qgis - How to visualize car park occupancy over time?

I am using QGIS Brighton 2.6.1.

I have a csv table with the exact entrance datetime and exact exit datetime of every car in an specific parking. Example of table:

Nº   DateTimeEntrance         DateTimeExit
--   ----------------         ------------
1    2014.01.01 20:15:16      2014.01.01 21:08:16
2    2014.01.01 20:15:17      2014.01.01 22:11:27
3    2014.01.01 20:15:17      2014.01.01 20:28:09
...      ....                     .....

I have the polygon of the parking and I know that the max capacity of the parking is of 300 cars.

I've been asked to make a heatmap or something similar to paint the polygon redder or lighter taking into account the occupation of the parking (number of cars inside the parking).

I first thought of using the Time Manager plugin but i can't display rasters (heatmaps) in that plugin, although i am starting to think that Time Manager is not the tool i need.

If I try to solve this with a vectorial layer, i don't exactly know how to store in the layer the current capacity of the parking in every single minute for later assign that layer to the Time Manager.

I need some light in this case.

Answer

Based on the description, you want to create an animation of one polygon feature (car park) with changing fill color (occupancy). This is not a heatmap. It's maybe a choropleth map with one feature ;)

I suggest the following steps:

1. decide animation frame length (e.g. one frame per minute)


2. aggregate number of cars in the car par within each given frame (done using scripting, Excel, or maybe group stats plugin) -> write to CSV


3. add a column containing the WKT of the car park polygon to each line of the CSV


4. load the resulting CSV and animate it using Time Manager