MAP SCALE Sizing the Model

Map Scale Ratio of a single unit of distance on map to the corresponding distance measured on the surface of the ground Gives idea of area covered Example: If Map scale = 1:24,000 Then 1 unit of measurement on map represents the 24,000 of the same units on the surface of ground

Scale Three types of scale depictions: Verbal: One Inch equals One Mile NumericRatio: 1:24,000, Fractional: 1/24,000 Graphic

Map Scale How to Calculate Corresponding Distance on Ground Example: Map Scale = 1:200,000 Given Map distance = 3 cm Required x = Equivalent distance on ground The above scale defines that 1 cm on map = 200,000 cm on ground 1/200,000 = 3/x x = 600,000 cm or 6 KM on ground

Quiz Question: Map Scale = 1:24, ft on ground = ________inch on map?

Large Scale vs. Small Scale Refer to scale shown as a fraction Large means small denominator and small means larger denominator Q: which map has a larger scale – 1:1000 OR 1:25,000? Why larger? – shows the features at a larger and more detailed size

Large Scale Map In larger scaled maps more details but less area covered (for a fix size) Relatively small portion is covered with higher local detail Usually maps that are 1:24,000 or larger are considered large scale** **

Scale 1: 3,000 Scale 1: 3,000 Large Scale

Small Scale Map Relatively large area of Earth is covered In a smaller scaled map certain features might be omitted Detail at global level with limited local detail Usually maps 1:250,000 or smaller are considered small scale** Any map with scale between large and small scale is intermediate scale maps **

Scale 1: Small Scale

Scale 1: 200,000 Medium Scale

Large Scale vs. Small Scale Reference:

Map Scale Selection of a scale depends on its intended use Select a scale which is convenient to handle Scale will change appropriately as paper scale changes

MAP DESIGNING Optimal Representation of Spatial Information

Purpose of the map (remember the message) Purpose of the map (remember the message) Context of the map Context of the map Potential users Potential users Available resources (data and tools) Available resources (data and tools) Important features which need to be highlighted and less important in the background (not prominent) Important features which need to be highlighted and less important in the background (not prominent) Design elements needed to properly communicate the message Design elements needed to properly communicate the message Format of the final projectFormat of the final project Mapping Prerequisites Keep the following points in mind before designing a Map

Map Designing Map Designing Steps Determine the objectives of the map Decide on the data layers to be included Plan a layout Select only the area of interest Choose colors and symbols Map should also look good in black and white 1 out of 10 people are color blind Printing in black and white Use low saturation colors in background Create the map

Selection of Layers Most important layers = clearest and largest symbols! Some ancillary layers help reader to orient themselves Too many ancillary layers can drown out your message Make the representation of some ancillary layers less prominent Use: smaller symbols smaller text transparency, etc.

Typography (Labeling) Simple and brief but accurate Make sure text is legible Placement should least obscure underlying information Font size hierarchy to indicate relative importance Use no more than four fonts or text sizes on a map Label outside area only if the purpose is to show the orientation of the study area

Legibility of Text Typeface Easy and clear to read Size Readable size Color Sufficient contrast between background and letters Line Length Longer lines are difficult to read Leading (space between two lines) Legibility may be increased by increasing the leading between rows of text

Legibility (readability) of Text Source:

Typography (Conti..) Traditionally plain font for land and italic font for water features Label spread out along the feature Several labeling styles available

Typography (Labeling) Scale 1: 200,000 Scale 1: 10,000

Bad Maps Poor symbols, poor color, poor design, hard to read, poor legends

Map Types 1. Planimetric (e.g municipal base map) A map designed to portray the horizontal positions of features; vertical information is specifically ignored. 2. Topographic (e.g. USGS 7.5 minute quads) A map designed to portray features on the surface of the Earth, including relief (elevation), hydrography, and cultural features 3. Cadastral (e.g municipal parcel map) A map representing boundaries of land parcels, ownership, land use, valuation, and other related information. 4. Image (e.g LANDSAT image ‘map’) A map representing a remotely sensed picture or reflection of all or part of the Earth's surface 5. Thematic A map used to visualize spatial relationships and patterns among information pertaining to some theme or concept Reference: Ron Brigg UT Dallas

Representation of Thematic Maps Choropleth map: uses zones or polygons to display information using shading, dot, density, or other techniques. e.g population change, ethnicity distribution Proximal (dasymetric) map: shows zones of constant attributes, such as soil type or vegetation (similar to choropleth except that data determines boundary lines; no pre-defined polygons) e.g. zoning, soil map Isopleth map (contour or isarithmic): shows a continuous three dimensional surface such as elevation using lines connecting points of equal value (contours). e.g elevation, travel time contours from a point(s), land values, income Point (dot) or symbol map: shows information relating to specific points using marker symbols whose size and/or frequency relates to magnitude of phenomena housing sales, code violations, crimes Reference: Ron Brigg UT Dallas

Source:pubs.usgs.gov/tm/tm11c2/images/coverphoto.jpg

Other Thematic Maps Single symbol maps Single symbol used for all features Unique value maps Different symbols or colors for each category or value

Which Map suites to what data types? Nominal data_________ Single symbol maps Categorical data_______ Unique values map Ordinal data __________ Unique values map Interval and Ratio data__ Quantities map (graduated color, graduated symbol, dot density)

Data Classification It is a key method of abstracting reality into simplified map Method of classification effects the ‘look’ of the map Classification should match data distribution Distribution of zones into classes Max of 6 number of classes recommended (such that reader can interpret between them)

Classification Options Natural Breaks Quantiles Equal Interval Standard Deviation

References Introduction to Geographical Sciences, Training Lectures and Presentations Prepared by National Center for Remote Sensing and Geoinformatics (NCRG) Karachi (undated) GIS Cartography: A Guide to Effective Map Design by Gretchen N. Peterson, 2009