## Friday, December 5, 2014

### Highly popular Lidar vocabularies

A
accuracy The closeness of an estimated value (for example, measured or computed) to a standard or accepted (true) value of a particular quantity. See precision.

absolute accuracy A measure that accounts for all systematic and random errors in a dataset. Absolute accuracy is stated with respect to a defined datum or reference system.

accuracyr (ACCr) The National Standards for Spatial Data Accuracy (NSSDA) (Federal Geographic Data Committee, 1998) reporting standard in the horizontal component that equals the radius of a circle of uncertainty, such that the true or theoretical horizontal location of the point falls within that circle 95 percent of the time. ACCRMSErr=×17308..

accuracyz (ACCz) The NSSDA reporting standard in the vertical component that equals the linear uncertainty value, such that the true or theoretical vertical location of the point falls within that linear uncertainty value 95 percent of the time. ACCRMSEzz=×19600..

horizontal accuracy The horizontal (radial) component of the positional accuracy of a dataset with respect to a horizontal datum, at a specified confidence level. See accuracyr.

local accuracy The uncertainty in the coordinates of points with respect to coordinates of other directly connected, adjacent points at the 95-percent confidence level.

network accuracy The uncertainty in the coordinates of mapped points with respect to the geodetic datum at the 95-percent confidence level.

positional accuracy The accuracy at the 95-percent confidence level of the position of features, including horizontal and vertical positions, with respect to horizontal and vertical datums.

relative accuracy A measure of variation in point-to-point accuracy in a data set. In lidar, this term may also specifically mean the positional agreement between points within a swath, adjacent swaths within a lift, adjacent lifts within a project, or between adjacent projects.

vertical accuracy The measure of the positional accuracy of a data set with respect to a specified vertical datum, at a specified confidence level or percentile. See accuracyz.
aggregate nominal pulse density (ANPD) A variant of nominal pulse density that expresses the total expected or actual density of pulses occurring in a specified unit area resulting from multiple passes of the light detection and ranging (lidar) instrument, or a single pass of a platform with multiple lidar instruments, over the same target area. In all other respects, ANPD is identical to nominal pulse density (NPD). In single coverage collection, ANPD and NPD will be equal. See aggregate nominal pulse spacing, nominal pulse density, nominal pulse spacing.
aggregate nominal pulse spacing (ANPS) A variant of nominal pulse spacing that expresses the typical or average lateral distance between pulses in a lidar dataset resulting from multiple passes of the lidar instrument, or a single pass of a platform with multiple lidar instruments, over the same target area. In all other respects, ANPS is identical to nominal pulse spacing
18 Lidar Base Specification
(NPS). In single coverage collections, ANPS and NPS will be equal. See aggregate nominal pulse density, nominal pulse density, nominal pulse spacing.
artifacts An inaccurate observation, effect, or result, especially one resulting from the technology used in scientific investigation or from experimental error. In bare-earth elevation models, artifacts are detectable surface remnants of buildings, trees, towers, telephone poles or other elevated features; also, detectable artificial anomalies that are introduced to a surface model by way of system specific collection or processing techniques. For example, corn-row effects of profile collection, star and ramp effects from multidirectional contour interpolation, or detectable triangular facets caused when vegetation canopies are removed from lidar data.
attitude The position of a body defined by the angles between the axes of the coordinate system of the body and the axes of an external coordinate system. In photogrammetry, the attitude is the angular orientation of a camera (roll, pitch, yaw), or of the photograph taken with that camera, with respect to some external reference system. With lidar, the attitude is normally defined as the roll, pitch and heading of the instrument at the instant an active pulse is emitted from the sensor.

## Friday, January 11, 2013

### LAStools - efficient tools for LiDAR processing: Conference

The International LiDAR Mapping Forum (ILMF), taking place from February 11-13 2013 in Denver, is delighted to announce that the special ‘hot topics’ sessions alongside the main conference.

ASPRS plays a vital role in the lidar industry as it is the key organization that sets data format and accuracy standards for kinematic laser scanning.  With a full morning dedicated to ASPRS on February 11, it will be sharing the results of crucial projects to benefit the lidar community; providing information to help improve accuracy and cost efficiency.

Lewis Graham, Lidar Division Director of ASPRS, will kick off the morning by revealing exciting new plans for the development of LAS validation software.  LAS is the standard data delivery format used throughout the world.  It is supported in all commercial lidar hardware and software and is also the required delivery standard for nearly all private and governmental kinematic lidar projects.  The new LAS validation software will be key in ensuring LAS file compliance and the software will be discussed publicly for the first time at ILMF.

Another session not to be missed will be the first public update of a major project funded by the United States Geological Survey.  The project is investigating new approaches of calibrating and geometrically adjusting broad area airborne lidar projects and over the past year ASPRS’ Airborne Laser Scanning committee has been assessing new techniques.  The committee will provide a fascinating insight into the project so far, which is expected to have a major impact on how airborne laser scanning data are adjusted in the future.