GIS blog for internet mapping

Metadata Mission!

2011-09-08T22:28:00.002-06:00

Spock teaches Kirk about the importance of metadata.

Groovy/Grails and Oracle Spatial (Part 1)

2011-01-06T12:23:00.027-07:00

Below I document a relatively lightweight approach to perform a distance based search in Oracle Spatial using Groovy and Grails. First some background, we need to calculate reporting metrics for an ocean observing system, one of those metrics is to find all XBT drops within a specified distance of high priority tracklines.

The ultimate goal is to create a web page where a user can specify a trackline and a distance to generate a report on the number of XBT drops along that transect. To begin I'll create a groovy service class to begin testing out my Oracle Spatial Query.

First we specify a database connection (see def serviceDbHandle). You'll also see a createDbHandle method which first checks to see if the db handle has already been made (which is the case when running in grails) otherwise it creates the connection (such as when we are running a unit test of the service in groovy).

Next, our serviceMethod accepts a parameter for sensor type, transect identifier, and a distance. In this example, we are looking for all XBT observations (points) that fall within 2KM of transect AX07. Lastly, we capture are query results as a list of domain objects representing the observations that meet our criteria.

SearchByDistance Service:

//requires Oracle jar in classpath
package osmcreporter

import groovy.sql.Sql

class SearchByDistanceService {

    static transactional = false
 
 def serviceDbHandle = null
 
 def setDbHandle(dataSource) {
   serviceDbHandle = new Sql(dataSource)
 }
 
 //This method allows us to test from Groovy and Grails
 //Lazy init the servicDbHandle
 def createDbHandle () {
  if (serviceDbHandle) return serviceDbHandle
  serviceDbHandle = Sql.newInstance(
   'jdbc:oracle:thin:@myserver:1521:MYINSTANCE',
   'myuser', 'mypasswd', 'oracle.jdbc.driver.OracleDriver')
  return serviceDbHandle
 }
 
    def serviceMethod(sensor_type, transect_id, dist) {
  
  println "\nBegin dsrs.serviceMethod()"
  def DailySummaryObservations = []
  def distance = "distance=$dist"
  createDbHandle()
        def sql = """select ds.platform_id as "platformId", ds.platform_code as "platformCode", ds.parameter_standard_name as "paramStandardName", ds.observation_value as "obsValue", ds.observation_depth as "obsDepth", ds.sensor_type as "sensorType", ds.observation_date as "obsDate", ds.observation_location.sdo_point.y as "obsLat", ds.observation_location.sdo_point.x as "obsLon", ds.platform_type_name as "platformTypeName" from OSMCV4.DS_XBT_2010 ds, OSMCV4.XBT_TRAJECTORY_TSQL xbt where sensor_type = ${sensor_type} AND xbt.line = $transect_id and SDO_WITHIN_DISTANCE(ds.observation_location, xbt.shape, '$distance') = 'TRUE'"""
  serviceDbHandle.eachRow(sql) { 
   DailySummaryObs dso = new DailySummaryObs(it.toRowResult())
   DailySummaryObservations << dso
     }
  println "End dsrs.serviceMethod()"
  return DailySummaryObservations
    } 
 
}

Domain class representing the observations:

package osmcreporter

class DailySummaryObs {

 Long platformId
 String platformCode
 String orgName
 String countryName
 String platformTypeName
 Date obsDate
 String paramStandardName
 String paramUnits
 String sensorCode
 String sensorType
 Integer sensorObsCount
 Integer dailyObsCount
 Double obsDepth
 Double obsValue
 Double obsLat
 Double obsLon 
 
}

Now we'll set up a test class to view our results.

package osmcreporter

import grails.test.*

class SearchByDistanceServiceTests extends GrailsUnitTestCase {
  protected void setUp() {
      super.setUp()
  }

  protected void tearDown() {
      super.tearDown()
  }

    void testSomething() {
        def dsrs = new SearchByDistanceService()
        def List dsos = dsrs.serviceMethod('XBT','AX07','200000') 
 assert dsos.size() >= 0
    }
}

And run the test (provide a program argument - test/unit/osmcreporter/SearchByDistanceServiceTests.groovy):

That's it! We have a working Oracle Spatial query running as a service in groovy whose results populate our domain object that holds the observational data. We also have a unit test case for the service. In our next post, we'll build out the rest of our grails architecture. Namely a GSP page to accept user input, a controller to handle the user's submission, and a barebones GSP page to display the results.

GIS Complex Event Processing Examples

2010-11-19T11:21:00.002-07:00

geocommons.com/maps/37577

http://esper.codehaus.org/

References Manning.com - See Event Processing in Action

EsperTech.com

Spring Web MVC registering multiple controllers

2009-01-23T15:14:00.021-07:00

I've recently been working on an OGC Sensor Observation Service (SOS) and wanted to split out some of the request mapping for different underlying data sources into separate controllers.

So for example I may have a separate controller for each SOS that is instantiated and which may have different presentations and models to support that view. It wasn't entirely obvious how to 'register' separate controllers into one web app using the Spring servlet config files and web.xml so thought I'd post an example. Note I am using Spring 2.5.x at the time of writing this post and using an annotation based controller.

First, we need to setup our web.xml file to register the Spring dispatcher servlet with the webapp and map which incoming URL requests will be handled by the Spring dispatcher. In the example below I've named the Spring DispatcherServlet sensorObsImpl and registered to incoming URL request /osmcObsService and /nosaObsService to the dispatcher.

Next we need to set-up the WebApplicationContext configuration file for Spring. This file has the same name as your dispatcher servlet with the addition of -servlet.xml extension, so in our case we will have a sensorObsImpl-servlet.xml file. This file sits in the same directory as web.xml. In our file we'll register two controllers one for our OSMC project and one for our NOSA project. Since we are going to leverage Spring's support of annotation based programming we'll begin by enabling auto detection of our annotated controllers by adding component scanning to our config file, followed by defining our to controller beans.

Now our controllers are registered with the dispatcher servlet and we can begin to handle incoming request params with the addition of some annotated methods in our controller classes. In our example below incoming URL requests like /nosaObsService?request=sosInitialize will map to the NosaObsController and be handled by the sosInitialize method.

@Controller
@RequestMapping("/nosaObsService")
public class NosaObsController {

@RequestMapping(params = "request=sosInitialize")
public ModelAndView sosInitialize(@RequestParam("request") String cmd){
.....
}

}

For more information check out the Spring docs at :
http://static.springframework.org/spring/docs/2.5.x/reference/mvc.html

ArcGIS Server REST Admin

2008-12-02T16:30:00.004-07:00

You can create a cache for a map service but it will not become available via the REST API until you clear the map cache via the REST admin page.

The REST Admin interface can be accessed via:
http://host:8399/arcgis/rest/admin/

Once the map cache has been cleared to check that the service recognizes it you should see:

Single Fused Map Cache: true

via the rest services directory e.g.
http://host:8399/arcgis/rest/services/myservicename/MapServer

Oracle SDO2FreeEarth Step 3

2008-10-21T11:05:00.007-06:00

Lastly we'll reference our javascript file in our HTML page to display our points in FreeEarth.

First reference our javascript file:

script type="text/javascript" src="javascript/myfreearthpts.js"

Next declare variables, and functions

var map;

function randomPtPan() {
var ll = map.getTargetLatLng();
var max = ptlocations.length-1; //normally total number of points
var randomPt = Math.floor(Math.random()*max+1);
ll.lat = ptlocations[randomPt][1];
ll.lng = ptlocations[randomPt][2];

map.panTo(ll, 4, 'easeinquad');

_timeout = setTimeout(randomPtPan, 6000);
}

function onMapLoad() {
// The pts variable is defined in myfreeearthpts.js
//map.zoomTo(90000, 1, 'easeinquad')
for(var i=0; i var code = ptlocations[i][0];
var label = new FE.Label(new FE.LatLng(ptlocations[i][1], ptlocations[i][2]), ptlocations[i][3]);
var icon = new FE.Icon('http://freeearth.poly9.com/images/fff/icons/anchor.png');
var marker = new FE.Pushpin(new FE.LatLng(ptlocations[i][1], ptlocations[i][2]), icon);
this.addOverlay(marker);
}
this.toggleAtmosphere();
setTimeout(randomPtPan, 1);
}

function load() {
map = new FE.Map(document.getElementById("map"));
map.onLoad = onMapLoad;
map.load();
}

Oracle SDO2FreeEarth Step 2

2008-10-21T10:56:00.002-06:00

Next will loop thru the result set and write the data out to a javascipt file using the FreeEarth API. We'll build an array or arrays where a single point is an array of latitude, longitude, and identifier. In this case getString(1) represents the identifier, getString(2) represents latitude, and getString(3) represents the longitude.

String dataLine = "var ptlocations = [";
StringBuffer sb = new StringBuffer();
sb.append(dataLine);
int cnt = 0;

while (rset.next()) {
dataLine = "[\"" + rset.getString(1) + "\"," + rset.getString(2)+ "," + rset.getString(3) + ",\"" + rset.getString(1) + "\"],";
sb.append(dataLine);
cnt++;
}
dataLine = sb.toString();
dataLine = dataLine.substring(0,dataLine.length()-1);
dataLine += "];";

// Create the file to output results
FileUtility fu = new FileUtility("webapps/freeearth_demo/myfreearthpts.js");
fu.openFileWriter();
fu.write(dataLine);
System.out.print(dataLine);
fu.close();
stmt.close();
conn.close();
System.out.println ("\nCount=" + cnt);

Oracle SDO2FreeEarth Step 1

2008-10-21T10:50:00.005-06:00

Been experimenting with visualizations in FreeEarth from poly9 http://freeearth.poly9.com/. The nice thing about FreeEarth is that it is Flash based so that it doesn't require any web plugins.

Here I'll take a look at writing point data out from an Oracle SDO table and format in as a variable in javascript required by the FreeEarth website.

First let's connect to Oracle and query for our points.

// Load the driver
Class.forName("oracle.jdbc.driver.OracleDriver");

// Connection URL
String url = "jdbc:oracle:thin:@myserver:1521:mysid";

// Connect to the database
Connection conn = DriverManager.getConnection(url,"myuser", "mypwd");

conn.setAutoCommit(false);
Statement stmt = conn.createStatement();

// SQL with reference to SDO objects for point data
String sql = "select pt_id,p.shape.sdo_point.y,p.shape.sdo_point.x from mypoint_layer p";
ResultSet rset = stmt.executeQuery(sql);

GeoServer 1.6.5 and Tomcat

2008-10-09T10:32:00.005-06:00

It's been awhile since I've had the opportunity to work with geoserver, so today ran thru the default install. Looks like embedded Jetty is now the standard implementation, if you want to run it under Tomcat you'll need to copy \webapps\geoserver to \webapps\geoserver

Also you'll need to either copy the data dir \data_dir into the tomcat webapps folder as \webapps\geoserver\data

Alternatively (perhaps preferably), you can set the environment variable for tomcat as documented here:

http://geoserver.org/display/GEOSDOC/Tomcat+-+data_dir+environment+variables

Conservation GIS Mashup

2008-02-11T11:30:00.000-07:00

A new mashup using web services from the Global Biodiversity Information Facility (GBIF) and Centro de Referência em Informação Ambiental (CRIA) allows users to pull data from the world's largest biodiversity data warehouse and model potential species distributions using CRIA's openModeller web service.

The mashup uses Spring Web MVC for middleware integration.

openModeller client source code available on the site... There's been talk of adding WMS support on the server to support viewing results in a full web based GIS.

check it out at http://www.geovelocity.com/bdmashup.html

Need JavaScript to convert decimal degrees to miles

2008-01-21T12:22:00.002-07:00

//Note this is an estimate based on a simple spheroid
function distanceConverter(x1,y1,x2,y2) {
  // distance between 2 points from decimal degrees to miles
  // where x values represent longitude
  // where y values represent latitiude
  dx = 69.172 * (x2 - x1) * Math.cos( y1 / 57.3);
  dy = 69.172 * (y2 - y1);
  var dist = Math.sqrt(dx * dx + dy * dy);
  return dist;
}

Fixing IMapServerProxy(Unknown Source) exception

2007-10-16T09:59:00.000-06:00

IMapServerProxy(Unknown Source) exception gets thrown when trying using exportMapImage and an underlying java.io.EOFexception occurs in the stack trace.

This bug/issue is a bear, as it seems to crop on some Windows2003 servers but not others.

We did two things to resolve this:
1) Upgraded to SP3 for desktop and server
2) Made sure that I created an ArcGISSOC and ArcGISSOM accounts during post install (i.e. don't use an existing account)
3) Copied the new arcobjects.jar (from SP3) into my deployed webapp.
Reload webapp.

Error is gone!

How to buffer features in ArcServer using Java

2007-08-24T14:40:00.000-06:00

Creating a map image of buffered features takes a lot of code!

This sample steps you through it all and works with the cities and places shapefiles located with ESRI sample data. One thing you'll need to do is create a BufferSample.mxd with cities as the first layer in the TOC, places as the second layer in the TOC. Set-up the map service in ArcGIS Server and plug in your host, username/password values and you should be good to go!

A key method to look in the code is createBufferGeometry:
/**
* Create the buffer geometry
* @param layerId the layer position in the MXD table of contents
* @param feaure ids of selected features to buffer
* @param distance to buffer features in decimal degrees
* @return the buffer geometry
* @throws Exception when buffer geometry fails
*/
public IGeometry createBufferGeometry(int layerID, IFIDSet2 fidSet2, double distance) throws Exception {
// lots of code here!
return buffersGeometry; }

and the full sample is located at geovelocity's website: http://www.geovelocity.com/downloads/BufferSample.zip

Migrating ArcGIS Server Java Code from 9.1 to 9.2

2007-08-22T11:42:00.000-06:00

When upgrading a ArcGIS Server Java application from ArcGIS Server 9.1 to 9.2, you'll notice that the way you instantiate objects from the server context has changed (become deprecated). The new method follows a more conventional Java cast.

Below are some examples based on a utility class used in symbolizing a polygon element for a buffer operation.

So for example in ArcGIS Server 9.1 to instantiate IRgbColor we would do the following:
IRgbColor color = new RgbColor(this.sc.createObject(RgbColor.getClsid()));

Whereas in ArcGIS Server 9.2 we do the following:
IRgbColor color = (IRgbColor) this.sc.createObject("esriDisplay.RgbColor");

The full source code for the files is available at geoVelocity's website:
http://www.geovelocity.com/downloads/RgbColorSample.zip

GeoServer WCS

2007-07-27T16:00:00.000-06:00

Looks like raster support via the OGC's Web Coverage Specification is now in the main distribution of geoServer's latest release!

http://www.geoserver.org/

ArcGIS Server and Java Integration

2007-07-27T15:45:00.002-06:00

geoVelocity (http://www.geovelocity.com) has just finished a risk management application. This application uses advanced ArcGIS Server functionality using Java, Service Oriented Architectures and Ajax. Modeling components using the raster api were also incorporated. Contact info[at]geovelocity.com

GIS Enterprise Monitoring Software

2007-07-27T14:51:00.000-06:00

Looking for a GIS enterprise monitoring software?

Check out http://www.geoxmf.com

They've got email and text message based notifications, and looks like some cool real-time reporting tools as well!