Surveying, Mapping,Remote Sensing and GIS

Surveying, Mapping, Remote Sensing and GIS Maps – Communicate spatial data/information through “graphic symbols” – a language of location

Cartography – the art and science of mapmaking – increasingly an automated, computerized process

Mapmaking process involves a number of interlinked steps: Data Gathering: Location Data, Attribute Data Data Compilation and Processing Cartographic Visualization and Design Map Drafting and Production

The tasks involved depend on Types of Maps

Types of Maps • General Purpose Maps:

General Reference Maps, Topographic Maps

Dot Density Map – shows discrete locations/data

Earthquakes in Southern California 2000

• Special Purpose/ Thematic Maps:

Choropleth Maps – area-based nominal, ordinal and continuous data

Ethnicity Map – Former Soviet UnionChoropleth Map with nominal data

Isopleth Map – point-based continuous data isohyets (also isotherms, isobars, isobaths)

and contours

• Complex Special Purpose/ Thematic Maps: Composite Map – shows discrete + continuous data

(+ proportionate circles)

3-D Topographic Map

World Ocean Floor Map

Map Basics Basic Elements of Maps:

• Title (plus any explanatory text)

• Legend or Key (See Appendix B)

• Direction / Compass:

True North, Magnetic North, Magnetic Declination, Isogonic Map (with isogonic lines)

Compass directions: Azimuth System (0˚ - 360˚) and Bearing System, with four 90-degree

quadrants (NW, NE, SW, SE), e.g., North, 20˚ East (20˚ east of due north)

• Map Coordinates: a. Latitudes & Longitudes (Geographic Grid)

b. Rectangular/alpha-numeric coordinates

Simple Alpha-numeric Location System

c. USPLS or Township & Range System

Map Basics – Continued

Map Basics – Continued• Map Scale: Map scale is the ratio of the distance between two points on the Earth’s surface and the distance between corresponding points on a map Verbal/Written/Stated Scale: 1 inch = 1

mile

Bar/Graphic Scale: a graph depicting distances

Representative Fraction:

One unit of measured distance on a map equal

some units of measured distance in the real world – 1:

63360

Also: • Map Projection Used

• Date, Author, Publisher, etc.

Large-Scale Maps show very small portions of the real world, but with great detail

◦ Large-Scale maps have small denominators i.e.,

1:12,000 or 1:24,000◦ Topographic maps are examples of large-scale maps

Small-Scale maps show very large portions of the real world, but with minimal detail

◦ Small-scale maps have large denominators, i.e., 1:100,000 or 1:1,000,000

◦ Wall maps are examples of small-scale maps

LARGE-SCALE vs. SMALL-SCALE

LARGE -SCALE TO SMALL -SCALELARGE SCALE

SMALL SCALE

Modern Technology inData Gathering, Mapping and GIS• Data Gathering: Surveying – Field Survey using compass, chains,

plane table, and theodolite – to GPS

The Global Positioning System or GPS consists of 3 parts:  

Originally developed for military use, GPS is being employed in a variety of ways: 

• GPS is widely used for ground, air, and sea navigation.

• And to produce accurate maps and study land deformation caused by earthquakes and volcanic eruptions. GPS is also showing up in more and more commercial products.

A set of 24 satellites constantly orbiting the Earth and broadcasting their position and time…..Signals from 3 or 4 of them are used to pinpoint a location on earth, using a procedure called trilateration.

1) Earth orbiting satellites

Trilateration

2) Control and monitoring stations across the Earth

3) GPS receivers owned by individuals and other entities

Remote Sensing Aerial photography to satellite imaging

Multiple Platforms ↓

a) Camera – Traditional and Digital

b) Radar (SLAR, Doppler, Sonar)

c) Near Infra-red (NIR) and Thermal Infra-red (TIR) Scanners

d) Multispectral Remote Sensing – Color Composite Image

Typical Remote Sensing Platforms

Polar vs. Geostationary Orbits

Remote Sensing to Digital MappingAll objects (natural or synthetic) reflect and emit electromagnetic radiation over a range of wavelengths characteristic of the object. The Distinctive reflectance and emitance properties are the spectral signatures of the objects.

Remote sensing operates in the wavelength regions of the electromagnetic spectrum where these spectral signatures occur, to identify, map and analyze image features

Remote Sensing and Maps

Landsat NIR image of San Francisco Bay

“Natural-color” Photograph

“False-color” Near infra-redSatellite Image

Thermal Infrared (TIR) Image of a Storm System from GOES Satellite

Landscape Visualization: The Physical Environments of Cape Town

Satellite imagery and elevation data were combined and computer enhanced to produce the 3-D perspective

Digital Mapping and Computer Cartography

Digital Mapmaking , involves:

Converting locational/spatial data into digital data → Cartesian Coordinates (x,y)

Automated Contouring

Digital Elevation Models: 3-D Representation

Dynamic Maps

Earthquake Map + Faults (Dynamic Maps)

3-D Perspective : Earthquake Hazard

Geographic Information Systems: GIS• Interface between Computer Cartography and Data

Base Management

• A geographic information system, GIS, is a

computer-based technology that enters, analyzes, manipulates, and displays geographic information

Watch this “GIS Day” video clip from ESRI for a more detail intro to GIS: http://www.youtube.com/watch?v=IL1SKqtWB9Q&feature=related

• In a GIS framework both spatial and non-spatial databases are combined into a “geodatabase”

• A GIS essentially creates Map Layers of specific thematic maps

• By layering the information one on top of the other, a geographer can show, for example, the relationship and degree of connectivity between various land uses and transportation routes in a region.

To summarize:

• A GIS involves Geocoding, Registration, Mapping, Display, Analysis and other operations

• Also, Visualization Models

• A Great Planning Tool

Watch this for a City’s GIS: http://www.youtube.com/watch?v=BG6XsFi4gfo&feature=related

For interactive GIS mapping, go to:GIS City of Santa Clarita

Example 1: Cities use GIS to locate vulnerable pipelines

Example 2: Identify City Parcels in 100-year Flood Zone