Data recorded on maps can be difficult to analyse unless the spatial extent is calculated into a number value in square metres. This can be done by digitising the maps that have been produced in the field. Software (for example ARCGIS) can be used to calculate the spatial extent of a plant directly from data on digitised maps. If a GPS unit is used then again data downloaded from this can be converted into an area figure.
Alternatively if you have installed ARCPAD on your GPS unit then this will allow you to generate area occupied statistics while still in the field. Area of occupancy statistics can then be most easily analysed by graphing them with the date or year on the X axis and the spatial extent in square metres on the Y axis. An alternative method is to compare the maps from different years by overlaying them either electronically or maps copied onto transparency sheets to demonstrate how the population is changing in extent.