Monday, January 4, 2010

Directions, directions

So I am returning in the new year with a major task at hand: finish work on UD campus maps. As I recall, the major loose end from where I left off was the matter of the basemap -- which resurrected old considerations about maintaining all layers on a cloud site (i.e. openstreetmaps) and send all operations to be dealt with on a local spatial database. During this diversion from the previous course I need to also keep in mind: the basemap issue only comes up because I want to offer national directions to campus in the same interface as the rest of the campus map ... otherwise I could just use local layers without need for larger extent basemap layers.

The OSM scenario is very appealing for a number of reasons:
-cloud hosting would free up local resources here
-the OSM platform is well designed according to collaborative logic, that would allow updates by data stewards on campus, if we were to move in that direction
-OSM is open source, it's free to us, and is very interoperable with other open software ... that would help in efforts to support open source on campus
-possibly better performance on the cloud
-use of existing renderers allows us to leverage existing cartographic/labeling rules

-layers could be edited by a third party with poor editing skills, inaccurate data, or malicious intent
-limited control over appearance of the map
-strange issues with spatial referencing ... OSM and existing UD layers do not agree ... these are also off with navteq streets, so problem is independent of OSM ... should note that the issue is probably not significant without sidewalks, since these tend to be more closely located to streets than buildings to streets
-still unresolved data sensitivity issues (we need to contact all data "owners")
-tendency to neglect local resources ... no redundancy

These disadvantages could mostly be overcome, but would probably require quite a bit of work, with some of the advantages becoming mooted
-OSM data could be stored locally, taking advantage of some tag which signifies campus data ... that is what UMd does. However, that is probably impractical for the national dataset (UMd only has part of the DC region), and would moot any advantages to using the cloud ... would however help with redundancy
-A custom renderer could be used to achieve more control over appearance ... this may be unwieldy to setup ... could try to tweak tags, etc. in OSM data as a work around ... could Mapnik default rendering be adequate?
-spatial referencing issues are independent of OSM

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