L'analyse de la couverture géographique vous permet de prendre en compte la disponibilité des services (c'est-à-dire la capacité des structures de santé à accueillir des patients) et d'en tenir compte en plus des contraintes d'accessibilité physique, afin de définir l'aire de captage associée à chaque structure de santé.
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Ensuite, les données peuvent être entrées pour la deuxième partie du panneau d'analyse, comme suit:
Analysis settingsParamètres d'analyse:
UnderSous:
(1) Type of analysis: Similar to the previous analysis, select whether you want an “anisotropic” or “isotropic” approach to be taken for the analysis. We choose “anisotropic” in the present exercise, in order to take into account the impact of slope on the speed for the WALKING and BICYCLING modes of transportation Comme pour l'analyse précédente, indiquez si vous souhaitez adopter une approche «anisotrope» ou «isotrope» pour l'analyse. Nous avons choisi «anisotrope» dans le présent exercice afin de prendre en compte l’impact de la pente sur la vitesse pour les modes de transport WALKING et BICYCLING.
(2) Direction of travel: Select the direction of travel of the patients. Please note that this field will only appear if the "anisotropic" option has been selected above. For the purpose of the exercise, choose "Towards facilities Sélectionnez le sens de déplacement des patients. Veuillez noter que ce champ n'apparaît que si l'option "anisotrope" a été sélectionnée ci-dessus. Aux fins de l'exercice, choisissez "Vers les structures".
(3) Facilities processing order: The geographic coverage analysis is done in a sequential processing order: one health facility is considered and processed, and then the next facility is considered, and so on, until all health facilities have been processed. At each iteration, the population identified as belonging to the computed catchment of a specific health facility is subtracted from the overall population layer. Such a processing order allows AccessMod to simulate both the saturation of services in populated areas and/or potential patient preferences when patients are within reach of many different health facilities. For this reason, the order in which individual health facilities are considered within the analysis can influence the results (although it is very difficult to predict how). Please see Annex 4 for details of how this analysis is done. Several choices are available to determine the order in which health facilities are considered. For the purpose of the exercise, you can select the first option: Facilities processing order: L'analyse de la couverture géographique est effectuée dans un ordre de traitement séquentiel: une structure de santé est prise en compte et traitée, puis la structure suivante est prise en compte, et ainsi de suite, jusqu'à ce que toutes les structures de santé aient été traitées. A chaque itération, la population identifiée comme appartenant au bassin calculé d'une structure de santé spécifique est soustraite de la couche de population globale. Un tel ordre de traitement permet à AccessMod de simuler à la fois la saturation des services dans les zones peuplées et / ou les préférences des patients potentiels lorsque les patients sont à la portée de nombreuses structures de santé différentes. Pour cette raison, l'ordre dans lequel chaque structure de santé est prise en compte dans l'analyse peut influencer les résultats (bien qu'il soit très difficile de prédire comment). Veuillez vous reporter à l’Annexe 4 pour des détails sur la manière dont cette analyse est effectuée.
Plusieurs choix sont disponibles pour déterminer l'ordre dans lequel les structures de santé sont prises en compte. Pour les besoins de l'exercice, vous pouvez sélectionner la première option: ""A field in the health facility layer". The goal here is to start with the center that has the largest capacity, and then to continue in a decreasing order. Two other possible choices for the processing order are currently availableLe but ici est de commencer par le centre qui a la plus grande capacité, puis de continuer dans un ordre décroissant.
Deux autres choix possibles pour l'ordre de traitement sont actuellement disponibles:
- "The population living within a given travel time from the facilities": by giving a maximum travel time (in minutes), AccessMod will first compute the catchment for that given time around each health facility, then determine the population living in each of these catchments, and use these estimates to determine the processing order for the health facilities. This approach would give precedence to facilities located in densely populated areas with easy travel accessen donnant un temps de trajet maximal (en minutes), AccessMod calcule d’abord l'aire de captage pour un temps donné autour de chaque structure de santé, puis détermine la population vivant dans chacune de ces aires de captage et utilise ces estimations pour déterminer l’ordre de traitement des structures de santé. Cette approche donnerait la priorité aux structures de santé situées dans des zones densément peuplées et faciles d'accès.
- "The population living within a circular buffer around the facilities": by giving a circular buffer radius (in meters), AccessMod will first compute a circular buffer around each health facility, determine the population living in each of these buffers, and use these figures to determine the processing order for the health facilities. Again, this approach would give precedence to facilities located in densely populated areas en donnant un rayon circulaire de zone tampon (en mètres), AccessMod calculera d’abord une zone tampon circulaire autour de chaque structure de santé, déterminera la population vivant dans chacune de ces zones tampons et utilisera ces chiffres pour déterminer l’ordre de traitement des structures de santé. De nouveau, cette approche donnerait la priorité aux structures de santé situées dans des zones densément peuplées et faciles d'accès.
(4) The field appearing in this step will change depending on the processing order option selected under step 3, namely:
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(8) Add short tags: Indicate short tags to be attached to the different outputs of the analysis. We will use "geographic analysis 120m" for the present analysis. Avoid very long name as it has been found to sometime prevent Excel to open the output generated xls files.
Facility selectionSélection de structure de santé
(9) As in the previous analysis, you can select the set of facilities for which the analysis will be performed. Keep all facilities selected for the exercise.
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- cat: unique identifier of the health facility as per to the field selected from the attribute table of the health facility layer.
- name: name of the health facility as per the field selected from the attribute table of the health facility layer
- capacity: maximum coverage capacity of the health facility expressed as the number of people that the facility can serve (as per the field selected from the attribute table of the health facility layer).
- amRankValues_capacity: values for the parameter used to define the processing order. In the present exercise, this column contains the maximum coverage capacity of each facility as this is the option that was selected above. Please see the boxed note below for more information regarding the label and content of this column when using the other options.
- amRankComputed: processing order applied during the analysis based on the content of the "amRankValues_capacity" field and the direction of processing (ascending or descending), as selected by the user.
- amTravelTimeMax: maximum travel time in minutes, as set by the user for the analysis.
- amPopTravelTimeMax: total population located within the maximum travel time set for the analysis (amTravelTimeMax).
- amCorrPopTime: Pearson correlation coefficient between the set of travelling times (t, from 0 to the maximum travel time) and the corresponding covered population within this time step (i.e. the sum of population in all cells that are located between t and t+1 of travelling time). This correlation measure gives a rough estimate of how the population is distributed through space as we move outward from the health facility. As an example, a large positive value (e.g. 0.707 in the third line of the above table) means that the population is relatively uniformly distributed as you expand outwards from the facility. A strong negative correlation would mean that there is more population close to the health facility than there is far away from it. A correlation close to zero means that there is no specific tendency in how the population is spread within the catchment. This correlation should really just be used as a relative indicator, as we do not provide the statistical significance of the correlation (you should use proper GIS analysis outside AccessMod if you need statistical insights about how the population is spatially located within the catchments).
- amTravelTimeCatchment: travel time to reach the maximum extent of the catchment area attached to the health facility. This value is either:
- Equal to the maximum travel time set for the analysis (amTravelTimeMax) when the maximum coverage capacity of the facility has not been reached within the set time (120 minutes in this example). In the current exercise, this is the case for the Queen Elizabeth Hospital.
- Smaller than the maximum travel time set for the analysis (amTravelTimeMax) when the maximum coverage capacity of the facility is reached before reaching amTravelTimeMax. This is the case of The Medka Health Centre in the exercise.
- amPopCatchmentTotal: population located within the catchment area for the travel time reported in the amTravelTimeCatchment field
- amCapacityRealised: part of the maximum coverage capacity of the health facility that is being used (realized) based on the total population located in the catchment area for the given travel time. This value is:
- Equal to the maximum coverage capacity of the health facility (capacity) when this value is reached before the maximum travel time (amTravelTimeMax). An example is the Medka Health Centre in the present exercise.
- Smaller than the maximum coverage capacity of the health facility (capacity) when such capacity is not reached within the maximum travel time (amTravelTimeMax). An example is the Chiradzulu District Hospital is in this the present exercise.
- amCapacityResidual: part of the maximum coverage capacity of the health facility that is not being used. This value is calculated by making the difference between the maximum coverage capacity (capacity) and the realized capacity (amCapacityRealised). This value is therefore equal to 0 when the maximum coverage capacity is being reached within the given travel time.
- amPopCatchmentDiff: Part of the total population located in the final catchment area (amPopCatchmentTotal) which does not experience facility coverage by lack of sufficient coverage capacity in the health facility. This value is calculated by making the difference between the total population in the catchment area (amPopCatchmentTotal) and the realized capacity (amCapacityRealised). This value is therefore:
- Equal to 0 when the maximum coverage capacity is not reached within the given travel time
- Greater than 0 when the maximum coverage capacity is reached within the given travel time
- amPopCoveredPercent: cumulative geographic coverage expressed as a percentage. This value corresponds to the percentage of the initial population distribution grid (i.e. the layer selected in the "Select population layer (raster)" field) that has been covered after having processes the health facility in question.
The header of the columns containing the unique identifier, the name, and the maximum coverage capacity of each health facility in the resulting table will be the same as the header of the field you have selected from the attribute table of the health facility layer.
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