Day 4 of the terrestris code sprint in Mallorca was dominated once again by the Bits and Bytes of Geographical Space. There were strong advances in the migration of GeoExt to ExtJS 4: During the course of our code sprint we have currently managed to adapt 12 classes of GeoExt 1.0 to ExtJS 4. Amongst them are the LegendPanel including WmsLegend and UrlLegend, as well as the GeoExt-Action-Class so that OpenLayers-Controls can be used in the UIs. The Sensor Observation Service that used to run with some test data was switched over to some real stuff. A parser now supplies the SOS with up-to-date data from a Geo-RSS-Feed. Due to the new interface that generates a WMS for the respective SOS the data can easily be published on an interactive map. The OL-Builder used to generate Custom-OpenLayers-Builds got a new face: A comfortable ExtJS 4 GUI now enables the selection of the necessary classes including the automatic detection of dependant classes. At the WMS front several approaches for the generation, rendering and performance enhancement were tested and evaluated. Amongst others an interface to Mapnik was created so that QGIS projects can be tagged as ‘to be rendered’ and as ‘TMS’. All in all the terrestris codesprint is being viewed favourably. Many things were approached and although there were only a few days an impressive amount was accomplished. Once we are back home we plan to improve on some of the things started and hope to present the odd goodie to the public as for example an OWS-test-site.