What's new in ArcGIS Spatial Analyst 10
The ArcGIS Spatial Analyst extension provides a broad range of powerful spatial modeling and analysis capabilities. With ArcGIS 10, Spatial Analyst provides improvements in performance and new tools.
New geoprocessing tools
The new Extract Multi Values to Points tool allows you to extract values from several input rasters, including multiband raster, based on a set of input points. The respective raster values are added to the input feature class as attributes, and you have the option to provide the output name. The similar Extract Values To Points tool available prior to ArcGIS 10 only extracts values from one raster at a time and creates a new output feature class.
A new multivariate analysis tool, Iso Cluster Unsupervised Classification, is introduced for the purpose of performing unsupervised classification.
Two new tools for performing overlay analysis for multi criteria decision making using fuzzy logic are Fuzzy Membership and Fuzzy Overlay. Fuzzy logic is based on set theory and is an alternative to the Weighted Overlay and Weighted Sum methods currently available in Spatial Analyst, but all approaches are particularly well suited to perform suitability modeling.
As in most overlay analyses, the significant layers are reclassed or transformed into a common scale, then added together or combined to identify the optimal locations for the phenomena being studied.
The Fuzzy Membership tool is used to scale (reclassify or transform) the input data into membership values ranging from 0 to 1 using a specified fuzzy function. The membership values represent subjectively defined degree of belonging to a set, where values that are closer to 1 are deemed as being more suitable.
The Fuzzy Overlay tool is used to combine two or more fuzzy membership results using fuzzy operators to create, for example, an output suitability raster dataset. The tool identifies those locations that are most likely to belong to the most preferred combination of sets; in the case of a suitability model, being the most suitable.
The new Raster Calculator tool is designed to replace both the previous Raster Calculator from the Spatial Analyst toolbar and the Single Output Map Algebra tool. The new Raster Calculator executes Map Algebra expressions using Python syntax. When used in ModelBuilder, the Raster Calculator supports variables in the expression.
The new Zonal Histogram tool is a replacement for the original functionality from the Spatial Analyst toolbar. The new tool allows you more control over the output and easy inclusion into your geoprocessing workflows.
The Zonal Statistics as Table tool was updated with a new parameter to give you more control over which statistics types are to be calculated.
At ArcGIS 10, Map Algebra has been seamlessly integrated into the Python environment, providing you with a more powerful analysis and modeling experience.
The Map Algebra syntax itself is basically the same, maintaining its familiarity and ease of use. In general, any changes to the syntax allow you to take advantage of the greater capabilities afforded by Python.
Some points and benefits of integrating Map Algebra with Python are:
It can be accessed from the integrated Python Interactive Window or through your own favorite Python scripting Interactive Development Environment (IDE).
Full autocomplete capabilities ease the construction of expressions, particularly for complicated ones.
All Spatial Analyst tools are available in Map Algebra.
It supports a comprehensive set of mathematical and logical operators.
Individual tools and operators can be strung together to create single complex statements.
Local (per-cell) expressions have been optimized to increase performance.
Python classes are available for certain parameter collections, which allows autocompletion and programmatic access to individual parameters. Following is a general list of the Spatial Analyst classes:
- Neighborhoods, Remap tables, Weighted Overlay and Weighted Sum tables, Vertical and Horizontal Factors, Topo To Raster input, and Fuzzy membership.
Spatial Analyst Toolbar
With all the benefits provided by geoprocessing, the limited selection of functionality available in the previous Spatial Analyst toolbar is removed at ArcGIS 10. The Create Contour and Histogram interactive tools remain on the toolbar as before.
In place of the ArcGIS 9.3 and earlier Raster Calculator dialog box, Map Algebra expressions can be entered into the new Raster Calculator tool or directly in the Python window.
Native Data Read/Write
Raster operations in Spatial Analyst were traditionally performed only on ESRI GRID datasets. Other specified input or output formats were internally converted from/to GRIDs as needed. Similarly, feature data was internally converted to the Shapefile format.
For ArcGIS 10, changes have been made to provide native format read and write capability to the Spatial Analyst engine, allowing faster and more robust processing of your data. The reduction in processing time and disk space consumption is made possible by avoiding the creation and internal management of temporary scratch files. Other benefits include:
- Any field name and path length limitations imposed by the ESRI GRID format are overcome.
- The 2.1 GB shapefile size limit is avoided by writing outputs to file GDB or SDE.
- If supported by the specified input and output formats, time values in the date fields are preserved, and nulls are treated as such and no longer being converted to zeros.
On a more technical level,
- Two new interfaces, IRasterAnalysisGlobalEnvironment and IRasterOpBase, are introduced with ArcGIS 10 to allow the processing of raster data in Spatial Analyst using ArcObjects without the need to convert to ESRI GRID format
- The default setting of False for IRasterAnalysisGlobalEnvironment::AvoidDataConversion ensures that the execution path is the same as in versions of ArcGIS prior to 10.
- Setting IRasterAnalysisGlobalEnvironment::AvoidDataConversion to True ensures that all processing is performed natively on raster and feature data.
- The IRasterOpBase interface provides a mechanism to specify the name of the output data and its workspace before the operation is performed. This results in the output being directly written permanently to the required format.
The Focal Statistics tool has a new algorithm that significantly improves its performance, particularly when using large neighborhoods such as rectangular neighborhoods of 12 x 12 or larger, and circular neighborhoods with a radius of 5 or greater. The improvements apply to all but one of the Neighborhood types and most of the Statistics types. The other Statistics types have the same performance as before.
When non-GRID rasters and non-Shapefile feature data is used as input or output, Spatial Analyst tools generally execute faster than they did in 9.3.1. This is a result of adding native format read and write capabilities to the Spatial Analyst engine. See the preceding Native Data Read/Write section for more details.
A new toolbar for image classification is introduced in ArcGIS 10. With the Image Classification toolbar, you can perform classification of multiband raster datasets with both interactive and geoprocessing tools.
The Image Classification toolbar is a single location to perform image classification. It provides interactive and easy-to-use tools for creating and evaluating the training samples needed for supervised classification. You can also access several geoprocessing tools for multivariate analysis.
This toolbar makes image classification tasks both faster and easier.
The Training Sample Manager provides the following functionalities that assist in performing classification:
- Lists of classes represented by the training samples
- Tools to manage the training samples
- Several training sample evaluation tools to create and display histograms, scatterplots, and statistics of the classes
- Allows you to create a signature file to use for classification