00A,EC086B3349B2,F81A677F5CD8,A0F3C1654BA6 2&>1
and will receive latitude and longitude. The BSSIDs in the above URL are from surrounded WiFi networks. The old ruby code just drops all characters up to the last splash and splits the BSSIDs by comma. The result array will be integrated into and SQL command which returns a position for each BSSID. The code for this part is non public, because the developer doesnt want to risk attacks by hackers. I started porting the old ruby code to golang. Currently I am working on the database connection. So in the next few days the backwards compatibility will be finished. The current code can be found here [1].


gps-share is a software which provides GPS informations in the local network, written in rust [2]. It supports many GPS hardwares and shares the GPS informations over a network-NEMA format. Zeeshan Ali, the maintainer of geoclue, has already released a first version of gps-share [3]. Zeeshan and I discussed on the Mozilla Location Service Mailing-list about that project [4] . As I told it in the last blogpost, the gps-share is an alternate project to the original idea. This helps geoclue to work directly with GPS-hardware´s and builds an defined interface via dbus to receive geopositions over GPS hardware, surrounding WiFis or other ways.

LEDE Package

The last  sub-project is a new LEDE-package, which provides geo positions received by their surrounding WIFIs. I have already built a first version of that package here [5]. I also started discussing with maintainers of the gluon framework, which is a popular framework in the Freifunk community. My plan is to integrate the goelocator also in gluon so routers can automatically receive its position. A first draft can be seen here:

An idea is that the Web interface of the router could detect installed packages and provide their options on the Web interface. This means, that in the drop down menu, the option “Automatic (geolocator)” will only be shown if the package geolocator is installed. This makes it easier for local (freifunk) communities to integrate new options of position detection into their firmware.
This is also my last week of my exam period. Now I can work full time on the project. Next plans are improving functionality of the new backend, building CI unit test for the new planed API and building the Mozilla Location Service communication interface to sync the requests between MLS and

geolocator (Software defined GPS)

Hi everyone,
My name is Jan-Tarek Butt. I am in my fourth term of computer science at Emden University in Lower Saxony (Germany). Some of you may know me from the last Google Summer of Code. I am one of the students who is participating for Freifunk in the Google Summer of Code 2017. In the following post I would like to introduce you to my Google Summer of Code project. I split up the project, same like last year, into 3 main subjects: web backend, gps-share, LEDE Package,

web backend

The first one is a restful API backend[0], which should include a backwards compatibly to the api format of the old openwifi web backend[1]. The new backend should be written in Go, which will be clearer in the next few days. The New API should use Mozilla Location Service as fallback if it is not possible to determinate a position based on the own db entries. Received WiFi information can also redirect to Mozilla Location Service[2]. So some of you might have the question what is Mozilla Location Service. It is simply a service with a big database full of wardriving informations from mobilephones. Mobilephones scan for surrounded wifi networks and send this with its own position to the Mozilla Location Service. These datas will be integrated into the database. If you want to know your position without having GPS, just send only your surrunded wifis to the Mozilla Location Service and you will receive your position based on the wifi informations see the picture below.


The first Idea was to create a software defined GPS as udev device which should provide NEMA-famata protocols over tty and receive the necessary informations over wifi. While discussing with people on the Mozilla Location Service Malinglist, it turns out that something similiar is already done in geoclue which provides geo coordiantes over dbus and can receive coordinates via Mozilla Location Service. geoclue works with network-NEMA and Mozilla Location Service. Over network-NEMA geoclue can receive GPS informations from Mobilephones and GPS modems working over local networks. To avoid of developing redundant software, i discussed with Zeeshan, the maintainer of geoclue, about building support in gps-share for standalone GPS instead [3]. This is a software which should provide GPS NEMA-Format from GPS hardware over network-NEMA for geoclue. gps-share is written in Rust for ensuring reliability.


The third subproject is a new lede package called geolocator, which should provided geo positions received by their surrounded WIFIs. The WiFi informations should be sent to the new above mentioned backend[4].
Jan-Tarek Butt