There are 2 approaches to integrate MCDM techniques with spatial data in GIS. In the first method, multi criteria evaluations (MCE) are carried out in a stand-alone computer software and the results are sent to GIS using a file exchange mechanism. In the second method, MCE functions that are fully integrated into GIS can be used (
13). In this study, the latter method was employed.
2.1. SAHP
SAHP, as a technique that combines AHP with spatial data in GIS environment, has 4 main steps as follows:
Step 1: Identifying the criteria, which decision makers are subjected to.
Step 2: Structuring the criteria in a hierarchical framework (including goal, criteria, and sub-criteria).
Step 3: Calculating the weights of the criteria and sub-criteria regarding the decision hierarchy.
Step 4: Ranking the spatial raster or polygons according to the obtained index.
Steps 1 - 3 are based on AHP developed by Saaty (
14,
15). In AHP, the criteria should first be identified. Then, the decision criteria should be broken down in form of a hierarchy. After all, a pairwise comparison should be made between the elements of hierarchy in each level based on Saaty’s scale (
Table 1).
| Intensity of Importance | Definition |
|---|
| 1 | Equal importance |
| 3 | Moderate importance |
| 5 | Strong importance |
| 7 | Very strong or demonstrated importance |
| 9 | Extreme importance |
| 2, 4, 6, and 8 | Intermediate values |
In AHP, pairwise comparisons aim at the calculation of the criteria’s weights and priorities. To calculate the weights, the eigenvector method (Equation 1) was proposed by Saaty:
AW = λmaxW
Where A is the n by n comparison matrix, n is the number of items being compared in the matrix, and λmax is the largest eigenvalue of A.

Where eT is the transpose of e = (1, 1, 1, … , 1).
Decision makers’ subjective judgments in AHP can lead to inconsistency in the comparison matrices (
16). Yet, the quality of a decision can be improved by identifying the inconsistencies (
17). If consistency ratio (CR) is less than 0.1, estimation of W will be acceptable; otherwise, the inconsistency must be improved (
18) by revising judgments.
CR = CI/RI

Where RI is the average consistency index for random matrices and CI is the consistency index.
After all, the priorities of the criteria and sub-criteria are determined based on their weights.
In this study, SAHP-based evaluation was performed via the following steps:
Step 1: In order to find the hospital location allocation criteria, an electronic database search was conducted via PubMed, ScienceDirect, and Google Scholar databases. The applied keywords were ‘location allocation’, ‘site selection’, ‘hospital’, ‘Geographical Information System’, and ‘healthcare organizations’. There was no limitation in terms of applied criteria or techniques in the search strategy. However, it was limited to studies published in 2011 - 2015. Review of the literature revealed 9 criteria, including population density, fair distribution of hospitals all over the city, fast and easy accessibility, proximity to the main roads, being far from airport, not being located on the river path, being far from industrial centers, proximity to fire stations, and land area.
Step 2: The criteria were classified into 5 main criteria and their sub-criteria.
Step 3: All the criteria were entered into a questionnaire and 18 experts were asked to complete the questionnaire. AHP is a non-statistically based process, and was originally developed to help a single decision maker in the decision making process. Therefore, it can be implemented with a sample size including just a single expert or more (
19). In this study, all of the experts who had experience in hospital development (at least 2 years) in the vice-chancellery for resource development and the vice-chancellery for treatment at Shiraz University of Medical Sciences were asked to complete the questionnaires. The total of experts was 18 people, including health managers, urban planners, community medicine experts, and technical team of Shiraz University of Medical Science who take part in selecting hospital locations (
Table 2). The aim of this questionnaire was to determine the relative importance of the mentioned criteria.
| Specialty | Number of Experts | Academic Degree |
|---|
| Health manager | 1 | MPH |
| 4 | PHD |
| 1 | M.Sc. |
| 1 | B.Sc. |
| Urban planner | 5 | PHD |
| community medicine experts | 1 | PHD |
| 1 | M.Sc. |
| Technical team of Shiraz University of Medical Sciences | 4 | M.Sc. |
Step 4: The spatial raster layers of all 9 criteria were created in GIS as follows:
1. Population density: Population density was calculated by dividing the number of people who settled in every census unit by the area of that unit. Accordingly, more populated areas got higher priority compared other areas.
2. Fair distribution of hospitals all over the city: In order to determine how the hospitals were distributed in the city, the distance of every land-use from the nearest hospital was calculated. To construct new hospitals, the land-uses that were located in further distances got higher priority compared to closer land-uses.
3. Fast and easy accessibility: In order to determine the accessibility level, the distance of every residential land-use from the nearest hospital was calculated. Accordingly, people who lived in closer distances had better accessibility. Therefore, to construct new hospitals, they got a lower priority compared to others.
4. Proximity to the main roads: at first, the roads whose width was more than 30 m were selected as the main roads. Then, the distance of every residential land-use from the selected roads was calculated. The land-uses located in closer distances from the main roads got priority over other land-uses.
5. Being far from airport: the distance of every residential land-use from Shiraz airport was calculated. The land-uses located in closer distances from the airport got lower priority compared to other land-uses.
6. Not being located on the river path: the distance of every residential land-use from Shiraz river (Saheli River) was calculated. The land-uses located in closer distances from the river got lower priority compared to other land-uses.
7. Being far from industrial centers: the distance of every residential land-use from industrial centers was calculated. The land-uses located in closer distances from the industrial centers got lower priority compared to other land-uses.
8. Proximity to fire stations: the distance of every residential land-use from Shiraz fire stations was calculated. The land-uses located in closer distances from the fire stations got higher priority compared to other land-uses.
9. Land area: according to the standards of Iran’s ministry of health, the least appropriate area for a hospital with 32 beds is 5000. Therefore, the lands with areas < 5000 got lower priority.
Then, the results of pairwise comparisons were entered into AHP extension tools of Arc GIS 10.3. After calculating the weights and CRs, the weights were exerted on the 9 layers and the layers were combined. The result of this combination was a unique raster layer. The final layer was classified into 5 classes based on quintile intervals. Therefore, the Shiraz area was divided into 5 groups, including areas with very low, low, moderate, high, and very high potentials for constructing hospitals. Afterwards, the obtained map was overlaid with the spatial layer of the existing hospitals’ locations. Accordingly, the location of the Shiraz hospitals (33 hospitals) was assessed in terms of suitability based on the applied criteria. After all, in order to exclude the served areas, the areas that were located in standard hospital service areas (1500 m) were erased from the obtained layer using network analysis and erase tools in Arc GIS. Network analysis is a spatial analysis technique to calculate distances between 2 points using network data, such as roads network. The final result was another map that indicated the priority of Shiraz deprived areas for establishing new hospitals. In the following, among the most appropriate areas, the most appropriate land parcels were selected based on 4 main characteristics, including: a) earth's tilt < 0.05, b) being non-residential, c) land area > 5000 , and d) located in proximity to the main roads.
It should be mention that the applied questionnaire in this study was approved by Shiraz University of Medical Sciences in terms of ethics. Furthermore, the experts had the option to fill the questionnaires or not. In addition, confidentiality and privacy of information was maintained in all steps of this study. Besides, an ethical commitment was given to the Municipality Organization of Shiraz for giving them a copy of results.