How Big is the Big Island?
A Tiny GIS Application
 
 

The island of Hawai'i is often referred to as the "Big Island." The name is accurate in that the Big Island is the largest of the Hawaiian archipelago. It's also the youngest (ignoring the still submerged Loihi) and most volcanically active. But just how big is the Big Island? Well, it boasts the world's largest mountain (and tallest if measured from the sea floor). It contains climactic zones ranging from rain forest to desert to glacial. This GIS (Graphical Information System) application allows one to explore the size of the island along major driving routes. Select starting and destination points from the drop down menu to the right.

The data for this application is stolen from James A. Bier's "Map of Hawai'i: The Big Island." Although, I've taken enough liberties that I certainly wouldn't use this application to plan my escape route from a tsunami or the onslaught of lava. The data is stored in a mysql database in several familiar data structures used for GIS vector data. The first contains segments (of roads) along with their starting and ending nodes in approximately the following format:

Segment ID From Node To Node Name Distance
18 Kailua-Kona Honalo Hwy 11 8.4


The second data structure contains the relative positions of the nodes for use on map overlays. It looks like:

Node Name x position y position
Kailua-Kona 0.778 5.528


The Dijkstra algorithm is used to find the shortest distance between two nodes in a network. In this case the network is comprised of roads between towns, intersections, and points of interest (the nodes). The Dijkstra algorithm is really just a variation of the brute force technique of finding all possible combinations of routes and then selecting the shortest. Instead, it follows routes in a systematic way and "knows" early in its run what routes to eliminate as being already longer than the possible answer.

Select a starting point.


Select a destination.

Miles  
Kilometers