Dept of Commerce / NOAA / OAR / PMEL / TMAP

Map Display Package

This page describes what we have in mind for the map display package we have been working on.

Comments are greatly appreciated: callahan@pmel.noaa.gov

Version 3.0 of the map display package is now available and demonstrated in the following demo: LiveMap v3.0



Introduction

Many geophysical data servers now exist on the Internet. The National Oceanic and Atmospheric Administration (NOAA) maintains a number of servers which allow direct access to some of the NOAA data holdings. A partial list of NOAA servers providing gridded data includes:
Each server requires the user to specify certain parameters which are included in the final data request sent to the server. Several of the parameters will be the same accross all servers, implying the possibility of a uniform interface. Standard parameters in the case of gridded data would include at least: With the Java programming language it is possible to provide an applet which would allow the user to specify the necessary parameter information interactively, submitting a data request to the data server only when all necessary parameters have been selected. Such an applet would be based on classes for selecting specific sets of parameters. This approach has several advantages: A key element of such an approach is the map display package which allows the user to select a region in x-y space. This selection can then be converted into latitude, longitude, depth/height or time. The rest of this document will discuss the design and implementation of a map display package which will be generic enough to be used in a variety of NOAA data servers. Special consideration will be give to the case of servers providing gridded geophysical data.


Goals

In determining the design specs for a map display package it is best to start with a minimal set of features which it must contain in order to be useful and portable.

Minimal Feature Set

Additional Useful Features

Additional features which might be included in the core package or may be added in classes extended from the core classes include the following:


Paradigm

The Paradigm for the map package is that of a white board. You may project an image onto the white board (MapCanvas) and then associate a MapGrid with that image. The MapGrid contains world coordinates and a particular grid cell spacing. The various MapTools can be thought of as objects which the user manipulates on the white board, like pens or erasers. At any time you may replace the image, the MapGrid or the MapTool while keeping the other components.

To allow text entry of values in some interface to geophysical data, Converters are supplied which are specific to the type of axis: lat, lon, length, etc. These Converters have intelligence specific to each axis: eg. The ConvertLongitude class can deal with multiple input formats and can handle comparisons between longitudes in the range -360:0, -180:180 or 0:360.

A new item called a MapRegion was introduced in v3.0. Currently, MapRegions can only be used to draw something at a specific latitude and longitude, moving appropriately as the user pans and zooms. In the future, this class will be used to implement hotspots for selection of data regions or specific tracks or locations. Anything that can be drawn can be a subclass of MapRegion.


Version History

LiveMap 3.0

LiveMap 2.3


Dept of Commerce / NOAA / OAR / ERL / PMEL / TMAP

Jonathan Callahan: callahan@pmel.noaa.gov
Last modified: Wed Mar 21 13:17:19 PDT 2000