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Project: Grenzhus Geo

August 12, 20192 min read


Grenzhus Geo is an Android App I developed back in middle school together with my classmate Adrian. It was a voluntary project to improve our history grades. Although it’s really some time ago (the app was last updated on November 23, 2014) I thought it could be interesting to write about it and recap our results.

So, whats the point of the app?

The App

Our school was located not far away from the former inner german border which split the DDR from the BRD. We contacted a border museum called ”Grenzhus” in Schlagsdorf. With their help we developed a concept for a geo-caching like app where the user needs to find barcodes which we placed on some historical points along the former border. Each point has its own descriptive text which included some historical facts about that point.

This way a user can walk around the area and search for barcodes while also learning something about history.

Technical challanges

I think one of the biggest challanges was reading out the GPS sensor and converting its coordinates to the correct pixel spots on screen. We decided to embed a own, simplified map and not Google Maps or Open Street Map. The app only makes sense if you are near Schlagsdorf so there is no need for a fancy, scrollable map.

To convert the coordinates we just used a linear interpolation between some points we determined empirically. This is definitly the wrong way to do it but the total area of we needed to support wasn’t that big it did work really good.


The map view The detail view
A screenshot of the map view A screenshot of the detail view


It was a fun project and one of my first contacts with Android App development. I’ve learned about our history and also about geological coordinates.

A big problem was the missing iPhone support. While it wasn’t possible to spend 79€ at that time for a yearly apple developer membership, the missing support excluded about half of our classmates.

Also, in retrospective the design of the app was really ugly.

A big shout out to our history teacher and Dr. Wagner who gave us this oppertunity and supported us during the development.

The App is not maintained anymore, neither digital nor were the barcodes replaced. But you can find it on the Google playStore.

Here are some german news articles regarding our app:

© 2022, Nicolas Hollmann