Warehouses

GeoMedia has the capacity to access data from a number of sources, make the necessary transformations to integrate the data into one consistent structure, and then allow you to perform analyses, make maps, and so on within GeoMedia. The sources of the data GeoMedia uses are called warehouses. There are a number of types of warehouses accessible by GeoMedia. They are MicroSoft’s Access; ESRI’s Arc/Info coverages and ArcView shapefiles; Intergraph’s Modular GIS Environment (MGE), Data Manager (MGDM), and Intergraph Segment Manager (MGSM); Bentley’s MicroStation with and without attribute linkages; and Oracle 7.x Spatial Data Option and 8.x Spatial Cartridge.

With the exception of the Access warehouse, all other warehouses are read-only and are created outside GeoMedia. This chapter provides details on creating and using an Access-based warehouse, and how to connect to data in ARC/INFO ArcView, MGE, and CAD formats. Except for Access warehouses, all warehouses are created by the source application system. GeoMedia connects to the data in read-only mode. This chapter is designed to get you up and running with these common warehouse types. Substantial additional details on all of these warehouses are found in Chapters 6 and 39. and For details on the Oracle warehouse see Chapter 36. in the INSIDE GeoMedia Web site modules.

The use of warehouse data requires a minimum of three key parts. These key parts are the warehouse, a data server, and GeoMedia. The warehouse (with the exception of Access) is simply the data in the form it is normally organized. For example, in ARC/INFO the warehouse structure is a standard ARC/ INFO workspace directory with the Arc coverages in their native (nonexported) form, along with the associated INFO files. The INFO files contain a variety of data associated with the coverages. In particular, they contain the attributes associated with each point, line, or polygon in the coverage.

When the current GeoMedia workspace is connected to the warehouse, GeoMedia reads the data to determine what types of data are present. The various coverages or layers in the warehouse are read, and a list of the available coverages/layers becomes a list of possible feature classes in GeoMedia. When a user requests that one of these feature classes be displayed or used in an operation, the original data is processed by the data server component of GeoMedia. The data server software component processes this data into a GeoMedia (Microsoft compliant) record set in memory.

Once the data is in a record set, any GeoMedia operation can be performed. It is often the case, however, that the data found in these various warehouses differs widely. For some types of warehouses, more detailed instructions are necessary to provide the specifics GeoMedia needs to properly process the data. This background data is provided in two different sources: the coordinate system file (.csf) and the .ini file.

The Coordinate System File

Many of the warehouses used by older GIS and desktop mapping systems do not have an internal specification that keeps track of or indicates in what projection (and datum) data is being stored. These systems require that the user somehow keep track of this (usually, it seems, on a scrap of note paper soon lost). In contrast, the projection and datum information about any set of data is an integral part of the GeoMedia data model, and is an integral part of any GeoMedia- created warehouse. In order for GeoMedia to deal with projection data from other warehouses, it must know the projection details.

Remember that GeoMedia automatically re-projects all warehouse data to the current workspace projection. The coordinate system file (.csf) is the structure GeoMedia uses to store information on the projection characteristics of data in warehouses that do not hold projection information internally. An Access warehouse does not need a .csf, nor does an Oracle SDO or SC warehouse. Other warehouses will require a .csf (or equivalent, covered in material that follows).

For most warehouses, the .csf file is created by the Define Coordinate System module. This module is not accessed within GeoMedia but from the Microsoft start menu: Start > Programs > GeoMedia > Define Coordinate System File. The details of using this module are discussed later in this chapter, and particulars of projection systems can be found in the INSIDE GeoMedia Web site module Chapter 37 "Projections and Datum Transformations." At this point, just remember that you will need to somehow determine the projection (and datum) of data you obtain from other sources if you want to properly re-project it to overlay with data from other sources. Information on how to do this for the various warehouse types is presented later in this cChapter 6, 36, and 39. and in the INSIDE GeoMedia Web site modules.

To determine the projection of data, you will need to know (1) whether the data is in latitude and longitude (geographic) or projected (e.g., UTM) form, and (2) the geodetic datum used (e.g., Clark66 or WGS84). If the data is projected, you will need (1) the horizontal resolution desired (2) the coordinates (offset) of the center (3) the projection algorithm (e.g., Lambert Conformal Conic), and (4) the projection parameters (e.g., origin latitude/longitude and zone).

If you are working with data from one source (e.g., all ArcView data or all ARC/INFO data) and you need relative accuracy only, not absolute accuracy, you could run GeoMedia without knowing the projection properties of the data, and would not need a .csf file. Generally, however, a .csf file is necessary.

The .ini File

The .ini file provides information on the file structure(s) and/ or location in which data resides, and sometimes instructions on how the data is to be processed. The .ini file is a simple text file, commonly created with the Notepad text processing utilityor with the new GeoMedia INI Wizard, available at the Intergraph web site.

Tip: It is recommended that you download the most current version of the INI Wizard from the Intergraph web site. Follow the links from http://www.intergraph.com to Mapping/GIS, then to Technical Support or Tools and Utilities to find the file.

In a simple case, an .ini file might be just one line, with the full path to the appropriate coordinate system (.csf) file, whereas in others it might be many lines, with details on data processing parameters. The following is a typical ArcView .ini file that provides the location of the coordinate system file for ArcView theme parcels.

COORDINATE SYSTEM

parcels=C:\myproject\parcels\parcels.csf

The .ini files for other warehouses can be much more detailedcomplex. Details on the various .ini files and the INI Wizard are provided in the INSIDE GeoMedia Web site modules.Chapters 6 and 39. Chapter 6 contains an overview of connections to each of GeoMedia’s data servers, and a discussion of required supporting files. Chapter 39 covers the same topics in much greater detail.