Accessing Multiple Software Packages from ArcGIS 8.x with MariCOM to Ease Marine Data Display

Helge Prestrud Astad,

Institute of Geography, University of Bergen, (NO)

The Problem
In a marine or coastal environment, the data comes in a wide range of varieties. Some data are images, some are tables and others are continuous lines. Marine data comes in all dimensions, 2D, 3D and time series. The amount of data available from satellites is increasing rapidly while other data sources can be too sparse to give meaningful information on their own. The technology and software used to display the different kinds of data is domain specific with their own terminology and approach to the data. The different types of data can be extremely difficult to compare. The result is that the threshold a user needs to cross to actually display marine data is very high. Without the proper skills planners or others in coastal management may miss important data sources for decision making or they may have errors displaying marine data. This paper shows how to ease the learning threshold by reducing the number of software packages seen on the screen and by reducing the number of operations one need to display a type of data. In addition to make it easier, the time it takes to perform certain simple tasks is reduced.
Since the most obvious common reference to almost all marine and coastal data sources is that their geographical coordinates is given, a GIS can be used to handle the locations and coordinates, and display the area of interest since (most) GIS's handles this well. In this paper, GIS is defined as a computer system and database that handles spatial data (Burrough 1998).
I have chosen ArcGIS 8.x as a starting point since it is a well known and widely used, and because it has Visual Basic for Applications (VBA) embedded in it. Since VBA is a COM (Component Object Model) -compliant programming language, it is possible for ArcGIS to interact with all Microsoft products and all other languages and programs that are COM-compliant (Ungerer and Goodchild, 2002).

The Solution
The combination of ArcGIS 8.x and VBA makes it possible to access multiple software packages from within ArcGIS 8.x. VBA can be used both to embed powerful and complex tools and functionality from other software into ArcGIS and to make new tools that are not already in ArcGIS or its extensions. This saves the time it would take to learn the other software and the actual moving of data between the different software packages.

MariCOM is an ArcGIS extension under development at Institute of Geography at the University of Bergen, scheduled for release the late summer 2003. MariCOM is started from a button in ArcGIS. This launches a Graphical User Interface (GUI) that gives the user some tools for displaying or handling marine data that are "buried" deep in ArcGIS or exist in other software packages. A beta version of the program is shown in Figure 1. MariCOM is made in VBA under ArcGIS 8.x and provides the user with simple methods for handling and displaying various marine data sources. MariCOM has functionality for adding custom filters and making 8-day or monthly average composites of AVHRR Sea Surface Temperature (SST) images.

Data sources used in MariCOM:
Data from a cruise in the North Sea undertaken by the research vessel "F/F Johann Hjorth" between April 27, 2002 and May 9, 2002, owned by Institute for Marine Research in Norway (www.imr.no) is used to test MariCOM.
AVHRR satellite images are used to display SST and to provide synoptic information over large areas of water, in contrast to point data from research vessels (Gibbs and Shaw 2002). AVHRR data can be downloaded for free from the NOAA website (http://www.saa.noaa.gov/ ). The data is downloaded in raw form, and needs to be processed to show SST-values. ENVI (www.rsinc.com/envi/) is used to process the images, and ENVI's programming language IDL (www.rsinc.com/idl) provides an ActiveX control that can be called from VBA or any computer language that supports ActiveX. IDL-scripts made for processing AVHRR SST images can be called and run from MariCOM.

CTD measurements (Conductivity, Temperature, Depth) measure temperature, conductivity and pressure from the surface to the sea-floor by lowering a platform with measuring devices to the bottom. To display these data, one can turn them into diagrams showing variables and depth or section diagrams between two or more casts. Extrapolating from the CTD-measurements makes isolines between each cast. MariCOM uses Excel to format the tables before the extrapolation is done with R, an open source statistical programming language. A COM-server is made (Baier and Neuwirth, 2001, 2003, Baier 2003) that makes it possible for VBA to "talk" to R. R is very powerful but have a command line user input which can be confusing for users that are used to click-and-point interaction. R can also add standard statistics like Morans I or find if there is any correlation between for instance SST surfaces and Chlorophyll a surfaces (Rubio 2003).

The ACDP (Acoustic Doppler Current Profiler) is a device mounted under a ship that provides data on the speed and direction of ocean currents. MariCOM gives the user the possibility to display these data. If the data needs to be formatted the user can start Excel from ArcGIS for data formatting. The program displays the formatted table into a stick-plot layer in ArcGIS showing the currents at a chosen depth.

A front-following algorithm for tracking temperature fronts on AVHRR SST images has been developed (Shaw and Vennell, 2000, 2001). The algorithm extracts not only the location of the front, but also variables describing the properties of the front such as temperature across the front, temperature at the front and direction of the front in each point. The algorithm is developed in Matlab, but is transformed into a language that can be accessed as a COM object from ArcGIS. This makes it possible for the user to extract fronts and properties of fronts from AVHRR images.

MariCOM provides a way of displaying marine data from different domains. Users that struggle to assemble all their data in one output form can use MariCOM to make this task easier.

References:



Figure 1 The opening window of MariCOM. The list on the left holds all the data layers in the project. The buttons opens new windows if more input than a mouseclick is needed. The window to the right is a log window to inform the user about what is happen