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I'd like to get an idea for what's involved in creating isochrones for a series of sites, with a reasonable degree of accuracy to the estimates. A general outline would be great, though my scenario would be for sites in London as I guess the problem varies with availability of data.

--thanks for comments so far, very useful (the london at night mashup's great :D), sorry the q was too vague. In this case I'm looking at travel time modelling for specific sites using transport network vectors and nodes. Data currently available are the OS Master Map Integrated Transport Network (ITN), National Public Transport Data Repository (NPTDR) which contains a snapshot of public transport timetables in "ATCO-CIF format (including its accepted variants) or in TransXChange TXC v2.1 format" (inc. bus stops), also most of the OS datasets. Tools to hand are MapInfo 10.5, Manifold 8, SQL server 08, an open source stack (postgres/pgis/qgis etc.). Trying to get a handle on the scale and complexity of the task, possible approaches and requirements. It looks big, complex and demanding, but on the other hand must be a common application of GIS technologies.

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It might be useful to provide a little more detail about your data. Generally, if you have a set of points with a magnitude value (you may need to normalize time data so the software can treat it more easily as an attribute), do a surface interpolation and then use an isoline generator. Many GIS packages have this functionality. For example: surfaces.co.il/?p=578 –  glennon Aug 6 '10 at 17:29
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This kind of "List of X" question should be set as community wiki. –  JasonBirch Aug 7 '10 at 4:25
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5 Answers

I'd suggest you look at this Q&A: Creating drive time polygons using open source tools

In particular this blog post might be exactly what you're looking for.

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Most of our software (from RouteWare) can create drivetime isochrones. Either as SDK's or as a plugin for MapInfo. We have a free importer for ITN data too, that sets up the data, almost ready for use.

Sorry I'm late with the reply - missed the question due to holiday.

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Three more links:

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Two more examples:

As for working with OS ITN data. Although not in the realm of FOSSGIS, this can be done fairly well using ArcGIS. ESRI UK offers ProductivitySuite tool that works well for importing and managing ITN data. Overview here. You could build a network dataset out of it, with various costs, connectivity attributes etc. This can be then used in Network Analyst extension to buid 'origin destination matrices' or 'service areas'. Work could be automated through Python scripting of course.

For more ideas about software working with OS data you might also consult their website.

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Here is a Google Map API Mashup for London that generates Isochrones (Time) based on time http://london.mapnificent.de/ The marker is draggable and will re-calculate on the fly.

But as euki suggests you need to be more specific on your scenario.

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+1 Great use of Google API! –  underdark Aug 7 '10 at 0:50
    
+1 excellent example –  radek Aug 7 '10 at 12:09
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