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APS is the Menci Software technology for the DTM, contour lines,orthomosaic, DSM and 3D point cloud automatic generation from aerial imagery, acquired by any low-altitude UAV (unmanned aerial vehicles) with GPS on board.The simple and intuitive interface allows the user an immediate interaction with the features offered.The workflow, passing through the management of the dataset up to the generation of the DTM, contour lines , orthomosaic and DSM is easy to be followed. Furthermore APS lets the control over results to the user.The immediate low resolution raster (Overview) allows an easier identification of the AOI, as well as the ability to evaluate the extents of specific areas.
Main interfaces: There are 4 main tabs, each of them has a list of specific commands within it. This is the “Tools” Tab, which is subdivided in 6 sections: Project: through this section you can decide to create a new project or to open one already processed. Measure: it is possible to take linear or areal measurement on the orthophoto you have got. View: you can check the Footprints of each photogram, the camera position at the moment of each snap, the image names, the tiles and the sheet layout. (slide over to see how to generate tiles). Overview: enabling this command by clicking on a single camera you can check the linked photogram Windows: you can decide to enable the command bar and the workflow window. Help: in project info you can check all the results, otherwise it is possible to consult a tutorial, get the latest version and send us back your feedback.
This is the “CAD” Tab, which is subdivided in 4 sections and related functions: - Import (import a DWG CAD drawing) - Scale selected entities - Export (export current drawing to DWG / DXF) - Mirror selected entities - Draw a Point, Polyline, Spline - Rotate selected entities - Insert a Text - Trim current line - Fill a closed poligon with Hatch - Select CAD Options - Call current entity Properties - Manage layers - Erase selected entities - Select layers order - Copy selected entities - Line Weight - Move selected entities - Toggle Object Snap - Extend current line up to entity - Toggle CAD Grid
This is the “OrthoPhoto” Tab, which allows the user to enable an editor such as Photoshop for applying corrections to your model: This is the “Stereo” Tab, which allows the user to export for Menci Stereo Tool to get stereoscopic view of photograms blocks, and make accurate measurements and carthographic vectorialization.
NEW PROJECT: In order to set a new project you need to follow a few easy steps. 1) Choose the reference folder and project name 2) Select the camera passport When uploading the camera passport if you have the required details you can fill a new one all by yourself, In case you need a passport for your camera we can provide it in no time, otherwise if you have a good dataset you can even try to extract it by using APS before getting started with a new project, slide over to know how to do.
APS CAMERA CALIBRATION To extract the camera passport it is necessary to have a good data set. In order to be considered good the images have to be at least 26 spread in 4 strips and depicting an area as even as possible. If you have this condition you can try to extract a suitable passport by clicking on the green mark on the left top of the main interface. You will be asked to choose the images along with the GPS/IMU data recorded by your device. The images can be selected by drawing specific area of interest, slide over to “upload images section” (step n°4) to see how to do.
3) Insert GPS/IMU data GPS and IMU data are recorded by your drone while flying, these informations are used by APS to geo-locate each image. This data are listed as Latitude, Longitude and Height and as yaw, pitch and roll. Once they are uploaded these will be listed as afore mentioned, furthermore make sure you are using the correct camera mounting for your device. If the data are correct through the command COORDINATE SYSTEM you can verify on Google Earth the exact location of your survey
4) Upload images Images can be uploaded either by explorer or by flight plane, if the second option has been chosen you can discard images by drawing with your mouse specific area of interest (AOI). If you are not interested in processing the whole area but just a portion of it you can get rid of the pointless images. This can be done by drawing specific area of interest (AOI), to draw this area you have to click around the images you want to discard, then right click to erase them.
5) Choose the suitable algorithm to bundle • GPU Descriptor Matching: this algorithm can be used only if the graphic card has the GPU, this algorithm is capable to tie images taken at different altitudes or rotated. • Descriptor Matching: this algorithm works like the previous one but when computing the data it proceeds more slowly. • Template Matching: in order to work properly this algorithm needs a minimum overlap of 80%, further the flight must be planned with a relative height of 200 m • Optical flow Matching: it must be used when there are chromatically homogeneous areas, but in order to work the IMU data has to be available. • Enhanced Descriptor Matching: it can be used when the flight is particularly drifted away and the GPU algorithm doesn’t work as it should.
6) Run the process To get started with the process you need to click on OK, otherwise you can run the whole procedure as batch Once the procedure has begun you are going through five automatic steps, which will lead you towards the final results. These five automatic steps can be grouped in a single set named “IMAGE PROCESSING”. During the IMAGE PROCESSING the whole set of images is imported at first, then the chosen algorithm runs in order to find and match all the alike features among the images, these alike points are known as TIE POINTS. Once all the features are tied among them the set of images will be packed in a bundle. Finding and matching features and the bundle procedure are the three main steps, which are the main processes of aerial triangulation to perform the external orientation. The five steps can be listed as follows: - IMPORT - FIND FEATURES - MATCH FEATURES - BUNDLE ADJUSTEMENT - RASTER OVERVIEW
RASTER OVERVIEW The raster overview is the first result coming from the aerial triangulation, it is a low resolution raster which is easy and fast to consult. At this stage external orientation is done and images have parameters of orientation ready for other use. Through the blue arrow lying beside the overview button it is possible to consult the bundle report. The main feature listed in this report is the RMS of residuals, this is a weighted average of the displacement along the X and Y axes for the tie points found during the bundle adjustment process compared to their original position.
POSITIONING GCP: The absolute planimetric and altimetric precision depends on the GPS station mounted in your device. In order to get a better precision it can be useful to add some ground control point (GCP). These points are acquired at first by a GPS station, which must be collocated on a visible point such as a target. Once you have got all the points homogeneously spread on the interested area, you have to upload the file in APS. This file must be set as: ID, Long, Lat, Height. This set of points needs to be collimated, Once you have uploaded your list of GCP these will be overlaid as targets to the raster overview, by clicking on each target you will start the collimation. The collimation consists in pointing the real target for each image containing that point. To add a collimation left click of the mouse, to remove a collimation right click. Eventually after running the evaluate command you will observe the residual error occurring for each collimated point.
AOI DEFINITION: To allow APS to compute data in specific area it is useful to set up an area of interest as tangent as possible to the flight plane stripes, these are overlaid to the raster overview. To set the area click on the related button and define it by clicking the four vertexes. If you want to discard an area within the afore mentioned AOI you need to set up an hole by clicking on the related button. Once these procedures are done you can go on in order to get DTM, ORTHOPHOTO, POINT CLOUD and DSM
DTM: The DTM provided by APS has a fifty times step larger than the GSD. It is a model which is related to the terrain, for this reason the algorithm uses a range of filters to reduce the noise that house and trees would give to the model. The DTM is used by APS to generate exclusively the OrthoPhoto. A final report with all its features is generated and it can be consulted by clicking on the blue arrow ,through this arrow it is also possible to export the DTM or import it as a model generated with an other software. To generate the DTM click on the following button Then choose the level of detail, it goes from very low to high. A high level is usually used for open field survey, otherwise a low level is often used for populated area .
Contour lines: Since you have a model such as the DTM, APS allows the user to extract contour lines. To get Contour lines click the following button. Contour lines can be exported as a DWG file through the blue arrow lying beside the afore mentioned command.
Seam lines: Each OrthoPhoto is a set of pieces which make a mosaic, these pieces are generated automatically by clicking on the seam lines command (see above). Each seam line represents the edge of each piece. Any seam line can be edited to rectify a certain kind of error witch can occur any time there are elements with a sudden difference in height compared to the surrounding area, such as Houses and bridges. The roof of this house is split by a seam line, the result occurring is a graphic mistake as the OrthoPhoto gets generated. By clicking on the lower pane it is possible to enlarge its area of interest and include the roof. By following this way the mistake gets corrected.
ORTHOPHOTO: Once the DTM has been done it is possible to get an OrthoPhoto of the surveyed area, an OrthoPhoto is nothing but a set of images whose projective rays are parallel to each other. This allows the user to get a product planimetrically correct. To get an OrthoPhoto click on the following button: The related window will be opened to set all the parameters which will be considered during the construction. These are: - Ground sample distance (this value is automatically obtained from the flight height and camera sensor) - Radiometric Balancing - Set up Tiles (slide over to see how to do) Once the OrthoPhoto is ready a report listing all the related information will be generated, it is available through the blue arrow lying beside the command OrthoPhoto.
ORTHOPHOTO: setup Tiles Before running the OrthoPhoto procedure if you want to split the area It is possible to set up a number of tiles through the following window. Through the button pick you are going to set the origin of your first tile, then it will be necessary to set Width and Height and according to the areal extension a number of tiles will be created.
POINT CLOUD & DSM Point cloud and DSM are gained all in once, you have to set the DSM step at first so that a point cloud will be generated with that defined step, after that the DSM will be developed with the same step. The minimum step is five times the GSD, further the user will be asked to fill holes, this allows to interpolate the points when some points can’t be recognized during the point cloud generation.
POINT CLOUD The point cloud is a set of points, each of them can contain both geographic and RGB information. The point cloud can be exported as file ASCII by clicking on the blue arrow.
DSM The DSM is a surface model, during its creation no filter is applied and the result is a model that takes into account every single object laid on the surface such as houses and trees
POINT CLOUD & DSM: report Alike to the other results even for POINT CLOUD and DSM it is possible to consult a report.
STEREO TOOL Through APS it is possible to enable the Menci module Stereo Tool by exporting the project. StereoTools is a standing alone software and can be used for blocks of oriented images. The only condition is that these pictures have a sufficient overlap to obtain the stereoscopic view. Once you are working with stereo tool you can draw points and lines in a CAD environment, eventually you can export them as a file DWG.
For any additional information Please contact us: www.menci.com
