Project idea: JSON HTTP server to control ~100 LEDs

I have a data feed available via JSON over HTTP that gives me the status of about 100 nodes on a map. Each node has two attributes: # of available parking spaces, and # of occupied parking spaces. Also, each node has lat/lng coordinates.

I want to make a large map, maybe 24"x48", that displays the current state of all the nodes. My thought is to get a large board, paint the map onto it, then drill holes where the nodes are located. I would put LEDs into each of the holes (internet research surfaced this product: http://www.adafruit.com/products/322). The Arduino would then be responsible for repeatedly downloading the JSON file, determining the current state of each node, and updating the color of the corresponding pixel to match its current state.

For instance, perhaps the red intensity would correlate to the number of empty spaces and the blue intensity would correlate to the number of occupied spaces. I considered led bar-graphs, which would look awesome, but I even if each node had only 2 5-bar graphs, that would still up my # of LEDs to 1000 which was scary.

As near as I can tell, I will need:

  • Arduino uno
  • Ethernet shield
  • ~100 RGB LEDs (serially addressable, like that product above)

I would love to hear people's opinions on my plan -- for instance, is there a cheaper way to get the LEDs to be addressed rather than buying those expensive strands? Are there smaller LED packages available (since I would prefer smaller points of light)? Am I overlooking anything huge? Also, thoughts on the general feasibility of this project.

About me: I am completely new to Arduino, though I have built medium-complex electronics projects before, one even involving a micro-controller (Rabbit, not Arduino). Thanks in advance.