"3D transformation to control guide" for iWitness (632kb PDF.)
Contents
1. it will become yellow as shown in Action 1 below See Figure 8 Control Label x z OfFset Closest Point DX DY Dz Total eal Pale 100 0124 9 6547 i 1 3416 l 0 0000 NjA NA NA NA NA cpu MA toosz7 2o55 15422 oodo NjA ONA NA NA NA a CP I 111 1310 19 9771 l 1 4784 0 0000 NjA NJA NjA NjA NjA CPM h 110 8155 SS 11846 00000 NYA NA NA NA Nja CSM_1 Action 2 407810 0 1645 00000 NA MA NA MIA NA 57610 6 595 0 1874 0 0000 dna O NA ONA ONA 12 0818 0 3 1034 0 2551 0 0000 NIA A Nia Nia E NYA NY Transformation Options Control poinks scale used Mew Point Unilink All Link Glose Points Quality Ni a ff 2 iD Help Import Control Points Remove Control Points Close Step 10 Now click the cursor in the Control Label box for the specific control point see Action 2 noted above Figure 8 Once the control point has been successfully accomplished you ll see a green tick mark as illustrated in Figure 9 Closest Point Control Label 2 OFFset Dx DY Dz Total 5 4 38 9811 12 1529 0 0930 0 0000 NJA NJA MJA WA MJA El B 65 9624 13 3813 0 1067 0 0000 hyd he BiA BiA MiA BASE 0 9662 16 9895 1 1907 0 0000 PA PIA MiA BiA BiA L 30 9971 22 1315 0 1040 0 0000 PA PMA BMA PMA CPS e 100 0124 9 6547 1 3416 0 0000 0 000 0 000 0 000 0 000 CPU 100 1271 20 5445 1 5422 0 000 MiA MiA MiA MiA Fig ure 9 CP Y 111 1310 19 9771 1 4764 0 0000 PA MiA MA MA M2. lower left of the dialog and name the DXF in this case name the DXF as Net1 dxf and save it to the Net 1 folder Then click close in the 3D Points dialog You are now complete with Net1l iwp Close out of Net1 iwp as we are ready to work with Net2 1wp Reiterated Network2 iwp is into the depth of Figure 1 NOTE how there aren t any of the markers in the Network2 area of Figure 1 That is because one can recycle the markers from Network1 to Network2 after Network1 has been imaged It is critical that the CP s remain in the same location throughout all of imaging Networki and also Network2 Step 5 Open the second network we named it Net2 iwp If all CP s are present in one image open the image in the workspace for control point marking The point IDs for the CP s in Network2 are not the same Point IDs unless you previously renamed them Figure 3 on the next page illustrates the 4 CP s ready for Control Point marking Note white lines were created Snapped between the 4 CP s when this project was originally completed These lines are not required but give a good visual reference Step 6 Use the file pull down and select Photogrammetry Transformation to control iWitnessPRO C Wocuments and Manual measurement mode Foot Image scan settings The Transformation to control dialog is now presented in Figure 4 Transformation Options Control poinks scale used pee os Unlin
3. 11 Control Label a Y z 2 OFFset Closest Point DX DY Dz Total A iE 30 9971 See eal Ss 0 1040 0 0000 Fa P4130067 JP 50 744 0 292 Salg 50 919 CPS 100 0124 3 6547 1 3416 0 0000 v crs 0 017 0 015 0 001 0 022 E 100 1271 20 5445 Lote 0 0000 v cru 0 001 0 013 0 001 0 013 CP 111 1310 See elie 1 4784 0 0000 v cry 0 002 0 004 0 001 0 004 CP 110 5155 3 0537 1 1546 0 0000 FA CP 0 018 0 002 0 001 0 018 CSM_1 0 7393 10 7810 0 1645 0 0000 Ea P41 30065 IP Bo 936 14 613 lag or 269 Transformation Options Control pont scale used Mew Point Unilink All Link Clase Points Ouale Rms e OF f 2D wip Help Remove Control Points Step 12 Click the Close button in Figure 11 Step 13 DXF export the same as identified in Step 4 but this time save the DXF in the Network2 folder and call it Net 2 dxf Step 14 At this point you can drag both Net1 dxf and Net2 dxf into your favorite CAD program as both networks are in the same coordinate system The process can be leapfrogged if there at least 4 common points from network2 to network3 etc etc HH Final thoughts Don t use it if it isn t necessary Using an average consumer grade 8 or more mega pixel digital camera our customers are routinely doing accident reconstruction mapping projects as long as 600 183m with just a single network i e no need for transformation to control The key is having enough common features in t
4. A Transformation Options Control points scale used Mew Point Unilink All Link Close Points Quality Nia f 3p 2p 1D Help i Import Control Points Remove Contral Points Close Figure 10 illustrates CP_9 control point after accomplishing Step 10 Figure 10 Step 11 Continue the same actions of Step 9 for the 4 control points NOTE once 3 noncollinear control points are marked a coordinate transformation is automatically invoked within iWitness We strongly recommend that you use a minimum of four control points In Figure 11 when all 4 control points have been successfully marked there will be 4 green tick marks in the column named Closest Point Additionally in the lower right corner of the dialog it states Quality RMS number The lower the number the better In this tip sheet example the control points were semi automatically centroid marked with iWitness X key so the Quality RMS number is going to be very small The RMS number is a function of how well the 2 XYZ data sets matched each other for image marking and as a rigid body fit to each other In real world applications where natural features are used for this process you might see these numbers as high as Quality RMS 0 100 or even as much as 0 200 The user can also see which of the 4 CP s in our example fit the best or worst by analyzing the results in the DX DY and DZ field as noted in Figure
5. Transformation to Control Procedure for iWitness This tip sheet was prepared for users with a basic knowledge of the iWitness close range photogrammetry software system The purpose of this tip sheet is to provide the basic understanding of the Transformation to Control dialog box within iWitness For the sake of brevity only the 3D transformation to control feature is discussed in this tip sheet For 1D block shift and 2D transformation within an XY plane see the iWitness User Manual Overview iWitness provides the user a method to stitch a series of multiple project images from different coordinate systems This stitching capability is beneficial in order to break sub sets of images into manageable smaller projects by keeping them all in the same coordinate reference system For example if an accident reconstruction practitioner has acquired terrestrial based images over a quarter mile in length it is often easier to break the projects up into 500 to 600 length sub projects and stitch them together This stitching is accomplished by using the iWitness Transformation to Control function along with measured Control Points CP s The CP s are simply four or more measured XYZ points that are observed in two or more iWitness networks For our project example we are simply using 4 traffic cones and DCS cone style Reference Point Markers RPMs to illustrate the CP marking procedure It s
6. he images this is why spreading the RPMS in the scene works well Fora good illustration of a 3D mapping project with a single network over 500 long see the presentation at http www iwitnessphoto com solutions auto ped fatality html Use it when it s necessary The iWitness 3D transformation to control is a very powerful tool that allows one to Stitch projects together A good example would be working a crash scene where one side of the street might be completely occluded by a jack knifed 18 wheeler semi truck In this example to stitch both sides of the streets crash scene together all it takes is 4 common points for use in iWitness Transformation to control dialog to get the multiple networks in the Same coordinate reference system 2008 All Rights Reserved DeChant Consulting Services DCS Inc www iwitnessphoto com
7. hould be noted the wider the CP s are separated in a real world project the better Further the CP s do not have to necessarily be the cone style RPMs as illustrated in the tip sheet or spread coplanar rather any natural feature in the images the user can accurately cursor mark in the images An example might be a vehicle crash scene perhaps marking the CP s on discrete features in the images such as including the top of a streetlight standard or anything that is stationary during the picture taking process Procedure to use the iWitness Transformation to Control The assumption is the user has completed two networks we will call them Network1 iwp and Network2 iwp for this tip sheet Step 1 Network1 has already been scaled with the 3 2 1 model rotation within iWitness Network 2 is also complete but it does not require scale or 3 2 1 as the 3D transformation to control function will scale and rotate the Network2 iwp into the same coordinate reference system as Network1 iwp Step 2 The user names the 4 control points from Network1 It is best to typically use six CP s but for this tip sheet we only use four as the minimum amount for the least squares coordinate transformation See Figure 1 for the named control points The named points are CP_9 CP_U CP_V CP_W Figure 1 Zoomed in view It should be noted the 4 CP s are located into the depth of the image whereas Networki camera pos
8. itions are generally observed closest or in common to the forward side of CP_9 amp CP_U reference the markers O B and N whereas Network2 is located into the depth or backside of Figure 1 behind CP_W and CP_V where the police vehicle is parked in the image Step 3 The user is ready to export the CP s you do this by clicking on the 3D Points dialog C3 iWitnessPRO C Docume See Figure 2 on the next page with the 3D Points dialog open 3D Points x Point Label z Offset Rays Quality Angle deg Description os 35 9011 12 1529 0 000 20 0 26 76 9 68 9624 13 35 ing Donon 0 9662 i Save As l x 35 9971 A Save ini B Nel s i i SCS Y 100 0124 E m backups 100 1271 2 cJ 111 1310 i Recent 110 8155 o Ee iz In the 3D Points dialog click TXT 5 7610 P and name the Control Point File we 12 0818 DA selected to name it control txt 18 0128 46 1172 34 0345 40 6322 0 0000 a 3 1833 W File name 15 1954 My Network Save as type Text Files r Places aisle i f Figure 2 54 2133 63 5265 24 6112 0 0194 Total RMS 5M DXF Process Show Hide code bits 33 points 0 codes 0 27 pixels Cea ie Save the control txt in the same folder as the project in our case the project folder is named Net 1 Click Save in Figure 2 Step 4 In Figure 2 the 3D Points dialog is still open Click on the DXF button in the
9. k All Link Clase Points Quality Nia Qo So Sr Help Sr Import Control Po ints _ Remove Control Points USE Step 7 Click on the Import Control Points as noted in Figure 4 Note The MS Windows Open dialog is presented now You will path to the Neti folder to select the control txt file you previously made in Step 3 then click Open See Figure 5 on the next page illustrates these actions Open Look in O Net 1 od S fe mg E F PA130030 JPG thumbnail pai30037 H PA130031 Gi PA130037 JPG thumbnai Recent control PA130031 IPG thumbnails i PAL 30038 m PA1 30032 E PA130038 JPG thumbnai E PA130026 E FA130032 JPG thumbnail Gi P41 30039 PA130026 IPG thumbnails PA130033 Gi P4130039 IPG thumbnai Desktop mipaiso027 PA130033 IPG thumbnails e Pai 30040 Gi PALS0027 IPG thumbnails i PA130034 PA130040 IPG ME Pa1300z amp P4130034 IPG thumbnails ei PA1s0041 PA130028 IPG thumbnails B PA130035 E PA 130041 JPG thumbnai Mu D t zoe i pA130029 E PA130035 JPG thumbnails E PA130042 Figure 5 m H PA130029 3PG thumbnaila E PA130036 E PA130042 JPG thuren aL mS Pa130030 PA130036 IFG thumbnals E PA130043 My Computer 7 e File name control gt My Network Files of type All Files PI aces Open as read only Step 8 You will be prompted to enter the UNITS see Figure 6 Note the uni
10. ts should be the same for all project networks In our case the Units were feet Select the proper radio button and then click OK Select Units Units inches C millimetres 0 metres Cancel feet The Transformation to control dialog box is now populated with the control txt file information Figure 7 illustrates this on the next page In our example there are only 4 Control Labels that we re concerned with using highlighted for illustration with a red box in Figure 7 Control Label a Y Z Z Offset Closest Paint Dr DY Dz Total A 100 0124 9 6547 1 3416 0 0000 MJA MIA NJA MA NJA e 100 1271 20 5445 1 5422 c 0000 NjA NA NA NJA NIA 111 1310 19 9771 1 4784 0 0000 NjA MIA MA MA NJA 110 8155 9 0537 1 1846 0 0000 NIA NA NjA WA NJA o 0ra 10 7610 0 1645 o o000 NIA NIA NjA NA NJA 5 7610 6 5985 0 1874 0 0000 WA MHA NJA NA NIA CSM_3 12 0818 3 1034 0 2551 0 0000 NA NjA Transformation Options 3p sp iD Help ae NA Ni nk al as Control points scale used Mew Point Unilink 4 Link Close Points Quality Mii Remove Control Points Clase Figure 7 Step 9 To begin the control point labeling the cursor is now presented in the shape of a blue triangle Hold the Ctrl key on the keyboard and the cursor temporarily becomes the white select arrow Marquee drag the cursor around the control point
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