Understanding and Interpreting maps GIS 421 Understanding and Interpreting maps

Outline Introduction to Maps Types of Maps Map Elements Map Uses and Interpretation Problems Interpreting Map Data References

Introduction to Maps Maps are a form of visual spatial communication. Can be dated back to over 40 000 years ago Maps are physical or digital representations of the real world and real world features. The earth is not perfectly represented on a map, it is therefore up to the map reader to interpret the map. Maps can be used as sources of information about an area, and as a tool to complete a task. Maps vary widely in quantity and quality of information, depending on their intended use.

Types of Maps All maps represent some form of real world information. Some common maps include: Physical maps Road maps Climate maps Political maps Topographical maps Thematic maps

Physical map Shows physical features of a landscape such as mountains, rivers and lakes. Colour is often used to show elevation changes and terrain. In most physical maps reds and browns are used to show areas of higher elevations and green lower elevations. Blue always represents water.

http://geology. com/world/the-united-states-of-america-physical-map http://geology.com/world/the-united-states-of-america-physical-map.shtml

Road map Shows major and minor roads depending on resolution, represented by different colours. Street names and places of interest are also often shown.

http://smart-traveler.info/map_of_san_francisco_ca_usa.html

Climate map Climates maps shows variations in climate in a specific region, often using colour to differentiate climate zones. Climate maps can show patterns in rainfall, temperate, humidity.

http://www.southafricaholiday.org.uk/travel_tips/climate_southafrica.htm

Political Map Political maps only show the borders of countries on provinces without any topographic features. These maps are often smaller resolution and normally only show major cities.

http://www. worldatlasbook http://www.worldatlasbook.com/images/maps/europe-map-political-countries.jpg

Topographical map Topographical maps show physical geographic features as well as man made features such as roads and buildings. Elevation is represented with contour lines. Topographical maps also have lines of latitude and longitude used to determine location.

www.lib.utexas.edu

Thematic map Thematic maps are used to convey specific information or themes to the map reader. These maps can consist of a traditional map (such as a political map) overlaid with other data showing spatial data of a particular theme. These maps are very useful for showing specific information and comparisons over time, such as change population density in a region.

http://sosregions. wikispaces. com/file/view/precipitation_map http://sosregions.wikispaces.com/file/view/precipitation_map.png/152578197/precipitation_map.png http://blog.mapsofworld.com/tag/africa-thematic-maps/

Map Elements 1. Orientation There are four basic elements of a map which are required for understanding the map data. 1. Orientation Maps are orientated with cardinal points. North is usually at the top of the map, otherwise it is indicated with a north arrow or compass rose.

Map Elements 2. Scale All maps require a scale. This is useful to the map user for determining real life distances, by measuring distance on the map and using the scale to calculate actual differences. This can be represented numerically such as 1:50 000 or as a bar scale . Large scale maps represent small actual area while small scale maps represent large area.

Map Elements 3. Location Lines of latitude and longitude are used on topographical maps to provide the exact location relative to the rest of the world. Finding locations of specific features on a map in terms or degrees, minutes and seconds can be done with accuracy.

Map Elements 4. Features Maps will often represent important features with symbols and a relative key or legend. Isopleths are often used maps to show change in a variable, by using a line to connect all points with equal values. This is most commonly found in topographical maps as contour lines, which connect points of equal height. Isobars are used in synoptic charts to connect all points of equal pressure, and similarly isotherms connect points of equal pressure.

http://weather.gladstonefamily.net/topoweb/guide_files/avalanche.gif http://sawdis1.blogspot.com/2012/12/sea-level-synoptic-chart-south-africa_23.html

Map Uses and Interpretation “Interpreting maps involves transformation of perceivable relationships of cartographic entities on the map to spatial information about the corresponding geographic objects.” - Barkowsky, & Freksa (1997) Maps are limited representations of the real world, and therefore require meta-knowledge to interpret. An understanding of both the map, and the maps context is required. By understanding how maps work, it can be used to provide information about a specific area.

Map Uses and Interpretation Maps can be simply used to find the location of something by interpreting the data provided. For example, if you are planning a route from one point to another using a map, the information the map provides would have to be interpreted and applied to find your location, the destination, and the possible routes to get there. This is where understanding of the map’s scale, direction and features is applied.

Map Uses and Interpretation Maps are not only useful for navigation, but for a wide variety of other uses depending on the type of map and what data is provided. Synoptic charts show pressure, wind direction and cloud cover at a particular point in time. These variables can be used to determine the weather at a specific point, and predict future weather. Crime can be mapped by showing the location of past crimes on a thematic map. Crime patterns can be interpreted by law enforcement agencies which can then be conveyed to the public.

http://www. lunasurf. co http://www.lunasurf.co.uk/product_images/uploaded_images/weather-chart-surf-report.jpg http://en.wikipedia.org/wiki/Crime_mapping#mediaviewer/File:DChomicides.jpg

Map Uses and Interpretation GIS maps are much more complicated, and can easily display any combination of data sets. This allows for patterns and trends between spatial data and meta-data to be interpreted. GIS also offers more in data manipulation techniques and spatial analyses. Map data can be manipulated by intersecting or joining overlapping layers. Spatial analyst tools in GIS software offer ways to interpret information regarding distances, densities and aspect analyses.

Problems Interpreting Map Data Interpretation of data itself can present a problem since every individual may perceive maps differently, depending on their specific knowledge and background. This may lead to misinterpretation of maps. Over-interpretation is the most common misinterpretation, and may occur when aspects of the map are not understood in the way the cartographer designed. An example of this could be when the direction and distance of a subway or bus route is taken literally.

Problems Interpreting Map Data http://cdn.iphonehacks.com/wp-content/uploads/2012/01/subway-windows-phone-design-inspiration.jpg

Problems Interpreting Map Data Misinterpretation is related to the concept of hierarchies of aspect. Certain aspects of maps are deemed more important that others by the cartographer when trying to depict a map. Map readers may misinterpret a map by assuming that an aspect, such as distance, is more important than connectedness and orientation. Understanding of the map’s intention is important to correctly interpreting the map.

Problems Interpreting Map Data Barkowskyn & Freksa (1997).

References Barkowsky, T., & Freksa, C. (1997). Cognitive requirements on making and interpreting maps. In S. Hirtle & A. Frank (Eds.), Spatial information theory: A theoretical basis for GIS (pp. 347-361). Berlin: Springer. http://geography.about.com/od/understandmaps/a/map-types.htm http://gitta.info/LayoutDesign/en/html/DefOrgMapEle_learningObject1.html