[Qgis-user] Re: File-based Mastermap

[Jukka Rahkonen]

 <jonathanmoules at ...> writes:

> 
> I need to deploy four stand-alone laptops with
> a basic GIS (data viewing only) and have chosen QGIS for this. The data
> held is for the entire county of Warwickshire, and one of the datasets
> I need to put on there is MasterMap. Specifically the datasets I'm using
> are:Topographic line: 3.7 million featuresTopographic Area: 1.3 million
featuresCartographic Text: 250,000 featuresGiven the dataset size, obviously the
first
> choice is a database, but as these are stand-alone laptops that must have
> the simplest setup possible (they're going to be used out in the field
> away from tech-support) I've ruled that option out.I tried shapefile's but it
turns out that

Hi,

I think that the best method for browsing that much of vector data would be to
use OpenJUMP or copy the way how it handles PostGIS layers in to QGIS.

What is special with the OpenJUMP native PostGIS driver is that PostGIS layers
are dynamic. Only the features from withing the map view are queried from the
database. They are cached for some time but previously used features are thrown
away periodically which keeps the memory consumption small. You can have
millions of features in the database but when you zoom in OpenJUMP is having
only a handful of features on the layer. Application makes a new query when user
is panning so all the millions of features are available when needed and the
system is practically as fast as PostGIS is.

What the user must do is to set scale limits for the database layers. It does
not make sense ever to show million features on a map. When zoomed out the
application must switch off the detailed layer and show some genaralised layer
instead. That could be done by making such a into PostGIS and addind that as
another layer into GIS project.

-Jukka Rahkonen-