Basic Concepts of Aerial Photography

          Aerial photography is an image of the real world in to a photograph taken by specific camera build in aircraft. Aerial photography provides a stereoscopic view of the earth surface in vertically and horizontally, it is a three dimensional viewing image.   

Film: Aerial photography missions are flown using black and white film, but colour, infrared, and false colour infrared film are sometimes used for special projects.

Focal length: It is the distance from the middle of the camera lens to the focal plane. As focal length increases, image distortion decreases. The focal length is precisely measured when the camera is calibrated.

Scale: The ratio between two points on an air photo and actual distance between the same two points on the ground.

Aerial Photo Scaling

Calculation of scale

There are a number of methods for calculating scale depending on what information is already known:

•      Focal length and flying height for flat terrain.

•      Focal length and flying height for variable terrain.

•      Photo distance and corresponding map or ground distance.

Calculation of scale

Method 01

If a 1 km stretch of highway covers 4 cm on an air photo, the scale is calculated as follows:

Another method used to determine the scale of a photo is to find the ratio between the camera's focal 

length and the plane's altitude above the ground being photographed.

•      If a camera's focal length is 152 mm, and the plane's altitude Above Ground Level (AGL) is  

7 600 m, using the same equation as above, the scale would be: 

The photo scale and representative fraction 

•      PS  =  f / H
Variables: PS - Photo Scale, f - camera focal length, H - altitude above the ground
Photo Scale is equal to camera focal length divided by the Height (altitude) of the plane.

•      RF = 1/(H / f)
Variables: RF - Representative Fraction, f - camera focal length, H - altitude above the ground Representative Fraction (RF) is equal to one divided by the ratio of altitude (H) and camera focal length.

GIS – EXPLORING THE FUTURE OF THE WORLD (Part – 1)

Introduction

1.            Since the beginning of civilization on the planet earth, military forces have played a dominating role. Mankind has since time immemorial has a fetish for warfare and this continues till today. Only methods have changed with tech, which is changing rapidly with tech revolution, which has not only changed the way wars are fought but has become a key factor in attaining dominance in military power. The battle victory is complete only after ground forces occupy the enemy land and take control of the area. To hold and maintain the control of the occupied land, armed forces need to know the spatial extent upon which they have the control.

2.            Spatial data is of crucial important to the military command in the battle as it is used by a decision maker in planning and developing of military operations. The regional conflicts, rapid deployment and flexible response imposes heavy burden on military commands, their staff and support system to keep up-to-date situation on the ground about enemy activities. Visualizing raw tabular data within a spatial framework has many benefits. Therefore digital mapping and Geographic Information System (GIS) occupy center stage in activities as diverse as battled field simulation, mission briefing and command planning, logistical management and command & control.

What is GIS

3.            GIS can briefly be defined as “a sys of computer hardware, software, and procedures designed to support the capture, management, manipulation, analysis, modularity and display of spatially referenced data for solving complex planning and management problems”. In a more detailed definition, a GIS is described as any information management sys which can:-

a.                Collect, store and retrieve info based on its spatial loc.

b.        Identify loc within a targeted environment which meet specific criteria.

            c.        Explore relationships among data sets within that environment.

d.    Analyze the related data spatially as an aid to making decisions about that environment.

e.     Facilitate selecting and passing data to application specific analytical models capable of assessing the impact of alternatives on the chosen environment.

f.      Display the environment both graphically and numerically either before or after analysis.

4.         GIS as a Database View.  A GIS is a unique kind of database of the world i.e. geographic database. Fundamentally, a GIS is based on a structured database that describes the world in geographic terms.

5.         GIS as a Map View.            A GIS is a set of intelligent maps and other views that show features and feature relationships on the earth's surface. Maps of the underlying geographic info can be constructed and used as "windows into the database" to support queries, analysis, and editing of the infomation.

6.         Why to use GIS.      Many organizations have data stored in a variety of formats at many different loc. We need a way to integrate data so that we can analyze it as a whole and use it to make critical decisions. GIS can integrate and relate any data with a spatial component, regardless of the source of the data. For example, we can combine the location of an accident, located in real-time by GPS devices, in relation to emergency response unit, located by address. GIS maps this data and give a visual tool to plan the best route for accident location or send the closest emergency response unit, thus saving tremendous time and money.

GIS Inputs

7.         Surveyor Maps.      The term map refers to a data set which contains accurate information about features on the surface of the earth. Manual digitizing and scanning of maps form part of a data type used as input for GIS.

8.       Remote Sensing Data.      Remote Sensing data converted to a suitable GIS format is another type of data used in a GIS. Digitized data from satellite/aerial imagery is main type of data used as input in a GIS.

  

9.       Field Sampling Data.         Attribute data is also incl in a GIS based study/project to make it more int surveyors. GPS is most widely used for collection of field data. Conventional svy data can also be incorporated in a GIS database like soil surveyor data.

10.       Stat Data.      GIS analytical capabilities can also be used to analyze statistical data like demographic data, hydrological data, education and health, census record etc. 

Cartography – 2

What is good map?

-          Accurate

-          Up to date

-          Only relevant information

-          Standard symbolistion

-          Clear and legible

-          Communicate its message

-          Designed for the purpose

Type of maps

-          Topographic maps

Topographic maps are replacing general image of the earth’s surface such as roads, river, vegetation, etc.  

-          Thematic maps

Thematic maps are focuses on particular phenomenon or subject area. This them or subject can be political map, rainfall in an area. Thematic maps divided in to three map category;

Choropleth map – choropleth map uses to demarked differences in shading, color or the placing of symbols variable being displayed on the map, such as population density.

            Isopleth map - continuous surface maps, like topographic contours.

            Area class map- Showing zones like, vegetation, soil type.

Map Scale

Map scale is one of the most significant elements on a map. Map scale is the ratio between map distance and corresponding ground distance in real world. There are three methods of map scaling;

-          Statement of scale

Ex. 1 centimeter to 6 kilometers

-          Representative Fraction (R.F)

Distance expressed in the same unit of measurement, 1:25000

-          Linear Scale (Graphic or Bar Scale )

It is graphic scale, plain scale or bar scale.

Representative Fraction

It is always written with the map distance taken as 1 unit. This unit measurement can be any unit(ie Centimeters, inches, feet) The R.F of 1:50000 means that one unit of the map equal to 50000 units in the real ground.  

Ie. Two point of the map A to B is 6 cm and the real ground distance is 3 km. fiend out map scale.

  Map Distance           6cm/3km        

Ground distance

          6cm      

3 x 100000cm

1: 50,000

Map Title

Title should be reference to map, it should included “ What, Where, How and When.

Cartography

What is Cartography?

Cartography is the manufacture of maps in printed and Digital media, with creation of projections, design, collection, drafting, and reproduction. It is the art, technique or science of making maps/charts.

The International Cartographic Association (ICA) defines cartography;

      ‘cartography as “the discipline dealing with the conception, production, dissemination and study of maps”.

Cartographic process is concerned with
•      Data manipulation,
•      Data capture,
•      Image processing
•      Visual display
 Basic cartography covers two data components, location data (mathematically) and attribution data (Spatial characteristics of the location).

What is a Map?

A map is a representation of whole or part of an area of real world on a flat surface. A map is a mode of communication. Language has words to communicate; maps have lines, symbols, colours, letters and digits as means to communicate. The map maker uses these elements in communicating with the map user. It is a way of representing on a two-dimensional surface model of reality and it included;

Graphical representation of the earth surface     Information system     Mode of Communication     Symbolized image of geographic reality     Graphic representation or scale

The International Cartographic Association (ICA) defines Map

;…”a representation, to scale and on a flat medium, of a selection of material or abstract features on the surface of the Earth…” 

What is map making?

Map making is the combination of scientific and imaginative elements. Map making is not just placing of the North arrow, legend, scale or how to combine colours. The traditional analog map making method replace by digital system. When making a map, it is required to select real world features and its classifications. Map should be simplified as much as possible, when we draw complex lines like rivers.   

What is digital cartography?

Cartographic representations of computer assisted mapping systems which replace existing traditional methodologies. It may appear in printed form or as dynamic images generated on a computer display screen. Principally the computer was used to automate the existing mapping system such as calculation of map projections, plotting of the grid. In digital system came to realize that calculations were possible with digitized data so that distances, areas, volumes etc. could be calculated using computers.

 Different between manual and digital maps.

Manual Maps

-          It takes more time to produce.
-          Required some essential tools.
-          It is difficult to calculate distance, area and volumes.
-          Difficult to product different maps types.
-          It is very difficult to update or re product.
-          More space required to store.
 

Digital maps

-          Easy to produce
-           It produce only computers
-          Printed form or as dynamic images.
-          Computer assisted mapping system.
-          Easy to calculate distances, area, volumes.
-          Easy to analyses the ground.

What is a good map?

-          Exact data and up to date.
-          Only the relevant information.
-          Uses proper symbolization.
-          Clear and readable.
-          Communicates its message.
-          Designed for the purpose required

Elements of a Map

-          Scale
-          Legend
-          Title
-           North arrow
-          Location information
-          Date of Publication
-          Source of information

Map Scale

Scale of a map is the ratio between distances on the map and corresponding distances in the real world. There are three methods in giving a scale.

-          Statement of Scale
-          Representative Fraction (R.F.)
-          Linear Scale (Graphic or Bar Scale)

Cartography Symbology

Symbologies represent the real world objectives. The quality of a map's design is its reader's ability. Cartographic Symbology has been developed in an effort to represent the world accurately and effectively convey information to the map reader.

Symbol design

There are two types of basic symbol designs in map producing, pictorial map symbols and abstract map symbols. 

How to import Google image in to ArcGis10 and Georeferencing the image and assign coordinating system (Part I )

            In this tutorial I will show you how to export Google image to ArcGIS 10. Some time it is difficult to find out maps in study area. To overcome this problem we are referring to Google earth but we are facing a difficult to take these images to Arc GIS 10 with georef.

First go to Google earth and find out your study area.

Make Ground Control Point.

         Ground control point is identifying location and prominent location to match both maps images. In this exercise we will zoom to required location and make points in four corners. First make folder in Google window and add 4 x Grounder control points into it and save it as kml

Right click – Add –Folder—Give a name to folder

Mark four Ground control points in Google map and save it in above folder

Save this folder as .kml file. Right click on the folder – Save as –

File name – Give a name to this folder

Save as type – kmz (*.kmz)

Now you have to save the Google image as a .jpg image. File – Save – Save image

Now go to ArcGIS 10 and start with new project. Assign your relevant coordinate system to project

IMAGE DISPLAY

        

         The image display is the method of image to visible in digital media. Digital image data displaying or concept of image sampling is the number of pixel in rows and columns. Each pixel has some value in RGB colours. (Read, Green, Blue), these dimensions are stored as Digital Number values (DN). Image create with pixels in regular grid format (rows and columns). DN numbers representing the value of brightness of the pixel. These digital images captured from RS satellite sensors according to their reflection wavelengths.

Location of a pixel

Pixel location measured from grid of columns and rows. The X coordinate specifies the column of the grid and the Y coordinate specifies the row. The upper left corner of the image always begin at 0,0 value.

Calculating File size

{(( x * y * b )) * n} = Output file size

Y = rows

X = columns

b = number of bytes per pixel

n = number of bands

As a example, in 7 band land sat image 8 bit file with 400 rows and 500 columns, find out how much space needed.

500 x 400 x 1 x 7 = 1400000 bytes

ERDAS IMAGINE files

When data imported into ERDAS IMAGINE, they converted to ERDAS IMAGINE file format. This ERDAS IMAGINE stored in two types

Thematic – This raster layer contain qualitative, categorical information about soils, Land use, Roads, Hydrology.

Continuous – This raster layer contain quantitative and related, continuous values. These layers can be Multiband like SPOT panchromatic data)

What is Multispectral Band?

Sat image or Digital image of an area captured in different spectral ranges or bands. This band can be dissimilar according to the type of RS sat.

Visualization of Image Data

Histogram

The histogram describes the distribution of the pixel values of that image, the range between 0 – 255.

Single band image

Histogram is used to obtain optimum display of single band images. Normal single band images display using grey scale. It digital value range is from 0 (Black) to 255 (White).

Color image

Combination of red, green and blue channels of a digital display images. In each pixel, the primary colors are combined in different scope depending on the 3 bands DN values to represent different colors.

                            GOOD COURSE PROSPECTUS FOR Part II

1.      Detail Syllables

a.         Basic computer training and Installation of ArcGIS 10

GIS applications basically relating to Computer base technology system, without basic computer knowledge, it is very difficult to continue with this course. In this section student will learned about basic computer technology and how to install ArcGIS 10.

                                            I.            Computer Fundamentals with windows XP/7

                                          II.            Application software (PowerPoint, Word, Excel)

b.         Introduction to GIS

Understanding what GIS is and what it can be used for. With a GIS application you can open digital maps on your computer, create new spatial information to add to a map, create printed maps customized to your needs and perform spatial analysis. In this training program we explore the basic concepts behind the GIS.

                                                        I.            Geographic Information Technologies

                                                      II.            What is GIS

                                                    III.            Components of GIS

                                                    IV.            Types of Data

                                                      V.            GIS Capability

c.         Familiarizing with ArcGIS 10

Understanding what ArcGIS 10 and what it can be used for. With a ArcGIS 10 application open digital maps on your computer and create new spatial information to add to a map.

                                                        I.            ArcMap

                                                      II.            ArcCatalog  

                                                    III.            Tools and operations

d.         GIS Analysis

GIS Analysis is the main difference of the GIS system from other information system. GIS analysis show you patterns, relationship, and trends in your geographic data that help you understand how the world works, make the best choice from among options, or plan for the future. In GIS Analysis student will get knowledge about the types of GIS analysis;

                                                        I.            Mapping

                                                      II.            Query

                                                    III.            Overlay

                                                    IV.            Dissolve

                                                      V.            Reclassify

                                                    VI.            Merge

                                                  VII.            Buffers

                                                VIII.            Clip

                                                    IX.            Joining

                                                      X.            Intersect

e.         Map digitizing

Digitizing in GIS is the process of “tracing”, in a geographically correct way, information from images/maps. The process of georeferencing relies on the coordination of points on the scanned image (data to be georeferenced) with points on a geographically referenced data (data to which the image will be georeferenced). By “linking” points on the image with those same locations in the geographically referenced data you will create a polynomial transformation that converts the location of the entire image to the correct geographic location. We can call it as Conversion of map data from graphic to digital form.

f.          Types of Maps

Maps are probably the biggest subsection of visualization types. There are many variations on map types, each with its own strengths. Maps are more effective in visualizing geospatial data. That enables user to locate spatial features, while the shape, color and symbols representing their characteristics. 

                                                        I.            Cartography   

                                                      II.            Topography

                                                    III.            Map producing in ArcGIS

g.         Georeferencing the Map and Image (Vector and Raster)

Understanding map and Image Georeferencing for spatial data. What it is all about and how to do it. Maps are very often produced for presentations and reports where the audience with no professional background in GIS.

h.         Satellite based, Positioning & Navigation (GPS)

            Understanding the basic satellites availability of the orbit and its plans, next generation satellite system, GNSS system, Segments and Frequency.

i.          Magellan triton 2000 GPS, software installation and function

With the flexibility to do it all, Magellan triton 2000 receivers deliver unparalleled freedom of choice in professional GIS data collection. As the next generation of GPS, lets you configure a solution to match a wide range of work situations:

                                             I.            Handheld or tablet data collector

                                            II.            Real-time or post processed workflows

                                          III.            Connectivity USB to desktop

                                          IV.            Waypoint, tracking, Geophoto,

j.          Project development in GIS

            Gain a basic, understanding of GIS concepts, techniques and real world applications. This small project development project will help you to create your own project with some analysis and quires. 

i.                    Exercise I - Exporting Maps using raw data

This is a indoor exercise, design to gain knowledge on manipulating raw data and how to build a small project.

ii.                  Exercise II - GPS

The GPS training is a mixture of practical outdoor exercises. This exercise gives you a practical experience in how to use and navigate with the GPS device. Introduction about use of the GPS and includes:

i.        Buttons & Keys and what the GPS screens show

ii.      How to Mark and Read your position

iii.    Correct GPS setup

iv.     How to create a Waypoint & edit its properties (Name, Symbol, and Location)

v.       What the map page shows and how to navigate using the map page

vi.     How to find a Waypoint and navigate to it (GoTo)

vii.   Routes creation and navigation

viii. Track creation and navigation

ix.     Learn which digital mapping is the most suitable for your needs

iii.                Exercise III

In this final exercise III, student will get knowledge what they have learned in GIS and build a GIS analysis base project. This exercise will make understanding GIS operations and there practical use.

i.                    Basics of visualizing and analyzing geographic information.

ii.                  Tables and queries.

iii.                Map creation/interpretation.

iv.                 Image Processing and digitizing.