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Important: Pix4Dmapper allows the user to process using a Processing Template. The templateswith the label Rapid/Low Res produce fast results at low resolution that can be used on the fieldas an indicator of how good the dataset is.If the Rapid/Low Res processing does not yield to good results, very probably, the dataset is notadequate and it is necessary to acquire images again. In some cases, the Rapid/Low Res optionfails while the Full processing successfully reconstructs the model.For more information about the difference between Rapid/Low Res and Full processing:202558949.Ideal image acquisition planThe ideal image acquisition plan depends on the type of terrain / object to be reconstructed.: General case: For projects that do not include forests, snow, lakes, agricultural fieldsand/or other terrain that is difficult to reconstruct.Forest and dense vegetation: For project with areas covered by forest or dense vegetation.Flat terrain with agriculture fields: For flat terrain with homogeneous visual content suchas agriculture fields.Building reconstruction: For 3D modelling of buildings.Special cases: For snow, sand, and water surfaces (oceans, lakes, rivers, etc).Corridor mapping: For projects with linear area of interest (roads, rivers, etc).Multiple flights: For projects with images taken using multiple flights.City reconstruction (visible facades): For 3D modelling of urban areas.3D interior reconstruction: For 3D modelling of the interior of buildings.Mixed reconstruction: For combined datasets (interior/exterior and/or aerial/terrestrialand/or nadir/oblique).Large Vertical Objects reconstruction: For 3D modelling of objects like power towers,wind turbines, etc.Tunnel reconstruction: For 3D modelling of a tunnel.Important: Below it is described the recommended different image acquisition paths andoverlap for different cases, despite it may work with lower overlap than the suggested ones, inorder to obtain the best possible results, it is suggested to use the recommended overlaps.General caseThe recommended overlap for most cases is at least 75% frontal overlap (with respect to theflight direction) and at least 60% side overlap (between flying tracks). It is recommended totake the images with a regular grid pattern (Figure 1). The camera should be maintained as muchpossible at a constant height over the terrain / object to ensure the desired GSD.

Figure 1. Ideal Image Acquisition Plan - General case.Forest and dense vegetationTrees and dense vegetation often have a very different appearance between overlapping imagesdue to their complex geometry (thousands of branches and leaves). Therefore, it is difficult toextract common characteristic points (keypoints) between the images. In order to achieve goodresults, it is recommended to use a grid image acquisition plan as the one described in theGeneral Case section by applying the following changes: Increase the overlap between images to at least 85% frontal overlap and at least 70%side overlap.Increase the flight height: At higher altitude, there is less perspective distortion(therefore causing less appearance problems) and the dense vegetation has better visualproperties. In other words, it is easier to detect visual similarities between overlappingimages in such areas. The flight height in combination with the image pixel resolutionand the focal length determine the Ground Sampling Distance (spatial resolution) of theimages. Best results are obtained with a GSD higher than 10cm/pixel.For more information about how to improve the results of dense vegetation areas selecting thecorrect processing options: 202560159.

Flat terrain with agriculture fieldsIn cases where the terrain is flat with homogeneous visual content such as agriculture fields, it isdifficult to extract common characteristic points (keypoints) between the images. In order toachieve good results, it is recommended to use a grid image acquisition plan as the one describedin the General Case section by applying the following changes: Increase the overlap between images to at least 85% frontal overlap and at least 70%side overlap.Fly higher. In most cases, flying higher improves the results.Have accurate image geolocation and use the Agriculture template. For moreinformation about the Agriculture (Ag) template: 205319155.Building reconstructionReconstructing 3D buildings requires a specific image acquisition plan (Figure 2): Fly around the building a first time with a 45 camera angle.Fly a second and third time around the building increasing the flight height anddecreasing the camera angle with each round.Note: For more information about oblique imagery: 202559859. It is recommended to take one image every 5-10 degrees to ensure enough overlap,depending on the size of the object and distance to it. Shorter distance and larger objectsrequire images every less degrees.Note: The flight height should not be increased more than twice between the flights, asdifferent heights lead to different spatial resolution. For more information: 202558979.Pix4Dmapper generates a high quality point cloud for oblique images of buildings.However, no orthomosaic is generated, when the selected template is 3DModels: 205319155.Important: By default, Pix4Dmapper generates orthomosaics that are parallel to the (X,Y)plane. Therefore, to generate mosaics of facades, the Orthoplane tool needs to be used. For moreinformation: 202559889.

Figure 2. Ideal Image Acquisition Plan - Building.Note: It is possible to combine aerial nadir and/or aerial oblique and/or terrestrial images.The images should have enough overlap in each dataset and between datasets. For such cases itis strongly recommended to use GCPs or Manual Tie Points to properly adjust the different setsof images. For more information: 202561599Special casesThis section presents some hints for terrain that is difficult to map such as terrains with snow,sand, lakes, etc.Snow and sandSnow and sand have little visual content due to large uniform areas. Therefore: Use a high overlap: At least 85% frontal overlap and at least 70% side overlap.Set the exposure settings accordingly to get as much contrast as possible in each image.WaterWater surfaces have almost no visual content due to large uniform areas. Sun reflection on thewater and waves cannot be used for visual matching. Oceans are impossible to reconstruct.

To reconstruct other water surfaces such as rivers or lakes, each image needs to haveland features. Flying higher may help to include more land features.Corridor mappingMapping corridors such as railways, roads or rivers requires at least 2 flight lines (Figure3). GCPs are not required, but are recommended to improve the georeference and accuracy ofthe reconstruction. For more information about the number and distribution of GCPs in corridormapping: 202559299.For a dual track it is recommended to use at least 85% frontal overlap and at least 60% sideoverlap.It is possible to use nadir images or oblique images (with an angle between 0º and 45º pointing inboth tracks to the center of the corridor). For flat terrain it is recommended to use nadir images.Figure 3. Dual track image acquisition plan for corridor mapping.If a dual track image acquisition plan is not possible, a single track image acquisition plan can beused if (Figure 4): Overlap is high enough: At least 85% frontal overlap.Ground control points (GCPs) are defined along the flight line in zig zag.Figure 4. Single track flight NOT RECOMMENDED.Multiple flightsPix4Dmapper can process images taken from multiple flights. When designing the differentimage acquisition plans, make sure that: Each plan captures the images with enough overlap.

There is enough overlap between 2 image acquisition plans (Figures 5 and 6).The different plans are taken as much as possible under the same conditions (sundirection, weather conditions, no new buildings, etc.).Important: The flight height should not be too different between the flights, as different heightleads to different spatial resolution. For more information: 202558979.There is a special way to process datasets taken from multiple flights, for step by stepinstructions: 202558579.Enough overlap between 2 flightsFigure 5. Overlap between 2 flights.Not enough overlap between 2 flightsFigure 6. Recommended image acquisition plan for 2 flights.

City reconstruction (visible facades)The 3D reconstruction of urban areas requires a double grid image acquisition plan, so that allthe facades of the buildings (north, west, south, east) are visible on the images. The overlapshould be the same as in the General Case.Figure 7. Double grid image acquisition plan.For the facades to be visible, the images should be taken with an angle between 10º and 35º, formore information about the definition of the angles: 202559859) and not pointing to the nadir. Ifmuch detail is needed, aerial and terrestrial images should be combined.Note: It is possible to combine aerial nadir and/or aerial oblique and/or terrestrial images.The images should have enough overlap in each dataset and between datasets. For such cases itis strongly recommended to use GCPs or Manual Tie Points to properly adjust the different setsof images. For more information: 202561599.

3D Interior reconstructionFor interior reconstruction, it is strongly recommended to use terrestrial images. High overlap isneeded (90%). Therefore, it is recommended to use a fisheye lens camera.Manual Tie Points improve the reconstruction and help to properly adjust the model. For moreinformation: 202970309.Mixed reconstructionIt is possible to combine interior/exterior and/or aerial/terrestrial and /or nadir/oblique. Anycombination is possible.The images should have enough overlap in each dataset and between datasets. For such cases itis strongly recommended to use GCPs or Manual Tie Points to properly adjust the different setsof images. For more information: 202561599.Large Vertical Objects reconstructionThe 3D reconstruction of objects like power towers, wind turbines etc requires a specific imageacquisition plan (figure 8): Fly close to the structure.Turn several times around the structure at several heights.Images should be taken with high overlap: 90% of overlap between images taken at thesame height and 60% of overlap between images taken at different heights.The optimal camera angle for the top circle is 45 degrees. By pointing to the ground, thecontent of the images is easier to be matched and the results are better.The images should be as focused as possible (both the main object and the backgroundshould be focused).Having image geolocation is recommended. For more information about the imagegeolocation: 202557499.

Power Tower reconstructed in the rayCloudPower TowerFigure 8. Image Acquisition Plan - Power tower.Note: For more information on how to map and measure pole and tower structures: 202560479.Tunnel reconstructionPix4Dmapper can reconstruct tunnels. The biggest challenge for tunnel reconstruction is thelighting conditions. If the lighting is good either with natural light (if the tunnel is not too long)or with artificial light, the reconstruction could be very good.In case of very dark tunnels, a tripod is recommended.Tip: It is recommended to: Use fisheye lens camera.Take images in more than one line (avoid single track shooting). If a multiple tracksimage acquisition plan is not possible, a single track could work. GCPs are highlyrecommended in this case.

Figure 9. Automatic Tie Points of a tunnel.Step 1. Before Starting a Project 1.Designing the Image Acquisition Plan b.Computing the Flight Height for a given GSDThe Ground Sampling Distance (GSD) is the distance between the center of two consecutivepixels on the ground. It influences the accuracy and the quality of the final results as well as thedetails that are visible in the final Orthomosaic.The flight height H that is needed to obtain a given GSD can be computed and depends on thecamera focal length, the camera sensor width [mm], and the image width [pixels].

Sw real sensor width [mm]FR real focal length [mm]H flight height [m]Dw distance covered on the ground by one image in the widthdirection (footprint width) [m]Some lens manufacturers give the focal length (F35) in the 35 mm equivalent. It is the real focallength that should be used in Pix4Dmapper. In order to find the real focal length, somecomputations are needed. In the case of a 4:3 ratio, the formula for the real focal length FR isgiven by:FR [mm] (F35 * SW) / 34.6(1)WhereF35 focal length that corresponds to the 35 mm equivalentFR real focal lengthSw the real sensor widthFor more information about the 35mm equivalent focal length concept: Wikipedia article.Using the fact thatH / FR DW / SW,the flight height H is given by:H (DW * FR) / SW .(2)The distance covered on the ground by one image in the width direction (footprint width) isgiven:DW (imW * GSD) / 100.(3)whereDW distance covered on the ground by one image [m] in the width direction (footprint width)

imW image width [pixel]GSD desired GSD [cm/pixel]Combining equation (2) and (3), the flight height is given by:H [m] (imW * GSD * FR) / (SW * 100)(4)Step 1. Before Starting a Project 1.Designing the Image Acquisition Plan c.Computing the Image Rate for a givenFrontal OverlapThe image shooting rate to achieve a given frontal overlap depends on the speed of the UAV/plane, the GSD and the pixelresolution of the camera.D distance covered on the ground by one image in theflight direction [m]overlap percentage of desired frontal overlap betweentwo imagesod overlap between two images in the flight direction[m]x distance between two camera positions in the flightdirection [m]v flight speed [m/s]t elapsed time between two images (image rate) [s]Figure 1.From Figure 1, we obtain the following equations:od overlap * D(1)x D - od(2)t x/v(3)

Two cases are possible: Camera oriented with the sensor width (long dimension) perpendicular to the flightdirection (usual case)Camera oriented with the sensor width (long dimension) parallel to the flight directionCamera oriented with the sensor width (long dimension) perpendicular to the flightdirection (usual case)D Dh (imH * GSD) / 100(4)Where:Dh distance covered on the ground by oneimage in the height direction (footprintheight) [m]imH image height [pixel]GSD desired GSD [cm/pixel]Figure 2. Sensor width placed perpendicular tothe flight direction.Combining Equations (1) and (4) into Equation (2):x Dh - overlap * Dhx Dh * (1 - overlap)x ((imH* GSD) / 100) * (1 - overlap)(5)Note: x is given in [m], considering that the GSD is in [cm/pixel].Combining the equations (3) and (5):t x / v ((imH * GSD) / 100) * (1 - overlap) / v(6)

Example: In order to achieve an overlap of 75% (overlap 0.75) and a GSD of 5[cm/pixel], supposing that the image height is 4000 [pixels] and the speed of the UAV/plane is30 [km/h] 8.33 [m/s], based on the equation (6), the image rate should be 6 seconds:t ((imH * GSD) / 100) * (1 - overlap) / v ((4000 * 5 ) / 100) * (1 - 0.75) / 8.33 6 [s]Camera oriented with the sensor width (long dimension) parallel to the flight directionIf the camera is placed on the plane / UAV having the sensor width (long dimension) parallel to the flight direction:D DW (imW * GSD) / 100(7)Where:DW distance covered on the ground by oneimage in the width direction (footprintwidth) [m]imW image width [pixel]GSD desired GSD [cm/pixel]Figure 3. Sensor width placed parallel to theflight direction.Combining equations (1) and (7) into the equation (2):x DW - overlap * DWx DW * (1 - overlap)x ((imW * GSD) / 100) * (1 - overlap)(8)Note: The result is given in [m], considering that the GSD is in [cm/pixel].Combining equations (3) and (8):t x / v ((imW * GSD) / 100) * (1 - overlap) / v(9)Pix4Dmapper is able to process images taken with any camera:

Lightweight compact cameras.DSLR cameras.Large format cameras.Action cameras.Camera Rigs.360 panorama cameras.CompactDSLRLarge formatActionRig360 panoramaUsing any lens: Perspective (narrow and wide focal length).Ultra wide focal length (Fisheye).The cameras can be loaded on any platform: UAVs from the hobby world.Professional UAVs.Manned aircrafts.Helicopters.Terrestrial vehicles.No platform, for terrestrial imagery (taken by hand).Pix4Dmapper can process images regardless of the spectral specifications of the camera: RGB cameras.NIR, Red Edge cameras for agriculture applications.Thermal cameras: 20275534.etc.SummaryCamera body and lens

Perspective and fisheye lens supported.The zoom should be stable.Fixed focal length is recommended.Video frames are not recommended due tolow pixel resolution.Camera settingsStabilization settings should be off.Shutter/aperture/ISO should be onautomatic.If images are blurry or noisy, manually setshutter/aperture/ISO. For moreinformation: Camera settings.Select Manual Focus on Infinity.Camera BodyAs a rule of thumb: Heavier cameras (higher pixel resolution) provide better results but require aflying platform with a higher payload.Recommended non IXUS 220HS (135 g)Sony RX 100 (240 g)Sony Nex 5/7 (270 g - 350 g)Canon 5D mark ii ( 800 g)GoPro Hero 4TipsLet parameters on automatic and disable imagestabilization.Use a fixed focal length lens to improve the results.Recommended for close range imagery (up to 50meters). Take the images with the widest angle andhighest resolution possible.Video cameras Videos are not recommended for accurate mapping: The quality of the results will almostalways be inferior to the results from still imagery.4K video from camera such as GoPro 4 and DJI provides reasonable results.Full HD video is usually not sufficient to get good results.

When using a video for processing, it is important to consider the following: 205294735.Recommended Camera Focal LengthThere is no limit in the focal length that can be used with Pix4Dmapper.ApplicationRecommendationWhyMapping: aerial project with Perspective lens: between 22 mm and To ensure a good GSD thata flight height above 5080 mm focal length (in 35 mmwill lead to highermeters.equivalent).accuracy results.Flexibility in dataIndoor / close rangeFisheye lens: very small focal length. acquisition: Ensuringreconstruction.higher overlap.Most lens manufacturers give the focal length (F35) that corresponds to 35 mm equivalent. Inorder to find the real focal length:FR (F35 * SwR) / 34.6 (mm)where:F35 focal length that corresponds to 35 mm equivalent [mm]FR real focal length [mm]SwR the real sensor width [mm]For a given height, the wider the field of view (small focal length), the fewer the images toachieve sufficient overlap. This is especially useful if a regular and dense flight plan cannot besetup. The spatial resolution, though, will be low leading to less accurate results.If the field of view is narrow (large focal length), more images will be required to ensure enoughoverlap when mapping the same area. The spatial resolution will be higher in this case, leading tomore accurate results.For more information about how to select camera focal length and flight altitude considering thedesired spatial resolution (GSD) and the area to map: 202558849.Tip: Use a fixed focal length lens, as it will usually result in sharper images with reduced noise.

Camera SettingsThe shutter speed, aperture and ISO should be set on automatic. If images are blurry or noisy, itis recommended to manually set these parameters.There is a tradeoff between the shutter speed, the aperture, and the ISO sensitivity. Forprocessing, the images should be sharp and have the least amount of noise. Such images can beobtained when the scene is well illuminated (scattered clouds should be avoided) and the cameraparameters ar

Pix4Dmapper Setup wizard starts. 2. (optional): If the Open file - Security Warning pop-up appears, click Run. 3. In the Pix4Dmapper Setup pop-up, in the Welcome to the Pix4Dmapper Setup Wizard screen, click Next . 4. (optional) Click Browse. to change the d