From the other side of the fence …

Like all good arguments, there are other sides. In what seems to be a two part OGC mini-series on Charlie Savage’s blog RE: problems with the OGC, I noticed a comment by Shane asking …

I’m surprised at the lack of outburst by the pro-standards community. This makes me think they are humbled by your views. I’d expect somebody out there to stick up for OGC and the other standards you mentioned. It would be intriguing to hear someone from DM Solutions or Ionic, for instance.

Even though i am not Ionic, DMsolutions … here are some thoughts from someone who thinks the OGC has created some pretty darned useful standards.

A retort to one of Charlie’s post if you will .. :)

Rendering Maps. The argument i often see with the WMS bashing goes something like, “WMS is slow. Who uses it in an Enterprise architecture. G/Y/M dont use it, therefore by my intelligent calculations, WMS must be useless”. Lets back up a second. If you want a high performance, slippy interface that can be easily cached, tiling is certainly your best bet. I get the distinct feeling that a lot of people forget the disadvantages of a tiled mapping cache,

  1. Fixed scales. The amount of people i see who simply generate their zoom levels based on GMaps is crazy. What about what your users want? If there are any papers detailing why splitting the world into 18 distinct zoom levels is ideal, please tell me. I’m yet to find one. One size will never fit all.
  2. Redundant data storage. Active caching mechanisms whereby caches are only populated once browsed is nifty, but it also negates somewhat the advantage of using a cache. Conversely, if you pregenerate your entire cache you are more than likely storing 80% (number plucked from the sky) more data than you need. We also arent even touching the storage of the source data either here, or considering the time required to maintain the cache when you are using volatile datasets.
  3. Lack of integration across clients. The whole benefit of standards it to enable cross-use, cross-communication amongst clients and servers. This is non evident amongst tile servers (beyond of course worldkit and openlayers). Sure, WMS-C / TMS are hopefully gathering steam at the moment, but if you are considering integration right now across a gamut of applications, nothing is better than WMS for transferring maps over the interweb to multiple clients. People seem to be losing sight of this purpose every day.
  4. And the kicker for me … Absolutely no customisation. Dont want that road layer? You better hope they duplicated the cache and removed them otherwise you’re in trouble. Want the map in a useful cartographic projection? Duplicate again! Hmmm, can you colour the cadastre yellow instead of red? No, but i can duplicate the cache again for you. I could go on, but you should get the idea ..

And finally, “Arbitrary bounding boxes” are your friends Mr Charlie! Let your users decide their output scale, not the magical we-chose-18-scales-coz-google-wanted-a-nice-single-square-tile-at-zoom-level-0 :)

Summing up, WMS is your friend regardless. Don’t toss it out with the bathwater just because you are using a cache with a slippy map. Implementing WMS and whatever tiling scheme you can easily abstract *AROUND* WMS will give you and your users the best of both worlds. The fact that you can quite easily use any random WMS server inside a tiling scheme surely highlights that the standard does have flexibility.

Time is at a premium at the moment so i wont reply to all Charlie’s points (especially sharing data because we could be here forever). All in all i can see his point of view however we need to remember that we can only work with what we have at the moment, despite their flaws. GeoRSS/Atom/OWS Context/KML ratifying are all coming, its just up to the rest of us to pick up the ball and keep running with it so this will never be true again,

Web mapping standards are going through a transitional state and haven’t kept up with GIS technology breakthroughs over the last few years.


2 thoughts on “From the other side of the fence …”

  1. I can not agree more strongly with you Chris. People are hung up on the G/Y/M mapping systems. WMS is a very important standard which and OGC standards have freed my ability to choose the right tool for the job, depending on the clients desired outcomes.

    Having been involved with pre-caching tiles for internet mapping systems I can tell you even minor changes to data / styling have huge impacts. For the WMS systems I also work with changing with customer demands is much simpler. Very different goals with each though.

    When I worked on selecting defined scale levels my head was in a spin. Trying to keep the right amount of continuity of features between the scales was a constant trade off. I wanted to draw on my paper cartography skills but felt constrained by the technology – that creepy feeling that something just isn’t quite right.

    Interactive maps are powerful and allowing the user to define their scale and area of interest is in my mind the huge difference between paper (street directories etc) and the choice of using interactive systems.

  2. Hello everybody, my name is Damion, and I’m glad to join your conmunity,
    and wish to assit as far as possible.

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