The referral analysis allows one to compute the travelling times and/or the distances along the least-cost paths (i.e. path between two locations that minimizes the total travel duration for those travelling along it, see Ray and Ebener, 2008) between two groups of health centers. Such path is different from a straight line as it does take into account the landscape constraints together with the modes and speeds of travel of the population.
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(5) The "Permute group" option allows one to improve computation time when more facilities are selected in the starting group than in the destination one. But if this option is selected, 'Limit the spatial analysis to the closest pair time-wise' is not possible. We will not use this option for the exercise.
(6) The option "Output the layer of the paths among selected facilities", if checked, will output a polyline shapefile with all least-cost paths among all the start-destination pairs of points. We will not use this option for the exercise.
(7) The "Enable parallelization" option, if checked, allows the referral analysis to be parallelized on all available CPUs/cores that your AccessMod isntance has access to. If you are using Virtual box, the numbers of available cores can be changed in the settings of VirtualBox (see section 4.2). Using this option can drastically decrease the overall computation time for this analysis. We will not use this option for the exercise.
(8) Select the “Limit the spatial analysis to the closest pair time-wise” option if you want to restrict the analysis and the output table to the closest health facility, in term of travelling time. We will not use that restriction in the present exercise.
(9) If "Measure distances from cell center" is checked, the resulting distance will be measured between the center of the cells in which the FROM and TO facilities are located (this corresponds to the shortest path by travel time). If unchecked, this measure of the distance will also include the (small) distance between each facility and the center of the cell in which they are located (this corresponds to an extended path compared to the shortest path by travel time). We will not use this option for the exercise.
(10) If you want to limit the travel time for the analysis, you can specify this maximum travel time here under "Maximum travel time (minutes)". If you do so, those health facilities that can be reached in a time that is greater than this specified maximum travel time will not appear in the output tables. We will not use a maximum travel time in the present exercise, and you can therefore specify "0" in the entry field.
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