Aerial Photogrammetry

- Basic concepts

GIS595/MEA792: UAV/lidar Data Analytics

Author

NCSU OSGeoREL at Center for Geospatial Analytics

Fall 2016

Objectives (1)

  • Understand the remote sensing crucial role in Earth Sicence, especialy in spatial data aquisition
  • Use the proper terminology and understand its meaning
  • Recognize the significance of aerial photography in collecting spatial data (also a need in historical context)
  • Outline the improvement of aerial photography and connect it with the knowledge of UAS development
  • Describe different types of aerial photography and associated with them challenges for measurements

Objectives (2)

  • Understand why photrogrammetry needs to be used in order to make mesurements based on aerial photographs
  • Describe the process of photogrammetric flight planning
  • Understand lateral and forward overlap, stereoscopic coverage, flight lines and focal length terms
  • Indicate the specific problems emerging when aerial imagery is aquired by low range UAS equipped in non-photogrammetric camera
  • Distinguish steps for processing UAS derived data in comparison with traditional photogrammetry

What is Remote Sensing?

  • Sensing without contact;
  • Gathering data from a distance;
  • Fundamental to all sentient life forms;
  • Two principle senses – sight and sound;
  • Sight and sound have similar physiological and psychological underpinnings.

Psychology of SIGHT

  • Sensors (eyes) take input and pass them along to the brain;
  • The brain makes the interpretations and connections;
  • Stereoscopic vision is amazing brain capability;
  • Color production for sight
    happens in the brain;
  • Eyes collect data– brain produces information.

    • Remote sensing for mapping explained

    Remote Sensing Development

    • Invention the photographic process (disputed time – inventor);
    • Pictures taken (from the bird’s eye view – buildings and high structures and... Using birds;
    • Invention of a flying vehicle aerial photography of larger areas;

    Remote sensing development- aerial photography

    • Aerial photography – the first form of remote sensing extremely useful for geography

    Aerial photography

    • First World War - aerial photography extensively used for recording human geography

    Photogrammetry – a broad spectrum

    Remote sensing, photogrammerty and GIS

    Source of diagrams: Schenk (2005), modified

    Geometry of aerial photograph

    San Francisco Earthquake

    Oblique aerial photography from 1906

    Aerial photography for map making in the past

    • Mostly the domain of the military;
    • Some photographs were taken from a vertical perspective during WW1
    • If you piece them together they look like a map
    • Widely used tool for mapping (accuracy not all that important at this point)

    Mapping with Photos

    Making Measurements

    • Photo mosaics were useful, but they only give you the overview and are not accurate maps.
    • In the late 1800’s the development of the parlor stereoscope was a source of entertainment before radio and TV were invented.

    Photogrammetry (1)

    • It is a 3-dimensional coordinate measuring technique that uses PHOTORAPHS as the fundamental medium for measurement;
    • The science of taking precise measurements from photographs;
    • The most important development in map making;
    • Very precise measurements can be taken from stereoscopic images.

    Photogrammetry (2)

    • 1851: French officer Aime Laussedat develops the first photogrammetrical devices and methods. He is seen as the initiator of photogrammetry;
    • 1911: The Austrian Th. Scheimpflug finds a way to create rectified photographs. He is considered as the initiator of aerial photogrammetry, since he was the first succeeding to apply the photogrammetrical principles to aerial photographs;
    • but... it took 80 years to make it useful for measurements

    Orthorectification

    Orthorectification

    Orthorectification

    Orthorectification

    Orthorectification

    Orthorectification

    Orthorectification

    Photogrammetry (3)

    • Correct distortions, and you have a remote mapping tool (heights, distances, areas);
    • Removes ground survey as a map making method;
    • some ground survey still necessary, but only of very small areas
    • All topographic maps are produced using this technology.

    Aerial survey

    Geoprocessing - workflow

    Geoprocessing - workflow

    Geoprocessing - workflow

    Geoprocessing - workflow

    Geoprocessing - workflow

    Geoprocessing - workflow

    Geoprocessing - workflow

    Geoprocessing - workflow

    Geoprocessing - workflow

    Geoprocessing - workflow

    Geoprocessing - workflow

    Geoprocessing - workflow

    Enough theory...

    Let's do it! - see Assignment 2