2003 June 18

Tenth Kentucky GIS Conference, August, 2003

10 Years of Discovery

2-Part Presentation - Wednesday August 20, 3:30pm

GeoDataBase: New Foundation for GIS

1.

Spatial Management and the GeoDataBase

The Shapefile format was developed by ESRI in conjunction with ArcView GIS (current Version 3.3).

Similarly, the geodatabase format was developed by ESRI in conjunction with ArcGIS (current Version 8.3).

While the Shapefile makes use of the standard dBase IV table format, the geodatabase is an application of the Microsoft Jet Engine, the basis of the desktop DataBase Management application named Access (current Version 2002). The JetEngine-based geodatabase is known as the Personal GeoDataBase, pGDB, and comes with ArcGIS ArcView 8, enabled for creation and editing. Microsoft SQL Server 2003 is an example of the basis for an enterprise GeoDataBase, eGDB, coupled with ESRI's Spatial Data Engine, SDE, an option that facilitates editing the eGDB by either ArcEditor or ArcInfo, and read-only access by ArcView 8.

Just as we appreciate how the Shapefile format has become the de facto standard GIS file format, facilitating sharing of geodata, the GDB will become the standard basis for enormously more advanced GIS capabilities. This session explores the GDB using the pGDB, with special attention to how coordinates are stored and managed within the constraints of the spatial domain, the basis for geometric topology. We consider the legacy file-based formats, including Arc/Info coverages and shapefiles, contrasting the innovation of storing unlimited numbers of feature classes within a single geodatabase file. We learn how topology, not implemented in shapefiles, is implemented in the GDB relational data model, obsoleting the old coverage model.

This background provides the foundation for considering the role of Survey Analyst in the total picture of spatial management within the enterprise GIS.

 

2.

The Survey Analyst and Spatial Management for the Enterprise GIS

Building on the GeoDataBase, Survey Analyst provides a new layer type in the GIS, adding to Vector, Raster, Annotation, and Graphic. We consider the Measurement Layer, for the Surveyor and for the GIS. It is the only layer provided with an explicit lock. Previously, the work of the Surveyor has been disconnected from the GIS, handed over like orphaned eggs in the form of coordinates, locations, points, from which features may be fostered.

Today, the gathering of data from field observations, with a growing variety of tools, is managed by the Surveyor with varying software that ultimately transforms observational measurements into more or less attributed doubles or triples: X,Y or X,Y,Z. From each measuring device, flows information, supplemented by the Surveyor, typically passing through a variety of data formats, and includes substantial information, characterizing the context of the point, the attributes of measurement, and the attributes of the computed result, generally in terms of Quality, i.e. accuracy, fidelity. Today, most of that information is outside the eggshell and lost to the GIS.

That information (type of metadata) is the basis for Quality -- the payoff to the GIS for these survey layers. Until now, the quality of a GIS can only roughly be stated, and typically cannot be verified. Successful implementation of the Survey Analyst into the enterprise GIS will provide for complete characterization and validation of accuracy on the feature layer in the GIS generally named Control, the foundation of the GIS.

Moreover, the previously irregular, multi-step workflow from field measurement to Control coordinate is now collapsed into a 2-step flow from the measurement device, to the collector, to ArcGIS software. All related information has a home in the GeoDataBase, and is available to built-in computations reducing the data to coordinate results while providing the algorithmic basis for Quality. We complete our study of spatial files for spatial management with a detailed look at the data structures supporting the Survey layers in the Geodatabase.

John R. Schmidt, Master of Science

President, NCAD Corporation

Authorized Softdesk Dealer 1988 - 1996

Instructor, ESRI Authorized Training Program

ESRI Business Partner since 1989

john@ncad.net

 

Type: Standard

Title: GeoDataBase: New Foundation for GIS