Ticket #293 (assigned Task: null)
Generating Random Pseudo-Absence Data from Extents, Lines, Grids, Etc
|Reported by:||bbest||Owned by:||jjr8|
|Component:||Tools - Spatial Analysis||Version:|
Attached is code to generate points along lines, which was initially used in the NMML MGET lab. This brings up the larger issue of pseudo-absence sampling for generating the null data to feed into a GAM/GLM/CART/etc multivariate model. A variety of approaches could be taken for generating these random pseudo-absences, of which the practical mechanics and statistical theory could easily constitute a worthwhile manuscript:
- BBOX. A simple bounding box.
- MASK. Either a mask raster or polygon.
- LINE. So the generate random points tool can work on a line. Or use the attached file for generating even points along the line.
- GRID. A grid, such as that generated by FISHNET, could be used as the presence-absence reference. Hence intersecting segments of lines falling within the cell, and points of observation are sampled by this grid to determine presence or absence. This is the approach taken with the SERDP project.
There remain issues of evenness when incorporating time, and suitable buffer distance in space and time to constitute an absence with respect to a presence.