Open Source GIS Clients

I have had a number of companies recently approach me about open source GIS options. This has something to do with my recently published articles. One interesting area has been an investigation into Flex GIS clients. Openlayers is the premier Web 2.0 GIS client; well supported, a rich library filled with an array of functionality .. but written in Javascript. Now I have nothing against Javascript, its free, has a big community behind it and runs in the browser. But I'm a Flex developer. I prefer it because .. it has an excellent IDE which makes for easy debugging, developing sophisticated interactive application is both quick and easy, applications run the same in all browsers, actionscript is object oriented. Actionscript is just nicer and easier to work with .. in my view.

So enough. Anybody who argues against these opinions I would not oppose. Its just how I feel about it. Anyway, the whole Flex GIS open source client issue. I have worked with Modest Maps for sometime now to develop mostly consumer maps. Stop right there! Consumer maps? The world of online maps remains somewhat split. GIS maps and consumer maps. Consumer maps I define as the use of basemaps - tiles which are derived from satellite images or vector road maps for example - to build mash ups; video, imagery, text using, often, the addition of map markers for access (or clickable icons geospatially placed on the map). Here is a simple example. Google, Yahoo, Bing, mapquest offer largely API's for developing consumer maps.

So what are online GIS maps. A simple question? Well maybe. GIS has moved from the desktop to the Web. It was very much a niche market. Geography type nerds generating applications and analyses in large part for government (a generalisation but close to reality). The frustration for GIS vendors was how do they broaden the market. ESRI and the other key private vendors struggled to sell into the enterprise. They still do in fact.

Suddenly google maps arrived on the scene. It shook the mapping industry to its core. Internet maps were everywhere. Its worth noting that Mapquest preceded Google, but the fanfare (and $) waited for Googles arrival. Suddenly the other GIS vendors needed to react. ESRI produced rival online products. But with a GIS twist.

So here we are today. A plethora of consumer map APIs. And ESRI sitting in a somewhat awkward position offering free API's hooking easily into their own server product(s) ArcGIS (not so easily into other providers). Offering consumer and GIS API functionality. With a focus to sell their complete stack to those interested. Their purpose is to make money.

So how about those of us wanting to build online GIS maps, but avoid the high cost of the private vendor solutions? The open source GIS stack is very mature. But how about Flex clients?

I've spent some time looking at the options. Base requirements include:

- Rendering both WFS and WMS in combination
- Overlays of these services on various basemaps
- Drawing tools for line point and polygons
- Identify functionality

I looked at both Modest Maps and OpenScales. Though not its focus there has been some work done on Modest Maps toward some level of interaction with spatial servers. I added a WMS layer at:

http://www.flexmappers.com/mapserving/mapservingWMS/

Note, I had to make some tweeks to the WMS provider, provided with the library.

Openscales is less mature. But very impressive for how long development has been underway. I built the following map application:
http://www.flexmappers.com/mapserving/openscales.html

It supplies much of the base functionality I was looking to include. WMS is proving a little challenging (but i suspect a style tag is mssing from the tile request) and the map interaction is not a smooth as Modest maps. Only openstreetmap is provided, but I am looking to port code from Modest maps to add this functionality.

Ultimately Flex should simply be rendering the points, lines, and polygons supplied by the server.

I am interested to see how easy it might be to port from one library to the other. Either way, Openscales is a very interesting project. One well worth supporting.

Map Technology Overview

I've been on a technology review of late. Mostly driven by client requests. I never cease to be amazed by what is now available. So far my thoughts in brief:

Mapserver is a pain to configure. Manually writing mapfiles, takes me back to the days of ArcIMS and axl files. Geoserver is far easier in every respect. It has a terrific admin interface. Setting up basic map services, WMS, WFS is easy. Exporting in formats read by google maps etc is also a piece of cake. If it were not for the need of a full application server, the choice of geospatial server would be easy. Geoserver also allows for easy generation of Georss, KML and viewing of map layers in openlayers.

Caching and tiling is another area which favours Geoserver. Geowebcache is integrated into geoserver. No need for additional work. The config screen allows for easy seeding. Mapserver works with tilecache. From the work I have done so far you tile mapserver by calling tilecache and passing the mapserver url.

I'm still working with openlayers but am so far very impressed. One thing I already notice is how much is there. I really like the Modest Maps Flex library. But with a smaller community, it does not have the same depth of code. I'm still playing here, so more feedback later.

I'd like to know one of the big fours - mapquest, MSN, Yahoo and Google - API's. I lean towards mapquest, largely due to the feedback I have read and my impressions from conferences. I recently signed up for their developer account. A couple of people were soon emailing me with contact info. On one side I thought this great, since support might be more forthcoming. On the other side, money reared its ugly head. Use of this service beyond local testing has a price tag! Reminds me why I so favour open source.

Other areas on my radar at the moment beyond testing the mapquest API include:
- Geodjango testing
- PostGIS and shapefile write up
- Javascript to Flex/Flash communication

I'll write more on this in due course. I asked Paul Ramsey (OpenGeo and PostGIS author) his thoughts on Geoserver versus Mapserver. Here is his repy:

If you are deep into OGC standards, Geoserver has a big advantage in
completeness of implementations of things like SLD and WFS. (Less on
WMS).

I did a talk last year which, though tongue-in-cheek addresses the
more important differences. Which are philosophical more than anything
else. Scriptable web rendering engine vs complete spatial web
environment.

http://s3.cleverelephant.ca/geoweb-mapserver.pdf

Most of the speed differences are gone at this point, they perform
very comparably for common use cases.

Modest Maps, WMS and Overview

Looking at the docs on wms and multiple providers the following proved a useful link:

http://getsatisfaction.com/modestmaps/topics/how_to_layer_two_maps_with_different_providers_for_blending_alpha_transparency_etc

I'll post my code in due course.

On a related note, here is a URL for an overview map with Modest maps

http://blog.modestmaps.com/2008/11/hello-world/

Flash Builder 4

The full release of Flash Builder 4 is scheduled sometime in July, replacing Flex Builder 3. I thought I'd take a look at what is different. Using the Modest Maps API I built a demo mapping application. I thought I'd post a brief snippet of that code. The first is the code in Flex 3:

<?xml version="1.0" encoding="utf-8"?>
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml"
minWidth="1024" minHeight="768" creationComplete="init()">
<mx:Script>
<![CDATA[

import mx.core.UIComponent;
import com.modestmaps.TweenMap;
import com.modestmaps.mapproviders.OpenStreetMapProvider;
import com.modestmaps.geo.Location;

private function init():void
{
}
]]>
</mx:Script>
<mx:Canvas id="mappanel" width="100%" height="97%"/>

</mx:Application>

This second is the same code using Flash Builder 4:

<?xml version="1.0" encoding="utf-8"?>
<s:Application xmlns:fx="http://ns.adobe.com/mxml/2009" xmlns:s="library://ns.adobe.com/flex/spark" xmlns:mx="library://ns.adobe.com/flex/halo"
minWidth="1024" minHeight="768" creationComplete="init()">
<fx:Script>
<![CDATA[

import mx.core.UIComponent;
import com.modestmaps.TweenMap;
import com.modestmaps.mapproviders.OpenStreetMapProvider;
import com.modestmaps.geo.Location;

private function init():void
{
}
]]>
</fx:Script>

<mx:Canvas id="mappanel" width="100%" height="97%"/>

</s:Application>

There are some interesting differences. I had expected to be able simply to extend my existing Flex 3 apps. Not so. I'll blog more on this when I have more time to poke around.

Adobe Flex Developer Center

I'm about to be published. No not a book. But an article. Adobe are assessing a first draft of an article I wrote using the soon to be released Flex 4 framework. Its an introduction to developing a rich internet mapping application using Modest Maps. The release date is mid July. I'll provide a link closer to this date. The article links to running versions of the applications, the code can be also downloaded from here. Take a sneak peek at:

http://www.flexmappers.com/mymodestmap

http://www.flexmappers.com/myadvancedmodestmap