present day technique in determination of geospatial data position for gis application
Download
Skip this Video
Download Presentation
PRESENT-DAY TECHNIQUE IN DETERMINATION OF GEOSPATIAL-DATA POSITION FOR GIS APPLICATION

Loading in 2 Seconds...

play fullscreen
1 / 21

PRESENT-DAY TECHNIQUE IN DETERMINATION OF GEOSPATIAL-DATA POSITION FOR GIS APPLICATION - PowerPoint PPT Presentation


  • 118 Views
  • Uploaded on

PRESENT-DAY TECHNIQUE IN DETERMINATION OF GEOSPATIAL-DATA POSITION FOR GIS APPLICATION. Geo-spatial data has got both physical dimension and geographic location on the earth. They represent the real world and can be represented in a map using colored symbols.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'PRESENT-DAY TECHNIQUE IN DETERMINATION OF GEOSPATIAL-DATA POSITION FOR GIS APPLICATION' - lona


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
present day technique in determination of geospatial data position for gis application

PRESENT-DAY TECHNIQUE IN DETERMINATION OF GEOSPATIAL-DATA POSITION FOR GIS APPLICATION

Geo-spatial data has got both physical dimension and geographic location on the earth. They represent the real world and can be represented in a map using colored symbols.

slide2

The spatial data stored in maps can be described

by three concepts:

i) Entity :- Distinct spatial feature or object.

Example: Building, church,

temple, road, lake etc.

ii) Attribute :- Description or characteristic of the entity in qualitative or

quantitative or in both format.

iii) Relationship :- Link between different entities.

slide3

TYPES OF FEATURES / ENTITIES

Again each spatial data can be represented by three geometric entities such as point (● ), line ▬, and polygon (or polyline) and a suitable label.

  A point in 3D-surface is specified by either Cartesian coordinates in x,y,z or by geographical coordinates in Φ, λ , h i.e., Latitude, Longitude and height.

A Line is a sequence of connected points.

A polygon is a closed area represented by lines.

data sources

DATA SOURCES

GIS relies heavily on SPATIAL and NON-SPATIAL data for its wide application in various fields.

SPATIAL DATA SOURCES

1. Conventional topographical maps, Aerial Photographs, Cadastral Maps and

many other sources.

2. From Ground Surveying.

3. Digital Information’s obtained through Global Positioning System (GPS), Total Station etc.

4. Many other departmental sources.

concepts and application of g p s technology

CONCEPTS AND APPLICATION OF G P S TECHNOLOGY

G P S (Global Positioning System) is the satellite based new technique in the field of data collection and for Mapping purposes

Though it started primarily as a navigation system but within a short period, it has revolutionized the positioning concepts.

It provides highly accurate position of the observer in x,y,z coordinates on any point of the globe at any instant of time.

slide6

DIFFERENT TYPES OF G N S S (Global Navigation Satellite System)1.The Global Positioning Satellite System is the only fully operational GNSS system controlled by USA with about 28 earth orbiting satellites that transmits continuously precise signals to the earth via electromagnetic waves. The system enables a G P S receiver to determine its location, speed, direction and time.

2. RUSSIAN GLONASS System:- With about 10 to 12 satellites are operational at present,but when it will be fully operational, there will be 24 satellites in the system. All these satellites are to be placed at an altitude of 19,100 km above the earth in 3 orbital planes.

3. The European unions GALILEO positioning system is the next generation GNSS and is expected to fully operational by 2010.

4. India’s IRNSS (Indian Regional Navigational Satellite System) is the regional GNSS System meant for Indian region and is likely to be fully operational around 2012.

g p s segments the g p s technology consists of three major segments
G P S SEGMENTSThe G P S technology consists of three major segments.
  • Space Segment:The Space segment consists of number of satellites in operation, altitude at which the Satellites are placed, inclination of Satellite orbital planes with the equatorial plane, period of complete revolution around the earth etc.,.
brief description about g p s space segment
BRIEF DESCRIPTION ABOUT G P SSPACE SEGMENT
  • G P S system consists of about 28 fully operational earth orbit Satellite system in six orbital planes.
  • Satellites are revolving around the earth at a height of 20200 km above the earth surface.
  • The orbital planes of the satellites are inclined at 55O with the equatorial planes at 60O separation.
  • At any instant of time there will be at least four operational satellites on any orbit.
  • Each Satellite makes two complete revolution in a day in its orbit around the earth.
slide9

US NAVSTAR GLOBAL POSITIONING SYSTEM

SATELLITE ORBITS

24 operational satellites (+ 3 or 4 spare)

6 orbital planes

4 equally spaced per orbit

20,200 kIn (10,900 n. mi.) altitude

12 hour orbital period

Solar powered, backup batteries, rocket boosters.

g p s segment control and user segments
G P S SEGMENT - CONTROL AND USER SEGMENTS
  • Control Segment:

1. Control segment consists of 05 (Five) trekking /Monitor stations spread over the globe at

Hawaii, Kwajalein, Asumsion Island, Diego Garcia, Colorado and the Master Station at Colorado Springs.

2. The Master Station collects the data about the Satellite health, positions etc through its five Monitor Stations.

3. Satellite Positions are corrected by uploading the data.

4. The data so uploaded in each Satellite System is termed as Broadcast Ephemeredes.

User Segment: In User Segment, we have to identify the various components of an integrated G P S instrument.

* A G P S Receiver with Micro Processor, Control and Display Unit with Power Supply, Recording device using a highly stable atomic clock and a R F (Radio Frequency) section. Some times a Receiver is designated by number of Satellites it can monitor simultaneously, for example 12 Channel or 06 Channel and some times by the number of frequency the data is received from the Satellites for example dual frequency (L1 & L2) and single frequency (L1).

* Antenna: There are various types of G P S Antenna now in use namely Choke antenna, helix antenna, zypher geodetic antenna etc.,.

slide11

HOW G P S WORKS

. There are 4 variables unknown:

. Longitude (X)

. Latitude (Y)

. Elevation (Z)

. Time (T)

. Therefore, you need info from four satellites.

. If only 3 satellites are present, the receiver will guess at elevation and compute latitude and longitude.

transmission of data code measurement
TRANSMISSION OF DATACODE MEASUREMENT

Signals from GPS satellites are continuously transmitted on two Carrier frequencies viz.

L1 and L2.

L1 = 1575.42 MHz i.e., 1575.42 x 106 million chips per second.(wave length λ = 19 cm).

L2= 1227.60 MHz i.e., 1227.60 x 106 million chips per second.(wave length λ = 24 cm).

Through L1 carrier, code like C/A code i.e.Coarse Acquisition, Precise code (P-Code) and the Satellite messages are sent to the earth continuously. Where as through L2 Carrier only P-Code and Satellite messages are sent.

Through Code measurements also known as Pseudorange measurements instantaneous position on the earth surface can be determined using G P S Satellites.

P (Pseudo range) = c x ε where ε = time delay

= c (tR – tS) + clock error = time difference between the generation

of code by satellite clock and its

receipt by the receiver clock.

The C/A code–frequency = 1.023 M Hz i.e., 1.023 million chips per second (λ = 293m)

and P-Code-frequency = 10.23 M Hz i.e., 10.23 million chips per second (λ = 29.3m)

carrier phase measurement
CARRIER PHASE MEASUREMENT

GPS receivers which record carrier phase, measures the fraction of one wave length (i.e. fraction of 19cm for L1 and 24cm for L2 carrier) when the receiver first locks on to a satellite and continuously measure the carrier phase from that time.

The number of full cycles between satellite and the receiver from the initial start up which is termed as Ambiguity together with the measured carrier phase gives the satellite – receiver range (i.e. the distance between satellites and a receiver).

Hence, we can say

Range = Measured fraction of carrier phase

+ Ambiguity x wave length + clock error

Higher positional sub meter accuracy is obtained by carrier phase measurements where as code measurements give lesser positional accuracy from 10m to 100m in GPS data.

g p s positioning technique
G P S POSITIONING TECHNIQUE

For both code and carrier phase measurements, a variety of positioning methods exists.

Code Positioning Technique:

1. Single Point Positioning: The coordinates of the antenna position on the surface of the earth can be achieved by intersecting the measurements from four (4) or more satellites. The accuracy achieved in single point positioning may be within +/- 100mtr. Single point Positioning is also termed as Absolute Positioning or Point positioning. In this method only one receiver is needed.

2. Relative Positioning or Differential Positioning: In this method of observation two receivers are needed. One of them is kept on a known station and the other is kept on unknown station. In Relative Positioning higher accuracies are achieved. Errors involved in the G P S observations are common in the known and unknown sites. During post processing of the field data the errors are compensated. Accuracy achieved in this type of observation may be within 2 to 10mtr horizontally.

g p s positioning technique17
G P S POSITIONING TECHNIQUE

Carrier Positioning Technique In Carrier Positioning, the observations taken may be Static, Kinematic, Semi-kinematic, Pseudo-kinematics and Rapid Static.

Static Carrier Positioning Technique: In this method two or more G P S receivers kept at the stations and longtime observation are taken. On post-processing the data with respect to the positional data of known station, a very good accuracy within millimeter level i.e., 1 cm + 1 ppm to 10 ppm can be achieved.

Rapid Static Carrier Positioning Technique: In this method one G P S is kept on a known station and observation is taken continuously on it, and the other G P S is kept on unknown station i.e, Rover Station and the observation taken on this points for about 10 to 15 minutes. Such type of observation is known as Radial Rapid Static Method. Some times G P S positions are alternately changed by taking observations on stations for 10 to 15 minutes such type of observation in known as Traverse Rapid Static Method. By post processing the G P S field data, the positional accuracy of the unknown points can be achieved within centimeter.

Kinematic Carrier positioning Technique: In Kinematic Carrier mode one G P S is kept at Static on a Known Station, and the other is used as a moving one.

Semi-kinematic: In Semi-kinematic one G P S called the Master GPS is kept on a known station, and the observation is taken on it continuously to resolve ambiguity.

Other GPS called rover is moved between each point by holding it stationery on the points for 10 to 15 seconds, and then moved to the next point without closing the instrument. This method for providing control is suitable for very small area.

sources of error in gps observation
SOURCES OF ERROR IN GPS OBSERVATION
  • Selective Availability (SA)
  • Anti Spoofing (AS)
  • Multipath
  • Atmospheric Effect

(Ionosphere & Troposphere)

  • Satellite Geometry (i.e. Dilution of Precision)
slide19

Atmospheric Effect

  • (Ionosphere & Troposphere)
g p s applications
G P S APPLICATIONS

The Technique of Global Positioning System fall into following kinds of applications:

  • Location: For Positional determination and is widely used in this field.
  • Navigation: To go from one location to another. G P S is initially designed.
  • Timing: G P S brings Precise timing as each Satellite is equipped with an extremely precise atomic clock.
  • Surveying and Mapping: Now a days, G P S technology is widely applied in the generation of maps by recording a series of locations.
  • Tracking: For monitoring people and movement of vechicle etc.
ad