2006 (old posts, page 18)

Heads in the Sand

In the comments of James Fee's AGX vs GE post (and others), ESRI users cling desperately to the mantra that ArcGIS Explorer and Google Earth do different things and aren't competitors. However, as Stephen Geens notes (at the end of this post), Google Earth users with a serious GIS background are ready, willing, and able to compete with AGX and ArcGIS services.


Re: Heads in the Sand

Author: James Fee

GE is a non-starter Sean. $400 a pop? I don't know about you, but I don't have that kind of money in my budgets. World Wind + Open Source GIS Server has much more potential competing with the AGS/AGX stack. AGX won't appeal to my clients as they don't really have the need or budgets for 3D Globe applications. I'm more interested in movement toward OpenLayers, integrating existing ArcIMS and WMS services.

Simplicity and the Corporate Development Firewall

Good post from Pete Lacey about how much of the IT industry can't hear the victory cheers. Thanks largely to Google, the situation is better in the geospatial business. Google Maps and Earth have utterly breached the firewall in our industry. Only the deepest of the deep corporate spider-holes could hide a geospatial developer from un-enterprisey ideas like the GMaps API, KML, GeoRSS, and REST.

Plone Conference Keynote Video

I didn't expect it to happen at all, but Eben Moglen's keynote address at the Plone Conference moved me. I admit that it's easier to do these days now that I'm a parent and feeling sappy. (How sappy? My wife and I almost lost it at the end of Peter Jackson's King Kong, that's how sappy.) I want my daughter to grow up in a more free, more fair, better world, and I'm proud to consider that my work on free software is helping to make that better world possible.

My favorite stretch of the keynote is where Moglen asks us to consider a world of proprietary math. Imagine that you can only use as much math as you can afford. Multiplication and division might be too expensive for the poor or underemployed. The means to solve simultaneous PDEs might be beyond all but the most wealthy.

What if Newton or Liebniz had been inclined and able to lock up Calculus with a proprietary license? Developments in the field of Mathematics would have slowed to a crawl, hamstringing the Enlightenment. What if Legendre had locked his Transform with a proprietary license? Mathematical Physics would never have flourished. There'd be no electronics, no atomic theory, no computers, no iPods. We'd be sitting around complaining about the price of newspapers and oil to keep our lamps lit.

According to Moglen, this is where we are at today with regards to software. Watch him make the case for free software in large (YouTube) or massive format (archive.org).

Stop Using Mapscript

Stop using MapScript. I recently gave this advice to an email correspondent, and I'm repeating it here for my readers. Cease, or at the very least, minimize your use of MapServer's various language bindings. Instead, embrace MapServer's domain-specific language (DSL) and write more of the declarative cartographic scripts known as mapfiles. Use the mapserv (or shp2img) program to compile these scripts into images. This is the path to happiness and prosperity.

A common complaint of the mapscript programmer is: "My program runs N times slower than the MapServer CGI". Of course it does. MapServer's code has been stressed and optimized over the years. It's faster and less buggy than anything you're going to write without serious effort.

MapServer's scripting APIs are inconsistent and not well documented, not friendly to the user. On the other hand, your favorite programming environment bristles with excellent tools for creating text documents such as a MapServer mapfile. Ed McNierney has long advocated the use of C preprocessors to generate mapfiles. A fine example for Python is Allan Doyle's ElementBuilder-based mapfile builder. I would be surprised if Ruby's Builder couldn't be extended in a similar fashion.

Another reason to embrace MapServer's DSL is the reasonable expectation that tools will evolve to port your MapServer mapfiles to other applications. Good luck getting help to port your thousands of lines of custom mapscript code to PrimaGIS, Mapnik, or MapGuide.

MapServer has but one obstacle to programming in such a completely declarative style: you can't pipe in a script. The script must be a file on disk (hence the "file" in mapfile), and this requires an often unnecessary I/O round trip. For the same reason, Allan has to write his mapfiles out of Python to disk before he can load them again into mapscript map objects: maps can not be instantiated from strings.

Why do these limitations persist in MapServer? Because developers lost the declarative trail when they found mapscript. Among them, I was caught up in writing too much code with mapscript.py. From a distance, it's clear to me that I overlooked many of the benefits of using MapServer in a completely declarative style.


Re: Stop Using Mapscript

Author: Christian

Hi M. Gillies, I am a programmer at the McGill University in Montréal, where I work on a GIS based surveillance and analysis system for TB cases. It's been a couple of weeks since I decided to use Mapserver for our system, and I am still prototyping it using a mix of PHP and Python Mapscript, PostGIS and the R statistical language. I am also studying the possible use of a dynamic client UI package (Ka-map seems an interesting one). Since I am a novice Mapscript programmer I had to gather infos about it from a variety of reference files and tutorials. I am satisfied with what I was able to achieve up to now, but I was quite intrigued today by your post with the advice that "we should stop using Mapscript" (I am reading your blog quite regularly by the way). I would like to know more about that idea of relying less on Mapscript, and more on the Mapserver DSL, through increased use of mapfiles. Could you expand on this change from the procedural paradigm to a more declarative one? Of course I woulndn't ask for a code tutorial, but I would like some more precise ideas, if you have time for that.

Start Using the Mapserver CGI Interface

Author: Paul Ramsey

90% of the stuff people are doing in Mapscript can be done just as well via the Mapserv CGI interface. Most of what Mapscript provides is the abilty to jimmy with settings in an existing mapfile, they hit the big red DRAW button. Well, you can do that just as well with the mapserv.cgi. Go here http://mapserver.gis.umn.edu/docs/reference/cgi/controls and then go right to the BOTTOM, to the obscure little section labelled "Changing map file parameters via a form or a URL". Then swear off mapscript for good.

Re: Stop Using Mapscript

Author: Sean

Paul, mapscripting via CGI query string is a smelly hack. On the other hand, you are right, it covers most of the same ground as mapscript.

Re: Stop Using Mapscript

Author: Paul Ramsey

Smellier than dumping mapfiles onto the filesystem and re-ingesting them? I would have thought using mapserver as a pure "web service" got more style points than the dump'n'read approach. A nice side-effect of my trick is that when you're deploying you can put your mapserv instance separate from your application server.

Landscape Words

Place names and class of names are the main points of our upcoming Pleiades milestone, so it's an interesting coincidence to hear about Barry Lopez's book about landscape words on NPR the other evening. Reading the excerpts, I became a little sentimental about the names of my favorite landscape, the Colorado Plateau: slot canyon, dry fall, reef, arch, tank, water pocket.

More on the Plone Conference Sprint

I've always done a poor job of explaining what these software sprints are all about. Jon Stahl does a much better job here. If you look closely you will see my chin in the very upper left corner of the fifth photo in his blog entry, sitting just behind Jackie, Martin, and Alexander.

Props to ArcMap


I just finished making a map of Tanacetum vulgare (Common Tansey) incidence for a visiting ecologist. I learned to do this kind of task with ArcView 3 back in the previous century, but left the data processing and analysis business before my employer upgraded. This means I never really tried out ArcMap until now. I must say that it's perfectly adequate for this kind of task, allowing me to add a new attribute to features and hack away at the attribute table using search and replace. A scriptable interface to the symbolization would be nice, but the provided tools are not too bad. Everything I remembered about good ole ArcView 3.2 seemed to transfer right over to use of ArcMap 9.1. The whole thing, not including the time to find and download decent data (North American Framework from GeoGratis) took about 20 minutes. There's no greater message to this story, I just feel that I owe the blogosphere a report of a good experience I've had with proprietary GIS software.

SDI in a Box

There's an accurate, well-written article on geospatial open source by Christopher J. Andrews in Directions Magazine. In the last paragraph, Andrews writes.

With the liberal licensing on some geospatial OSS, I hope an industrious company will develop a 'map server in a box' appliance. Such an appliance, coupled with a basic methodology to package up an organization's available data, would greatly accelerate the adoption of geospatial OSS and further decrease the TCO for geospatial open source.

People having been talking about mapservers or spatial data infrastructures in a box for a while. It's bound to happen any day now, but almost certainly without the box, instead using "elastic" arrays of virtual machines.


Re: SDI in a Box

Author: Allan

Three relevant papers from FOSS4G: GDIdevl - running a GDI Lin-on-Win Geospatial Virtual Appliance - MapSnack How to fit 5 Kilos of Software into a 1.3 Kilo Box See what you missed? And that's not all!