ch-4 field survey

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Survey and Map Study


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Field survey Typical survey activities

Preparations

Field activities

Checklist for survey of existing stations

Different types of terrain Survey Report

Difficult areas for microwave links

Typical survey equipment


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What is survey ?

A visit in the field in order to plan a microwave system

A visit in the field in order to plan a microwave system is planned

A visit in the field to existing microwave sites in order to verify detailson the existence and condition of infrastructure and site facilities.

A study of the propagation conditions for a planned system, includingclearance criteria.z


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Typical survey activities-1

Preparations Minimize field work

Detailed map study

Locating a site on map

Preparation of path profile

Los obstacles Preliminary antenna heights


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Field work Confirmation of line-of-sight (check critical obstacles)

Verification of position and altitudes of the sites

Soil investigation

Checking of site access, road construction

Availability of power (existing shelters and towers) Investigate propagation conditions

Make interference measurements


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Path Survey

Microwave Planning can be broadly classified into:- City link surveys and planning

- Backbone surveys and planning

For city link planning an outdoor survey is required by directly

establishing the Line of Sight between the two stations to beconnected.

For Backbone Planning a detailed study on the maps is required prior tocarrying out an outdoor survey. The maps used for planning areobtained from Survey Of India Publication. This is done in order toestablish an optical visibility between the two sites separated over along distance.


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Survey report Finally it is time to prepare a detailed report from the field survey.

Remember that a photo may tell more than a thousand words.The survey report may also contain the system performancecalculations.

Survey report format


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Checklist for survey of existing stations

Type of building: Concrete, wood, prefabricated shelter. Material used in ceiling, walls, floor. Measurement of rooms, height of ceiling. Space for new equipment in the equipment room. How to fix waveguide and cables to walls, ceiling. Waveguide outlets through walls, etc.

New air dryer for waveguides necessary? Available power (AC - DC). Existing battery capacity. New batteries necessary? Can existing towers be used? Distance from building to tower. How to install the waveguide safely outside.

Space for new antenna at the right height in the tower. Check of grounding system for the tower and station. Possible interface problems when connecting to existing equipment. Possible interference problems with existing equipment in the area.


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Different types of terrain

Hilly terrain with some trees If reliable, contoured maps are available, site locations arenormally easy to verify. Optical confirmation of line-of-sight maybe difficult without some mobile masts. Use combination of mapsand altimeter measurements.

Hilly terrain with jungle or dense forest Difficult to verify site locations. Use satellite navigationequipment if possible. Line-of-sight can normally only be checkedby use of altimeters, maps or satellite navigator.

Mountainous terrain

Easy to verify site locations. Line-of-sight can normally be verifiedoptically.

Flat areas, desert Difficult to verify site locations. Use satellite navigation

equipment. Line-of-sight can be verified using altimeters or

optically by use of mobile masts.


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Difficult areas for microwave links

Over water paths Always difficult due to sea reflections with a high reflection coefficient. The ducting

probability is also high. Reflections may be avoided by selecting sites that are shielded fromthe reflected ray.

Swamp and rice fields May cause strong ground reflections. The probability for multi path fading is high. The

propagation conditions may look different at different times of the year. Critical periods arethe rainy season (monsoon).

Desert areas May cause ground reflections, but sand does not have a high reflection coefficient. The

most critical is the high possibility for multi path fading due to large temperature variations.

Hot and humid coastal areas High ducting probability.


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Typical survey equipment

The list below gives an idea about typical survey equipment. Some of theitems may be substituted or omitted, and other types of equipment may beadequate as well. Topographical Maps Camera Binoculars Compass Altimeters

Signaling/Flashing mirrors Anchored Balloons Walkie talkies Tape measure Global Positioning System Receiver (GPS) Portable personal computer


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Map study

Types of maps Reference map

Topographic map

Thematic map

Reference map Topographic map is location based

Scaled map ( Ratio 1:50,000)

Two-dimensional representations

Latitude & Longitude


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Contour Lines

Contour Lines are lines drawn on a map connecting points ofequal height.

Contour lines are parallel lines with a difference of elevation ofatleast 20m between them.

Elevation means height above sea level ( HASL)


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Contour Lines


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Reading Contours

0

1

2

3

44.4

500

580

At point 0

closest Contour = 500

Reading = ?


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Step-I

Select the Map which contains the point.

Calculate the distance on the map , equivalent to change incoordinates by one second.

Draw the line corresponding to latitude of the point.

Draw the line corresponding to longitude of the point.

The point of intersection of the two lines gives the location of thepoint on the Map.


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Select the Map that contains the point

Lets say the point is

(15 25 30 S , 30 42 40 E )


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Calculate the distance on the map ,

equivalent to change in coordinates by one sec

54 cm

Dx = 54 cm / 15 x 60 sec= 0.06 cm/sec

60cm

Dy = 60 cm / 15 x 60 sec

= 0.066 cm/sec


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Draw the line corresponding to latitude of the point

15 25 30 S

(15 25 30)

Minus (15 25)

= 30 sec

Dy x 30sec


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Draw the line corresponding to longitude of the point

30 42 40 E

15 25 30 S

(30 42 40)

Minus (30 40)

= 240 sec= (2x60)+40 sec

= 160 sec

Dx

x 160sec


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Joining of 2 points Draw Line b/w these points

If other point not in the same map

Joining of 2 map of more if required

How to join?

Index to adjoining sheetsA1

B2

C1B3

B1 A2

C2 B4 A3

Step-II


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Line of Sight Coverage

Station A: Station B:

Ant Ht A: 66 Ant Ht B: 66 Distance (Km) 66

HASL A 666 HASL B 666 Freq (GHz) 6

Tot ht A 666 Tot ht B 666 K value .666

Distance HASL HASL + EB LOS LOS-F 6

Kms Mtr Mtr Mtr Mtr

6 666 666 666 666

6 666 6 6 6 666 6 6 6

6 666 666 666 666

6 666 666 666 666

6 666 666 666 666

66 666 666 666 666

66 666 666 666 666

66 666 666 666 666

66 666 666 666 666

66 666 666 666 666

66 666 666 666 666

66 666 666 666 666

66 666 666 666 666

66 666 666 666 666

66 666 666 666 666

66 666 666 666 666

66 666 666 666 666

66 666 666 666 666

66 666 666 666 666

66 666 666 666 666 Reflection Point

66 666 666 666 666 Distance from Station A, d 6 66

66 666 666 666 666 LHS exp (h / d -d / )6 6 666 - .666666

66 666 666 666 666 RHS exp (h /d -d / )6 6 666 .6666666

66 666 666 666 666 LHS - RHS - .666666

66 666 666 666 666

66 666 666 666 666 Reflection pt from Station A 66

66 666 666 666 666

66 666 666 666 666 Fresnel clearance F = .6 6666[ (d .d )/(D*F GHz)]6 666 666 666 666 666 Earth bulge (Mtr)

66 666 666 666 666 H= (d (Km).d (Km))/( . K)6 6 66 66 for K= /6666 666 666 666 666 Free space Loss

66 666 666 666 666 FSL (db) = . + log D(km) + log F (MHz)66 66 66 6666 666 666 666 666 Reflection point

66 666 666 666 666 h /d - d / = h /d - d /6 6 666 6 6 666 for k= /66

66 666 666 666 666 h ,h =mt r d , d =kms6 6 6 6

66 666 666 666 666

666

666

666

666

666

666

666

666

666

666

6 666

6

6

6

6

66

66

66

66

66

66

66

Distance in Kms

H

eightinMetre

Line of Site Coverage


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LOS example true earth


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LOS example effective earth

Sep 6666

Mahamudabad

Latitude . N6 6 6 6 6 6 6 6

Longitude . E6 6 6 6 6 6 6 6 6

Azimuth . 66666

Elevation m ASL666

Antenna CL . m AGL666

Biswan

Latitude . N66666666

Longitude . E6 6 6 6 6 6 6 6 6

Azimuth . 66666

Elevation m ASL666

Antenna CL . m AGL666

Frequency (MHz) = .66666

K = .666

%F = .6 66666

Path length ( . km)6666

6 6 6 6 6 66 66 66 66 66 66 66 66

Elevation(m)

666

666

666

666

666

666

666

666

666

666


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ch-4 field survey

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