Introduction

Environmental investigations typically involve the collection of extensive sets of data that describe hydrological,

geochemical, and biological processes, as well as terrestrial and

ecological conditions, occurring within a geographic region.

Because of their common spatial attributes, these data are particularly suitable for analysis and interpretation within a geographic information system (GIS). A GIS stores and manages

diverse information according to its common spatial attributes.

It uses points, lines, areas, and grids to represent features. A GIS

can also accommodate time-varying data by relating sequences

of this temporal information to their spatial location(s).

Vast amounts of spatial and temporal data are currently

being collected and compiled by the U.S. Geological Survey

(USGS) and other State and Federal agencies in support of the

ecosystem restoration efforts in South Florida. Spatial data that

are being “mapped” include vegetation characteristics, aquifer

properties, soil conditions and types, land-surface elevations,

physical features, and embayment bathymetry. Temporal data

depicting seasonal changes in the distribution and abundance of

species, constituent concentrations, water levels, wetland flows,

and canal discharges, as well as meteorological data, such as precipitation, wind speed and direction, temperature, and solar radiation, are also being collected. A GIS-based tool has been

developed within the USGS and is being used to assimilate, interpret and analyze the spatial and temporal data in support of the

development of hydrologic, hydrodynamic/transport, and ecological models of the South Florida ecosystem.

Until recently, GIS users have been relatively few in number due to the inherent need for both an extensive knowledge of,

and facility with, the complex programming language required to

interact with the various GIS functions. Now, a graphical user

interface (GUI) has been developed and incorporated into a GIS

framework as illustrated in figure 1. The GUI insulates a user

from underlying GIS complexities. A user can now create a GIS

Figure 1. Map graphic of a portion of South Florida showing the main graphics area, map scale and orientation box, legend information area and

overview inset map generated by a GIS interface developed by the U.S. Geological Survey (USGS). This illustrates the framework of what a user

sees on the computer screen when running the GIS graphical user interface called DBView.

A GIS Interface for Environmental System Analysis:

Application to the South Florida Ecosystem
working environment that does not require any prior programming-language knowledge or GIS experience. A properly

designed GUI can automate GIS tasks, can be customized to

reflect the science of the user, can employ terminology that the

user readily understands, and thus, ease the use of a GIS. By

means of pre-defined investigative paths, a GUI can guide a user

through a sequence of GIS functions and thereby enable the

investigator to more easily and comprehensively analyze a particular set--or several sets--of environmental data.

The objective of this project has been to develop a userfriendly, interactive GUI to enable scientists to easily and readily

analyze and assess comprehensive data that describe complex

environmental systems, such as the South Florida ecosystem. The

GUI described here provides a GIS interface to comprehensive

databases that anyone can use, and allows a user to browse and

manipulate with ease their own spatial data, called “coverages”,

as well as, coverages that have been compiled by others. This GIS

database viewing tool, called DBView, uses ARC/INFO’s1 Arc

Macro Language (AML) to maintain computer hardware and

operating system portability with many computer platforms.

DBView consists of a number of general-purpose GIS tools that

offer an intuitive means for assessing GIS databases, and can display and identify mapped features and their attributes. DBView

is a GIS interface that provides a fast, yet powerful means-ofaccess to a variety of environmental databases, such as those

maintained for the South Florida ecosystem by the Everglades

National Park, the South Florida Water Management District, and

other State and Federal agencies. Although DBView is proving to

be useful in conducting the South Florida ecosystem investigation as illustrated herein, it is a portable generic tool that also can

be useful in other environmental studies.

DBView Overview

Certain design principles guided the development of this

GIS interface. The objectives were to provide users with: 1) an

intuitive, easy-to-use tool with comprehensive GIS functionality,

2) an ability to convey a general overview, yet capable of providing detailed information when requested, and 3) the flexibility to Pan and Zoom to any geographic area of interest.

Consistent button placement within the DBView framework, as

well as consistent terminology and behavior, makes the interface

easy to learn. Knowledge gained in executing one menu of the

interface readily transfers to other menus. A graphic overview of

the region of interest provides the ability to readily visualize and

maintain the spatial relevance of the data. Pan and zoom options

allow the user to select and display an area of particular interest

and to magnify such areas where more specific details are

needed. Specific information about the characteristics of the spatial and temporal data can be readily requested and displayed.

For example, users can determine which types of data, if any, are

available for a particular location. Users also can determining

the sampling frequency and temporal extent of the data. These

features significantly reduce the burden of data compilation and

permit investigators to focus more directly on their analyses.

Spatial Data Characteristics

DBView features the ability to use spatial coverages that

are in vector, raster, and image formats. Vector coverages represent features as points, lines and areas, such as the USGS digital

line graphs (DLG) map products. Raster format pertains to data

represented in rows and columns of cells that make up a rectangular grid of values. Each cell contains attributes about the geographic area that it represents, such as elevations in USGS digital

elevation model (DEM) grids. Image data include digital satellite

photographs or map products such as USGS digital orthophoto

quadrangles (DOQ) and digital raster graphics (DRG).

Interface Framework

Spatial data are displayed by DBView in a map graphics

framework (fig. 1) that consists of a main map-graphic area, map

scale and orientation box, overview inset map, and a legend

information area. The map scale and orientation box, which consists of a scale bar and a north arrow, and the inset map are recalculated to correspond to the geographic area currently being

displayed. The legend information is also updated to always

reflect the map-information layers selected by the user. The

USGS 1:100,000-scale DLG layers (hydrography in blue and

transportation in red) for a portion of South Florida are illustrated in the main graphic area of figure 1. Also displayed are

data-collection stations (green dots) and 1:24,000-scale topographic quadrangle map boundaries (dark gray dashed lines).

Quadrangle names are indicated in blue text.

Using DBView

A typical DBView user scenario would be to define a

geographic area, select the desired map-information layers and

map features to be displayed, and then utilize the provided GIS

tools and extensions to analyze the available temporal and spatial data. The functional components of the Tools, Extensions

and Pan/Zoom options of DBView are offered in pulldown

menus from the toolbar (fig. 1).

Defining the Geographic Area

The Pan/Zoom options, included on the main pulldown

menu bar, offer the user a number of ways to define and display

a geographic area of particular interest. Zoom-in options permit

the user to magnify an area of interest by 1) defining a rectangle

on the screen using the mouse, 2) keying in latitude/longitude

coordinates, 3) specifying cover features, 4) identifying a particular 1:24,000-scale topographic quadrangle map, and 5) selecting

data-collection sites. Three pre-defined zoom-out options enlarge

both x and y dimensions of the currently displayed region by 10,

30, or 80 thousand meters or feet, depending on the units of the

map projection. A fourth zoom-out option allows the user to specify the enlarging dimensions using units of their choice of feet,

meters, or miles. The Pan option provides the ability to display

the region adjacent to the one currently displayed. A Previous

1 Use of this product name is for descriptive purposes only

 and does not imply endorsement by the U.S. Government.
option permits the user to re-display the area that was previously

displayed. This enables the user to readily zoom in and then zoom

back to the original area with ease.

DBView Tools and Extensions

DBView consists of several general purpose tools and

extensions that automate specific GIS functions to help users

compile, analyze, and interpret their data. These tools allow the

user to find, display, and identify mapped features by listing their

attributes. Most menu tools within DBView contain a Help

option that briefly describes how to use the menu and what the

tool expects as input. The Tools and Extensions options, also

located on the main pulldown menu bar, contain the following:

Identify Menu - provides the capability to point and

click on a displayed map feature and have DBView present the

feature’s attributes in either a popup window or as annotation in

the map-graphic area, depending on the identification presentation option (List or Annotate) selected by the user.

Select Sites - contains a number of options that provide

the capability to select data-collection sites that meet user-specified criteria. DBView will highlight and display sites that meet a

user’s criteria -- for instance, sites that are in a specified area and

at which desired parameters were collected during a specified

time period. The functional capability to access the actual temporal data that are associated with the selected sites is currently

being developed. (For the South Florida Ecosystem Program, the

temporal database is currently under development and will be

maintained by the USGS office in Miami, Fla. DBView will provide users remote access to this database.)

Select Land-Cover Types - provides the capability to

specify land-cover types to be displayed. Once the land-cover

types have been specified, DBView will calculate a statistical

summary identifying the number of acres, square meters or

square miles, and percent of each selected land-cover type. This

summary information is presented to the user in a popup window.

This tool can be used, for instance, with the vegetation map of the

South Florida region (fig. 2) and with other USGS products such

as the 1:250,000-scale land-use digital data.

Grid Data Points - provides the capability to select data

points using a variety of methods and to create contour maps

using one of the attributes of the data. A gray-scale contour map

Figure 2. Vegetation image grids of South Florida displayed in DBView. The top-left image displays all vegetation types for the entire South

Florida area. The region within the white box is expanded in the lower image, which displays only the selected mangrove, sawgrass, cattail and

rush communities as partially identified in the top-right graphic area. (Vegetation grid, consisting of more than 80 million 28.5-meter-square cells of

vegetation classified into 68 different types using the Nature Conservancy southeastern classification scheme, compiled from 1993/1994 Landsat

thematic imagery by the former National Biological Service and the University of Florida.)
Figure 3. Contour map generated and displayed by DBView showing roads (red lines), elevation data points (yellow dots), and

streams, canals, and shoreline (blue lines). Lighter colored areas indicate higher land-surface elevations whereas darker

colored areas indicate lower elevations.

of land-surface elevations created using high-accuracy, Global

Positioning System (GPS) derived data, that have been collected

in the South Florida region by the USGS, is illustrated in figure

3. A number of interpolation options, including kriging, are

offered for grid generation. The user also can specify the cell size

of the grid to be generated and have the newly generated contour

map added to DBView as a map layer.

Grid Generation

The grid generation capabilities of DBView are currently

being expanded in support of a variety of numerical simulation

models. Existing grid editing functions provide the capability to

use vector map layers to adjust and modify (add, subtract, multiply, or divide) cell elevation values. For example, a “roads layer”

can be used to add a specified value to the cells that are intersected in an elevation grid, and/or a “hydrography layer” could be

used to subtract a specified value -- the resultant elevation grid

would then more accurately reflect the physically mapped features and produce a better representation of the land surface.

Grids generated by DBView can be saved to text files and used in

other applications, such as hydrologic simulation models. The

grid generation functionality is currently being enhanced and

extended in support of implementation of the USGS two-dimensional surface water integrated flow and transport (SWIFT2D)

model for a portion of the South Florida ecosystem.

Ongoing Developments

Extension of DBView’s functional capabilities is an ongoing effort within the USGS. Some of the developmental work

currently being conducted includes:

• enhancing grid editing capabilities

• generating hardcopy graphic output plots

• plotting hydrographs of retrieved data

• integrating a variety of simulation models.

It is anticipated that continued development and enhancement of GIS interface capabilities, such as those provided by

DBView, will contribute to an increase in the thoroughness of scientific investigations by providing a robust tool for the synthesis

of a wide variety of environmental data. This additional capability should facilitate environmental decisions based on the analysis of such comprehensive interrelated data.

For more information, please contact:

David W. Stewart

450 National Center

Reston, Va. 22192

(703) 648-4879

dwstewar@usgs.gov

http://sflwww.er.usgs.gov

Gridding Elevation Points

U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet FS-0193-97

December, 1997