Essential I load the map once then 'pan', render, save image, and repeat till all of map is saved. Each time I
pan/render/save, the metawriter creates the json file, but it over-writes the previous iterations file.
Is there a way that the meta writer could append to an existing file so that a single file is created for all iterations?
I have a simple work-around that creates a new file for each iteration by programmaticaly changing a replacement variable,
then post-process the discrete files into a single one.
(Reported by David Eastcott)
Closing this bug as metawriters have been removed from mapnik.