Archive for April, 2010

Using Definition Expressions in the AGIS API for Flex to Restrict Feature Display

Posted on April 26, 2010. Filed under: AGIS Server API for Flex, ESRI, GeoSpatial Training Services |

The next session of our instructor guided, Internet based course “Programming the ArcGIS Server API for Flex” begins June 7th and runs through July 16th. Register before May 1st for only $567. Regular price is $715. All course materials are self-paced so you don’t have to be logged in at any particular time, but you do have access to the instructor to answer any questions or problems.

In the first article in our series on the ArcGIS Server API for Flex we covered some basic concepts including how to create maps and add layers. We covered both tiled and dynamic map service layers. In this brief post you will learn how to apply a definition expression to your dynamic map service layer to restrict the features displayed from a layer.  For instance, in the figure below we are plotting only those counties that suffered a population loss from 2000 to 2007. 

Definition expressions are used to display only features that meet certain attribute requirements. As of ArcGIS Server 9.3 layer definitions can only be applied against an instance of ArcGISDynamicMapServiceLayer. As you can see in the code example below the <esri:layerDefinitions> tag, which is a property of ArcGISDynamicMapServiceLayer, is nested inside an instance of this class.
In this case we are applying the layer definition to the ESRI_Census_USA map service which contains the layers you see in the figure below.
What we’ll need to do is create an array of string values for each layer that you see above. This string value is the layer definition that will be applied to the layer. Since there are six layers (0 to 5) in the service we’ll need to define a string value for each layer. For layers that do not need to have a layer definition applied (census block points, census block groups, and states) we will simply create an empty string.
Now let’s spend a few minutes discussing what this code accomplishes. We first create an Array with the <mx:Array> tag. Inside our Array we define one String value for each layer. In the event that you do not want to apply a layer definition to a layer you simply leave the <mx:String> tag empty. In this exercise we are only applying layer definitions to the county layers. Our layer definition query is to find counties where the population was greater in 2000 than it was in 2007. This query needs to be surrounding by a CDATA tag which simply informs the web server that the contents are to be interpreted literally. Without this tag the web server would view the greater than sign (>) as part of either an MXML or HTML tag.
 
ArcGIS 10 and Version 2.0 of the API for Flex
With the release of version 2.0 of the ArcGIS Server API for Flex at the ArcGIS Server 10 release you will be also be able to apply a definition expression to the new FeatureLayer object.
Next time we’ll examine spatial and attribute queries using the ArcGIS Server API for Flex
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ArcGIS Server Bootcamp – Coming in June

Posted on April 21, 2010. Filed under: Uncategorized |

Join us this summer for our first ever ArcGIS Server Bootcamp! Beginning in June and ending in late August this self-paced, instructor led, Internet based course will teach you all the fundamental skills you need to fully take advantage of the new ArcGIS Server 10 platform. The course is self-paced and is designed to accomodate busy work and family schedules as well as summer vacations.

ArcGIS Server provides an integrated solution for managing, disseminating and analysis of GIS data. Starting with the basic concepts of ArcGIS Server and moving to advanced web application development techniques with JavaScript, Flex, or Silverlight you will acquire the skills necessary for publishing your GIS content to users over the web or through traditional desktop means.

We have space for only 15 students in this bootcamp so reserve your seat now.

For more information please visit the course page.

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What’s New in the ArcGIS API for JavaScript Version 2.0?

Posted on April 18, 2010. Filed under: Uncategorized |

Here is a new Prezi demonstration that I put together containing high level details of the ArcGIS Server API for JavaScript at release 2.0.

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What New E-Learning Courses Do You Want?

Posted on April 12, 2010. Filed under: Uncategorized |

Please take a few moments to tell us what e-learning course you’d like to see us add to our catalog.

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Google Maps Adds Elevation Service

Posted on April 5, 2010. Filed under: Google Maps |

The Google Maps team continues to add really useful functionality to the Maps API.  Now the Google Maps API team has  introduced a new Elevation Service that enables applications to determine elevation profiles.  The Maps API v3 contains an ElevationService class or you can simply use the Elevation Web Service as an HTTP request from v2 applications.  You can request the elevation in meters for one or more sets of coordinates, or you can request a specific number of elevation samples spaced along a path.

The figure below shows a sample application that uses the Google Visualization API to plot elevation profiles. You can add additional points by clicking on the map or entering an address, and you can switch between different modes of travel to see the affect on the profile. If you roll your mouse over the profile chart you can see on the map the point that the given sample relates to

I’ll have some code examples on this new service soon.

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