GISWiki.NEWS.Reader » GIS Matters » October 2006

GISWiki.NEWS.Reader » GIS Matters » October 2006

Feeds

Englisch Newspages

Englisch Newspages

Deutsche Newsseiten

Deutsche Newsseiten

Blogs

Jobs

Jobs

Map-Services

Spanish Newspages

Spanish Newspages

GIS Matters

Open Source GIS: 52°North and ESRI

Posted: October 21st, 2006, 12:23am CEST by GIS Matters

On September 21, 2006 in Muenster, Germany, I signed documents on behalf of ESRI, and along with representatives from con terra GmbH Muenster, the Westfaelische Wilhelms Universitaet Muenster, and the International Institute for Geo-Information Science and Earth Observation (ITC) Enschede, to establish the 52°North Initiative for Geospatial Open Source Software GmbH.

Traditionally, ESRI has been an open systems, closed source software vendor. From the earliest releases of ArcInfo in the early 1980s, ESRI has always tried to provide open access to geographic data and functionality by publishing details of our formats (e.g. shapefiles and geodatabase XML), by supporting all mainstream de facto and de jure GIS data standards (e.g. SDTS, DXF and ISO 19115 metadata), by publishing details of application programming interfaces (e.g. ArcSDE C API, ArcObjects.Net and Java APIs, and ArcGIS Server WSDL) and by supporting web services standards (e.g. SOAP/XML, WMS, and WFS). This was a direct response to requests from our users, but also a realization that such an approach would maximize ESRI market penetration.

It is no secret that community software development and open source licensing have emerged as an alternative software model in recent years. Although there is a lot of hype associated with the open source software model and many overblown claims, it is clear to me that it can work (e.g. Apache and MySQL) and that there is significant interest in community development in the GIS industry. This is the backdrop to our positive decision to join the 52°North Initiative as a founding member of the oversight company.

52°North is an open initiative whose purpose is the development of open source software for Spatial Data Infrastructures (SDI). The current focus of development is Sensor Web Enablement, Security and Digital Rights Management. The emphasis will be on research and development in these new areas. Products will be available using two licensing models: GNU General Public License (GPL); and a commercial use license. The initiative is open to anyone who would like to participate.

There are two primary reasons why ESRI joined the group: the opportunity to work at a peer to peer level with smart developers so that we can build useful GIS code that will advance the GIS field; and to explore the community software development and open source licensing model. Frankly, we are unsure about where this adventure will take us, but we are committed to trying it out and seeing where it leads.

More information about the work of the group can be found at http://www.52north.org.
Simulation and Modeling Geoprocessing with ArcGIS 9.2 (Part Two)

Posted: October 14th, 2006, 1:26am CEST by GIS Matters

The first post on Simulation and Modeling Geoprocessing with ArcGIS 9.2 described the geoprocessing framework and the set of tools for processing geographic information. In this part I will look at the new capabilities for simulation modeling.

One of the key goals for geoprocessing at ArcGIS 9.2 was to extend the existing framework beyond the bounds of static cartographic-style, descriptive modeling into the world of dynamic, stochastic, process modeling. Simulation modeling has many applications in GIS including modeling errors (what is the effect of errors in a DEM on the derived stream network?), sensitivity analysis (how sensitive is my housing suitability model to the slope parameter in the terrain input layer?), or what-if scenarios (how will a fire move across a landscape, based on information about land cover, terrain and wind direction?). The following new capabilities have been added to ArcGIS 9.2 to support this type of work:

Branching. Branching has in fact been available for several releases, but I’ll cover it here because it is so useful in dynamic simulation modeling. Branching can be used to control the flow of a model. ArcGIS includes both If-Then-Else logic and precondition tests that output True/False. For example, in a fire model If-Then-Else logic can be used to branch depending on whether an area is Forest or Grassland.

Iteration. Iteration is a general term that describes how many times a model (or part of a model) will run. There are several ways to control iteration including looping (execute a model n times), conditional logic (looping until value=true), and running a model for all values in an input list.

Feedback. This is the ability for a downstream process to influence an upstream process. For example, as a fire burns the amount of fuel will reduce until it is all used up and the fire can no longer burn. The amount of fuel can also control the temperature (and therefore the rate at which the fire can burn). During the first run of a fire model, the amount of fuel is reduced and this can then feedback into the next iteration to control burning subsequent burning.

Random functions/values. Both random functions and values can be incorporated into ArcGIS 9.2 models. For example, the location of a fire can be determined using a random function to generate a raster with a random point. A random value can be generated using one of the nine supported distributions (and a seed value) to simulate sparks jumping from a fire to start another fire.

List/series processing. ArcGIS 9.1 only supported one data layer as input to a tool. ArcGIS 9.2 additionally supports both lists and series of data values as input. Lists force all downstream processes to execute once for each value in the list, whereas series force entire model execution once for each input value.

Result visualization. Iterative models typically generate one output layer for each iteration. To mange and visualization model output two new capabilities have been added to 9.2: geoprocessing layers and animation. A geoprocessing layer allows the symbology for an output to be specified once and then new reused for each subsequent iteration. Each time the model runs the output is written to the same layer, over-writing the previous output. An alternative approach is to write each iteration out to a separate layer. If the output layers of a model are of type raster then the layers can be managed as a raster catalog (a collection of rasters). The animation framework at 9.2 can be used to visualize multiple layers in either 2D or 3D. Animations can be displayed directly onscreen and can be saved as animated movies such AVIs.

Several of these capabilities are shown in the two parts of a fire model. Random variables are used to define wind speed and direction (using weights in a kernel), random values are used to represent fire temperature, feedback connectors (blue lines) provide a control over the number of iterations that vegetation can burn, and branching with random variables determines when sparks jump from a fire to initiate new sub-fires.

In summary, ArcGIS 9.2 has many new capabilities for creating dynamic process models that represent or simulate aspects of real world ecological, environmental, and social systems which focus on geographic patterns and processes.

← September 2006 (1 item) November 2006 (2 items) →