Sensitivity Mapping

Strategic Technology >> AXSES - Pioneer In Sensitivity Mapping


Earth Observation Magazine, July 1994.
AXSES pioneers a system approach to environmental assessment and sensitivity analysis)

A Sensitivity Map attempts to show the relative importance and priority of points or areas within a region. It is used by resource managers, emergency response teams and environmental scientists to respond to emergencies and make informed decisions about land development, disaster response and contingency planning as well as to assess the Environmental Impact of real or hypothetical events.

By combining information about land, habitat and vegetation cover etc., the user builds a cumulative index of a region which relates to the issue being assessed. The objective is to provide rapid response to varying scenarios and contingencies, which themselves have differing demands and effects and thus require unique responses, resource allocation and priority.

GIS provides the ability to integrate divergent data from multiple sources in order to compile the relative sensitivity indexes. But the traditional approach often requires specialized skills and training. It is frequently not appropriate technology for the managers or scientists who have to make the ultimate decision. In rapid response systems, managers cannot afford to wait for the GIS specialists to modify and run the model.

This article suggests an information system approach that mirrors the conventional analytical process of the manager and scientist and uses GIS as an enabling technology rather than the focus of the exercise. The technique is described in the context of several applications.


The systems approach relies on the use of the familiar database and spreadsheet tools rather than a GIS to provide the analytical model. The GIS provides the ability to view the results of the model which determines sensitivity and priority based on Valued Ecosystems of the target area. The systems described here require no specialized programming and are ready to use with the appropriate databases.

The solution is built using GeoAXSES for GIS related presentations together with a spreadsheet type application developed in FOXPRO for the sensitivity model. It is supplied with a basic outline map of the world from which the user can select the Region Of Interest (ROI), an Information Atlas (InfoATLAS™) utility to classify and organise data and a dynamic grid overlay which provides the analytical framework. ….. more .. (please contact us for more about this concept)

Sensitivity MappingSensitivity Mapping


The solution is built using GeoAXSES for GIS related presentation together with a spreadsheet type application developed in FOXPRO for the sensitivity model. It is supplied with a basic outline map of the world from which the user can select the Region Of Interest (ROI), an Information Atlas (InfoATLASTM) utility to classify and organise data and a dynamic grid overlay which provides the analytical framework. .

To use the system two databases must be populated, these are the grid information (what valued ecosystems are in the area represented by the grid) and the Ecosystems value (what is the relative weighting of each ecosystem variable)

The Ecosystems information can be entered using a traditional GIS digitizing process but the grid technique provides an alternative methodology which is often preferred by scientists and non-GIS experts. In field work, for example, the region is divided into grids with each grid cell being represented as a spreadsheet element. The scientist enters evidence of the ecological parameters for the grid into the spreadsheet or database and assigns a weighting (level of significance) for each topic and classification in a separate look up table. The model calculates the total cumulative weighting for each cell and automatically groups the individual cells into a compound index. The model considers any number of topics (wetlands, vegetation, habitat etc.) and provides any number of classifications for each topic (vegetation = shrub land, mature coniferous forest etc.). Topics and classifications are weighted according to their significance for a particular sensitivity analysis or priority rating.


The consulting team consisting of several socio-economic, marine biology, coastal engineering, legal and system professionals gathered on location in Sulawesi, Indonesia. They were part of the FENCO Shawinigan Engineering group asked to “perform a baseline study on Coastal Zone Planning and Management”. The study was to be used as a basis for “future integrated development, protection, planning and management of the coastal zone”.

The project considered many aspects related to collaborative planning and management in the coastal zone and resulted in several recommendations for the establishment of a Distributed Environmental Information System using concepts of the Dynamic Information Messaging Environment (GeoDIME) developed by AXSES and MACLAREN Plansearch Limited. Sensitivity Mapping was an important component of the solution and was used to illustrate areas of concern within the proposed buffer zone. The new sensitivity mapping system developed by AXSES and MACLAREN proved to be very popular with the local consultants and the client. It was immediately put into effect and was easily understood by the systems and management personnel who were responsible for using it.

A team of local specialists was assigned to identify the valued ecosystems and their relative importance. Mangrove swamps, reefs, seagrass beds, and the habitat of rare or endangered species were assigned highest weightings. Fishing villages, mariculture sites and tourism facilities were next on the list. Areas of high agricultural productivity were selected for special attention and ranked with respect to crop suitability and activity. The values were entered into the ecosystems value table (spreadsheet or database). Next a series of Grid maps were produced and observations were made on the grids to depict the existence of the eco-sensitive areas. All available source material was used to populate the grid information which was a simple matter of ticking off those grids that contained each classification. Information was obtained from published maps, aerial photography, field observations and traditional knowledge.

Finally the information was loaded into the database and the model was ready to run. A section of coast line containing grids of 250 meters square for 3 thousand meters either side was used. The model for a target area of some 1,000 cells took only several seconds to compute the index running on a 486 computer with less than 1Mb of memory.

The user could choose to display the map index as a series of colors depicting various statistical ranges and aggregation techniques. The process is entirely menu driven with a simple point and click for all options. The map sensitivity index clearly illustrated the Valued Ecosystems Components according to the particular values assigned from the Coastal Zone Management prospective reflecting the local concerns and issues. It highlighted points that should be included in the buffer zone and provided guidelines for establishing the zone. Just as important however, was the ability to modify the entire system by changing the ecosystems values to reflect alternative concerns.


The framework for sensitivity mapping applies equally well to other issues and the basic model requires only adjustment to the ecosystems values to reflect other priorities.

For fire, slope and exposure effect the rate of spread. Remote camping sites or villages may require special evacuation priority and vegetation and land cover must be weighted to reflect its burning propensities.

Oil and chemical spills require an entirely different response and priority. The sensitivity of the area will vary based on physiography, habitat and land use. Smooth rock surfaces are less susceptibly to oil spills than a developed beach. Spills in the area of turtle nesting sites require special consideration for the use of heavy equipment, which can crush the delicate eggs and hatchings which are nested just under the sand. The larvae of various shell fish species, which are normally protected by a water column, float freely during breeding seasons making the new generation highly susceptible to surface contamination. The model can be modified to reflect these temporal perspectives.


The advantages of the systems approach is that it requires no prior knowledge of GIS or specialized GIS programming training. Multiple scenarios and sensitivities can be instantly computed and displayed using a spreadsheet or database model. “Unlike many GIS oriented analyses, it is extremely easy to understand the process, all that is required to change the sensitivity is to modify the weighting value for any topic and classification, this is achieved by adjusting values in a simple spreadsheet” says Dr. Bassem Eid, President of MacLAREN PlanSearch. “The breakthrough from our point of view is that the AXSES MACLAREN system can be used immediately by managers and scientist, with minimum training. It was designed for our own use as a environmental engineering company with the needs of our clients clearly in mind” .

Simon Melrose, project manager with AXSES MACLAREN DATA SYSTEMS LTD says: “We believe that there is something wrong with technology that can only be used by highly trained technicians. We are building systems that leverage traditional information products and development environments as opposed to proprietary GIS languages and techniques”.

AXSES MACLAREN is a joint venture of AXSES INC. a research and software development company specializing in environmental applications, and MacLAREN PlanSearch an environmental engineering division of SNC LAVALIN. The sensitivity model is a component of a Distributed Environmental Information System being designed with the Gulf of Maine Council on the Marine environment.

Ian Clayton is a consultant and systems analyst over 15 years experience in systems design and implementation. He has been involved with many GIS and environmental projects and is currently developing new enabling technology for a variety of multimedia mapping applications.