Overview. GIS Data Output Methods

Transcription

1 Overview GIS Output Formats ENV208/ENV508 Applied GIS Week 2: Making maps, data visualisation, and GIS output GIS Output Map Making Types of Maps Key Elements Table Graph Statistics Maps Map Making Maps are created to communicate the information present in spatial data to a map-reader Goal is to communicate the spatial information portrayed on the map as effectively and efficiently as possible Ideally, reading a map is both a pleasing and enlightening experience for the map-reader Most popular use of GIS is for making maps GIS Data Output Methods 1. Monitor display 2. Exporting to a digital file 3. Printing or plotting on paper GIS Data Output Methods 1. Monitor display Take computer and data to client Most easily updated On the spot modifications Cheapest Ephemeral 1

2 GIS Data Output Methods 2. Exporting to a file Data in digital format Transferred to other computer or software system Disc, USB easily transportable 3. Printing or plotting on paper Most common Generates hardcopy Knowledge of cartography desirable Important Considerations Need to be clear about intended audience Who is the product for? Specialist or general public? Adult or child? Type and form of presentation? Scale and accuracy needed? Budget constraints Technological constraints Appropriate file format Delivery mode Success of GIS is often gauged by quality of the output! Cartography The Cartographic Process The science or art of making maps Purpose to transmit information, knowledge or location and/or facilitate travel Greek.. Chartis (map) and graphein (to write or draw) Oldest maps date back to 7-6 th century BC Thrower, N. J. W. (1999) Maps & Civilization: Cartography in Culture and Society, Chicago: University of Chicago Press, 326 p. The Cartographic Process Cartography The science or art of making maps The Cartographic Process 1. Think about what the distribution of the phenomenon might look like 2. Decide on the purpose of the map and the intended audience 3. Collect data that are appropriate for the purpose of the map 4. Design and construct the map using appropriate cartographic principles 5. Determine if the map reader understands the map content Types of Maps Two general map types: Reference or formal maps (location, navigation) Thematic or transitory (visual display, information analysis) Maps contain distortions from: Scale Projection Symbology 2

3 Charles Darwin University to Darwin NT - Google Maps 8/ 03/ :16 pm 9/03/2015 Types of Maps Reference or formal maps Depict selected details of the environment as accurately as possible Road maps, political maps, physical maps, topographic maps Location, distance, orientation, reference, known features Types of Maps Drive 13.0 km, 16 min Reference or formal maps Charles Darwin University, Ellengowan Dr Darwin NT Charles Darwin Depict University, selected Ellengowan Dr details of the environment as accurately as University possible E Dr Dripstone Rd Road maps, political maps, physical maps, topographic maps University E Dr Location, University E Dr distance, orientation, reference, known features north-west right 3rd University E Dr Bagot Rd National Highway 1 Knuckey St 2nd Dripstone Rd 2nd Lakeside Dr right Trower Rd Bagot Rd right Bagot Rd National Highway 1 left McMinn St right Knuckey St Darwin NT Types of Maps Depict the general spatial pattern of selected data or features (e.g. population distribution) Qualitative (categorical data e.g. soil type) Quantitative (numerical data e.g. ph values of soil) Usually have a base map with a thematic graphical overlay Producer includes only the amount of information necessary to convey the map message Emphasise a particular feature or set of data Choropleth maps Dot-density maps Proportional symbol maps Flow maps Isoline maps Cartograms Choropleth maps: use colour shading to represent different quantities or values - From Greek choros (place) and pleth (value) - Use when data occur within well-defined units or are numeric interval data - Involves some method of data classification - Generally derived from values describing attributes of non-overlapping polygons Choropleth maps: use colour shading to represent different quantities or values - From Greek choros (place) and pleth (value) - Use when data occur within well-defined units or are numeric interval data - Involves some method of data classification - Generally derived from values describing attributes of non-overlapping polygons Choropleth maps: use colour shading to represent different quantities or values 3

4 Dot-density maps: use points on a map to correspond with occurrence Isoline maps: use lines to connect points of equal value (isotherms for temperature, isohyets for rainfall, contours for elevation) Average annual rainfall Isoline maps: use lines to connect points of equal value (isotherms for temperature, isohyets for rainfall, contours for elevation) Temperature and sea level pressure Graduated symbol maps: draw attention to big concentrations of your distribution by varying symbol size to concentration in an area 4

5 Flow maps: show the origin of some flow/movement between places, with line width proportional to quantity of movement. Cartograms: spatial features are drawn (distorted) in proportion to the value of an attribute Cartograms: spatial features are drawn (distorted) in proportion to the value of an attribute Typographic maps: use typography as line and area map symbols Activity Find an example of each of the following maps: Reference Choropleth Dot-density Isoline Graduated symbol Landofmaps.com What data/information layers were necessary to create the map? How is it effective in communicating its message What audience is the map intended for? What do you really like about the map? Would you make any adjustments to improve the map? Keep the maps saved/open for later 5

6 Key map elements 1. The map itself Two basic components: 1. The map itself 2. Information about the map ( marginalia ) It is completely up to the map maker to decide where this information is shown on their map Title Orientation Date Map Legend/symbols Datum/projection Scale Location Grids and Graticules Product Information 2. Title: What is the purpose of the map? What is being mapped, where, when? Orientation: Which direction is north? North arrow Compass rose North is usually pointing towards the top of a map N 6

7 Date: When the map made (or updated) Map symbols and Legend: What do the classes and symbols on the map represent? Keep the design of any symbols as simple and as different from each other as possible Give sufficient information to ensure your map is not misread Map symbols and Legend: Describe what is on the map Shape a rectangle for a building, a tree for a forest Size the larger a feature the higher the importance of the feature Colour blue for water, green for vegetation A single tree? A forest? A national park? has become pretty standardised, so that even foreign maps are not all that hard to read Map symbols should be readily recognizable and suited to the scale of the map Three main categories: pictorial symbols colour symbols value symbols Colour symbolism Blue water features Green vegetation Brown topography or terrain Black human artefacts such as individual buildings, railroads Red larger human artefacts such as highways, roads, urban built-up areas Purple human artefacts since previous map revision Use existing standard symbols/colours if possible 7

8 Use existing standard symbols/colours if possible Use existing standard symbols/colours if possible Human limitations - About 12 colours - After that use patterns as well - About 7-8 shades of the same colour Colour blindness Contrast Common sense Value symbols - Identify something - Show it s location - Tell something about the amount of that something in that location Map types: - Dot maps - Graduated symbol maps - Divided circle map - Bar chart map Datum/Projection: The system whereby the information of the Earth is transferred to a two-dimensional area (a map) Often sought by map users, often many years after the map was published Map scale: How does distance on the map relate to distances on the ground? Scale statement (e.g. one cm equals one kilometre ) A ratio or fraction (unitless value) A scale bar A map without a scale is basically just a diagram or picture 8

9 Scale A small scale map generally shows less detail but cover larger parts of the earth A large scale map is one in which a given part of the Earth is represented by a large area on the map (usually show more detail) Location: The location of the map on the Earth Draw a recognisable region with an indication of the mapped location Grid and Graticules : How to find places on the map Alphanumeric grids: Columns are lettered and run down the page, rows are numbered and run across the page Latitude and longitude: geographical coordinates in degrees, minutes, and seconds Cartesian: More useful where the area of interest is a relatively small portion of the Earth s surface Key map elements Product information: Who produced/published the map? (including organisations, sponsors etc.) Date of publication and/or information shown on the map Known limitations of the information (e.g. accuracy) Methodology used to produce the map Edition (unless it is the first edition) Copyright Generally, too much information is better than too little Product information: Who produced/published the map? (including organisations, sponsors etc.) Date of publication and/or information shown on the map Known limitations of the information Methodology used to produce the map Edition (unless it is the first edition) Copyright Generally, too much information is better than too little Two basic components: 1. The map itself 2. Information about the map ( marginalia ) It is completely up to the map maker to decide where this information is shown on their map 9

10 Create final product that is informative, accurate, and aesthetically pleasing Overall layout Visual balance is very important Map should be centre of display and have the most visual impact Exercise in graphic design Legibility Colour schemes Use contrast to enhance the infromation from the background (contextual information) Use colour appropriately Activity Go back to the maps you found earlier and consider the key map elements. Title Layout Orientation Date Legend/symbology (shape, size, colour) Datum/projection Colour Scale Location Grids and Graticules Product information Do your maps have all/any of these features? Would the addition of any of these features help an audience to understand their message? 10