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PhotogrammetryArcGIS_V202108.pdf
- 1. ArcGIS Course Topic: Photogrammetry Gómez,F. August 2021 www.fgtraining.com.co
- 2. Definition “Photogrammetry is thescience of obtaining reliable information about the properties of surfaces and objects without physical contact with the objects, and of measuring and interpreting this information” is derived from the three Greek words: phos or phot light gramma letter or something drawn metrein measure
- 3. HOW TO MAKEMAPS WITH DRONES TYPES OF MAPS: ORTHOMOSAICS, 3D MODELS, OTHERS. UAVs can produce a number of different types of maps: orthorectified maps, elevation models, termal maps, and 3D maps or models. The photogrammetry is used here. The simplest way to create a mosaic from aerial imagery is by using photo-stitching software, which combines a series of overlapping aerial photographs into a single image. An orthotmosaic is a series of overlapping aerial photographs that have been geometrically corrected.
- 4. TYPES OF MAPS:ORTHOMOSAICS, 3D MODELS, OTHERS. 3D models, which permit researchers to make volume calculations from a set of aerial images, are increasingly common outputs from UAV technology. Other data products that can be made from UAV-collected imagery include digital elevation models (DEM), NDVI (vegetation) maps, and thermal maps, which require specialized payloads and processing software.
- 6. TYPES OF MAPS:NDVI MAPS NDVI maps are made from specialized Normalized Difference Vegetation Index (NDVI) images, which are taken with cameras that can see in both the visual and the near- infrared spectrum. Standard point-and-shoot cameras, such as the Canon A490, can be modified to capture the wavelengths required for the imagery used to create NDVI images, considerably bringing down the cost of gathering this data.
- 7. Data adquisition • GeometricInformation involves the spatial position and the shape of objects. It is the most important information source in photogrammetry. • Physical Information refers to properties of electromagnetic radiation, e.g., radiant energy, wavelength, and polarization. • Semantic Information is related to the meaning of an image. It is usually obtained by interpreting the recorded data. • Temporal Information is related to the change of an object in time, usually obtained by comparing several images which were recorded at different times.
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- 13. TYPES OF MAPS:THERMAL MAPS. Thermal maps image the temperatures of a given mapping area, and are useful for applications such as detecting structural damage to roads, identifying the source of groundwater discharge, spotting hidden archaeological ruins, and detecting roe deer fawns. Specialized thermal imaging cameras, such as those made by FLIR are light enough to be mounted on a UAV and are increasingly being adopted by civilian pilots interested in gathering thermal imagery.
- 14. CAMERAS FOR THERMALMAPS: FLIR DUO
- 15. FLIGHT PLANNING The flightwill be done under autonomous control between GPS waypoints or will be controlled manually.
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- 17. FLIGHT PLANNING FORIMAGE QUALITY Resolution in aerial photography is measured as ground sampling distance (GSD)—the length on the ground corresponding to the side of one pixel in the image, or the distance between pixel centers measured on the ground (these are equivalent). GSD is also affected by the camera’s focal length, as well as its pixel size. The larger pixel size means the sensor will be more sensitive, allowing for a faster shutter speed in given light conditions and better image quality generally.
- 18. Canon S100 lens,zoomed out, has a focal length of 5.2 mm (26 mm zoomed in). So if we wanted, say, to be able to resolve 1 cm-sized features on the ground using a zoomed-out S100, we would have to fly at 1 cm x 5.2 mm / 0.0019 mm = 27.3 m = 89.7 feet
- 19. SENSORS Most cameras usedfor UAV mapping are lightweight and can be programmed to shoot pictures at regular intervals or controlled remotely. Some specialized devices that can be mounted on a UAV include LiDAR (light detection and ranging) sensors, infrarred cameras equipped for thermal imaging, and air- sampling sensors. Cameras with wide-angle lenses, like the GoPro, are very popular for video and photography uses. However, these lenses create distortion that isn’t ideal for mapping work and has to be edited out in post-processing, meaning they’re not well suited to this kind of project.
- 20. SENSORS The internal GPSfunctionality of Canon’s lightweight S100 and SX260 models makes them particularly popular for UAV mapping. They can be used with the Canon Hack Development Kit, which can program the camera to take pictures at a certain interval or to take a picture based on distance or upon encountering a certain waypoint . Gimbals are also used for changing the angle of the camera from vertical (straight down) to oblique. Some mappers do not use gimbals at all or construct their own from other components.
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- 22. VIEWS The two aerialviews most commonly used in UAV mapping are known as nadir (overhead) and oblique. Photos taken from these two different angles can be combined in photogrammetry software (such as Agisoft Metashape, UASMaster or Pix4Dmapper)
- 23. Software for UAS/ Photogrammetry Tomado de https://geoinnova.org/blog-territorio/comparativa-de-programas-para-fotogrametria/
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- 28. Pix4D forums inLatin America
- 29. GPS AND GEOREFERENCING Somedigital cameras, such as the Canon S100, come with the ability to track the GPS location of where each image was captured, producing data that can then be used to georeference the image with processing software. Some UAVs use direct georeferencing techniques that do not require the use of ground control points, including specialized mapping UAVs such as the MAVinci SIRIUS Pro and the SenseFly eBee RTK model. Real Time Kinematic (RTK) satellite navigation is a positioning technique capable of producing survey-grade accurate results down to the centimeter level by measuring the phase of the radio wave sent by GPS satellites.
- 30. GROUND CONTROL POINTS Aground control point, as previously mentioned, is a target in the desired mapping area with known coordinates, which can be used to find the coordinates of other locations on the map.
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- 33. REFERENCIAS • T. Schenk,2005. Introduction to Photogrammetry. Department of Civil and Environmental Engineering and Geodetic Science. The Ohio State University.