Scaling problem with Occupancy Grid and (Google) Maps

[Mario2407]

Hi,
I want to visualize an occupancy grid and also the Google Maps map. I use https://github.com/danielsnider/MapViz-Tile-Map-Google-Maps-Satellite for getting the maps data and I use some sort of SLAM with RTK (GPS) and building the map via Octomap.
I set the map frame origin with the first RTK message I receive.

The problem is, that I set the transform from /wgs84 to the map with the exact same coordinates and the origin of the occupancy grid (0,0) exactly matches with the coordinates of google maps (lat/lon 45,.../12,...).

For some reason when i go +1m in the map with my cursor, also the lat is changing +1. So it is out of scale.

Is there any known solution for scaling the map and/or occupancy grid?

Thanks!
Mario