ContextCapture

CC Orientations

CC Orientations is an XML format that stores Images and Point clouds positioning information, for usage in ContextCapture API or ContextCapture desktop applications.

File format

Root node

<?xml version="1.0" encoding="utf-8"?>
<BlocksExchange version="2.1">

</BlocksExchange>

This is the node that will contain all the subsequent sections.

Spatial Reference Systems

    <SpatialReferenceSystems>
        <SRS>
            <!-- SRS Identifier -->
            <Id>0</Id>
            <!-- User-friendly SRS name. -->
            <Name>Lambert 93</Name>
            <!-- The spatial reference system definition can be either a Well Known Text definition (e.g. WGS84), "EPSG: " or a PROJ.4 definition. -->
            <Definition>EPSG:2154</Definition>
        </SRS>
    </SpatialReferenceSystems>

This node is used to provide the list of SRS used in the CC Orientations. Multiple SRS can be defined here. <Id>s have to be integer.

Block

The block is the main component of the CC Orientations. We will split it in different section for easier understanding.

Base information

<Block>
    <!-- Block name and description are optional but recommended -->
    <Name>My first CCOrientations</Name>
    <Description>This is my first CCOrientations</Description>
    <!-- The type of block is optional. Supported types: Generic (default if not specified), Aerial, Nadir and Orbit. -->
    <Type>Nadir</Type>
    <!-- Minmum and maximum viewing distance can be optionally provided with <MinimumViewingDistance> and <MaximumViewingDistance> tags -->
    <MinimumViewingDistance>150</MinimumViewingDistance>
    <MaximumViewingDistance>500</MaximumViewingDistance>
    <!-- ID of the base SRS used in the block. By default, the spatial reference system is assumed to be a local Cartesian coordinate system. -->
    <SRSId>0</SRSId>
</Block>

Name and Description are optional, but we recommend you use them for prettier import in ContextCapture.

Type is optional. If your acquisition corresponds to an aerial flight - that is Nadir+Oblique images - we recommend you use the Aerial type. If your acquisition consists only of nadir images, use the Nadir type. Finally, if you are orbiting around a structure - like a Telecom Tower, use the Orbit type.

MinimumViewingDistance and MaximumViewingDistance are used for more robust computations. They apply to all the images in the CC Orientations. If you are using Nadir block type, we strongly recommend you set these values based on the height of your flight.

Finally, SRSId should point to an existing id in the SpatialReferenceSystems section.

Photogroups

A photogroup regroups images sharing the same optical properties - image dimensions, focal length, sensor size, distortion, etc. Multiple photogroups are allowed in a CC Orientations.

<Photogroups>
    <!-- All photos taken using the same physical camera, with identical focal length and dimensions must be gathered in a photogroup. -->
    <Photogroup>
        <!-- Optional a different spatial reference system can be specified for each photogroup with the <SRSId> tag. By default, the SRS of the block is assumed. -->
        <SRSId>0</SRSId>
        <!-- Optionally, a name with the <Name> tag, and a description with a <Description> tag. -->
        <Name>Sony A5000 - 50mm</Name>
        <Description>Acquired on 2020-09-06</Description>
        <!-- Image dimensions, in pixels. -->
        <ImageDimensions>
            <Width>5456</Width>
            <Height>3632</Height>
        </ImageDimensions>
        <!-- Optional camera model type Perspective (default) or Fisheye -->
        <CameraModelType>Perspective</CameraModelType>
        <!-- Optional camera model band Visible (default) or Thermal -->
        <CameraModelBand>Visible</CameraModelBand>
        <!-- Optional multicamera rig index (no rig is used if this tag is unspecified). -->
        <!-- <Rig>1</Rig> -->
        <!-- Sensor's largest dimension, in millimeters. -->
        <SensorSize>23.5</SensorSize>
        <!-- Focal length, in millimeters. This can be either the nominal specification or a closer estimate. -->
        <FocalLength>50</FocalLength>
        <!-- CameraOrientation: XRightYDown (default), XRightYUp (more frequent in photogrammetry), XLeftYDown, XLeftYUp, XDownYRight, XDownYLeft, XUpYRight, XUpYLeft -->
        <CameraOrientation>XRightYDown</CameraOrientation>
        <!-- Principal point, with respect to the sensor center. This field is optional: by default, the sensor center is used as an initial estimate of the principal point. -->
        <PrincipalPoint>
            <!-- 2D image position of the principal point, in pixels. -->
            <!-- The origin is the center of the upper-left image pixel, the x-axis is oriented to the right side of the image, and the y-axis is oriented to the bottom of the image. -->
            <x>2799.72836989663</x>
            <y>1664.19084530151</y>
        </PrincipalPoint>
        <!-- Lens distortion coefficients. This field is optional: by default, no distortion is assumed as an initial estimate. -->
        <!-- Distortion coefficients correspond to the classical Brown's distortion model, as described in http://en.wikipedia.org/wiki/Distortion_(optics). -->
        <Distortion>
            <K1>0.091784043461384</K1>
            <K2>-0.389773692160792</K2>
            <K3>-0.164530007624487</K3>
            <P1>0.00338559469641398</P1>
            <P2>0.00195577545434898</P2>
        </Distortion>
        <!-- Fisheye focal matrix used only for the camera model type Fisheye. -->
        <FisheyeFocalMatrix>
            <M_00>1960</M_00>
            <M_01>0</M_01>
            <M_10>0</M_10>
            <M_11>1960</M_11>
        </FisheyeFocalMatrix>
        <!-- Fisheye distortion coefficients used only for the camera model type Fisheye. -->
        <FisheyeDistortion>
            <P0>0</P0>
            <P1>1</P1>
            <P2>0</P2>
            <P3>0</P3>
            <P4>0</P4>
        </FisheyeDistortion>
        <!-- Multiple photos in a photogroup -->
        <Photo>
            <!-- The ID of a photograph must be unique over the whole block (in other words, even across other photogroups). If you are using Rig, we use this id for photo order-->
            <Id>0</Id>
            <!-- Path of the image based on its CCImageCollection id -->
            <ImagePath>3e4742f9-87fc-4bfa-8ee3-6103555f325f/DSC03885.jpg</ImagePath>
            <!-- Optional path of the image mask based on its CCImageCollection id -->
            <MaskPath>7f7a664f-e11b-4658-84fa-5ada1b0ee7c1/DSC03885_msk.jpg</MaskPath>
            <!-- Optional component Id: 1 is the main component (default), 0 is no component. Photos with incomplete pose cannot belong to the main component -->
            <Component>0</Component>
            <!-- Exterior orientation of the camera, as estimated by navigation devices or aerotriangulation. This field is optional. -->
            <Pose>
                <!-- 3D rotation of the camera in the spatial reference system defined above. -->
                <!-- It defines the rotation matrix transforming world coordinates (in the specified SRS)-->
                <!-- into camera coordinates (with axes defined by the CameraOrientation of the photogroup). -->
                <!-- The rotation is optional: the pose can be limited to the 3D position of the camera center (e.g. when GPS position only is available). -->
                <Rotation>
                    <!-- A 3x3 matrix, using the <M_ij> tags, where M_ij denotes the coefficient of the (i+1)th row and the (j+1)th column of the rotation matrix. -->
                    <M_00>-0.9999982912233401</M_00>
                    <M_01>-0.001636319085375301</M_01>
                    <M_02>-0.0008602425863163225</M_02>
                    <M_10>-0.001631068695467463</M_10>
                    <M_11>0.9999802528616577</M_11>
                    <M_12>-0.00606906089589293</M_12>
                    <M_20>0.0008701565192966738</M_20>
                    <M_21>-0.006067647409696231</M_21>
                    <M_22>-0.9999812130648239</M_22>
                </Rotation>
                <!-- 3D position of the camera center in the spatial reference system defined above. -->
                <!-- Depending on the SRS, x/y may stand either for longitude/latitude, for map projection coordinates, or for something else. -->
                <!-- Depending on the SRS, z may stand either for a geoid height, for an orthometric height, or for something else. -->
                <Center>
                    <x>651999.7159189156</x>
                    <y>6863073.633923346</y>
                    <z>1318.897690166719</z>
                </Center>
            </Pose>
            <!-- Optional depth information can be provided with <NearDepth>, <MedianDepth>, and <FarDepth> tags -->
            <!-- Optional Exif data (each exif data property is optional) -->
            <ExifData>
                <ImageDimensions>
                    <Width>5456</Width>
                    <Height>3632</Height>
                </ImageDimensions>
                <PixelDimensions>
                    <Width>0.02</Width>
                    <Height>0.02</Height>
                </PixelDimensions>
                <GPS>
                    <Latitude>45.5686684</Latitude>
                    <Longitude>2.6551104</Longitude>
                    <Altitude>1589.5469</Altitude>
                </GPS>
                <FocalLength>50</FocalLength>
                <FocalLength35mmEq>75</FocalLength35mmEq>
                <Make>SONY</Make>
                <Model>ILCE-5000</Model>
                <LensModel>E 50mm F1.8 OSS</LensModel>
                <DateTimeOriginal>2020-04-29T06:40:26</DateTimeOriginal>
            </ExifData>
        </Photo>
    </Photogroup>
</Photogroups>

Some precisions:

  • FocalLength is the nominal or closer estimate of the focal length in millimeters. SensorSize is the largest dimension (usually the width) of the sensor in millimeters.
  • CameraOrientation describes the camera. For more information on this topic, on rotations and distortions, see this documentation page.
  • If you are using the Rig option: this option enforce a rigid registration between corresponding images in photogroup. Images correspondence is based on photo ids: if you have two photogroups with 3 images each, numbered 0–1-2 and 3–4-5 that are rigged, 0 goes with 3, 1 with 4 and 2 with 5.

The simplest photogroup you can create will look like this:

<Photogroup>
    <Name>My Photogroup</Name>
    <ImageDimensions>
        <Width>5456</Width>
        <Height>3632</Height>
    </ImageDimensions>
    <CameraModelType>Perspective</CameraModelType>
    <CameraModelBand>Visible</CameraModelBand>
    <FocalLength>50</FocalLength>
    <SensorSize>23.5</SensorSize>
    <CameraOrientation>XRightYDown</CameraOrientation>
    <Photo>
        <Id>0</Id>
        <ImagePath>3e4742f9-87fc-4bfa-8ee3-6103555f325f/DSC03885.JPG</ImagePath>
        <Component>0</Component>
    </Photo>
    <Photo>
        <Id>1</Id>
        <ImagePath>3e4742f9-87fc-4bfa-8ee3-6103555f325f/DSC03886.JPG</ImagePath>
        <Component>0</Component>
    </Photo>
    <Photo>
        <Id>2</Id>
        <ImagePath>3e4742f9-87fc-4bfa-8ee3-6103555f325f/DSC03887.JPG</ImagePath>
        <Component>0</Component>
    </Photo>
</Photogroup>

Across photogroups, we need at least 3 images in order to process a CC Orientations in ContextCapture or CCCS.

Control points

<ControlPoints>
    <!-- Optionally, a different spatial reference system can be specified with the <SRSId> tag.-->
    <!-- By default, the SRS of the block is assumed. -->
    <ControlPoint>
        <Name>Control point #1</Name>
        <!-- Optionally, a different spatial reference system can be specified for each control point with the <SRSId> tag.-->
        <!-- By default, the SRS of the control points container is assumed. -->
        <!-- If specified, a control point can be Full (default), Horizontal or Vertical -->
        <Category>Full</Category>
        <!-- 3D position of the control point in the active spatial reference system. -->
        <!-- Depending on the SRS, x/y may stand either for longitude/latitude, for map projection coordinates, or for something else. -->
        <!-- Depending on the SRS, z may stand either for a geoid height, for an orthometric height, or for something else. -->
        <Position>
            <x>652788.0525588237</x> <!-- Not needed if Category:Vertical -->
            <y>6863015.362218254</y> <!-- Not needed if Category:Vertical -->
            <z>78.07000000122935</z> <!-- Not needed if Category:Horizontal -->
        </Position>
        <!-- Optionally, a control point may be a check point (default: false)-->
        <CheckPoint>true</CheckPoint>
        <!-- If specified, a control point may have accuracies -->
        <HorizontalAccuracy>0.01</HorizontalAccuracy> <!-- Not needed if Category:Vertical -->
        <VerticalAccuracy>0.10</VerticalAccuracy> <!-- Not needed if Category:Horizontal -->

        <!-- Image measurements -->
        <Measurement>
            <!-- ID of the photo where the measurement is taken. The measurements of a control point must have different photo IDs. -->
            <PhotoId>151</PhotoId>
            <!-- 2D image position of the measurement, in pixels. -->
            <!-- The origin is the center of the upper-left image pixel, the x-axis is oriented to the right side of the image, and the y-axis is oriented to the bottom of the image. -->
            <x>7270.31</x>
            <y>6599.44</y>
        </Measurement>
        <Measurement>
            <PhotoId>158</PhotoId>
            <x>1496.69</x>
            <y>6589.94</y>
        </Measurement>
        <Measurement>
            <PhotoId>2104</PhotoId>
            <x>4820.34</x>
            <y>5631.15</y>
        </Measurement>
    </ControlPoint>
</ControlPoints>

ControlPoints are not mandatory. They are used to register the images in a specific SRS if needed, or to check the quality of the calibration.

Tiepoints

<TiePoints>
    <!-- Optionally, a different spatial reference system can be specified with the <SRSId> tag. By default, the SRS of the block is assumed. -->
    <TiePoint>
        <Name>Left window corner</Name> <!-- Optional, recommended for User Tie Points -->
        <Description></Description> <!-- Description field is only used for internal metadata, do not modify it -->
        <!-- Optionally, a different spatial reference system can be specified for each tie point with the <SRSId> tag. By default, the SRS of the tie points container is assumed. -->
        <!-- Optional id (required for a User tie point if it is referenced in a positioning constraint). -->
        <id>0</id>
        <Color> <!-- Optional, value between 0 and 1 -->
            <Red>0.59</Red>
            <Green>1.0</Green>
            <Blue>0.0</Blue>
        </Color>
        <!-- If specified, a tie point may be a check point (default: false)-->
        <CheckPoint>true</CheckPoint>
        <!-- Optional position of the tie point in the active spatial reference system -->
        <Position>
            <x>652119.8871409688</x>
            <y>6863304.305716386</y>
            <z>87.79328384995461</z>
        </Position>
        <Measurement>
            <!-- Optional measurement type User or Automatic (default) -->
            <Type>User</Type>
            <PhotoId>146</PhotoId>
            <!-- 2D image position of the measurement, in pixels.-->
      <!-- The origin is the center of the upper-left image pixel, the x-axis is oriented to the right side of the image, and the y-axis is oriented to the bottom of the image. -->
            <x>3324.26001</x>
            <y>9930.269531</y>
        </Measurement>
    </TiePoint>
</TiePoints>

Tie points can be stored in an external file:

<TiePoints>
    <Path>TiePoints.xml</Path>
</TiePoint>

With TiePoints.xml looking like:

<?xml version="1.0" encoding="utf-8"?>
<TiePoint>
    <Position>
        <x>-34.4750012078745</x>
        <y>1.15274149210525</y>
        <z>-8.18177676215297</z>
    </Position>
    <Color>
        <Red>0.501960784313725</Red>
        <Green>0.498039215686275</Green>
        <Blue>0.450980392156863</Blue>
    </Color>
    <Measurement>
        <PhotoId>0</PhotoId>
        <x>1660.05517578125</x>
        <y>3084.59497070313</y>
    </Measurement>
    <Measurement>
        <PhotoId>1</PhotoId>
        <x>1346.03332519531</x>
        <y>3067.69970703125</y>
    </Measurement>
    <Measurement>
        <PhotoId>2</PhotoId>
        <x>1366.38330078125</x>
        <y>2920.05126953125</y>
    </Measurement>
</TiePoint>
<TiePoint>
    <Position>
        <x>-28.2683141902494</x>
        <y>0.235531157377353</y>
        <z>-8.31343880296754</z>
    </Position>
    <Color>
        <Red>0.584313725490196</Red>
        <Green>0.592156862745098</Green>
        <Blue>0.513725490196078</Blue>
    </Color>
    <Measurement>
        <PhotoId>0</PhotoId>
        <x>3169.814453125</x>
        <y>3148.72875976563</y>
    </Measurement>
    <Measurement>
        <PhotoId>1</PhotoId>
        <x>2818.83056640625</x>
        <y>3156.552734375</y>
    </Measurement>
    <Measurement>
        <PhotoId>2</PhotoId>
        <x>2755.80639648438</x>
        <y>3047.31640625</y>
    </Measurement>
    <Measurement>
        <PhotoId>3</PhotoId>
        <x>2708.74145507813</x>
        <y>3092.60327148438</y>
    </Measurement>
</TiePoint>

Constraints

<PositioningConstraints>
    <OriginConstraint> <!-- Maximum one Origin constraint -->
        <O>2</O> <!-- Tiepoint id -->
    </OriginConstraint>
    <ScaleConstraint> <!-- Multiple allowed -->
        <A>0</A>
        <B>3</B>
        <DistanceAB>56.350</DistanceAB>
    </ScaleConstraint>
    <AxisConstraint> <!-- Maximum one Axis or Orientation constraint -->
        <A>0</A>
        <B>3</B>
        <AxisAB>z</AxisAB> <!-- x, y, or z -->
    </AxisConstraint>
    <OrientationConstraint> <!-- Maximum one Orientation or Axis constraint -->
        <A>0</A>
        <B>3</B>
        <C>2</C>
        <AxisAB>z</AxisAB> <!-- x, y or z -->
        <AxisSideC>upperX</AxisSideC> <!-- lowerX, upperX, lowerY, upperY, lowerZ, or upperZ -->
    </OrientationConstraint>
</PositioningConstraints>

Positioning constraints are optional.

Upload CC Orientations on RDS/PWCS

You can save the file as CCOrientations.xml. For lower space usage, you can zip it and name it as CCOrientations.xmlz. Tie points file can also be zipped. We recommend the tie points file be named CCOrientations - Tiepoints.xml or CCOrientations - Tiepoints.xmlz. Once the files are saved, create a Reality Data using Reality Data API with reality data type CCOrientations, and upload the file(s) to the root of the reality data.