Resource Mapping

Sunday, March 25, 2007

DIFFERENCES, ADVANTAGES AND DISADVANTAGES OF A GIS. DIGITAL MAP AND PRINTED MAPS


Introduction

For the majority of us, maps represent a useful tool which we often use in daily life be it while navigating new hiking trails or when we are looking for a specific landmark, shopping centre or street name in an unfamiliar town or city. The common road atlas is now being replaced with more sophisticated and interactive digital forms which in some vehicles are now being built in as standard features. These systems use computer programmes and GPS (Global Positioning System) satellite technology to assist with voice prompts and are a form of GIS (Global Information System). GIS though still a relatively new technology is becoming more and more useful for a vast range of applications which include every day life, science and agricultural fields, and the military. In this assignment, I will touch on the essence of maps, digital maps, and GIS to provide a basic introduction to their uses, advantages and disadvantages.

Printed maps

Printed maps are used to portray the whole Earth’s surface or a part of it on a flat surface [1]. The term “map” actually refers to the mathematical meaning of transferring information from one form into another [2]. Maps can be presented as different projections which each have their own advantages and disadvantages. Maps generally show true distance, true direction, true area, and true shape, however no maps can represent all four at the same time [1]. A 1:50 000 scale map is restricted to the total area that can be portrayed, but the scale is true between the distance on the map and the distance on the ground [1].

Maps are still the main source of data for GIS systems [2]. The term “map” in mathematics explains the transfer of information from one source to another [2]. To produce a map, the requirements include the selection of various features which are to be included on the map, the characterisation of these features into groups such as “Roads” or “built-up areas,” the simplification of detailed outlines of areas including the coastline, the exaggeration of some features on the map that are often too small in reality to represent, and the use of symbols to classify the different classes of the chosen features for the map. To interpret most symbols and features, a representative key is usually supplied [2]. Without a good knowledge of the many symbols on a map, it is often difficult to find what you are looking for in a short space of time.

Other disadvantages of basic maps is that they are also often stylised, meaning that they are often portrayed in an unnatural way, and require some level of interpretation [2]. Maps are often out of date because they have to be printed and therefore the date of publication is the latest date of accuracy. They also show only a situation that is static and is a reflection of one section in time only. Some maps are very artistic which can make them more difficult to interpret, and area on a map can be rather difficult to determine accurately. It becomes increasingly difficult to use a map of the area if you are positioned on top of a high location within the map location as perspectives change and some objects are blocked from view by other objects. Maps cannot pan or give an oblique angle view on the map location [2]. Due to the cost of producing and making certain maps, the information that they contain is often a compromise with what can be afforded [2].

Printed maps have four general roles to play today. The first role is that of displaying data. Maps display information in a meaningful way, in other words, maps provide information that is directed for a specific use [2]. Maps also useful stores of data in the form of selected information about the map area. In a 1: 50 000 map, about 1000 place names are common. Interestingly the information stored on a common British topographical 1: 50 000 map equates to the requirement of 25 Million bytes of storage when converted to a digital format [2]. Maps show boundaries of areas and land uses that cannot be discerned from merely surveying the landscape [2], and most importantly, maps can be used to analyse. Transparent overlays (invented by Ian McHarg) are often used to test the relationship between two distributions of various objects or situations or resources, and hypotheses can therefore also be formulated and tested with the aid of maps [2].

One of the most useful advantages of having maps, and in this I mean printed maps of the same area over periods of time, i.e., maps that are out-dated, is that these maps can actually be useful in determining and storing information about changes in land use and zonation of properties [2]. Examples of this include the first large scale zonation of land in the United Kingdom in the 1930s by Sir Dudley Stamp, and again in the 1960s by Professor Alice Coleman that used maps to interpret the information [2].

Digital maps

Digital maps are similar in a lot of ways to the printed map in that they are constrained by the same disadvantages, though updating digital maps is generally a lot easier and a much quicker process. Maps that are accessed online are often up to date or updated regularly. One obvious disadvantage here is the need for technology, be it computers that are capable of downloading the map information, or the simple presence of a reliable Internet access point or even electricity. Digital maps are often not practical for this reason for many out door activities unless pre-loaded into portable devices, which can often be unreliable, or isolated rural settlements.

Digital maps became useful tools through the requirements of scientists who wished to produce quick maps to visualise digital modelling, or censuses. For these uses, the quality of digital maps was often not of major significance, and in 1967 the first ever modelling computer mapping package was released by Harvard University called SYMAP [2].

By creating digital maps, normal map production time and costs, including editorial costs are drastically reduced [2], however, before the development of faster and more efficient computers, the cost of hardware to produce digital maps was also high.

An interesting form of digital mapping includes the creation of Expert systems (which those of you who are doing the Conservation Biology course will be familiar with). In Expert systems, the computer chooses the correct techniques based on the data that has been provided, the map scale, and its purpose [2]. Digital maps are far more common today than printed maps and today [2]. Importantly, digital maps, because they are made up of digital data, can be used for a larger range of purposes than printed maps [2].

The primary advantage of digital maps is their comparative cost. They are cheap to produce and faster to produce. Digital maps can also be tailored to specific requirements of the user, which includes ease of perspective change or scale changes. The digital data within the maps can be used in applications of a GIS [2].

One large disadvantage is the difficulty in producing one complete digital world map or full-scale maps because of the costs involved and the mass of information that would need to be stored and accessed [2]. Another disadvantage is the initial requirement to invest in suitable computers that are not only capable of creating the digital maps, but also saving and storing the mass of data, therefore capital expenses can be high [2]. Through mass production and the loss of the traditional art of cartography that was seen in the creation of printed maps, quality of digital maps is often also inferior, and is often referred to as “cartojunk.” [2] Maps and digital maps are not searchable in the sense that you can type in key words in a search field to access the place or additional stored information on the search as is often the case with a GIS.

The digital maps produced by Lorraine Innes for MAPTRIX, an interactive educational tool, hi-lights the importance that digital maps can have as future components of school curricula, particularly Geography. MAPTRIX educates the user not only about the use of maps as discussed above, but also how they should be interpreted, which is often something most of us are not taught [3]. As part of the Resource mapping module, both the digital and printed MAPRTIX versions were introduced. Although problems were experienced with the speed at which the digital maps’ perspectives could be changed in order to view different locations, some errors were also encountered in the interpretation of particularly the secondary roads, and several spelling and grammatical errors were also encountered within the set question field, eg. “Road of trees” instead of “Row of trees” (Colchester Map, Eastern Cape, South Africa). I can only conclude that the data fed back to students or learners is only as accurate in digital format as what was originally programmed.

GIS

A GIS is a computer-based tool for mapping and analysing events and places on the Earth’s surface. A GIS integrates common data base operations, which include query as well as statistical analysis of the data, and the geographical analysis with better visualisation than is achievable with maps [4]. A GIS has the power to not only to create maps, but also integrate different information and visualise scenarios, present ideas, and provide solutions for complicated problems [4]. A GIS performs six tasks which include data input, data manipulation, data management, query and analysis, and finally visualisation.

GIS can be used for a vast range of tasks for nearly everything. In Industry and particularly in agriculture, GIS is used extensively for mapping of crop yield and crop rotation cycles, as well as projecting future soil loss on farms, be it from erosion, or poor use [5]. Since a GIS can be used to manage information from wherever it is located, GIS are becoming increasingly valuable in business management, allowing information to be obtained about where the customers are, what their preferences are (market research), spending patterns, and how to optimally exploit this information to maximise overall market share to minimise effective competition [5]. Cities and city planners cannot do without GIS to track maintenance, keep inventories and map locations, and model scenarios and distribution of services etc. [5]. GIS is used daily in the conservation of the environment. Species and resources can not only be mapped but can also be modelled, which allows for a preventative view on possibilities or scenarios, allowing greater resolution about a specific problem [5]. Managing forest is also more sustainable with the use of a GIS, and geologists can also use GIS to study geological features and model seismic activity [5].

GIS is primarily made up of hardware and software (the tools for the manipulation of the data and data management system), the data itself, which is the most important component of any GIS because without it, the GIS would not function, the people component who are responsible for running the GIS system since technology has limited intelligence, and the method by which the GIS functions according to a well organised plan which is often referred to in business as the operating practice [6].

GIS is made up usually of vector and raster structures for data input. Raster is also referred to as grid information, while vector provides a basic visual representation from which no mathematical or statistical analysis can be easily deduced. There are advantages and disadvantages to both methods, and GIS that integrate both structures of data input generally have a better range of data manipulation [7].

Advantages of vector data include the representation of data at its original resolution and form without losing its uniqueness, otherwise referred to a generalisation of objects (as explained in printed maps above) [7]. The graphic representation of the data is more detailed and often more pleasing to the eye, and data obtained from printed maps required no additional conversion since printed maps are in vector form anyway [7].

Disadvantages of vector data include analysis of data, which can only be done if the data is converted into a topological structure [7]. Topology is the study of geometric properties and spatial relationships, which remain unaffected by smooth changes in shape or the size of objects. It is also difficult to process large maps using vector data because of the sheer size of the information that needs to be stores, and elevation data is not well represented in vector form [7].

Advantages of raster data include the implication of geographic location by its position in the cell matrix, in other words, an objects location at the top right hand corner no longer requires the storing of its actual geographic co-ordinates [7]. The analysis of data is also relatively quick and is also therefore suitable for mathematical modelling as well as quantitative analysis [7].

Disadvantages of raster data include the relative loss of resolution where the resolution is actually determined by the cell size selected [7]. Linear features are rather difficult to represent, and associated large amounts of attribute data can be slow to process [7]. Some data integrity or data corruption can also occur as a result of data conversion from vector to raster forms, which will be expressed in the end product, and unfortunately raster structures often produce lower quality imagery that does not conform to many of the needs of cartography [7].

General advantages of a GIS over a map or digital map include the ability to pan to observe different perspectives on objects at oblique angles, with the ability to access additional information about a location or site, take measurements at any relative scale without the restriction of the printed map scale, and the searchability of the entire GIS. GIS are also relatively easy to integrate into various aspects of our modern lives in many forms to assist with a variety of functions, where maps generally have a limited use. The ability of GIS to be integrated and connected to other computer operated system such as GPS and credit card transaction and cell-phone operations, not only has a huge potential for expansion, but may also provide future problems regarding the accessability of daily information about our personal lives. This may lead to problems relating to the violation of privacy.

In conclusion, although it is easy to compare maps to a GIS and source information about their advantages and disadvantages, GIS is certainly the fastest growing form with the most applications, without which many of our daily functions that we take for granted would not be possible.

David Vaughan
Senior aquarist, Quarantine
Two Oceans Aquarium
Cape Town, South Africa
+27 21 418 38 23
dvaughan@aquarium.co.za


References

[1] Kansas GIS: http://www.kansasgis.org/catalog/projections.html Accessed on 20 March 07, 16:58.

[2] Internet source: http://www.geog.ubc.ca/courses/klink/gis.notes/ncgia/u02.html#SEC2.2.2 Accessed on 19 March 07, 13:15.

[3] Innes L. (date not given). Evaluating learning material for map reading. Pdf Internet source: Accessed 19 March 07, 13:19.

[4] Internet source: http://centrin.net.id/~agul/gis_what.html Accessed on 19 March 07, 13:52.

[5] Internet source: http://centrin.net.id/~agul/gis_apl.html Accessed on 19 March 07, 14:00.

[6] Internet source: http://centrin.net.id/~agul/gis_comp.html Accessed on 19 March 07, 14:15.

[7] SANBI: http://bgis.sanbi.org/GIS-primer/page_19.htm Accessed on 19 March 07, 15:16.

10 Comments:

Post a Comment

Links to this post:

Create a Link

<< Home