FloraMap^TM is an algorithm for mapping the distribution of plants and other organisms in the wild. It works on the premise that we know nothing about the organism other than the geographic location of a calibration set of collection points. From these we fit a climate probability model. This approach has had considerable success, and is being used widely. However, it has some major drawbacks for many applications: it requires a calibration set, it only works on climate, and it has not been used successfully on cultivated crops where the farmer alters the environment.

So, what do we do for those who ask the simple question, "Where else in the world is like my plot of land?" We have no calibration set. We do not know what species we are considering. We do not have an algorithm for predicting the probabilities of relevant soil characteristics. The question may be simple, but the answer is not. Homologue has been developed to cope with the complexities of this simple question. Homologue uses the basic algorithm of FloraMap, generalized to fit a range of generic species designated by the user. It incorporates statistical probability calculations for the mapping of soil characteristics. If we know where else in the world is like my plot of land, we can infer, from the agricultural practices there, what may be applicable to my plot.

Homologue also can be used in the reverse sense. If we find an instance of the cultivation of an interesting species, we may look at where else it might be used. If we have a number of these instances, we might look for an environmental envelope, or "Cloud" as James Cock terms it, where the species might fit. Homologue therefore allows the combination of the probability maps for various sites that circumvents the problem that FloraMap has with small sample sizes.

This version of Homologue is the Beta demonstration release. It has been specially crafted to give an idea of the final operational capacity of the full release version that will work with the 30 arc-second climate grids. It is designed to load as much data as possible into RAM in order to speed operation. It is designed as a "What if?" tool, and we hope that scientists will use it in that exploratory way. Sit with it, and try out ideas to see if they fit with the world and your conception of it. It should be fast enough to play with. In its present state, it does not try to prove or disprove hypotheses, unless you are perspicacious enough to find a way to do it.