L'analyse de mise à l'échelle permet de tester différents scénarios visant à étendre un réseau de fourniture de services existant ou de générer un réseau complet de fourniture de services s'il n'en existe pas déjà un.
Les scénarios pouvant être testés à l'aide de cet outil prennent en compte:
- Zones d'exclusion dans lesquelles il est interdit de créer de nouvelles formations sanitaires (voir section 3.3.1.5)
- Différents facteurs de pertinence répartis géographiquement qui sont combinés dans un indice d'aptitude de pertinence pour définir les sites les mieux adaptés à la localisation d'une nouvelle structure de santé. Ces facteurs peuvent être basés sur la distance par rapport à des caractéristiques éléments spécifiques, le temps de trajet entre ces caractéristiqueséléments, la densité de la population ou la définition des zones dans lesquelles les établissements structures de santé doivent être prioritaires par rapport aux autres (voir Section 3.3.1.10).
- Different geographically-distributed suitability factors that are combined together in a suitability index to define the most suitable sites for locating a new health facility. These factors can be based on the distance to/from specific features, travel time to/from features, the population density, or the definition of areas where health facilities should be placed in priority compare to other ones (see Section 3.3.1.10)
A physical accessibility analysis is then performed on all the raster cells presenting the highest value, outside of the exclusion areas, in the suitability distribution layer.
The site (cell) covering the largest population is the one selected for location of a new health facility. The type of facility placed on this site is then decided based on the content of the new health facility information table (see Section 3.3.2.3).
The above is repeated until:
- Either the number of new health facilities set by the user have been located; or,
- The population coverage set by the user has been reached.
The above description is only a summary of the overall process which is applied during this analysis. Please refer to Appendix 7 for more details.
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There is currently no function in AccessMod to automatically change and/or optimize the maximum coverage capacity of some of the health facilities, or to simulate the impact of these changes on population coverage. This might be part of future AccessMod functionalities. In the meantime, this approach can be implemented through the following steps:
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The following set of screenshots explains how to fill the sections used to input the different layers and parameters to perform the scaling up analysisUne analyse de l'accessibilité physique est ensuite effectuée sur toutes les cellules raster présentant la valeur la plus élevée, en dehors des zones d'exclusion, dans la couche de distribution de pertinence.
Le site (cellule) couvrant la population la plus nombreuse est celui sélectionné pour l’emplacement d’une nouvelle structure de santé. Le type de structure placé sur ce site est ensuite décidé en fonction du contenu de la nouvelle table d’informations sur la structure de santé (voir section 3.3.2.3).
Ce qui précède est répété jusqu'à ce que:
- Le nombre de nouvelles structures de santé définies par l'utilisateur ait été localisé; ou,
- La couverture de population définie par l'utilisateur ait été atteinte.
La description ci-dessus n'est qu'un résumé du processus global appliqué lors de cette analyse. Veuillez vous référer à l’Annexe 7 pour plus de détails.
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AccessMod n’a actuellement aucune fonction permettant de modifier et / ou d’optimiser automatiquement la capacité de couverture maximale de certaines structures de santé ou de simuler l’impact de ces changements sur la couverture de la population. Cela pourrait faire partie des futures fonctionnalités d'AccessMod. En attendant, cette approche peut être mise en œuvre à travers les étapes suivantes:
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L'ensemble des captures d'écran suivantes explique comment remplir les sections permettant de saisir les différentes couches et paramètres permettant d'effectuer l'analyse de mise à l'échelle:
Data input:
(1) Under “Select population layer (raster)”, select the raster format layer containing the spatial distribution of the original target population - "population". This layer will be used as the denominator for calculating the population coverage reached through the scaling-up analysis.
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(6) The two tables, in the lower-right hand corner of the above figure (empty now), contain the list of the suitability factors and exclusion areas set by the user. The method to fill these tables is explained in the following two sections.
Using the "Scaling up tables" section
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The table below describes the interface and input parameters associated to each of the above-mentioned suitability factors.
Sum of population within a radius
| Euclidean distances from features  | Travel time
| Generic priority
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(1) Under “Select a factor for the suitability index”, select the "Sum of the population within a radius" option from the pull-down list. (2) Set the radius (in kilometers) to be used. (3) A message indicating how many cells will be processed at each iteration will appear. (4) “Direction of prioritization” allows the analyst to define if higher values for this factor are more suitable or less suitable for locating a new health facility. (5) “Select factor weight” allows for the attribution of a relative weight to the factor. (6) “Select attribution layer” field selects the raster format population distribution that will be used to generate the factor distribution layer (see below). (7) The “Add” button allows you to add the factor to the list of suitability factors that will be used in the final index. | (1) Under “Select a factor for the suitability index”, select the "Euclidean distances to features" option from the pull-down list. (2) “Direction of prioritization” allows the analyst to define if higher values for this factor are more suitable or less suitable for locating a new health facility. (3) “Select factor weight” allows for the attribution of a relative weight to the factor. (4) “Select available layer” selects the vector format layer that will be used to generate the factor distribution layer (see below). (5) The “Add” button allows you to add the factor to the list of suitability factors that will be used in the final index | (1) Under “Select a factor for the suitability index”, select the "travel time from/to feature" option from the pull-down list. (2) The “Type of analysis” field allows the analyst to specify if the travel time will be based on an isotropic or anisotropic approach. Selecting the anisotropic approach will result in a new field to open, in order to indicate the direction of travel (from, or to, the selected features). (3) The “Direction of prioritization” field allows the analyst to define if higher values for this factor are more suitable or less suitable for locating a new health facility. (4) “Select factor weight” allows for the attribution of a relative weight to the factor. (5) “Select available layer” allows selecting the vector format layer used to generate the factor distribution layer. (6) The “Add” button allows you to add the factor to the list of suitability factors that will be used in the final index. | (1) The “Select suitability analysis” factor takes into account a raster data set with priorities as values (2) The “Direction of Prioritization” field allows the analyst to define if higher values for this factor are moresuitable or less suitable for locating a new health facility. (3) “Select factor weight” field allows for the attribution a relative weight to the factor. (4) “Select available layer” selects the raster format layer containing the generic priority map (5) The “Add” button allows you to add the factor to the list of suitability factors that will be used in the final index. |
Each of the suitability factors defined by the user is stored as a separate record in the "suitability factors" table appearing in the Scaling up section of the module panel (middle part of the panel). This table looks like the following figure and contains the following fields:
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You can then press the "Add" button to add this combination of parameters as a suitability factor into the "Suitability factors" table.
Suitability factor 2:
For the second suitability factor, we also would like for new facilities to be located as close as possible to the road network. For this priority, we will be using the "Euclidean distances from features" suitability factor.
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We now turn to the "Exclusion areas" section to define the excluded zones in which no new health facilities should be located.
Exclusion area 1:
First, we would like to exclude new health facilities from being located within 5 kilometers from an already-existing health facility.
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(4) Under “Maximum travel time [minutes]”, specify the maximum travel time (in minutes) that AccessMod will use to draw the catchment area(s) for the most suitable site(s) identified at each iteration. The population located within the catchment area attached to the final suitable site will be used to define the type of health facility to be located on that site. We use 120 minutes for this exercise.
Computation limits
The computation will stop as soon as one of the values set here are reached. Please note that a value needs to be indicated in each of these fields in order for AccessMod to run and that a value of zero indicated in any of these fields will be considered as 'no limit'.
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(8) Under “Add short tags”, give short tags to be attached to the different outputs of the analysis. We will use "scaleup53" for the present analysis.
Facilities selection
(9) As in the previous analysis, you can select in this section the facilities on which the analysis will be performed. Please note that:
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