PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
July 2014
585
ence necessary to fully understand how to properly implement
geomatics, photogrammetry and related remote sensing tech-
nologies to support the intended uses of the contracted deliv-
erables. Following are specific examples of some of the many
areas of use wherein the accuracy and quality of photogram-
metric mapping services directly affects decisions that could
potentially impact life, health, safety, property and/or the pub-
lic welfare:
1. Engineering design of roads, bridges and public facili-
ties;
2. Water resources planning and design;
3. Natural hazards assessment, including landslide as-
sessment, dam site/reservoir assessment and flood haz-
ard mapping;
4. Emergency services applications;
5. Municipal planning;
6. Disaster recovery;
7. Transportation planning;
8. Route planning for power distribution facilities
Some implementations of the tasks listed may be considered
surveying by state law, depending on the nature of the work
and end use of the project deliverables; other implementations
may not meet state law or National Council of Examiners for
Engineering and Surveying (NCEES) definitions of survey-
ing, but still require the level of professional expertise and
ethical conduct that define professional service. In the opin-
ion of ASPRS, projects and contracts that include any of the
following services should use procurement methods that rely
on qualifications as the primary selection criteria; the most
widely accepted example of which is the Brooks Act Qualifica-
tions-Based Selection (QBS) process. The list below provides
examples of services for which ASPRS
recommends
the QBS
procurement process.
•
Ground Control
- Coordinates established at iden-
tifiable locations within geospatial data sets (e.g., im-
agery, lidar, GIS, etc.) to support the preparation and/
or QA/QC of geospatial project deliverables. The coor-
dinate values should include metadata that references
the accuracy, collection procedures, methodologies, and/
or source data of said locations. Ground control may be
considered a professional service as determined through
the analysis of individual state regulations regarding
the practice of surveying where the work is completed.
•
Aerial Imagery Mission Planning for Orthopho-
tography and Photogrammetric Mapping
- Aerial
imagery acquisition (both film and digital) that is in-
tended to be the source for orthophoto or photogram-
metric mapping with an expectation of geospatial
accuracy is considered a professional service. Flight
coverage, equipment/calibration requirements, flight
altitude, flight window, overlap and other acquisition
specifications directly affect the quality and accuracy of
all subsequent mapping tasks.
•
Directly Georeferenced Aerial Image Acquisition
Incorporating Airborne-GPS, Inertial Measure-
ment Unit (IMU) or Similar Technologies)
- These
technologies involve the direct determination, during
image acquisition, of some or all of the image georefer-
encing parameters. Imagery acquisition for which spe-
cific coordinate and orientation parameters that are re-
quired as a deliverable implies an expectation of accura-
cy and requires professional services to ensure reliable
results that will support intended applications.
•
Analytical Aerial Triangulation
- This process com-
bines the ground control with the sensor metric param-
eters, and then applies precise photogrammetric mea-
surements to accurately georeference the imagery. The
accuracy and reliability of the aerial triangulation pro-
cess affects all subsequent mapping tasks.
•
Determination of Topographic, Elevation Mod-
el, or Planimetric Feature Mapping
- Point and
feature extraction from remotely sensed data for the
purposes of mapping topographic features, planimetric
features or development of elevation and terrain models
have an expectation of accuracy and affect subsequent
decisions and activities that affect life, health, safety,
property and/or the public welfare. Feature extraction
requires precise photogrammetric orientations and
measurements, specific knowledge and skill using the
photogrammetric mapping technologies and a broad un-
derstanding of the intended applications. Professional
expertise is critical to adequately represent planimet-
ric, topographic and elevation model features within the
contracted accuracies.
•
Digital Orthophoto Mapping
- A digital orthophoto
by definition is an image that has been differentially
rectified to within a specific 2-dimensional (2D) geo-
spatial accuracy and resolution. Rectifying and georef-
erencing remote sensing imagery to systematically cor-
rect for image orientation parameters, distortion, and
earth surface topography requires rigorous knowledge
of photogrammetric mapping principles and technol-
ogies. Production of orthophotography is considered a
professional service if the resulting orthophotography is
to be produced to meet a scope of work defined by a spe-
cific client or published for use in any application where
the reliability of the geospatial accuracy is of critical
importance. Such uses may include planning, engineer-
ing, natural resources, agriculture, disaster recovery,
emergency services, and development of other mapping
layers or other similar applications.
•
Lidar Acquisition and Processing
. Lidar is an ac-
tive remote sensor that emits short wave electromag-
netic energy (light), records the reflected return signal,
and provides a direct measurement of the location and
range (e.g., elevation) of features on the Earth. The li-
dar sensor must be continuously georeferenced during
its operation by use of airborne-GPS and IMU. Exten-
sive knowledge of all these systems, their calibration
and operational integration, and related mathematical
