[OSGeo-Boston] Switching From ArcIMS to "something else"

Christopher Schmidt crschmidt at metacarta.com
Wed Nov 21 10:01:24 EST 2007

So, I got 3 personal (count 'em, 3) emails yesterday on what to switch
away from an ArcIMS server solution to. Since I hate answering anything
in private (shared knowledge > non-shared knowledge), I thought I'd
address them here, since I know that a fair number of the local people
work in/around MIT, which uses (as I understand it) ArcIMS to do their
WMS-style work.

The first question to answer when switching away from an ESRI-based
solution is what type of data you're serving from. Moving away from ESRI
can be hard if you've got all your data in a giant ArcSDE database --
not impossible, but it makes things more difficult. If, on the other
hand, you have things like shapefiles, then it may make the switch

Next, figure out what you want to do with the data: Do you want to serve
it up to GIS clients (ArcGIS, etc.)? Do you want to create a web
interface? Do you want to help people to create mashups? Do you want to
let users edit it? etc. 

If I were to take something like MIT's 'whereis' map datasource, I would
probably (personally) do something like:
 * Dump the data to a PostGIS interface
 * Load it up into MapServer (this requires converting the existing
   style information into MapServer's mapfiles, which is possibly
 * Set up a WMS against that, using MapServer
    * This will be used by clients who consume WMS, a la ArcGIS/qgis
 * Set up TileCache in front of it, picking a small number of
   projections that are acceptable to pre-cache. I'd probably just build
   this on a machine with lots of disk: it seems unlikely that you'd get
   more than 100GB of cache even with three different layers. These
   TileCache layers are 'basemaps' -- you probably want EPSG:4326 (for
   most 'unprojected' maps), EPSG:900913/SphericalMercator (for use with
   Google Maps), and the local projection (for local-only maps).
 * Use OpenLayers to load the relevant layers into a map
 * Use either a small overlay WMS layer or OpenLayers vector support to
   display selected features and the like.
 * Stand up FeatureServer, with attribute querying on useful attributes,
   to get WFS-like services for GeoJSON, GeoRSS-Atom, KML, etc. This can
   also have read-write layers for user input. 
Then, you document all these things and see who comes along and uses
them :)    

Specific use cases, of course, matter. If your primary goal is to make
data available for use in ArcGIS, this might not work for you. But
MapServer (5.0) + TileCache + OpenLayers makes a great, fast map
browser: see http://boston.freemap.in/ for an example of my personal
attempts at that.

Christopher Schmidt

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