(Reprinted from flex888.com. View original post.)
Finally, GeoWeb is Complete and Born
Posted by Moxie | March 19, 2008 .
What’s is the best RIA application ever created? If your answer is something aroundFlex or Flash, then it’ll be wrong answer. The right answer is Google Map. It’s Google Map makes AJAX known and RIA a reality. Google even goes above and beyond claimed the term “GeoWeb“. However, up till now, Google Map is still just the best client, the visualization end, of GeoWeb. The “Geo” part of GeoWeb was missing.
Yesterday, ESRI, the shy, but true and real “Geo” dude behind all, I mean ALL, the web map buzz and technologies, released its very own JavaScript API and REST based Geo Process services to the world. The GeoWeb is finally complete and born.
The JavaScript API has three parts, the ESRI JavaScript API, the Google Map extension, the Virtual Earth extension. That means you can use the top three GeoWeb clients with this simple API to do the real “Geo” things.
What is the “Geo” things and why it’s a big deal to GeoWeb?
Well, everyone and his/her grandma knows what Google Map does, plans the trip and shows locations. What’s the most mashed up platform? Google Map. What 99% Google Map mashup applications do? Put pins (markers) on the map? But what if we want to ask some questions beyond the pushpins:
- Within 5 minutes driving time, show me the areas that I can reach. Don’t fool me with a circle. That is cheating. Because there might be highway, service street, or river among the 5 minutes driving range. The area you can cover by driving is a irregular polygon. But how do you get that polygon drawn on the map to show the 5 minute driving range?
- Three of my friends want to meet for lunch. We want to meet at a Starbucks where everybody has the least driving time to get there. Fair enough? But how do you quickly give me that Starbucks location and provide driving direction for each of us.
The questions can go on and on. How these questions are answered? Through a thing called Geoprocessing, which is provided by the technology called GIS (geographic information system). But why you’ve never heard of it and it’s not well known in the Web 2.0 space? That’s because it’s a very hard nut to crack and only a few dudes know how to do it inside out. ESRI is the one does it the best, and now, it gets everything figured it out. The whole web can have it.
If I tell you, with three lines of JavaScript codes, plus some regular JavaScript programming you can easily answer the above question visually on either ESRI map, Google Map or Earth Map. Do you believe me?
You don’t have to because I’ll show you how.
First Line:
var map = new esri.Map(“mapDiv”, { extent: startExtent });
Looks familiar, isn’t it. Indeed, it’s just like Google Map or Virtual Earth API.
Second Line:
var streetMap = new esri.layers.ArcGISTiledMapServiceLayer
(“http://server.arcgisonline.com/ArcGIS/rest/services/
ESRI_StreetMap_World_2D/MapServer”);
Something new here. Well, if you head to ArcGIS Online, a free gwoweb resource from ESRI, you would find out there are lots of good free base maps you can choose. Or, you can use any map published to a ArcGIS Server. It’s long story here for those map publishing goodies, I’ll tell you later, piece by piece. But just you know this line of code gives you a whole big world of maps to works with. Just remembering that is enough for now.
Third Line:
var gp = new esri.tasks.Geoprocessor
(“http://sampleserver1.arcgisonline.com/ArcGIS/rest/services/
Network/ESRI_DriveTime_US/ GPServer/CreateDriveTimePolygons”);
This is “Geo” part of the GeoWeb. One line, it consumes a geoprocess, in this case, a services called CreateDriveTimePolygons. This geoprocess called is actually via REST API (as the URL reveals) . The returned result can be in JSON, KML or XML. That means you really don’t have to use this JavaScript API. As matter of fact, I do have Perl or PHPexamples consume the very same gepprocess, but that’ll be another post.
The rest code is really just parse the result and draw the polygon on the map. If you know Google Map API, there are no surprises there.
The following is the true GeoWeb application I’ve introduced to you. You can zoom in to any city just like you would do with gmap (scrolling mouse, drag the map, etc.). Then click the map. The 1, 3 and 5 minutes driving time polygon will be shown.
Click Here to Run the Application (view source for detail code).
I will post another example to solve that other problem using Flex. Stay tuned.
