Tracking and Data Relay Satellite System (TDRSS)

Analog image

Images with continuous gray tone or color like a photograph

is called analog image

Digital image is the numerical record of the radiance leaving

each of the pixel in each of the spectral bands

Rayleigh Scattering: dominant scattering mechanism in the upper

atmosphere ( 9-10 km), also called clear atmosphere scattering

Mie scattering:Occurs when the particles are just about the same size as the

wavelength of the radiation (Dust, pollen, smoke and water

vapour), occurs in lower atmosphere. (0 – 5 KM)

By measuring the energy that is reflected (or emitted) by targets

on the Earth's surface over a variety of different wavelengths,

we can build up a spectral response for that object, termed a

spectral reflectance curve. Specular Reflection: angle of incidence is same as angle of reflection

Diffused Reflection: angle of incidence is different from angle of reflection The spatial property defines the dimensions of the

corresponding ground area.

The spectral property defines the intensity of the

spectral response for a pixel in a particular band

Spatial resolution refers to the size of the smallest possible

feature that can be detected by the sensor.

Spectral resolution describes the wavelength intervals

in the electromagnetic spectrum that a sensor can

record or sense

The ability of an imaging system to record many levels of

Brightness is Radiometric Resolution.

Geography - Pattern and process of human and

physical phenomena on the surface of earth.

URISA Urban and Regional Information Systems Association

DIME Dual Independent Map Encoding

TIGER Topologically Integrated Geographic Encoding And Referencing

CAD: Computer Assisting Drawing, e.g. AutoCad, Micro station

GDS: Graphic Design System, e.g. CorelDraw, Illustrator

DBMS: Database Management System, e.g. Oracle, Sybase

DIPS: Digital Image Processing System, e.g. PCI, Erdas

GPS: Global Positioning Systems, e.g. Garmin, Trimble

� Using the tools and helping to build the tools of

geographic information systems (GISystems)

� Studying the theory and concepts that lie behind GIS and

other geographic information technologies (GIScience)

� Study the societal context of geographic information –

legal context, issues of privacy, economics of geographic

information (GIStudies)

ESRI: Environmental Systems Research Institue

Arcinfo uses Arc Macro Language (AML)

ArcView uses Visual Basic and Python

ArcGIS comes in three different versions based on the capabilities

provided by the software: ArcView, ArcEditor and ArcInfo.

Gis data types:

Feature data

Image data

Grid data

Attribute data

A data model is a :

Logical Construct for representing real world phenomenon and objects in a

computer

Coverages and shapefiles are examples of the Georelational

Data Model

Geodatabases are examples of the Object‐Based Data

Model.

The Georelational Data Model stores spatial and attribute data separately in a split system Spatial data in ‘graphic files’ Attribute data in ‘relational database files’. The link between the two ‘systems’ is usually a “Feature Label” or ID Object‐based data model stores spatial and attribute data of spatial features in a single system. Spatial data are stored in a field using a data type called “BLOB” (binary large object)

Topology is the science and mathematics which defines the spatial or

geometrical relationship between spatial features or vector objects in a GIS.

Topology is the study of those properties of geometric objects that remain

invariant under certain transformations such as bending or stretching.

Adjacency and Incidence are two relationships that can be established

between nodes and arc in digraphs. If a line joins two points, the points are said

to be adjacent and incident with the line.

Topological properties:-

Connectivity, Contiguity/Adjacency, Direction ,Containment

Topological data model makes spatial analysis feasible, automatic corrections

in plottings, faster processing of larger datasets. But it is expensive and time

consuming. Updating topology becomes necessary once spatial data is

updated. Complex data form making it difficult for developers to interpret.

Spaghetti Data model is the simplest and direct vector representation of a real

world object. Easy to produce, display and understand but no spatial analysis

possible.

TIGER- census data linked to boundary data of counties, block groups etc.

ESRI Coverage model:-

Point coverage: node ID + coordinates

Line coverage: arc IDs + S and E node, arc ID + coordinates.

Polygon coverage: arc IDs + L and R polygon, polygon + arc IDs, arc IDs +

coordinates

DIME:- Arc IDs + S and E node + L and R polygon, Coordinate file for nodes

Composite features refer to those spatial features that are better represented as

composites of points, lines, and polygons.

TINS: Triangulated Irregular Networks

Formed by using Delaunay Triangulation which is an iterative process of

connecting points with their two nearest neighbors to form triangles. Raster data model:-

Storage increases with the square of the resolution.

Elements:

1. Cell value. Each cell in a raster carries a value, which represents the

characteristic of a spatial phenomenon at the location denoted by its row and

column. The cell value can be integer or floating-point.

2. Cell size. The cell size determines the resolution of the raster data model.

3. Raster bands. A raster may have a single band or multiple bands.

4. Spatial reference. Raster data must have the spatial reference information so

that they can align spatially with other data sets in a GIS.

Attribute data is stored logically in flat files.

Cell by cell: row n: 0110

Run length encoding: 23

Quad tree or hierarchical encoding

DOQ is a image prepared from an aerial photograph or other remotely sensed

data, in which the displacement caused by camera tilt and terrain relief has

been removed.

DEM is a digital representation of a topographic surface. It is mutli-faceted.

Data sources:

Data capture: Surveys,RS,Digitization

Data inputs/ sources: Maps, orthophotos, statistical reports, Satellite Imagery,GPS

Input is :

- Time consuming

- Labour intensive and error prone

- Accuracy of GIS analysis rests on accuracy of input data

- Expensive

Selection of input data: depends on price, availability, spatial analysis required,

scale, format, available skills and hardware and software

• Federal Geographic Data Committee (FGDC)

• Geospatial One‐Stop (GOS)

• US Geological Survey (USGS)

Metadata describes the characteristics, development and origin of the spatial

data.

FGDC

- Identification Information (Title, geographic data covered)

- Data Quality Information (positional, attribute, completeness, sources of

information, methods to produce spatial data)

- Spatial Data Organization Information (Raster or Vector)

- Spatial Reference Information (Datum, Projections, Coord Sys)

- Distribution Information (Information about obtaining dataset)

- Metadata Reference Information (currency of the metadata and

responsible party)

Geodesy, is the scientific discipline that deals with the measurement and

representation of the earth, its gravitational field, and other geodynamic

phenomena, such as crustal motion, oceanic tides, and polar motion.

Coordinate systems:

PCS (Flat, inches feet metres), GCS( curved , Degrees minutes seconds).

60 N 45 E

Conversion of polar to Cartesian:

Transformation is the projection of a digitized map or image, in some cases from

its original coordinate system, onto a new coordinate system.

Two main types :- map to map and image to map.

4 methods: Affine( angular distortions but parallelism preserved, similarity shape

preserved not size, equiarea (area and shape preserved), projective( angular

and shape distortions).

Affine transformation allows: skew, rotation, differential scaling and translation

Affine used for above mentioned trans. , aerial photos need projective trans.

And satellite imagery needs polynomial or warping trans.

A geometric transformation typically involves three steps.

•Step 1 updates the control points to real-world coordinates.

•Step 2 uses the control points to run an affine transformation.

•Step 3 creates the output by applying the transformation equations to the input

features.

A quantitative measure of the displacement (the deviation) between the actual

(true) and estimated (digitized) locations of the control points is RMS.

Resampling in this case means filling each pixel of the new image with a value

or a derived value from the original image.

– Nearest neighbor: fills each pixel of the new image with the nearest pixel value

from the original image

– Bilinear interpolation: uses the average of the four nearest pixel values from

three linear interpolations

– Cubic convolution: uses the average of the 16 nearest pixel values from five

cubic polynomial interpolations

Map algebra is a language specifically designed for

geographic cell‐based systems and provides the

basis for cartographic modeling. Uses mathematical expressions to create new

grid themes.

Arithmetic operators, relational operators, Boolean operators, Functions (trig,log)

Raster functions (Output grid generated using input grid as argument): Zonal

(cells chosen), local (more than one or one argument), global and focal (cells

immediate neighbours only).

Uses: Surface generation and analysis (hillshade, viewshed), Data

reclassification, Transformations, Distance Analysis (shortest path, cost

weighted).

Buffer made. Layer of important features created, all queries applied and select

by attributes for final results.

Statistical local function

Overlay functions: union , intersect , identity

No data in cell no data in output ( set condition otherwise default value is -9999)

Raster data model Vector data model

Advantages

Can store photos Processing of large data sets is easier

once topological relations between

features are established

Simple data structure Prints are aesthetically pleasing

Easier Spatial analysis especially

overlay (Grid based coincidence)

-

Can accurately represent continuous

phenomena

Can accurately represent discrete

features

Disadvantages

Prints appear blocky Cannot store photos

Processing of large datasets is time

consuming

Cannot represent continuous spatial

variability accurately

Quality and productivity largely

depends on resolution

Spatial Analysis is time consuming

without a developed topology

- Complex data structure

Photo vs remote

Quantitative and qualitative

Geometry vs radiometry

Visible vs invisible

Small area coverage vs large area coverage

Uses metadata:

Identification of source, techniques of obtaining/ Projection and coordinate systems/

scale/cost/availability

Organization of spatial data/ developmental history

Data sharing possible

Data interpretation techniques

Uses GIS: Monitoring weather, disaster management, traffic management, urban and regional

planning, Crop yields, Effects of different phenomena on environment.

Uses Spatial analysis: Identifying developmental patterns, trends , making predictions,

modeling, monitoring changes in environments and their effects.

Digitizing adva. And disadva.:-

Automatic error detection vs error prone

Enabling spatial analysis and easier interpretation vs Slow process

Transformation possible vs need of digitizing equipment

UTM: 84 n to 80 S, 60 zones (6 deg. Each) East –west, Transverse Mercator projection, Alphabet

zones 20 north-south. Cartesian system.

Clipping, dicing

Mosiacing, raster bands

AOI, Inquire box, Coordinates

Annotations, dynamic labels

Graduated color , graduated symbol, dot density, proportional symbol

Discrete color, unique color, classified,

Natural breaks is the default method. Developed by the cartographer

George Jenks, it creates

classes according to clusters and gaps in the data.

Equal interval creates classes of equal va lue ranges. If the range of

values is 1 to 100 and the

number of classes is 4, this method will create classes from 1-25,26-

50,51-75, and 76-100.

Defined interval resembles equal interval except that the interval

determines the number of

classes rather than the other way around. If the range of values is 1 (Q

100, and you choose

an interval of 10, this method will create 10 classes: 1- 10, 11-20, 21-30,

and so on.

Quantile creates classes containing equal numbers of features. If you

choose five classes for a

layer with 100 features, this method will create class breaks so that 20

features fall into each

class. The value range varies from class to class.

Standard deviation creates classes according (Q a specified number of

standard deviations

from the mean value.

Geometric intervals creates classes based on class intervals that have a

geometric series. A

geometric series is a pattern where a constant coefficient multiplies each

value in the series. It produces a result that is visually appealing, cartographically

comprehensive, and minimizes

variance within classes.