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Computer Cartography
Kernel Density Estimation
| Question | Answer |
|---|---|
| What is kernel density estimation (interpolation)? | method for discrete point data |
| What is continuous data? | Exists everywhere on the surface of the Earth |
| What is discrete data? | Exists at a specific location |
| What happens when you apply kernel estimation to discrete data? | Get raster of cells with density values |
| How do we go from discrete to continuous surface using kernel density estimation? | Place a 3-dimensional kernel function over each point so that the point is in the center of the kernel function |
| How do you calculate the density for a grid cell? | Take the cumulative distance of all the 3-dimensional kernel functions that are above the center of cell |
| What does it mean if you have a grid cell with a high density? | High concentration |
| What are the six kernel functions? | normal, quartic, triangular, negative exponential, and uniform |
| Which two functions should you use? | Normal or quartic |
| What is bandwidth? | The distance from the center of function to outer edge |
| What are two characteristics of a long bandwidth? | flat and generalized |
| What are two characteristics of a short bandwidth? | tall and less generalized results |
| How many bandwidth options are there? | 2 |
| Which bandwidth option do you vary the bandwidth by specifying the minimum number of points falling under each kernel function? | Adaptive |
| Which bandwidth option do you vary the bandwidth by specifying the bandwidth to a value and having all kernel functions drawn to the value? | Fixed |
| If you specify a large number of points to fall under your kernel function, how will it look? | Long and more generalized |
| If you specify a small number of points to fall under your kernel function, how will it look? | Short and more detailed |
| Which bandwidth type is preferred? | Adaptive |
| How should you set the minimum number of points that you want to fall under your kernel function? | Using a few percent of the entire points, like 2 or 3% |
| Will changing the cell size change the results or how they are visualized? | How they are visualized |