i’m having trouble creating a custom geostationary projection with Basemap. what i’d need is not a full globe projection, but the upper third of a full disc (full width, one third from the top down ). i found an example here: explaining how to make a projection for the upper right quadrant of the disc using the llcrnrx, llcrnry, urcrnrx, and urcrnry keywords. following the example, i thought i would get my result like this: which gives me a weird plot. from the example i though that for the new projection the lower left corner is always (0,0), then you just calculate the width and height coordinates (upper right). this obviously is not the case. with just bare experimentation i have this now: which gives me a rough estimate on what i’m after, but i have no idea why this works and what the corner points really represent. or the pyproj module (with preserve_units=True because pyproj assumes that your coordinates are in meters and this is not the case for EPSG:2227): Source.