The function of layers within a GIS

With a paper map all the information is contained within a single sheet of paper. This information may tell you all you need to know about some basic features of the map. However, if you want to carry out more specific tasks involving spatial queries and analysis the paper map has many limitations.

Firstly, to avoid the original map from being marked the answer is to use some form of overlay such as a plastic sheet. With this technique you are able to put points, lines and polygons on the map without effecting the original. Whilst this is one way of using a map to analyse data it is far from satisfactory. This is where a GIS system is far more effective. With a GIS you can have a base map similar to a paper map and then add as many layers as needed to this to create the analysis you require.If you were a local authority you may want to have layers for lamp posts which would be represented by a points layer, land boundaries which would be represented by polygons or roads which would be represented by line layers. The same base map would be used by different departmental users for completely different applications without the problems normally associated with paper maps.

GIS can for instance automatically calculate lengths and areas. Data can be analysed which falls within a specific boundary. How many points of interest within a defined area for example? How far is one object from another can be identified very easily. For instance, properties within a certain location could be identified by price or by how near they are to facilities such as schools, hospitals and other local amenities. Businesses can analyse the most suitable location for new outlets based on proximity to criteria which they can define. In this way the best location can be calculated using GIS techniques. GIS can perform these tasks very accurately and quickly. Scanning over a paper map could mean missing many important factors which a GIS would easily highlight based on specific criteria.

Finally, linking map layers to external databases is now a well tried and trusted method of enhancing the use of a GIS. The combination of the map data linked to these external sources can enable many complex problems to be solved. The results can be quickly displayed in a visual format which databases and spreadsheets alone are not able match. In this way a GIS can display data which can give insights to organisations to make better decisions.If you would like to further explore how GIS could help your organisation jps services offers one and two day training courses in QGIS, ArcGIS and MapInfo.