Glossary

Glossary#

ASP and stereo photogrammetry vocabulary, with links to the deeper concept pages.

ASP#: Ames Stereo Pipeline. NASA’s open-source stereo photogrammetry toolkit. Docs.
asp-plot#: The Python visualization companion to ASP. Reads ASP output files and produces diagnostic plots + PDF reports. Docs.
ATL06-SR#: ICESat-2 Land Ice Height (sliderule edition) — the canonical Earth-altimetry product used for DEM alignment. Fetched on the fly via SlideRule.
base-to-height ratio (B/H)#: Ratio of inter-satellite baseline to satellite altitude. Larger B/H = better height precision; typical 0.3–0.6 for Earth-orbiting satellites.
bundle adjustment#: Joint optimization of camera parameters and 3D tie-point positions to minimize reprojection error. ASP tool: bundle_adjust. See Bundle adjustment.
camera model#: The mapping between image pixels and ground coordinates: where the sensor was, how it was oriented, and how its optics project the scene onto the detector. Supplied with the imagery (as RPC or a rigorous sensor model) and refined by bundle adjustment. See Stereo photogrammetry.
CCD artifact#: Sub-pixel discontinuity at the boundary between adjacent CCD chips on push-broom sensors. WorldView-1 and -2 exhibit this; corrected by wv_correct. WorldView-3 does not.
convergence angle#: Angle between the two viewing directions of a stereo pair at the ground point. Sweet spot for natural terrain: 15–30°.
Copernicus DEM (COP30)#: Globally-available 30 m DEM, openly distributed on AWS Open Data. Default reference DEM for Earth tutorials.
CSM#: Community Sensor Model. A standard interface for rigorous sensor models; ASP ships the open USGS implementation (usgscsm). CSM state files expose the sensor’s trajectory and orientation over time, which is what lets jitter_solve correct jitter. See Stereo photogrammetry.
disparity map#: Per-pixel (x, y) shift between matched pixels in a stereo pair. ASP writes it in stages: *-D.tif (initial), *-RD.tif (subpixel-refined), and *-F.tif (filtered, final — the input to triangulation).
DEM#: Digital Elevation Model. A regular grid of heights — the final product of an ASP run. ASP file: *-DEM.tif. The umbrella term covering both DSM and DTM.
dh#: “Difference in height”. Pixel-wise difference between two DEMs (or between a DEM and altimetry).
DSM#: Digital Surface Model. A DEM whose heights are of the first surface the sensor sees: rooftops, tree canopy, snow. Stereo DEMs, ASP’s included, are surface models.
DTM#: Digital Terrain Model. A DEM whose heights are of the bare ground, with buildings and vegetation removed. Deriving one from a stereo DSM requires additional filtering.
ellipsoid#: Smooth mathematical model of a planet’s shape (WGS84 for Earth). ASP heights are relative to the ellipsoid unless you convert them.
geodiff#: ASP tool that computes the difference between two DEMs and reports statistics.
geoid#: Equipotential surface approximating mean sea level (EGM96 or EGM2008 for Earth). Geoid and ellipsoid heights differ by tens of meters depending on location; mixing the two is a classic source of vertical bias. See Orthorectification.
ground sample distance (GSD)#: Pixel size of imagery on the ground, in meters. WV3 pan-sharp GSD ≈ 0.30 m; ASTER GSD ≈ 15 m.
hillshade#: Shaded-relief rendering of a DEM under a synthetic light source. The standard way to inspect DEM quality by eye; produced by gdaldem hillshade or asp-plot.
ICESat-2#: NASA’s Ice, Cloud, and Land Elevation Satellite 2. Provides global laser altimetry used for DEM alignment.
ICP#: Iterative Closest Point. Registration algorithm that alternates pairing each point with its nearest reference neighbor and solving the rigid move that best fits the pairs. What pc_align runs. See Alignment.
interest point (IP)#: Distinctive corner or blob detected in an image, used as a candidate feature for matching across images.
jitter#: High-frequency satellite attitude variation that violates the rigid-camera assumption of standard sensor models. ASP corrects via jitter_solve (CSM cameras only).
LOLA#: Lunar Orbiter Laser Altimeter. Reference altimetry for Moon DEMs.
match file#: ASP file containing tie-point matches between two images. File extension .match (binary) or .csv.
MOLA#: Mars Orbiter Laser Altimeter. Reference altimetry for Mars DEMs.
NMAD#: Normalized Median Absolute Deviation — robust scale estimator. 1.4826 × median(|x - median(x)|). Equals std for normal distributions; resistant to outliers. Used everywhere asp-plot reports DEM error.
NTF#: NITF (National Imagery Transmission Format). Image format used by some commercial sensors.
orthorectification#: Resampling input imagery onto a regular geographic grid using a coarse reference DEM. Makes stereo matching dramatically easier. ASP’s tool for this is mapproject, and ASP docs call the step “mapprojection”. See Orthorectification.
parallax#: Apparent shift of a pixel between two images of the same ground point taken from different viewpoints. Encodes the height of the ground point.
pc_align#: ASP tool for ICP-based registration of point clouds. Used to align a DEM to ground-truth altimetry. See Alignment.
point cloud#: Unstructured 3D points produced by stereo triangulation. ASP file: *-PC.tif (encoded as a GeoTIFF for compactness).
point2dem#: ASP tool that grids a point cloud into a regular DEM.
reprojection error#: Distance, in pixels, between an observed image feature and the predicted position of its 3D ground point reprojected through the camera model. Bundle adjustment minimizes this.
residual#: Per-tie-point reprojection error. asp_plot.bundle_adjust plots these before and after bundle adjustment.
RPC#: Rational Polynomial Coefficients. A camera model that replaces the vendor’s rigorous sensor model with fitted ratios of polynomials mapping longitude, latitude, and height to pixels. Compact and sensor-agnostic, and it keeps the physical camera details private; standard for commercial Earth-observation imagery. See Stereo photogrammetry.
SfM#: Structure from Motion. The general algorithmic family that bundle adjustment + stereo belongs to.
SGM / MGM#: Semi-Global Matching / Modified Global Matching. The stereo-correlation algorithms ASP uses to produce highest quality results (asp_sgm, asp_mgm).
SlideRule#: Cloud-native API for on-demand ICESat-2 processing. asp-plot uses it to fetch ATL06-SR data.
SpaceNet#: Open dataset of high-resolution commercial satellite imagery, hosted on AWS. The UCSD WV3 scenes used in this guide come from the SpaceNet CORE3D collection.
stereo#: ASP’s master command for stereo correlation + triangulation. The parallel version (parallel_stereo) is what tutorials actually use.
subpixel mode#: Setting that controls how parallel_stereo refines integer-pixel matches; e.g. mode 9 (Bayes EM with MGM).
tie point#: A single 3D ground point observed (and matched) in two or more images. Bundle adjustment optimizes camera parameters using tie-point reprojection errors.
WorldView#: DigitalGlobe / Vantor high-resolution Earth-observation satellite series (WV1, WV2, WV3, WV4). All push-broom; the vendor XML carries both an exact linescan camera model and an RPC fit.