ps_1.1 -tutorial (bl) - orthophoto, dem (with gcp).pdf

7/21/2019 PS_1.1 -Tutorial (BL) - Orthophoto, DEM (with GCP).pdf

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Tutorial (Beginner level):

Orthophoto and DEM Generation with Agisoft PhotoSan Pro !"!

(with Ground #ontrol Points)

PhotoScan PreferencesOpen PhotoSan Preferenes dialog from Tools menu using corresponding command.

Set the following values for the parameters in the General tab:Stereo Mode:Anagl$ph (use%ardwareif your graphic card support Quad Buffered Stereo)

Stereo Parallax:!"&

Write log to file:speif$ diretor$ where Agisoft PhotoSan log would 'e stored

(in case of contacting the software support team it could be required)

Set the parameters in the Open#tab as following: #he on an$ Open# devies deteted '$

PhotoSan in the dialog and redue the nu*'er of ative #P+ ores '$ one for eah Open#

devie ena'led"

Set the following values for the parame

ters in theAdvanedtab:

Project compression level:,

Keep depth maps:ena'led

Store absolute image paths:disa'led

Check for updates on program startup:

ena'led

Enable !" support:ena'led


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#dd Photos!o add photos selectAdd Photos"""command from the -orflowmenu or clic"Add Photosbutton

located on -orspaetoolbar.

#n theAdd Photosdialog browse the source folder and select files to be processed. $lic" Openbutton.

$oad Camera Positions %t this step coordinate system for the future model is set using camera positions.

%ote: #f camera positions are un"nown this step could be s"ipped. !he align photos procedure&

however& would ta"e more time in this case.

Open.eferenepane using the corresponding command from the /iewmenu.

$lic" 0*portbutton on the.eferenepane toolbar and select file containing camera positions

information in the Opendialog.

!he easiest way is to load simple characterseparated file ('.tt) that contains and y coordinates

and height for each camera position (camera orientation data& i.e. pitch& roll and yaw values& could also

be imported& but the data is not obligatory).

#n the0*port #S/dialog indicate the delimiter according to the structure of the loading file and selectthe row to start loading from. ote that * character indicates a commented line that is not counted while

numbering the rows. #ndicate for the program what parameter is specified in each column through setting

correct column numbers in the #olu*nssection of the dialog. %lso it is recommended to specify valid

coordinate system in the corresponding field for the values used for camera center data.

$hec" your settings in the sample data field in0*port #S/dialog.

$lic" O1button. !he data will be loaded into the.eferenepane.

0*port E203button located on the.eferenepane can also be used to load camera positions

information if +,#- metadata is available.


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!hen clic" on the Settingsbutton in the.eferenepane and in the.eferene Settingsdialog select

corresponding coordinate system from the list.

$lic" O and camera positions will be mar"ed inModel /iewusing their geographic coordinates:

#f you do not see anything in the /odel view& even valid camera coordinates have been imported&please chec" that Show $ameras button is pressed on the !oolbar. !hen clic" 0eset 1iew button also located

on the !oolbar.


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#lign Photos%t this stage 2hotoScan finds matching points between overlapping images& estimates the camera

position for each photo and builds the sparse point cloud model.

SelectAlign Photoscommand from the -orflowmenu.

Set the following recommended values for the parameters in theAlign Photosdialog:

#ccurac&:%igh(lower accuracy setting can be used to get the rough camera positions in the

shorter time)

Pair preselection:.eferene (in case camera positions are un"nown Generi preselection

mode can be used)

Constrain features b& mask:Disa'led(Ena'ledin case any areas has been mas"ed prior to

processing)

Ke& point limit:4&&&&'ie point limit:!&&&

$lic" O1button to start photo alignment. %fter some time you3ll get sparse point cloud model

shown in the /odel view. $amera positions and orientations are indicated by blue rectangles

in the view window:


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Place Markers /ar"ers are used to optimi4e camera positions and orientation data& which allows for better model

reconstruction results.

!o generate accurately georeferenced orthophoto at least 56 7 58 ground control points (9$2s) should

be distributed evenly within the area of interest.

!o be able to follow guided mar"er placement approach (that would be faster and easier) you need to

reconstruct geometry first.SelectBuild Meshcommand from the -orflowmenu and specify following parameters in theBuild

Meshdialog:

$lic" O button.

!hen& when the geometry is built (it usually ta"es a few seconds to reconstruct mesh based on thesparse point cloud)& open a photo where a 9$2 is visible in 2hoto 1iew by doubleclic"ing on its icon in

thePhotospane. oom in to locate the 9$2 on the photo and place a mar"er in the corresponding point

of the image using #reate Marercommand from the photo contet menu available on rightclic" on

the opened photo in the corresponding position:


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Select the mar"er on the.eferenepane. !hen filter images inPhotospane using 3ilter '$ Marers

option in the contet menu available by rightclic"ing on the mar"ers label in the -orspaepane.

ow you need to chec" the mar"er location on every related photo and refine its position if necessaryto provide maimum accuracy. Open each photo where the created mar"er is visible. oom in and drag

the mar"er to the correct location while holding left mouse button. 0epeat the described step for every

9$2.


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(nput Marker Coordinates -inally& import mar"er coordinates from a file. $lic" 0*portbutton on the.eferenepane toolbar

and select file containing 9$2 coordinates data in the Opendialog. !he easiest way is to load simple

characterseparated file ('.tt) that contain mar"ers name& & y coordinates and height.

#n0*port #S/dialog indicate the delimiter according to the structure of the file and select the row to

start loading from. ote that * character indicates a commented line that is not counted while numbering

the rows. #ndicate for the program what parameter is specified in each column through setting correct

column numbers in the #olu*nssection of the dialog.

%lso it is recommended to specify valid coordinate system in the corresponding field for the values usedfor camera center data.

$hec" your settings in the sample data field in0*port #S/dialog:

$lic" O1button. !he data will be loaded into the.eferenepane.

"ptimi)e Camera #lignment !o achieve higher accuracy in calculating camera eternal and internal parameters and to correct

possible distortion (e.g. ;bowl effect< and etc.) optimi4ation procedure should be run. !his step is

especially recommended if the ground control point coordinates are "nown almost precisely 7 within

several centimeters accuracy (mar"er based optimi4ation procedure).

$lic" the Settingsbutton in the.eferenepane and in the.eferene Settingsdialog select

corresponding coordinate system from the list according to the 9$2 coordinates data.


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Set the following values for the parameters inMeasure*ent aura$section:

Camera accurac&:!&

Marker accurac&:&"&&5 (!he mar"er accuracy is recommended to be set at 6.668 value if

the real mar"er accuracy is within 6.6= m).

Scale bar accurac&:&"&&!

Projection accurac&:&"!

'ie point accurac&:4

$lic" O button.

On the.eferenepane uncheck all photosand chec" on the mar"ers to be used in optimi4ation

procedure. !he rest of the mar"ers that are not ta"en into account can serve as control points to evaluate

the optimi4ation results. #t is recommended since camera coordinates are usually measured with

considerably lower accuracy than 9$2s& also it allows to eclude any possible outliers for camera

positions caused by the onboard 92S device failures.

$lic" Opti*i6ebutton on the.eferenepane toolbar.

Select camera parameters you would li"e to optimi4e. $lic" O1button to start optimi4ation process.


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Set !ounding !ox Bounding Bo is used to define the reconstruction area.

Bounding bo is resi4able and rotatable with the help of 0esi4e 0egion and 0otate 0egion tools

from the !oolbar.

(mportant: !he redcolored side of the bounding bo indicates the plane that would be treated as

ground plane and has to be set under the model and parallel to the ,> plane.

!uild *ense Point CloudBased on the estimated camera positions the program calculates depth information for each camera to

be combined into a single dense point cloud.

SelectBuild Dense #loudcommand from the -orflowmenu.

Set the following recommended values for the parameters in theBuild Dense #louddialog:

+ualit&: Mediu* (higher quality ta"es quite a long time and demands more

computational resources& lower quality can be used for fast processing)

*epth filtering:Aggressive(if the geometry of the scene to be reconstructed is comple with

numerous small details or untetured surfaces& li"e roofs& it is recommended to set

Milddepth filtering mode& for important features not to be sorted out)


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2oints from the dense cloud can be removed with the help of selection tools andDelete7#rop

instruments located on the !oolbar.

!uild Mesh%fter dense point cloud has been reconstructed it is possible to generate polygonal mesh model based

on the dense cloud data.

SelectBuild Meshcommand from the -orflowmenu.

Set the following recommended values for the parameters in theBuild Meshdialog:

Surface t&pe:%eight 3ield

Source data:Dense loud

Pol&gon count:Mediu* (maimum number of faces in the resulting model. !he values

indicated net to%igh7Mediu*7owpreset labels are based on the number of points in

the dense cloud. $ustom values could be used for more detailed surface

reconstruction).)

(nterpolation:Ena'led

$lic" O1button to start mesh reconstruction.


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Edit ,eometr&Sometimes it is necessary to edit geometry before building teture atlas and eporting the model.

?nwanted faces could be removed from the model. -irstly& you need to indicate the faces to be

deleted using selection tools from the toolbar. Selected areas are highlighted with red color in the /odel

1iew. !hen& to remove the selection use @elete Selection button on the !oolbar (or @el "ey) or use $rop

Selection button on the !oolbar to remove all but selected faces.

#f the overlap of the original images was not sufficient& it may be required to use #lose %oles

command from the Toolsmenu at geometry editing stage to produced holeless model. #n #lose %oles

dialog select the si4e of the largest hole to be closed (in percentage of the total model si4e).


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2hotoScan tends to produce A@ models with ecessive geometry resolution. !hat3s why it is

recommended to decimate mesh before eporting it to a different editing tool to avoid performance

decrease of the eternal program.

!o decimate A@ model selectDei*ate Mesh"""command from the !ools menu. #n theDei*ate

Meshdialog specify the target number of faces that should remain in the final model. -or 2@- eport

tas" or webviewer upload it is recommended to downsi4e the number of faces to 566&666=66&666.

$lic" O1button to start mesh decimation procedure.

!uild 'exture!his step is not really needed in the orthophoto eport wor"flow& but it might be necessary to inspect

a tetured model before eporting it or it might be useful for precise mar"er placement.

SelectBuild Te8turecommand from the -orflowmenu.

Set the following recommended values for the parameters in theBuild Te8turedialog:

Mapping mode:Orthophoto

!lending mode:Mosai

'exture si)e-count:5C=(width D height of the teture atlas in piels)

Enable color correction: disa'led (the feature is useful for processing of data sets with

etreme brightness variation& but for general case it could be left unchec"ed to save the

processing time)

$lic" O1button to start teture generation.


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,enerate "rthophoto

SelectE8port OrthophotoE E8port 9PEG7T0337PGcommand from3ile menu.

Set the following recommended values for the parameters in theE8port Orthophotodialog:

Projection t&pe:Geographi

Projection:by default the proFection set in the.eferene Settingsis used

!lending mode:Mosai

Enable color correction: disa'led (the feature is useful for processing of data sets withetreme brightness variation& but for general case it could be left unchec"ed to save

the processing time)

Pixel si)e:maimum effective resolution is shown by default (please note that for G9SH

coordinate system units should be specified in degrees. ?seMetresbutton to specify

the resolution in metres).

Split in blocks: !&&&& !&&&&(if the eported area is large it is recommended to enable

Split in Blos feature& since the memory consumption is rather high at eporting

stage)

.egion:set the boundaries of the model3s part that should be proFected and presented as

orthophoto.

$lic"E8port"""button and then specify target file name and select type of the eported file

(e.g. 9eo!#--). $lic" Savebutton to start orthophoto generation.


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,enerate *EM

SelectE8port DEME +port 9eo!#--IB#JI,> command from3ilemenu.

Set the following recommended values for the parameters in theE8port DEMdialog:

Projection t&pe:GeographiProjection:by default the proFection set in the.eferene Settingsis used

Crop invalid *EM:chec" this option to crop the regions with unreliable elevation data& since

they are visible on less than two source photos

Pixel si)e:you can increase the effective resolution compared to the default value

Split in blocks: !&&&& !&&&& (if the eported area is large it is recommended to enable

Split in 'los feature& since the memory consumption is rather high at eporting

stage)

.egion:set the boundaries of the model3s part that should be presented as @+/.

$lic"E8port"""button and then specify target file name and select type of the eported file

(e.g. 9eo!#--). $lic" Savebutton to start @+/ generation.

ps_1.1 -tutorial (bl) - orthophoto, dem (with gcp).pdf

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