Digital Terrain Modelling (Benin City)

7/26/2019 Digital Terrain Modelling (Benin City)

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INTRODUCTION

1!1 B"#$%&'()* +' +- .+(*/

A digital elevation model (DEM) is a digital model or 3D representation of a terrain's

surface commonly for a planet (including Earth), moon, or asteroid created from

terrain elevation data (Wiipedia)! DEM is often used as a generic term for D"Ms and

D#Ms, only representing height information $ithout any further definition a%out the

surface!All datasets $hich are captured $ith satellites, airplanes or other flying platforms are

originally D"Ms (lie "M or the A"#E& DEM)! t is possi%le to compute a D#M

from high resolution D"M datasets $ith comple algorithms (*i et al!, +-)!

A DEM can %e represented as a raster (a grid of s.uares, also no$n as a heightmap

$hen representing elevation) or as a vector/%ased triangular irregular net$or (#0)! #he

#0 DEM dataset is also referred to as a primary (measured) DEM, $hereas the &aster

DEM is referred to as a secondary (computed) DEM! (Wiipedia)#he DEM could %e ac.uired through techni.ues such as photogrammetry, lidar, f"A&,

land surveying, etc! (*i et al! +-)! DEMs are commonly %uilt using data collected using

remote sensing techni.ues, %ut they may also %e %uilt from land surveying! DEMs are

used often in geographic information systems, and are the most common %asis for

digitally produced relief maps! While a D"M may %e useful for landscape modeling, citymodeling and visuali1ation applications, a D#M is often re.uired for flood or drainage

modeling, land/use studies, geological applications, and other applications!2lder methods of generating DEMs often involve interpolating digital contour maps that

may have %een produced %y direct survey of the land surface! #he .uality of a DEM is a

measure of ho$ accurate elevation is at each piel (a%solute accuracy) and ho$

accurately is the morphology presented (relative accuracy)!

ommon uses of DEMs include Etracting terrain parameters for geomorphology,

Modeling $ater flo$ for hydrology or mass movement, reation of relief maps,&endering of 3D visuali1ations, &ectification of aerial photography4satellite imagery,

eographic nformation "ystems ("), *ine/of/sight analysis, 5ase mapping, "urface

Analysis etc!

1! AIM AND OBECTIVES


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A2:

6roduce a digital elevation model (DEM) of 5enin ity 0orth/West of Edo "tate,

0igeria!

O-#+5-.:

Digiti1e 5ase Map to produce contours and spot height

7se ontours and "pot 8eights to create DEMs

reate 9ector and &aster DEMs (#0,DW,:riging)

Analy1e4nterpret created DEMs

9ie$ 3D model of generated DEMs $ith Arc"cene

!0 STUDY AREA

"tudy area for this pro;ect is 5enin ity< sheet +=> 0!W! at a scale of ?@-,!

5enin ity is a city (+ est! pop! ?,?BC,?>>) and the capital of Edo "tate in southern 0igeria! t

is a city approimately B ilometers (+- mi) north of the 5enin &iver! t is situated 3+

ilometers (+ mi) %y road east of *agos! 5enin is the center of 0igeria's ru%%er industry, %ut

processing palm nuts for oil is also an important traditional industry! (Wiipedia)

ollo$ing 0igeria's independence from 5ritish rule in ?=, 5enin ity %ecame the capital of

Mid/Western &egion $hen the region $as split from Western &egion in une ?=3< it remained

the capital of the region $hen the region $as renamed 5endel "tate in ?=C, and %ecame the

state capital of Edo "tate $hen 5endel $as split into Delta and Edo states in ?==?! (Wiipedia)


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5enin ity is home to some of 0igeria's institutions of higher learning, namely, the 7niversity of

5enin located at 7g%o$o, the ollege of Education Eiadolor, g%inedion 7niversity, the

5enson dahosa 7niversity and Wellspring (Wiipedia)

Attractions in the city include the 0ational Museum 5enin city, the 2%a 6alace, gun "treet (/

famous for %ron1e casting and other metal $ors for centuries)! 2ther attractions include variousfestivals and the 5enin Moats (measuring a%out + to B ft), the famous :ing's ".uare (no$n as

&ing &oad) and its traditional marets! #he 5ini people have four maret days@ Eio%a, Eenaa,

Ag%ado and Een! (Wiipedia)

F%! !0 M"6 '7 S+(*/ A&-"

METHODOLOGY

3!1 D"+" S'(-.

#opographic map ?@-,, 5enin ity< sheet +=> 0!W! produced in ?=- %y 0igeria ederal

"urvey $as gotten from the Department of eography, aculty of "ocial "ciences, 7niversity of

*agos! A folder $as created on the drive $here the map $as stored and added to Arcatalog!

A&MA6 ?!3!? $as used for this $or! #he original map $as added to ArcMA6, the map $as

georeferenced %y adding control points to the four corners of the map $hich $as then rectified

and saved!


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A ile geodata%ase $as created, under $hich feature classes $ere also created for the features to

%e vectori1ed %efore the digiti1ing process %egan! #he t$o ma;or features vectori1ed are contour

lines and the spot height! #he %ase map and feature classes $as pro;ected to W" ?=>B!

#he soft$ares used are A&MA6 ?!3!? and Microsoft Word +?, the font is #ime 0e$

&oman, font si1e used $as ?+pt for the tet $hile ?Bpt $as used for the headings! 86 laser ;et

++ $as used to print this $or on an AB paper si1e!

3! M"6 C"&"#+-&.+#.

M"%)-+# V"&"+') ")! 19: Magnetic 0orth C ??F W, rid 0orth C 3F E!

Annual hange (-!-

E)G&*: 0igerian olony West 5elt

P&'-#+'): #ransverse Mercator

S6-&'*: lare ?>>

U)+ '7 2-".(&-2-)+: oot

M-&*") '7 '&%): B3F East of reen$ich Meridian

L"++(*- '7 '&%): BF 0orth

S#";- F"#+'& "+ O&%): !===C-

F";.- C'


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ANALYSIS AND PRESENTATION OF RESULTS

4!1 A)";/..

#he contours used sho$ an interval of - meters $ith the highest at + meters $ith the least at

- meters! #he contour has an interval of - meters! #his generated #0 and DEM sho$ the

ruggedness of the terrain in the study!We can see that the 5enin ity 0!W! has rugged terrain in some areas and smooth areas in some

parts!


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F%! 4!1!1 M"6 .'=)% S6'+ -%+.


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F%! 4!1! M"6 S'=)% C')+'(& L)-.


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F%! 4!1!3 M"6 S'=)% TIN DEM


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F%! 4!1!4 M"6 S'=)% TIN +' R".+-& DEM


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4! C'26"&-* 2"6.

F% 4! TIN DEM 2"6 T) +' R".+-& DEM 2"6

C'26"&.') -+=--) TIN ")* G&* S>("&- M-+'*.:

#he #0 map sho$s continuous triangles compare to the #0 to &aster DEM method!

#0 to &aster method sho$s softer edges compared to the #0 map!

rid s.uare map has a %etter output $hen compared $ith #0 map

#0 Map sho$s %etter Elevation!


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CHALLENGES, SUMMARY AND CONCLUSION

?!1 C";;-)%-.

#he process of digiti1ing (especially for contours) is rigorous, time consuming as it taes more

time to complete a feature vectori1ation! nterpretation of results also posed a serious challenge

as DEM maps $ere difficult to interpret! #hese pro%lems $ere solved %y reading relevant

materials, using Arc"can for contours and Arc"cene $as used to help in understanding the

DEMs produced!

?! S(22"&/

rom the digital elevation models (DEM) of the study area produced, there $as noticea%le

difference %et$een DEM map produced using #0 method and that of the grid s.uare method!

#hese maps represent the terrain surface of the study area, $hich is %etter than other surface

models techni.ues! #he generated DEMs helped $ith understanding of the elevation

characteristics of the study area!

?!3 C')#;(.')

DEMs are needed in numerous human disciplines such as Military operations, Engineering,

#elecommunications, 7r%an 6lanning, 6recision Agriculture, &esources Management, orestry,

lood management, Disaster monitoring and management etc! #his study has sho$n the use of

contour lines and spot height in generating digital elevation models of any part of the country!

#he data used had sho$n that spot heights and contour lines are %est for representing surfaces!

#his study has also sho$n the importance of " as a tool in the production of Digital ElevationModel maps that depict the real $orld earth surface!


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REFERENCES

5enin ity! (n!d!)! n Wiipedia! &etrieved Decem%er +B, +?-, from

https@44en!$iipedia!org4$ii45eninIity

Digital Elevation Model! (n!d!)! n Wiipedia! &etrieved Decem%er +B, +?-, from

https@44en!$iipedia!org4$ii4DigitalIelevationImodel

*i, J!, Jhu, K! and old, ! (+-)@ titleLDigital terrain modeling@ principles and methodology!

& 6ress! 5oca &aton!

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Digital Terrain Modelling (Benin City)