Photogrammetry 2nd Year- Civil
Photogrammetry2nd Year- Civil Flight PlanningBy D. Kamal M. Ahmed
مالحظات محاضراتي تغطي االبواب التاليه من الكتاب : الثاني و الثالث و الرابع االسبوع الثاني من الترم عملي في الفصول هذه المحاضرات ليس المقصود منها ان تغطي كل المعلومات المطلوبه و الطالب مسئول عن إضافه مالحظات وشرح و كل ما يضيفه المحاضر خالل المحاضرات يغلق باب قاعة المحاضره عند بدئها و يفتح بعد عشر دقائق فقط و اليسمح بالدخول بعدها سيعقد قبل امتحان منتصف الترم و قد يعقد خالل المحاضره او لطالب منفردا غير مسموح بالحضور في فصل غير الفصل المسجل فية الطالب By D. Kamal M. Ahmed
Basic concepts and Units Stereoscopic 3D Air base: the distance between exposure stations, pointswhere photos are taken. H: flying height above datum, h is height of point abovedatum or elevation of a point, H-h: above ground Uppercase letters refer to ground space, while lowercaseletters refer to photo space: A is a point in “reality” or inground system, while a is a point on a photograph. Standard film cameras are of 9X9” frame size and 6” focallength I ft 12 inch, 1 yard 3 ft, 1 mile 5280 ft I inch 2.54 cm 1 m 3.2808333 ft cm,D. 1Kamalkm 0.6213699 mileM. Ahmed
Symbols used G: Length of a side of ground area covered by a photographR: End lap (overlap)P: Side lapS: distance between adjacent stripsf: focal length of the cameraL: exposure stationH: flying height above DATUMh: Elevation above datum,H-h: flying height above groundB: air base, b: photographic baseNs : Adjusted number of strips in a block.By D. Kamal M. Ahmed
Summary of equations G2 area of photograph x S.N2Overlap R {(G-B)/G} x 100Sidelap P {(G-S)/G} x 100Lateral advance per strip (S) [1-(P/100)] *GLinear advance per photo (B) [1- (R/100)] * Gnumber of strips {(l2 - 0.4G)/S} 1 adjusted distance between strips (l2 - 0.4G)/NsBy D. Kamal M. Ahmed
الفكره االساسيه ? The basic idea تلتقط صور من االرض او الجو ثم نوجد العالقه الفراغيه بين الصوره و الواقع ننشئ محاور علي الصوره و نقيس س و ص بدقه عاليه نطبق معادالت للحصول علي اللحداثيات االرضيه من احداثيات الصوره المقاسه تستخدم االحداثيات االرضيه لكافة التطبيقات المساحيه مثل انتاج خرائط و عمل مقاطع و توليد اسطح و حساب كميات قد تلتقط الصور من االرض او الجو من طائرات او اقمار صناعيه للقياس الدقيق او لتفسير الصور ما هي العالقه بين الفوتجرامتري و االستشعار من بعد؟؟ By D. Kamal M. Ahmed
تؤخذ صور متداخله من طائرات ثم نولد نموذج ثالثي االبعاد و نقيسه By D. Kamal M. Ahmed
PSR President of The American Society for Photogrammetryand Remote Sensing, 2002Washington-USA and British Columbia-Canada
Airborne and SpaceborneImagery
Why Flight Planning? To ensure coverage of the area to be mappedat the required scale with no gaps, andprovide stereo models by an efficient design. The product of a flight plan is basically a map, A flight plan will determine the spacingbetween successive photographs, locations offlight lines, and start and end locations of eachflight line.By D. Kamal M. Ahmed
Strip StripB BlockGGBy D. Kamal M. Ahmed
Factors Affecting Flight Mission1- Ground Coverage (G x G) المنطقه المغطاه How much of the ground will show in asingle photograph? Depends on:– format (photo) size. طرديه – Flying height above ground– Camera focal length. عكسيه By D. Kamal M. Ahmed طرديه
By D. Kamal M. Ahmed
To increase ground coverage, you increase flyingheight, decrease focal length, or increase the sizeof the photograph. If a single photograph covers a square of side Gon the ground, then; The area on the ground G2 covered by onephotograph at a scale 1 : S.NG2 area of photograph x S.N2 For example: ground coverage G X G or G2 of a 9X 9” photograph taken at a scale of 1: 25,000 is(9X9) X (25,000X25,000) /144 364,050,000 ft2(1 ft 12 inch بوصه 12 )القدم By D. Kamal M. Ahmed
2- Overlap (R%) and Sidelap (P%) التداخل االمامي و الجانبي A reasonable size photogrammetric project usuallyinclude several photographs. A pair of overlapping photographs make a stereopair and provide a stereo modelADVANCEBy D. Kamal M. Ahmed
Stereo pairs taken at thesame flight line خط طيران make a “STRIP” شريحه More than one stripmake a “BLOCK”. Overlap (endlap) isneeded to providestereoscopic coveragewhile the sidelap isneeded to ensure that nogaps exist betweenstrips.By D. Kamal M. Ahmed
Overlap (endlap) (P%) To ensure stereo coverage At least 50% of the area photographed isshown in both photographs to providestereoscopic coverage of the entire strip withno gaps in the direction of flight. For example, photos 1 and 2 in strip I arecovered as shown in the following figure. Now, what happens if photo 3 overlaps withphoto 2 with more or less than 50%?Photo 1Photo 2Strip IBy D. Kamal M. Ahmed
Usually, the overlap is more than 50 % toensure that the entire area is covered in stereo,minimum of 60 % is most common as shownbelow.The overlap can be as much as 90% to providetriple coverage if needed.By D. Kamal M. Ahmed
Computation of overlap (R%) In the figure below, if:G: is the length of a side of the square on groundcovered by the photograph;B: is the air base, the distance between the successivephotos; then the overlap percent of G is:Overlap R {(G-B)/G} x 100Note that B cannot be larger than G For example, if the area on ground covered be asingle photograph is 15,000 X 15,000 ft, and the airbase was 9,000 ft, calculate the overlap.Answer: overlap {(15,000-6,000)/15,000}X100 60%By D. Kamal M. Ahmed
By D. Kamal M. Ahmed
Computation of Sidelap (P) In the figure below, if:G: is the length of a side of the aquIre on groundcovered by the photograph;S: is the distance between adjacent strips; then thesidelap percent of G is:Sidelap P {(G-S)/G} x 100 For example, if the area on ground covered be asingle photograph is 15,000 X 15,000 ft, and thedistance between two slides was 10,500 ft,calculate the sidelap.Answer: sidelap (S.L) {(15,000 -10,500)}/15,000 30%By D. Kamal M. Ahmed
By D. Kamal M. Ahmed
The Neat Model The neat model is the area on ground thatcorresponds to the area between theexposure stations of four photos for example. The length of the neat model is (B) The width of the neat model is (S)Neat ModelBBy D. Kamal M. Ahmed
3- Purpose The camera should be selected to serve thepurpose of the survey best, one importantfactor is the angular field of view. Field of view of the camera is controlled bythe focal length of the camera and the size ofthe frame. The most commonly used aerialcamera is 6 inch focal length and 9 inch X 9inch frameBy D. Kamal M. Ahmed
Angular Field of View ( )Normal: up to 75 Wide: 75 to 100 Super Wide: greater than 100 FrameWhat is the angle ofview of a 9X9” cameraof focal length 6” ?By D. Kamal M. Ahmed
Effect of the field of view:ababa) Normal field of view is more suitable if tall features suchas buildings exist. Two tall buildings such as (a) and (b) atthe edge of the ground coverage are shown above forcameras of different angle of view. A wider angle results inBy D. Kamal M. Ahmedtotal disappearance of buildinga as shown to the right
Effect of the field of view:b) Normal angle of view Will result in smaller reliefdisplacement (shift on the photograph of a point becauseof its relief (height)By D. Kamal M. Ahmed
Effect of the angle of view:B’BHH’c) Normal angle of view results in a smaller base/height or(B/H) ratio, and a less accurate elevations when computedfrom photographs. This is because the intersection solutionis worse as the intersection angle is reduced, WHY?By D. Kamal M. Ahmed
Effect of the angle of view:In summary For generating contours, you need betterelevation values, you need a larger base to heightratio, you need a wider filed of view (topographicmapping) For interpretation or reconnaissance purposes,you need to see as much as you can, less featuresobscured by others and less effect of relief, youneed a camera with smaller field of viewBy D. Kamal M. Ahmed
4- ScaleThe scale of photographs is also determinedaccording to purpose: for interpretation purposes, you need to seefeatures bigger, you chose a larger scale for topographic mapping purposes, usuallyfive times enlargement form photo to map scaleis preferred. For example, Engineering maps atthe scale of 1:500 are often produced from1:3,000 scale aerial photography using anenlargement ratio of 6.By D. Kamal M. Ahmed
Scale of a vertical photograph focal length/ flying height The scale gets larger if– The flying height is reduced(the closer the camera to theground, the larger the featuresappear on the photograph)– The focal length is increasedBy D. Kamal M. Ahmed
Severe changes in ground elevation (topography) result invariable scale and stereo coverage, and may result in gaps.By D. Kamal M. Ahmed
By D. Kamal M. Ahmed
5- Wind Effect The intension was that theplane travels from A to B,but the wind pushes in aNW direction as shown inthe figure, the plane willtravel along the resultantvector AB BC , that is AC. Then, the plane will travelfrom A to C not to be, butwill be oriented in thedirection of AB.By D. Kamal M. Ahmed
By D. Kamal M. Ahmed
The plane will travel as shown to theright. The problem is that the photographswill not be oriented in the direction offlight as intended, which may result inloss of stereoscopic coverage. The solution is simple, thecamera is rotated by the angle ofcrabBy D. Kamal M. Ahmed
Gyro stabilizers and MotionCompensators Camera mounts maycontain a gyroscope tosense and record the threetilts of the aircraft ( roll,pitch, yaw) and keep thecamera properly oriented. Image motioncompensators reduce theeffect of movement as thepicture is taken, how?By D. Kamal M. AhmedLeica Gyro – stabilized aerialcamera mount
Design of Flight Map A flight map is a map ( or a photograph in absenceof a map) to guide the mission, it should show, toscale:1. Boundaries of the area to be covered(photographed): usually extended by about 30% Gat each of the sides2. Direction of flight lines (strips) : usually selected inthe direction of long side of the area covered3. Location of each exposure station: determinedaccording to the length of the strip and endlap.By D. Kamal M. Ahmed
By D. Kamal M. Ahmed
By D. Kamal M. Ahmed
Design of Flight Map Flight plan is shown on a map to show flyinglines (location, start, and end), and thelocation at which each photograph is to betaken (location of exposure station). Given the dimensions of ground coverage andthe percent of end and side lap (R and P %),you should be able to compute the number ofstrips and the number of photographs to betaken.By D. Kamal M. Ahmed
Design of Flight MapCalculations Assuming that the area that needs tobe mapped is l1 Xl2, then; Lateral advance per strip (S) is the neatside distance covered by each strip, notcounting the area that is repeated inthe adjacent strip. The new groundcovered in each strip in lateral direction(perpendicular to the direction of thestrip) Lateral advance per strip (S) S [1-(P/100)] *GWhere G is the side of a square coveredby each photo.By D. Kamal M. Ahmed
Then, the number of strips {(l2 - 0.4G)/S} 1 The value 0.2 may be different in problems This number should be rounded UP to Ns you then compute the adjusted distance between strips (l2 - 0.4G)/ NsBy D. Kamal M. Ahmed
Now to calculate the number od photos perstrip, you divide the length of a strip by theLinear advance per photo (B), which is alsothe air base, whereLinear advance B [1- (R/100)] * GLinear advanceBy D. Kamal M. Ahmed
In the figure to the right,assume that you have 4pyramids , the distance l1is 4 meters, and the distanceB is 1 meter, the number ofpyramids 4/ 1 4Bl1 Same logic applies to the stripTo cover the length l1 , you need ( l1 /B) photos.To ensure that the width is covered, the planeusually continues flying and take two extra photosbefore it turns around and outside of theboundaries to be covered. Thus,Number of photos in a strip ( l1 /B) 4By D. Kamal M. Ahmed
Design of Flight Map Example 2-1Calculate the total number of photographsneeded to be taken by a standard camera tomap an area that is 12 X 8.5 miles, the averagescale of the photographs is 1:15,000, overlapand sidelap are 60% and 25% respectively.Answer:G 9 X 15,000/12 11,250 ftBy D. Kamal M. Ahmed
Lateral advance per strip (distance between strips)S [1- (25/100)) * 11,250 8437.5 ftNumber of strips [ (8.5*5,280) – (0.4 *11,250)]8437.5Adjusted S 1 5.79 strips, assume 6 strips [ (8.5*5,280) – (0.4 *11,250)]5 8076 ftAdjusted sidelap [(G-S)/G] *100 28.2%Linear advance per photo B [1-(60/100)] *11,250 4500 ftNumber of photos per strip [12*5,280/4500] 4 18.08Assume number of photos per strip is 19, thenTotal number of photos in the project 19*6 114 photosBy D. Kamal M. Ahmed
Airborne GPS Airborne GPS is used to measure the location of thecamera at the instant of exposure. This gives thephotogrammetrist XL, YL, and ZL. GPS can also be used toderive the orientation angles by using multiple antennas.Unfortunately, the derived angular relationships only havea precision of about 1’ of arc while photogrammetristsneed to obtain these values to better than 10” of arc. To compute the position of the camera during the project,two geodetic GPS receivers are commonly employed. Oneis placed over a point whose location is known and theother is mounted on the aircraft. Carrier phase data arecollected by both receivers during the flight with samplingrates generally at either 0.5 or 1 second. Generally, on-thefly integer ambiguity resolution techniques are employed.By D. Kamal M. Ahmed
By D. Kamal M. Ahmed
ADVANTAGES OF AIRBORNE GPS The main limitation of photogrammetry is theneed to obtain ground control to fix the exteriororientation elements (three rotations of thephoto around the three axes, and threecoordinates of exposure station L) . Thenecessity of obtaining ground control is costlyand time-consuming. GPS gives the photogrammetrist the opportunityto minimize (or even eliminate) the amount ofground control and still maintain the accuracyneeded for a mapping project.
Flight Planning for Airborne GPSWhen planning for an airborne GPS project, specialconsideration must be taken into account for theaddition of the GPS receivers that will be used torecord the location of the camera. The first issue isthe form of initialization of the receiver to fix theinteger ambiguities. Next, when planning the flightlines, the potential loss of lock on the satellites has tobe accounted for. Depending on the location of theairborne receiver, wide banking turns by the pilot mayresult is a loss of the GPS signal. Banking angles of25 or less are recommended which results in longerflight lines
The location of the base receiver must also be considered duringthe planning. Will it be at the airport or near the job site? Thelonger the distance between the base receiver and the rover on theplane the more uncertain will be the positioning results. When planning, try to find those times when the satellite coverageconsists of 6 or more satellites with minimum change in coverage Also plan for a PDOP that is less than 6 to ensure optimal geometry.Additionally, one might have to arrive at a compromise betweenfavorable sun angle and favorable satellite availability. Make sure that the GPS receiver has enough memory to store thesatellite data. There may also be some consideration on the amount of sidelapand overlap when the camera is locked down during the flight. Thiswill be important when a combined GPS-INS system is used. Finally, a flight management system should be used to precalculate the exposure station locations during the flight
GPS-Aided Navigation One of the exciting applications of airborneGPS is its utilization of in flight navigation. The ability to precisely locate the exposurestation and activate the shutter at apredetermined interval along the flight line isbeneficial for centering the photography overa geographic region.
PSR President of The American Society for Photogrammetry and Remote Sensing, 2002 Washington-USA and British Columbia-Canada . orne ery. Why Flight Planning? To ensure coverage of the area to be mapped at the required scale with no gaps, and provide stereo models by an efficient design.
Photogrammetry is a cost efficient surveying method for mapping large areas. Photogrammetry may be safer than other surveying methods. It is safer to take photographs of a dangerous area than to place surveyors in harms way. Photogrammetry provides the ability to map areas inaccessible to field crews.
photogrammetry. He developed the analytical solutions to space resection, orientation, intersection, rectification, and control extension using direction cosines. Church, a professor at Syracuse University and one of the founding members of the American Society of Photogrammetry, is referred to as the "American Father of Photogrammetry".
Photogrammetry has been previously validated as an effective technology for documenting both damaged vehicles and scenes [1,2,3,4,5,6,7,8,9,10,11,12]. Modern photogrammetry uses the same photogrammetric principles, but requires less user input and delivers more data points in its solution. Photogrammetry software is capable
Unity Photogrammetry Workflow 3 1. Overview 1.1. Introduction What is photogrammetry? Photogrammetry is the process of authoring a digital asset using multiple photos of the original real-
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What is Civil Engineering? Civil Engineering: The Present The first self-proclaimed civil engineer was John Smeaton (1724 -1792). What is Civil Engineering? Civil Engineering: The Present In 1818 the Institution of Civil Engineers was founded in London and received a Royal Charter in 1828, formally recognizing civil engineering as a profession.File Size: 2MBPage Count: 17Explore furtherIntroduction to Civil Engineeringwebpages.uncc.edu[PDF] Civil Engineering Books Huge Collection (Subject .learnengineering.inEngineering Books Pdfwww.engineeringbookspdf.comRecommended to you b
4.1.4 Aerial Photogrammetry Aerial photogrammetry is the science of deducing the physical dimensions of objects on or above the surface of the Earth from measurements on aerial photographs of the objects. The end result produces the coordinate (X, Y, and Z) position of a particular point, a planimetric feature, and a graphic representation
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